Browse Topic: Three-way catalysts

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Experimental and Kinetic Modeling Study of Aged Natural Gas Three-Way Catalyst Performance2026-01-03734/7/2026
The applicability of three-way catalyst (TWC) models for system-level aftertreatment simulations under transient operating conditions of natural gas engines depend on accurate integration of reaction kinetics as a function of the air-fuel equivalence ratio lambda(λ). A comprehensive global kinetic model has been developed for an aged commercial three-way catalyst (TWC), incorporating key reaction pathways including oxidation of CO, CH₄, C₂H₆, and H₂; reforming of CH₄ and C₂H₆; the water-gas shift reaction; and NO reduction via CO and H₂. The model also accounts for oxygen storage capacity (OSC) and its dynamic interaction with CO and H₂. To calibrate kinetic parameters, systematic bench-scale flow reactor experiments were conducted under lean, stoichiometric, and rich conditions. Performance metrics focused on CH₄ and C₂H₆ oxidation and reforming across varying O₂ and CO concentrations, and NO reduction with CO and H₂ under different oxygen levels. Experimental results revealed that CO suppresses the reforming of CH₄ and C₂H₆. NO conversion was observed between 150°C and 600°C, with H₂-driven reduction producing NH₃, N₂, and N₂O depending on lambda (λ). Under rich conditions, complete NO conversion occurred from 150°C, while lean conditions showed reduced NO conversion at elevated temperatures due to H₂ oxidation. NO reduction with CO initiated at 250°C, achieving full conversion under rich conditions. The model accurately captures the influence of λ on NO reduction with both H₂ and CO, predicts NH₃ formation under rich conditions, and simulates H₂ generation via the water-gas shift reaction above 400°C. It successfully reproduces λ sweep data (λ = 0.95–1.02) and demonstrates CO inhibition effects on H₂ oxidation and NO reduction. This global model is validated with dithering reactor data and qualitatively captures key trends in data which aids in catalyst sizing, calibration robustness and the system level modeling of end of useful life parts. Further validation of the current developed model with lean-rich cycle tests confirms the model’s ability to predict NOx slip at the onset of rich cycles impacting the ability to accurately predict NOx emissions during engine braking events in system level models.
Raj, Richa, Kim, Mi-Young, Aigbiremolen, Grace, Srinivasan, Anand
Impact of Hydrogen on Methane and Pollutant Emissions over Three-Way Catalysts with Natural Gas–Hydrogen Blends2026-01-03574/7/2026
Blending natural gas (NG) with hydrogen (H₂) can improve combustion and engine performance while potentially facilitating the catalytic conversion of methane and other pollutants, resulting in cleaner tailpipe emissions. This study evaluates the impact of H2 on the conversion of methane, CO, and NOx emissions on a commercial three-way catalyst (TWC) in a flow reactor using synthetic gas mixtures that simulate stoichiometric engine exhausts with NG or NG+H₂ combustion. The work examines whether, and how, the additional amount of H₂ in the exhaust stream affects the conversion efficiency of methane and other pollutants. Experiments were conducted with both degreened and aged catalysts under controlled conditions, systematically varying temperature, the air-to-fuel equivalence ratio (λ), and λ modulation. Test conditions covered λ values from 0.996 to 1.000 to represent nominally stoichiometric engine operation with different λ modulation amplitudes, as well as a range of temperatures to inform control strategies for effective CH₄, CO, and NOₓ reduction. Overall, the results show that hydrogen addition significantly improves the conversion efficiency of CH₄ and NOₓ, particularly at temperatures below 500 °C. More significantly, this study highlights that exhaust gas composition, operating temperature, λ management, and the oxygen storage capacity of the TWC all play major roles in affecting the tailpipe emissions from NG and NG+H₂ combustion.
Prikhodko, Vitaly, Wang, Min, Park, Yeonshil, Chen, Hai-Ying, Pihl, Josh
Comparison of Ammonia Emission Characteristics Between Different Gasoline Vehicles Equipped with Three-Way Catalysts2026-01-03744/7/2026
In recent years, the tightening of vehicle emission regulations has led to a decreasing trend in regulated pollutants such as NOₓ and CO. However, the emission of ammonia (NH₃), which is unintentionally generated during the purification process in three-way catalyst of gasoline vehicles, has become a growing concern. NH₃ emissions from vehicles can serve as a precursor to PM2.5 and have been reported to cause local roadside pollution. Therefore, there is a growing need for on-road testing to identify conditions under which NH₃ is likely to be emitted. Furthermore, since engine control strategies vary among vehicle types, it is desirable to consider differences in emission behavior across different models. In this study, on-road NH₃ emissions were measured for multiple vehicle models with different powertrains, and the effects of engine behaviors and engine operating duration across vehicles on NH₃ emissions were investigated. To analyze differences in NH₃ emission behavior among vehicle types, conventional gasoline vehicles and series-type hybrid vehicles were employed. Additionally, vehicle control parameters were obtained via an OBD (On-Board Diagnostics) interface unit and utilized for analysis. The analysis revealed that, for the conventional gasoline vehicles, aggressive accelerator pedal control induced rapid fluctuations in engine speed, which in turn led to NH₃ emissions. In contrast, for the series-type hybrid vehicles, NH₃ emissions were primarily observed when the engine started under specific conditions, whereas differences in driver behavior had only a minor direct impact on NH₃ emissions. In addition, longer engine operating durations resulted in higher emission levels. A common characteristic observed across both vehicle types was that NH₃ emissions were elevated during periods corresponding to CO emissions, which serve as precursors to NH₃ formation.
Ashizawa, Keigo, Fukunaga, Chisato, Gao, Tianyi, Sato, Susumu
Experimental Evaluation of After-Treatment Solutions for Heavy-Duty Natural Gas Vehicles to Meet Future CNVII Regulations2026-01-03764/7/2026
The heavy-duty truck market in China has seen a significant increase in the adoption of natural gas-powered engines over the past two years. Simultaneously, the anticipated release of the China VII emissions regulation proposal by the end of 2025 is expected to impose stricter emissions limits on all heavy-duty engines, including new particulate number (PN10) thresholds analogous to those in the Euro 7 regulation. While tailpipe oxides of nitrogen (NOx) and methane (CH4) emissions from natural gas engines can be mitigated through tighter lambda control and adjustments to catalyst volume and precious metal (PGM) loading, addressing NOx and particulate number (PN) emissions necessitate more advanced after-treatment solutions. Although natural gas combustion is virtually soot-free, the entrainment of lubricating oil into the combustion chamber, especially during cold-start conditions, poses a challenge, leading to potential exceedance of the proposed future China VII limits. Additionally, PN emissions from natural gas vehicles are highly dependent on duty-cycles and the state of the actual engine, with applications involving frequent stop/go operation experiencing increased piston ring wear, and thus, higher oil consumption, and elevated PN emissions. This study aimed to evaluate the performance of different after-treatment solutions for natural gas engines in meeting future China VII emissions standards, with a particular focus on the efficacy of particle filters for controlling PN10 emissions. Three different after-treatment configurations, comprising close-coupled and underfloor three-way catalysts, as well as bare and coated filters, were tested on a 15L China VI commercial natural gas engine in a controlled laboratory environment. Emissions and PN10 data were collected over regulatory cold and hot World Harmonized Transient Cycle (WHTC) test cycles, and analyzed for light-off behavior, conversion efficiencies, system pressure drop, and filtration effectiveness for particles as small as 10nm. The relative advantages and challenges of each configuration are discussed. The results indicate that natural gas engines will likely require the integration of particle filter devices to comply with future China VII PN10 limits. The results also show that NOx compliance is challenging and fine-tuning of the lambda calibration is essential for CNVII.
Gao, Jiahui, Besch, Marc, Ding, Ning, He, Suhao, Zhao, Yuxin, Yixiao, Li, Shen, Ye
Effect of Exhaust Gas Components on Oxygen Storage Capacity Measurements of Automotive Catalysts2026-01-03604/7/2026
Three-way catalytic converters (TWC) are one of the most popular methods to help reduce harmful tailpipe emissions emitted from internal combustion (IC) vehicles. To help improve conversion efficiency, TWCs can store and release oxygen via an oxygen storage capacity (OSC) mechanism. During engine control unit (ECU) calibration, on board OSC measurements are correlated to TWC and vehicle emissions to monitor emissions performance throughout the full useful life (FUL) of the vehicle. It is known that different test conditions, including temperature, space velocity and background gases in the exhaust stream affect OSC measurement, potentially altering the calculated OSC values and thus the perceived level of OSC and emissions preformance during operation. This study utilises an OMEGA test bench to complete OSC measurements on the full-scale automotive catalyst samples to quantify the effects of different background gases including carbon monoxide, hydrocarbons and nitric oxide on OSC measurements, concluding that all background gases studied affect measured OSC values. The study revealed that hydrocarbons had the largest effect on OSC measurement increasing OSC values by up to 50%. It was concluded that the increase in OSC measurement with injected hydrocarbons was due to the breakdown of hydrocarbons on the catalyst surface during rich periods of operation increasing the amount of oxygen required to fully oxidise the catalyst resulting in a larger perceived OSC measurement. During the initial ECU calibration original equipment manufacturers (OEM) should consider these effects on OSC measurement and understand how this will affect perceived OSC and vehicle emissions performance for FUL and onboard diagnostics (OBD) applications. This will help ensure emissions compliance and guide optimized catalyst and engine calibrations.
Mc Grane, Liam, Douglas, Roy, Irwin, Kurtis, Woods, Andrew, Elliott, Matthew, Istrate, Oana, Nockemann, Peter
Optimization of Combustion Stability and Fuel Economy for Dedicated Hybrid Engines with High Exhaust Gas Recirculation Rate03-19-02-00082/26/2026
In recent years, the rapid growth of hybrid vehicles has driven the development of dedicated hybrid engines (DHEs) as a key powertrain technology for achieving high thermal efficiency and low emissions. Driven by stringent emissions regulations and demand for improved fuel economy, enhancing thermal efficiency in gasoline engines remains a critical industry challenge. Exhaust gas recirculation (EGR) technology dilutes oxygen in the intake charge, suppresses knock, and optimizes combustion phasing. However, excessive EGR rates compromise combustion stability by inducing elevated cyclic variability and potential misfire, posing challenges in maintaining stable combustion and improving fuel efficiency at high EGR levels. Thus, combustion stability and fuel efficiency optimization in Geely’s DHEs under high EGR conditions was investigated in this article. In this study, a high tumble combustion system was designed to enhance charge motion and promote stable flame propagation. Furthermore, exhaust gases were drawn from the upstream side of the three-way catalyst to realize high EGR rate. Additionally, high-energy ignition system was applied to ensure stable combustion under high EGR dilution conditions. Compared with the 1.5T engine with a similar technical route, the optimized DHE achieved a 5.4% increase in EGR rate and a 7.2 g/kWh reduction in brake specific fuel consumption (BSFC). These results demonstrate the feasibility of high EGR operation in gasoline engines through synergistic combustion system design and ignition enhancement, offering a scalable solution for meeting future fuel efficiency and emissions targets.
Li, Qiang, Deng, Xiaorong, Ren, Siming, Zhang, Peiyi, Zhu, Yunfeng, Li, Hongzhou, Yan, Pingtao, Gu, Xiangsheng
All New 1.2L Turbocharged Gasoline Direct Injection Engine from Tata Motors2026-26-00711/16/2026
There is continuous push from the legislation for stringent fuel economy and emission regulations while the modern customers are demanding more engaging driving experience in terms of performance and refinement. To meet this Tata Motors has developed an advanced 1.2L 3-cylinder turbocharged gasoline direct injection engine. This next-generation powertrain delivers optimum efficiency, reduced emissions, superior performance with refined NVH characteristics. The key features used to enable these demanding requirements includes a 35 MPa fuel injection system, Miller Cycle operation and electrically actuated variable nozzel turbocharger (VNT). A uniquely designed BSVI complaint (WLTP ready) exhaust after-treatment system with Four-Way Conversion Catalyst (FWC+TM) ensures optimum emission control. A centrally mounted variable cam phaser minimizes pumping losses. The lightweight yet rigid all-aluminum engine structure, featuring an integrated structural oil sump, enhances durability and stiffness. These technology packages coupled with right engine management system results in over 15 % better brake thermal efficiency (BTE) and 24% higher low end torque as compared to its predecessor 1.2L TC MPFI engine. The engine delivers 208 Nm/l transient torque density and 225 Nm of Maximum Torque along with 125ps Maximum Power. This paper details the engine’s layout, combustion system optimizations and comparative studies on injector selection, fuel spray patterns for achieving right performance, emissions and NVH.
Hosur, Viswanatha, Ghadge, Ganesh Narayan, Joshi, Manoj, Jadhav, Aashish, Panwar, Anupam
Introducing a New Catalyst Family in Gasoline Aftertreatment2026-26-02311/16/2026
This paper is to introduce a new catalyst family in gasoline aftertreatment. The very well-known three-way catalysts effectively reduce the main emission components resulting from the combustion process in the engine, namely THC, CO, and NOx. The reduction of these harmful emissions is the main goal of emission legislation such as Bharat VI to increase air quality significantly, especially in urban areas. Indeed, it has been shown that under certain operating conditions, three-way catalysts may produce toxic NH3 and the greenhouse gas N2O, which are both very unwanted emissions. In a self-committed approach, OEMs could want to minimize these noxious pollutants, especially if this can be done with no architecture change, namely without additional underfloor catalyst. In most Bharat VI gasoline aftertreatment system architectures, significant amounts of NH3 occur in two phases of vehicle driving: situations with the catalyst temperature below light-off, which appear after cold start or at low-speed urban driving and hot, high mass flow phases. In this paper, we will compare several approaches to reduce NH3 starting with an existing gasoline technology, diesel technologies modified to gasoline conditions and the especially developed novel gasoline Secondary Emission Treatment (SET) catalyst, providing both ammonia abatement and underfloor three-way functionality. SET is the combination addressing both the cold start phase and hot driving conditions. In addition, it fulfills the role of an underfloor three-way catalyst, responsible for CO and NOx hot phase treatment.
Kuhn, Sebastian, Magar, Avinash, Kogel, Julius, Lahousse, Christophe
Performance Analysis of a Hydrogen-blended Naturally Aspirated Gas Engine with a Dedicated Exhaust Gas Recirculation System2025-32-004611/3/2025
With the publication of the Renewable Energy Directive (RED) III in 2022, the European Union increased its renewable energy consumption target to 42.5% by 2030. Consequently, gaseous fuels derived from renewable electricity, particularly green hydrogen, are expected to play a pivotal role in the decarbonization of the energy sector. One promising application of green hydrogen is its integration into combined heat and power (CHP) plants, where it can replace natural gas to reduce CO2 emissions. Pure hydrogen as fuel or blended with natural gas has demonstrated potential for lowering both pollutant emissions and fuel consumption while maintaining or even enhancing engine performance. But it is expected, that the amount of available green hydrogen will be limited in the beginning. So new engine systems with hydrogen and natural gas for CHP plants are required, that offer more CO2-benefit and NOx reductioon than from fuel substitution only. In the LeanStoicH2 project, a novel approach was developed to optimize the operation of a four-cylinder stationary gas engine for hydrogen utilization. The project introduced a customized exhaust gas recirculation (EGR) system in which the exhaust gas from a hydrogen-fueled cylinder is fully recirculated into the intake mixture of three other cylinders operating stoichiometrically with natural gas. This configuration leverages the benefits of both lean and stoichiometric combustion strategies. After passing a lower temperature condenser, the dry recirculated exhaust gas, which is CO2- and H2O-free, dilutes the intake mixture of the three cylinders, mimicking lean operation and thus increasing engine efficiency due to the higher isentropic coefficient (κ). Simultaneously, this approach reduces combustion temperatures, thereby lowering knock tendency and engine wear. Furthermore, the stoichiometric operation of the EGR-receiving and emission relevant cylinders allows for the effective use of a three-way catalyst, significantly reducing pollutant emissions. Experimental results confirm that this innovative combustion strategy enhances indicated efficiency from 41.5% to 43.5% compared to series operation, and maintains low NOx tail pipe emissions. These findings highlight the potential of advanced hydrogen combustion strategies to improve the sustainability and performance of gas engine CHP plants, supporting the transition toward a greener energy landscape.
Salim, Naqib, Beltaifa, Youssef, Kettner, Maurice
Reactivity Retention of Modern Converters for Stringent Emission Control2025-01-040110/7/2025
The growing emphasis on environmental protection and sustainability has resulted in increasingly stringent emission regulations for automotive manufacturers, as demonstrated by the upcoming EURO 7 and 2027 EPA standards. Significant advancements in cleaner combustion and effective aftertreatment strategies have been made in recent decades to increase the engine efficiency while abiding by the emission limits. Among the exhaust aftertreatment strategies, three-way catalyst has remained the primary solution for stoichiometric burn engines due to its high conversion efficiency and ability to simultaneously allow both oxidative and reductive reactions in a single stage with spatial separation due to the oxygen storage capabilities of ceria. However, fuel and lubricant-borne sulfur and phosphorus compounds have been shown to have a significant long-term effect on the activity of three-way catalysts, particularly during the lean-rich transitions and oxygen storage processes. In the present study, the impact of sulfur contamination on the conversion efficiency and oxygen storage capacity of the three-way catalyst has been investigated on a heated flow reactor bench platform. The influence of sulfur accumulation on the water-gas shift reaction and activity of ceria has been studied. Additionally, the process of sulfur removal at high temperature (~700-750°C) has also been explored. Relevant engine-out exhaust conditions from the SI engine platform, including flow, temperature, and exhaust species (individually), were replicated on a heated aftertreatment flow bench during contamination and regeneration cycles. A comprehensive analysis of species before and after the catalyst sections was performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species including sulfur species (sulfur dioxide and hydrogen sulfide) and hydrogen, under different catalyst conditions. The conversion selectivity of sulfur species during regeneration is also investigated. The results show that sulfur contamination causes a substantial reduction in oxygen storage capacity. Effective sulfur removal required a combination of high temperature (~700°C or higher) and lean-rich cycling; absence of either condition resulted in incomplete desulfation and the selectivity towards sulfur dioxide and hydrogen sulfide was largely dependent on the reductant species used during high temperature desulfation.
Sandhu, Navjot Singh, Yu, Xiao, Jiang, Chuankai, Ting, David, Zheng, Ming
Combined Virtual and Experimental Approach to Develop Highly Efficient Metallic Catalyst for New World Wide Emission Legislation2025-24-00809/7/2025
The market penetration of Battery Electric Vehicles (BEV) in Europe is not following the foreseen scenario. This is related to several factors, such as uncertainty of the second-hand value of BEV, real driving range under cold conditions and availability of charging stations. Even if the European Community is still planning a full ban of Internal Combustion Engines (ICE) by 2035, in the rest of the world a more technology neutral approach is being pursued. Car manufacturers are developing different powertrain architectures, from mild- to full-hybrid and Range Extenders (REEX). In this context of different emission regulations, and wide range of powertrain architectures, the focus of the development will be the increase of catalyst efficiency without any big impact on exhaust aftertreatment cost. In previous work [1] the authors have used a 1D simulation approach to support the optimization of metallic TWC substrate for the High Power Cold Start use case. Additionally, a 3D CFD was used to investigate the effect of flow rate peaks where maldistribution appears to have a major impact on the overall abatement efficiency. Additionally, a complete validation of the 3D tool was made using roller bench data, measured by Aurobay on a representative production car. This step served also as an opportunity to deeply validate the tool. The limitation of the heat losses, along with a tailored choice of the thermal mass and properties of the substrate, allowed to guarantee the desired abatement. In this work a comprehensive 3D CFD approach is used to assess the possibility to simulate the efficiency of a metallic substrate during typical emissions cycles. Moreover, a dedicated test, using lambda-step, will be used to assess the response of metallic substrates to lambda perturbation.
Montenegro, Gianluca, Della Torre, Augusto, Marinoni, Andrea, Onorati, Angelo, Klövmark, Henrik, Laurell, Mats, Pace, Lorenzo, Konieczny, Katrin
Water Injection as an Enabling Technology for Stoichiometric High Performance Normally Aspirated Engines2025-24-00279/7/2025
The mainstream automotive market is rapidly transitioning to electrified and fully electric powertrains. Where gasoline engines are still employed, they are frequently turbocharged units with relatively low maximum engine speed and modest power density. The hypercar class, in contrast, has recently seen somewhat of a renaissance in high performance, high speed, naturally aspirated gasoline engines, which are prized for their emotional contribution to the vehicle. In order to guarantee high conversion efficiency of a Three Way Catalyst in the exhaust system, an engine must be operated at stoichiometric air-fuel ratio. At high power density, this may result in very high exhaust gas temperature, which poses a risk to engine and vehicle hardware. A number of technological interventions to extend the maximum stoichiometric performance whilst respecting component limitations have already been described in the literature, but many of these are not applicable to specific engine architectures in the hypercar niche. This work describes some of the unique challenges for such vehicle types in achieving stoichiometric operation in all conditions and identifies water injection as a key enabling technology. An experimental campaign on a high speed normally aspirated mule engine with water injectors installed in the intake ports is described. This is supported by Computational Fluid Dynamics calculations with detailed chemistry and bench testing of the injectors using Phase Doppler Anemometry and momentum flux techniques. It is shown that stoichiometry can be maintained at peak power, but some further complementary technologies may be of interest to limit water consumption and ensure an adequate combustion stability.
Corrigan, Dáire James, Villa, Davide, Penazzi, Eugenio, Meghani, Amit, Knop, Vincent, Caroli, Giacomo, Frigeri, Davide, Ruggiero, Federico, Malaguti, Simone, Postrioti, Lucio, Maka, Cristian
Investigation of a Lambda Leap Strategy for Hydrogen Internal Combustion Engines to Balance Efficiency with Performance and Vehicle Packaging2025-24-00709/7/2025
The paper reports an investigation into employing a “lambda leap” (λ leap) strategy for hydrogen internal combustion engines (H₂ICEs), wherein inherently low emissions of oxides of nitrogen (NOx) are afforded at light load via operation at lambda 2.5, and at higher load by operation at stoichiometry utilizing a three-way catalyst (TWC) for NOx control. This approach means it is necessary under transient operation to “leap” between high values of lambda and stoichiometry from one cycle to the next, in order to avoid completely the λ ≈ 1.3 area where high combustion NOx is generated away from lambda equal to 1; this is because lean catalysis of NOx will be extremely challenging at the rate that it is generated there. To achieve this, a short cam profile was introduced to reduce air mass flow by 57.5%, enabling this leap without changing the fuel injection amount, while preserving favorable combustion characteristics via an early Miller cycle. The study models a 2.0 L inline four-cylinder turbocharged engine converted to hydrogen operation and equipped with the necessary valvetrain functionality. Engine maps show that the λLeap strategy increases peak brake efficiency to 38.6% and positions the high-efficiency region in a more usable part of the operating range of the engine. Vehicle-level simulations across three driving cycles (NEDC, WLTP, FTP75) and three vehicle classes (sedan, medium SUV, large SUV) show fuel consumption reductions of up to 9.9% and engine-out NOx reductions exceeding 50% compared to stoichiometric-only operation. The paper also explains why the strategy would be especially beneficial for light-duty H₂ICEs, given that they have different operating areas compared to heavy-duty ones, and why vehicle packaging, mass, and drag advantages would accrue as well. Finally, some discussion is made regarding how H₂ICEs might benefit from upsizing of their swept volumes if this strategy is successfully employed.
Fong Cisneros, Eric J., Kodaboina, Raghu Vamsi, Vorraro, Giovanni, Turner, James W. G.
Development of After-Treatment Systems and Control Strategy for a Hybrid-Dedicated Homogeneous Lean Burn Engine2025-01-02176/16/2025
The development of lean-burn gasoline engines has continued due to their significant improvements in thermal efficiency. However, challenges associated with NOx emissions have hindered their mainstream adoption. As a result, the development of an effective NOx after-treatment system has become a key focus in lean-burn engine research. Additionally, HC emissions pose another challenge, as they tend to increase under lean combustion conditions while their conversion efficiency simultaneously declines. This study presents a novel after-treatment system incorporating a lean NOx trap(LNT) and a passive SCR(pSCR) system. This configuration enables efficient NOx reduction at a competitive cost while maintaining operational simplicity. Moreover, conventional catalyst technologies, including three-way catalysts (TWCs) and fuel-cut NOx traps (FCNTs), were optimized to maximize conversion performance under lean operating conditions. To further enhance system performance, various control strategies were explored, including advanced temperature management of after-treatment systems, the regeneration strategy of LNT, and optimized catalyst purge strategies during the cold-start phase. The proposed after-treatment system and control strategies were validated through vehicle testing on a chassis dynamometer. The results demonstrated that a hybrid vehicle equipped with a lean-burn gasoline engine and new after-treatment system can achieve a 10% improvement in fuel efficiency while remaining compliant with future emission regulations, underscoring its viability for real-world applications.
Oh, Heechang, Lee, Jonghyeok, Sim, Kiseon, Lim, SeungSoo, Park, Jongil, Park, Minkyu, Kang, Hyunjin, Han, Donghee, Lee, Kwiyeon, Song, Jinwoo
Effect of Ignition Condition and Fuel Octane Number on Knock Intensity in a Small 2-Stroke Engine2025-01-02116/16/2025
Internal combustion engines (ICEs) remain widely used in automotive transportation for their high energy storage system efficiency and economic benefits. The 4-stroke engine has dominated all other forms to date, because the Otto cycle is relatively simple to understand. However, the significant benefits such as less pumping work and friction, lighter construction of 2-stroke engine, are attractive for applications that prioritize the simplicity and power density as well as meet the emission regulations. The disadvantages of the 2-stroke engine are mainly caused by the lack of sufficient scavenging process. Also, the overlap of the intake and exhaust phases results in charge short-circuiting, more fuel consumption and high unburned hydrocarbon emissions. For these reasons, it is difficult for 2-stroke engines to achieve stoichiometric combustion, making them incompatible with three-way catalyst to control emissions. The residual exhaust gas in the cylinder makes the spark ignition application leads to incomplete combustion and a higher coefficient of variation. Hence, it is imperative to investigate the effect of spark ignition strategies (ignition position, ignition timing conditions) on a portable small 2-stroke engine with complex in-cylinder gas flow distribution. In this study, we discussed the effect of spark ignition strategies on a small 2-stroke engine. In-cylinder combustion characteristics, emission characteristics and flame propagation process were observed by an optical 2-stroke engine with loop-scavenging. Additionally, in terms of fuel properties, gasoline, dimethyl carbonate/gasoline blend fuel and primary reference fuel are used to investigate the influence of ignition method on knock intensity with different octane numbers. To analyze the effect of fuel properties on combustion characteristics, the computational fluid dynamic (CFD) simulation using CONVERGE were conducted to predict the flame propagations. Through the experimental and CFD results, the potential for combustion improvement on 2-stroke spark ignition engine was evaluated by the optimization of ignition strategies.
Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Yokota, Takumi, Iijima, Akira
Influence of Exhaust Gas Recirculation on Knock in a Spark Ignition Engine Fueled with Ethanol–Gasoline Blends03-18-03-00194/28/2025
Exhaust gas recirculation (EGR) is widely used in spark ignition engines to reduce throttling losses, decrease exhaust gas temperatures, increase efficiency, and suppress knock. However, the effectiveness of EGR as a knock suppressor is dependent on the fuel type and operating condition. In this study, the effectiveness of EGR to suppress knock was tested with E10, E30, E50, E75, and E100 at a moderately boosted condition. It was found that EGR was effective at suppressing knock with E10, but high EGR rates were required to achieve a knock suppression effect with E30 and E50. No knock suppression effect was observed with E75 and E100 across all tested EGR rates. With E30 and E50, EGR that was passed through a three-way catalyst was more effective at suppressing knock at all EGR rates. Chemkin modeling with neat ethanol revealed that nitric oxide enhanced ignition by increasing the hydroxyl radical concentration in the end gas, resulting in earlier auto-ignition. Directly seeding nitric oxide in the intake system with neat ethanol resulted in an increase in knock intensity, which required a knock-limited CA50 retard of 3.5 crank angle degrees with 660 ppm of nitric oxide.
Gandolfo, John, Gainey, Brian, Lawler, Benjamin
Coupled Analysis of First Principle Calculation and Chemical-Kinetics Simulation to Predict the Activity of Three Way Catalyst2024-32-00044/18/2025
This study proposes a technique to predict the catalytic activity of the CO-NO-O2 reaction using the first principle calculations without experiment. The proposed method consists of four steps. (1) Assuming the detailed chemical reactions based on the Langmuir-Hinshelwood mechanism. (2) Estimating the activation energy (Ea) for each detailed chemical reaction using first principle (e.g. Density Functional Theory: DFT) calculations. (3) Defining frequency factors (A) theoretically. (4) Inputting the estimated Ea and A values into simulation software for chemical-kinetics (e.g. exothermia suite) and running the simulation. The validity of the proposed method was evaluated by experiments. This study predicted the catalytic activities of Pt, Pd or Rh(111) surfaces. The predicted results qualitatively matched the experimental outcomes obtained from the Pt, Pd or Rh thin-film catalyst prepared by the “arc plasma method”.
Miura, Kazuya, Kusaba, Hiroki, Miyoshi, Tomoya, Yoshida, Hiroshi, Tsuchizaki, Hiroyuki, Machida, Masato
Gasoline Particulate Filter Modeling with Catalytic Washcoat and Ash Accumulation and Transient Soot Distribution Prediction2025-01-84834/1/2025
The upcoming EURO 7 and EPA Tier 4 regulations and the possible China 7 are expected to tighten the tailpipe particulate emissions limits significantly. High performance Gasoline Particulate Filters (GPFs) with high filtration efficiency and low pressure drop would be mandated for gasoline engines to meet these stringent regulations. Due to packaging constraints, GPFs are often coated with three-way catalyst (TWC) materials to achieve four-way functionality. Ash accumulation in GPFs also has a significant impact on the performance of GPFs. This paper utilizes 3D CFD to predict the transient filtration efficiency and pressure drop of a washcoated GPF with ash accumulation during the soot loading process. Simulation results show a decent match with experimental data. The 3D CFD model also provides detailed information on soot penetration in the GPF wall substrate and soot cake characteristics on the wall. These information can be crucial for GPF wall substrate design and washcoating strategy design.
Yang, Pengze, Cheng, Zhen
Impact of Oxidation Catalyst Formulation and Space Velocity on Performance with Conventional and Renewable Fuels2025-01-84954/1/2025
Prior study with biodiesel and its blends with ultra-low sulfur diesel (ULSD) and renewable diesel (RD) showed that a commercial diesel oxidation catalyst (DOC) is unable to effectively oxidize neat biodiesel (B100) or high-level biodiesel blends injected into the exhaust of a diesel engine at challenging conditions of low temperature, high exhaust flow rate and high dosing rate. In steady-state performance tests, the performance of blends up to B50 in ULSD or RD was nearly equivalent to ULSD at the lowest exhaust flow rate or for exhaust temperature over 340°C for medium and high flows. ULSD blends above 50 vol% biodiesel exhibited reduced thermal efficiency and DOC outlet temperature with increasing dosing rate and required exhaust temperatures over 400°C to achieve similar performance as ULSD. For RD blends at higher flow rates and temperatures below 300°C even B10 blends showed some loss in performance at the highest dosing rates. Data showed an increase in lightoff temperature with an increase in biodiesel concentration in both the ULSD and RD blends. Here we conducted a limited study with higher catalyst volume and increased platinum group metal (PGM) loading to see if these factors would improve DOC performance with B100. ULSD, RD and B100 were run on steady-state performance test with the same DOC used previously. To assess the impact of PGM loading and catalyst volume we also used a three-way catalyst (TWC) for comparison to the DOC. The TWC consisted of two bricks and the test was run with one and both bricks to assess the impact of catalyst volume. The data showed that the single brick of TWC was marginally better than the DOC with better light off performance for B100 at low temperatures and exhaust flow rates. The entire TWC (two bricks) was significantly better than the DOC showing marginally better performance at low temperature and exhaust flow rate and significantly improved performance at low temperature and medium flow rate. The additional catalyst volume and higher overall catalyst loading produced better oxidation of B100 even at the most challenging conditions – with increased catalyst volume (increased residence time) have the largest effect.
Lakkireddy, Venkata, Weber, Phillip, McCormick, Robert, Howell, Steve
High-Efficient and Cost-Effective Three-Way Catalyst Substrate Design for Plug-in Hybrid Electric Vehicle2025-01-85284/1/2025
China 6b regulation was fully implemented since July 2023 with very strict emission standards for HC, NMHC, NOx, and CO. The country is now also in the process of developing China 7 regulation, which will perhaps impose even stricter emission limits and extra criteria pollutants including NH3. Moreover, increasingly strict fuel consumption regulation has been implemented as well and it is highly possible that greenhouse gas emission limits will be included in the China 7 regulation. With the hybrid technology innovation, PHEVs are effective in fuel economy and emission reduction, which are favored by manufacturers and consumers, and leading to a rapid increase in market share. Through the optimization of hybrid architecture and the synergy of electric motors, the operating conditions of the hybrid engine have been optimized, making it more stable and avoiding extreme engine operating conditions compared to traditional ICE, which also provides possibilities for optimizing the after-treatment system design to achieve low cost and high efficiency at the same time. In this study, engine operating conditions and engine out emissions of a PHEV were analyzed through vehicle testing with WLTC cycle in lab. Emission tests were conducted using different catalyst systems to study the impact of different substrate design options including low mass Corning® FLORA® substrates with higher cell density on gaseous pollutant emissions. As a byproduct of secondary reactions on catalysts, the generation of NH3 is closely related to catalyst efficiency. This study also investigated the characteristics of NH3 emissions and proposed appropriate design to reduce NH3 emission. Additionally, the influence of thermal aging conditions on catalyst conversion efficiency was studied to explain the correlation between anti-ageing performance and the substrate design.
Wang, Jiming, Li, Chunbo, Feng, Xiangyu, Chen, Xiaolang, Boger, Thorsten, Tian, Lichen, Hu, Xianli, Zeng, Jun, Tian, Tian, Gao, Bojun, Li, Dacheng, Liu, Shicheng, Jiang, Fajun
Catalyzed Gasoline Particulate Filter Performance from Fresh to Full Useful Life2024-01-431111/5/2024
The gasoline particulate filter (GPF) represents a durable solution for particulate emissions control in light-duty gasoline-fueled vehicles. It is also seen as a viable technology in North America to meet the upcoming US EPA tailpipe emission regulation, the proposed “Multipollutant Rule for Model Year 2027”. The goal of this study was to track the evolution of tailpipe particulate emissions of a modern GTDI light duty vehicle under typical North American mileage accumulation; from a fresh state to 4000-mile, and finally to its full useful life of 150,000-miles. For this purpose, a production TWC + GPF after-treatment system was installed in place of the T3B85 TWC-only system. Chassis dyno emissions testing was performed at the pre-determined mileage points with on-road driving conducted for the necessary mileage accumulation. This report will show the outstanding filtration durability and enhanced particulate control and of the current GPF technology all the way to 150,000 miles for the typical North American application. The report will also demonstrate that a coated CC2 GPF solution is an acceptable substitution for a flow through TWC catalyst for gaseous emissions performance, using an older 1st generation GPF washcoat technology without system optimization efforts. Noting that the investigation is an extension of previously reported results from the GPF performance from 0 to 4000-miles which characterized the early life evolution of tailpipe particulate emissions, specifically mass (PM) and number (PN).
Craig, Angus, Warkins, Jason, Beattie, James, Nipunage, Sanket, Moser, David, Day, Ryan, Banker, Vonda
Emission Optimization of the Cold Start Behavior of a CNG Engine with Electrically Heated Catalyst and Secondary Air Injection2024-24-00289/18/2024
Decarbonization and a continuous reduction in exhaust emissions from combustion engines are key objectives in the further development of modern powertrains. In order to address both aspects, the DE4LoRa research project is developing an innovative hybrid powertrain that is characterized by the highly flexible combination of two electric motors with a monovalent compressed natural gas (CNG) engine. This approach enables highly efficient driving in purely electric, parallel and serial operating modes. The use of synthetic CNG alone leads to a significant reduction in CO2 emissions and thus in the climate impact of the drivetrain. With CNG-powered engines in particular, however, methane and other tailpipe emissions of climate gases and pollutants must also be minimized. This is possible in particular through efficient exhaust gas aftertreatment and an effective operating strategy of the powertrain. This publication presents measurement results that examine the critical aspect of cold starts. The engine is operated with a three-way catalyst with a coating specially tailored to CNG as well as an electrically heated disk and secondary air injection. The powertrain operating strategy makes it possible to preheat the catalyst when the engine is not running, which enables the catalyst to reach higher temperatures prior to the engine start, thus effectively reducing methane slip and other emissions during cold start. The combination of electrical heating power, secondary air mass flow and pre-heating duration are three of the factors in the optimization carried out here. Added to this is an analysis of the most efficient and low-emission engine start using a serial operating mode.
Noone, Patrick, Herold, Tim, Beidl, Christian
TOC99-06-03-0TOC6/21/2024
TOC
Tobolski, Sue
Sulfur Impact on Methane Steam Reforming over the Stoichiometric Natural Gas Three-Way Catalyst2024-01-26334/9/2024
The steam reforming of CH4 plays a crucial role in the high-temperature activity of natural gas three-way catalysts. Despite existing reports on sulfur inhibition in CH4 steam reforming, there is a limited understanding of sulfur storage and removal dynamics under various lambda conditions. In this study, we utilize a 4-Mode sulfur testing approach to elucidate the dynamics of sulfur storage and removal and their impact on three-way catalyst performance. We also investigate the influence of sulfur on CH4 steam reforming by analyzing CH4 conversions under dithering, rich, and lean reactor conditions. In the 4-Mode sulfur test, saturating the TWC with sulfur at low temperatures emerges as the primary cause of significant three-way catalyst performance degradation. After undergoing a deSOx treatment at 600 °C, NOx conversions were fully restored, while CH4 conversions did not fully recover. Experimental data under fixed lambda conditions reveal that sulfur stored on the catalyst leads to reduced CH4 conversions by steam reforming at high temperatures under rich conditions. In contrast, CH4 conversions by oxidation at high temperatures under lean conditions remain consistent, indicating a greater impact of sulfur on CH4 steam reforming. Analysis using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the potential for sulfur-induced deterioration of active sites and oxygen storage capacity, resulting in the formation of carbonaceous species on the catalyst surface.
Kim, Mi-Young, Dadi, Karthik Venkata, Gong, Jian, Kamasamudram, Krishna
Methane Conversion in Stoichiometric Natural Gas Engine Exhaust2024-01-26324/9/2024
Stoichiometric natural gas (CNG) engines are an attractive solution for heavy-duty vehicles considering their inherent advantage in emitting lower CO2 emissions compared to their Diesel counterparts. Additionally, their aftertreatment system can be simpler and less costly as NOx reduction is handled simultaneously with CO/HC oxidation by a Three-Way Catalyst (TWC). The conversion of methane over a TWC shows a complex behavior, significantly different than non-methane hydrocarbons in stoichiometric gasoline engines. Its performance is maximized in a narrow A/F window and is strongly affected by the lean/rich cycling frequency. Experimental and simulation results indicate that lean-mode efficiency is governed by the palladium’s oxidation state while rich conversion is governed by the gradual formation of carbonaceous compounds which temporarily deactivate the active materials. Lean/rich cycling around stoichiometry enables a higher CH4 oxidation as the oxygen storage seems to balance the individual effects of Pd oxidation and rich deactivation. In this work, the catalytic reaction mechanisms involved in CH4, CO and NOx conversion were studied by means of a multi-scale experimental campaign and mathematical modeling. Initially, a detailed kinetic study was performed on the synthetic-gas bench to understand the underlying phenomena and formulate the appropriate reaction mechanisms. The model was then evaluated under transient reactor experiments while final validation was performed against driving cycle measurements on the engine bench.
Karamitros, Dimitrios, Ibraimova, Adjer, Konstantinidis, Konstantinos, Koltsakis, Grigorios, Choi, Sungmu, Cho, Jiho
Effective Utilization of Pt Catalyst in Three-Way Catalytic System by Employing Calcined Ceria with Alumina2024-01-21334/9/2024
To satisfy the stringent regulations for exhaust gas emissions from gasoline-powered vehicles, large amounts of Rh and Pd have often been employed in three-way catalysts (TWCs) as the main active components. On the other hand, Pt-based TWCs are not often used in gasoline vehicles because Pt is readily sintered by its exhaust gases at approximately 1000 °C [1, 2]. In general, Pt-based TWCs must be located away from large thermal loads to maintain the active sites for gas purification. Based on this background, we previously reported that employing a small amount of CeO2 calcined at 1000 °C (cal-CeO2) in Pt-based TWCs was one of the most effective approaches for improving the catalytic activity without increasing the amount of Rh and Pd [3]. The effect of cal-CeO2 was attributed to the higher redox performance and Pt dispersion derived from the strong interactions between Ce and Pt. Therefore, the resulting Pt-based TWCs exhibited high catalytic performance, despite the low specific surface area (SSA) of cal-CeO2 due to high temperature calcination. In this study, we demonstrated that the low SSA of cal-CeO2 can be easily improved by adding Al2O3. The SSA of Al2O3-modified CeO2 calcined at 1000 °C (Al2O3-CeO2) was 45% higher than that of cal-CeO2 owing to the inhibition of CeO2 sintering by Al2O3. In addition, the interactions with Pt were significantly improved, leading to higher redox performance and Pt dispersion compared to the corresponding Pt catalyst supported on cal-CeO2. To determine the effects on the catalytic performance, vehicle evaluations were performed after aging treatment by gasoline-powered engine. Al2O3-CeO2 was employed in a Rh/Pt double-layered TWC placed at the rear bed in a close-coupled system. The results of the FTP mode test cycles on a dynamometer indicate that the addition of Al2O3-CeO2 to Rh/Pt double-layered TWCs is clearly more effective for suppressing exhaust gas emissions than the addition of cal-CeO2.
Morita, Itaru, Tanaka, Hiroki, Saeki, Shohei, Isayama, Akihiro, Iwashina, Katsuya, Nagao, Yuki, Endo, Yoshinori, Wakabayashi, Takashi, Haneda, Masaaki
Post-Oxidation Phenomena as a Thermal Management Strategy for Automotive After-Treatment Systems: Assessment by Means of 3D-CFD Virtual Developmen t2024-01-26294/9/2024
The target of the upcoming automotive emission regulations is to promote a fast transition to near-zero emission vehicles. As such, the range of ambient and operating conditions tested in the homologation cycles is broadening. In this context, the proposed work aims to thoroughly investigate the potential of post-oxidation phenomena in reducing the light-off time of a conventional three-way catalyst. The study is carried out on a turbocharged four-cylinder gasoline engine by means of experimental and numerical activities. Post oxidation is achieved through the oxidation of unburned fuel in the exhaust line, exploiting a rich combustion and a secondary air injection dedicated strategy. The CFD methodology consists of two different approaches: the former relies on a full-engine mesh, the latter on a detailed analysis of the chemical reactions occurring in the exhaust line. The coupling between experimental data and simulation results provides a complete assessment of the investigated phenomena. After the validation of the numerical methodology for one fixed engine operating point, a specific investigation is performed to assess the benefits of post-oxidation in terms of catalyst light-off time. Finally, the simulation strategy is applied considering a different fuel: hydrogen. Accordingly, both the full-engine mesh simulation and the detailed analysis of the exhaust line are performed. The 3D-CFD virtual development allows a comparison between the results obtained through gasoline and hydrogen, thus highlighting the differences and the possible improvements associated with the application of the alternative fuel and the exploitation of its peculiar features.
Barillari, Loris, Pipolo, Mario, Della Torre, Augusto, Montenegro, Gianluca, Onorati, Angelo, Vacca, Antonino, Chiodi, Marco, Kulzer, André
Ultra-Downsizing of ICEs Based on True Atkinson Cycle Implementations. Thermodynamic Analysis and Comparison on the Indicated Fuel Conversion Efficiency of Atkinson and Classical ICE Cycles2024-01-20964/9/2024
Ultra-Downsizing (UD) was introduced as an even higher level of downsizing for Internal Combustion Engines ICEs, see [2] SAE 2015-01-1252. The introduction of Ultra Downsizing (UD) aims to enhance the power, efficiency, and sustainability of ICEs while maintaining the thermal and mechanical strain within acceptable limits. The following approaches are utilized: 1 True Atkinson Cycles are implemented utilizing an asymmetrical crank mechanism called Variable Compression and Stroke Ratios (VCSR). This mechanism allows for extended expansion stroke and continuous adjustment of the Volumetric Compression Ratio (VCR). 2 Unrestricted two or more stage high-pressure turbocharging and intensive intercooling: This setup enables more complete filling of the cylinder and reduces the compression work on the piston, resulting in higher specific power and efficiency. 3 The new Load Control (LC) approach is based to continuous VCR adjustment. By adjusting the VCR without resorting to excessive throttling or external Exhaust Gas Recirculation (EGR), a stoichiometric Air Fuel Ratio (AFR) can be maintained. This facilitates easier exhaust gas aftertreatment using a three-way catalyst. 4 Fuel Flexibility: The continuous VCR adaptation capability enables the engine to operate in multi-fuel mode. In addition to gasoline or diesel, the engine can also run on alternative fuels like pure hydrogen (H2) or H2 blended with gases like CNG, Biogas, e-fuels, or even ammonia (NH3). This versatility allows for reduced carbon emissions and increased sustainability. By combining these approaches, the UD concept aims to achieve higher power output, improved efficiency, and reduced environmental impact in ICEs, all while ensuring the durability and strength of engine components remain within acceptable limits. The thermodynamic analysis is done separately for ideal and real cycles in order to determine the Indicated Fuel Conversion Efficiency (IFCE), formulaically (for ideal cycles) and quantitatively (for real cycles). AVL BOOST © is used to simulate the real cycles (within cylinder and turbocharger) and MATLAB © to process the simulation results.
Gheorghiu, Victor
A Three-Way Catalyst Model for a Bio-Methane Heavy-Duty Engine: Characterization at Different Lambda2024-01-20844/9/2024
Given the spread of natural gas engines in low-term toward decarbonization and the growing interest in gaseous mixtures as well as the use of hydrogen in Heavy-Duty (HD) engines, appropriate strategies are needed to maximize thermal efficiency and achieve near-zero emissions from these propulsor systems. In this context, some phenomena related to real-world driving operations, such as engine cut-off or misfire, can lead to inadequate control of the Air-to-Fuel ratio, key factor for Three-Way Catalyst (TWC) efficiency. Goal of the present research activity is to investigate the performance of a bio-methane-fueled HD engine and its Aftertreatment System (ATS), consisting of a Three-Way Catalyst, at different Air-to-Fuel ratio. An experimental test bench characterization, in different operating conditions of the engine workplan, was carried out to evaluate the catalyst reactivity to a defined pattern of the Air-to-Fuel ratio. Through the detection of key performance parameters and indicated signals, numerous insights into the combustion process and the amount of chemical species in the upstream and downstream TWC gas flow are provided. The experimental test campaign has provided an in-depth analysis of the engine behavior in such operating conditions together with a consistent dataset for a subsequent validation of a “quasi-steady” 1D model of the reactor. A surface reactions kinetic mechanism to simulate the main transport and chemical phenomena inside the catalyst has been set-up in 1D simulation platform. To reproduce the dynamics of oxygen storage and release, reactions involving Cerium are included in the kinetic reaction scheme. As a final step, a dedicated experimental campaign in two very lean conditions, maintaining the same operating condition and fuel composition, proving to be an evaluable tool to assess the catalyst performance in reproducing the main pollutants formation and conversion.
Di Maio, Dario, Guido, Chiara, Napolitano, Pierpaolo, Beatrice, Carlo
Improved Coated Gasoline Particulate Filters for China 7 and US Tier 4 Legislations2024-01-23874/9/2024
The impending emission regulations in both China (CN7) and the United States (Tier 4) are set to impose more stringent emission limits on hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM). CN7 places particular emphasis on reducing particulate number (PN) thresholds, while the forthcoming United States Tier 4 legislation is primarily concerned with reducing the allowable particulate matter (PM) to an assumed limit of 0.5 mg/mile. Given the more stringent constraints on both PN and PM emissions, the development of enhanced aftertreatment solutions becomes imperative to comply with these new regulatory demands. Coated Gasoline Particulate Filters (cGPFs) play a pivotal role as essential components for effective PN and PM abatement. These filters are typically deployed in one of two configurations: close-coupled to the turbocharger positioned downstream of a primary three-way catalyst (TWC) or located further downstream of the exhaust system in an underfloor configuration. Each application imposes distinct technical requirements and specifications on cGPFs, necessitating tailored solutions for both close-coupled and underfloor applications. This research introduces a novel generation of particulate filters optimized for pressure drop and underfloor applications, which exhibit improved performance in terms of light-off and hot conversion efficiency while maintaining comparable backpressure levels to its predecessors. Moreover, a suite of advanced technologies for close-coupled applications is presented, featuring improved three-way conversion efficiency and enhanced thermal durability compared to previous iterations. Significantly, these new technologies demonstrate equivalent three-way conversion capabilities, irrespective of whether employing bi-metallic Pd/Rh or tri-metallic Pt/Pd/Rh Platinum-group-metal (PGM) architectures. Lastly, the study undertakes an analysis of the trade-off between backpressure and the gain in three-way conversion activity provided by these innovative technologies.
Schoenhaber, Jan, Kawashima, Shota, Gotthardt, Meike, Schühle, Johannes
A Mechanism to Maintain Negative Crankcase Pressure in Turbocharged Gas Engine to Reduce Particulate Number to Meet Euro-VI Emission Regulation2024-26-01451/16/2024
Emissions regulation continually drives the automotive industry to innovate and develop. This pushes to introduce mechanism to maintain negative crankcase pressure in gas engine to meet this changing regulation. The way a turbocharger is used, to meet engine performance, can impact the pressure balance over the compressor and turbine end seals. This pressure difference can allow oil to leak through turbocharger seals. In normal engine operating condition the pressure in the turbocharger end housings is higher than the bearing housing and oil/gas flows into the bearing housing, through the oil drain to the crankcase. Under certain operating conditions, such as low idle and motoring, this pressure difference can be reversed with a higher bearing housing pressure than the pressure behind the turbine wheel. Under this condition oil will flow out of the bearing housing to the recess behind the turbine wheel, will increase the exhaust tail pipe emission, high oil consumption and damages the three-way catalyst. The bearing housing pressure will always track the crankcase pressure through oil drain pipe connected to the crankcase. With negative crankcase pressure control management, the pressure in the bearing housing can be maintain lower than pressure behind the turbine wheel throughout all engine operating conditions.
R, Mahesh Bharathi
Experimental Emission Characteristics Study of Ethanol-Gasoline Fuel Blends on a GDI Engine with a Three-Way Catalyst2024-26-01551/16/2024
Ethanol-gasoline blended fuels have been widely implemented in Indian markets followed by the Govt of India’s road map as ethanol reduces life-cycle greenhouse gas emissions and improves anti-knock performance. However, effects of Ethanol Blending on engine out emissions characteristics including particulates from gasoline direct injection (GDI) engine remains under development and investigation. In this study the effect of ethanol blended gasoline fuels with two blending rates 10% and 20% (v/v %) on catalyst conversion efficiencies and emissions on a 1.2 litre 3-cylinder turbo GDI engine is investigated. The addition of ethanol to gasoline fuel enhances the Octane rating (RON) of the blended fuels, oxygen content and changes Reid vapor pressure (RVP). The influence of lambda biasing, and lambda trim controller has been tested. The approach for calibration was adopted based on achieving the target pollutant conversion efficiencies. Test bench results indicated that with E10 blend all pollutant conversion is more than 98% at all engine operating points. However, with E20 blend using the same lambda bias, fuel enrichment was required to retrieve the NOX conversion efficiency, which was improved back to 98% via suitable trim controller correction.
R, Navaneetha Kannan, S, Easwar Ram, S, Satish Kumar, Karthi, Ramanathan, Ramakrishnan, Muthu
Three Way Catalyst with Faster Light-Off Substrates – A Promising Approach to Reduce Tailpipe Emissions2024-26-01421/16/2024
The ever-tightening regulation norms across the world emphasize the magnitude of the air pollution problem. The decision to leapfrog from BS4 to BS6 – with further reduction in emission limits -showed India’s commitment to clean up its atmosphere. The overall cycle emissions were reduced significantly to meet BS6 targets [1]. However, the introduction of RDE norms in BS6.2 [1] demanded further reduction in emissions under real time operating conditions – start-stop, hard acceleration, idling, cold start – which was possible only through strategies that demanded a cost effective yet robust solutions. The first few seconds of the engine operation after start contribute significantly to the cycle gaseous emissions. This is because the thermal inertia of the catalytic converter restricts the rate at which temperature of the catalyst increases and achieves the desired “light-off” temperature. The challenge becomes more prominent in the turbocharged engines (where some part of exhaust heat energy is used by the turbine to power the compressor) leading to lower exhaust gas temperatures, specifically at ambient/cold starts. In order to achieve better emission performance, an innovative approach is needed to attain quicker catalyst “light-off” as any change in only the PGM material content/composition may not yield an optimum solution. Though in-cylinder based strategies to increase EGT exist, they impose an additional fuel penalty along with issues like oil dilution. A much better way – avoiding the issues above - to improve the EGT profile is to reduce the thermal inertia of the catalytic converter. This is the idea behind introducing high-porosity substrates. A new Corning© FLORA© substrate with a higher porosity (55%) compared to the standard substrates (35%) was adopted as the primary substrate (CC1) in a twin brick catalyst design. Higher porosity reduces the thermal inertia of the substrate which in turn aids in rapid catalyst temperature rise and faster light-off. The advanced FLORA® substrate when combined with key contributor’s improvements on catalytic converter design and engine calibration strategy on 1.2 L MPFI RevotronTM engine, resulted in an improved emissions performance even with a lower PGM content. A reduction of 10 to 30% in regulated pollutants was demonstrated with an approximately 10% lower PGM material loading. The paper describes the multipronged approach taken here to tackle the cold start emissions - redesign of the close coupled catalyst, innovative calibration methodology & the introduction of the high porosity substrate popularly known as FLORA®. The work was conducted on a Tata Motors passenger car powered by a 1.2L MPFI RevotronTM gasoline engine that successfully met the BS6 Stage II emission norms.
Kale, Vishal Maruti, M, Ravisankar, Hosur, Viswanatha, Sridhar, S, Bhimavarapu, Aditya, Lende, Nilesh Ashok, Rose, Dominik, Tao, Tinghong
Characterization of an Integrated Three-Way Catalyst/Lean NOx Trap System for Lean Burn SI Engines2023-01-165810/31/2023
The push for environmental protection and sustainability has led to strict emission regulations for automotive manufacturers as evident in EURO VII and 2026 EPA requirements. The challenge lies in maintaining fuel efficiency and simultaneously reducing the carbon footprint while meeting future emission regulations. Alcohol (primarily methanol, ethanol, and butanol) and ether (dimethyl ether) fuels, owing to their comparable energy density to existing fuels, the comparative ease of handling, renewable production, and suitable emission characteristics may present an attractive drop-in replacement, fully or in part as an additive, to the gasoline/diesel fuels, without extensive modifications to the engine geometry. Additionally, lean and diluted combustion are well-researched pathways for efficiency improvement and reduction of engine-out emissions of modern engines. Modern spark ignition (SI) engines typically employ various in-cylinder emission reduction techniques along with a three-way catalyst (TWC) based exhaust after-treatment system to comply with emission standards. However, the periodic lean-rich oscillations for this TWC system necessitate the SI engine to operate at near stoichiometric mixture conditions, which limits the viability of lean burn for SI engines. Lean NOx trap (LNT) system can reduce the engine out NOx under lean conditions at a cost of fuel efficiency penalty due to regeneration. In the present study, the feasibility of using a coupled TWC-LNT system with extensive dilution to achieve ultra-low tailpipe emissions is investigated. Relevant engine-out exhaust conditions from an SI engine, including flow, temperature, and exhaust species, operating at different dilution conditions were replicated on a heated aftertreatment flow bench. A comprehensive analysis of species before and after the catalyst sections was performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species, including ammonia, methane, and hydrogen, under different engine-out conditions. The results the integration of LNT to a TWC catalyst improves the conversion efficiency of reducing species during the lean operation period. TWC and LNT catalyst simultaneously achieve high conversion efficiency at ~350°C. The LNT regeneration behavior is noticeably affected by the presence of preceding TWC catalyst. The temperature rise because of the oxidation reactions on TWC can deteriorate the LNT regeneration efficiency beyond 400°C.
Sandhu, Navjot Singh, Leblanc, Simon, Yu, Xiao, Reader, Graham, Zheng, Ming
Ammonia Emissions from Combustion in Gasoline Engines2023-01-165510/31/2023
Forthcoming worldwide emissions regulations will start regulating ammonia emissions from light duty vehicles. At present, most light duty vehicles are powered by gasoline spark ignition engines. Sources of ammonia emission from such engines can be in-cylinder reactions (i.e. combustion) or downstream reactions across aftertreatment devices, particularly three-way catalysts. The latter has been known to be a major source of ammonia emissions from gasoline vehicles and has been extensively investigated. The former (combustion), less so, and thus is the subject of this work. A two-zone thermodynamic spark ignition engine model with a comprehensive chemical kinetics framework (C3MechV3.3 mechanism), after being validated against experimental ammonia emissions data, is used to study ammonia formation during combustion. Reaction pathways responsible for its generation are analysed and the effects of changing the following engine operational and combustion parameters are explored: engine load, start of combustion, combustion duration, fuel-air equivalence ratio, and exhaust gas recirculation fraction. Ammonia production was found to be slower than that of other major pollutant species - starting late during the heat release stage, peaking around the time when the cylinder pressures and temperatures were at their highest, and having a late, prolonged production stage after the end of heat release. Ammonia concentrations did not ‘freeze’ until late into the expansion process. Initial ammonia production was driven by three body elementary reactions involving hydrogen radicals produced from the fuel oxidation/reduction, and the late-stage production was dominated by H2O reactions with amino radicals. The net effect of these production pathways on ammonia emissions in response to changes in engine operation was non-monotonic and depended on the dominant pathway at the particular thermal conditions. However, overall trends suggested that emissions increased when engine load increased, combustion duration shortened, combustion timing advanced, fuel-air mixture became richer and exhaust gas recirculation fraction decreased.
Bajwa, Abdullah, Shankar, Varun, Leach, Felix
Improvement of the EGR Dilution Tolerance in Gasoline Engines by the Use of a HSASI Pre-Chamber Spark Plug2023-01-180510/24/2023
Charge dilution in gasoline engines reduces NOx emissions and wall heat losses by the lower combustion temperature. Furthermore, under part load conditions de-throttling allows the reduction of pumping losses and thus higher engine efficiency. In contrast to lean burn, charge dilution by exhaust gas recirculation (EGR) under stoichiometric combustion conditions enables the use of an effective three-way catalyst. A pre-chamber spark plug with hot surface-assisted spark ignition (HSASI) was developed at the UAS Karlsruhe to overcome the drawbacks of charge dilution, especially under part load or cold start conditions, such as inhibited ignition and slow flame speed, and to even enable a further increase of the dilution rate. The influence of the HSASI pre-chamber spark plug on the heat release under EGR dilution and stoichiometric conditions was investigated on a single-cylinder gasoline engine. The performance of the HSASI spark plug was compared with a passive pre-chamber spark plug (PPCSP) and a conventional spark plug (SI) for different combustion phasings. Detailed combustion analyses were conducted and the signal from an ion current sensor located inside the pre-chamber as well as the engine out NO emissions were examined. Operation with the HSASI pre-chamber spark plug allows the ignition timing to be advanced when misfiring occurs with PPCSP and unstable engine operation prevails with SI. With the same combustion phasing, HSASI allows for retarding the ignition timing compared to PPCSP and SI by up to 28 °CA due to a faster flame development. HSASI operation shows less NO emissions than SI and similar to PPCSP for same combustion phasing. However, HSASI has higher efficiency losses due to incomplete combustion and higher wall heat losses compared to SI.
Holzberger, Sascha, Kettner, Maurice, Kirchberger, Roland
Exhaust Aftertreatment Technologies for PN Reduction of Motorcycles2023-01-184610/24/2023
The objective of this experimental investigation was to analyze the effect of various exhaust gas aftertreatment technologies on particulate number emissions (PN) of an MPFI EU5 motorcycle. Specifically, three different aftertreatment strategies were compared, including a three-way-catalyst (TWC) with LS structure as the baseline, a hybrid catalyst with a wire mesh filter, and an optimized gasoline particulate filter (GPF) with three-way catalytic coating. Experimental investigations using the standard test cycle WMTC performed on a two-wheeler chassis dynamometer, while the inhouse particulate sampling system was utilized to gather information about size-dependent filtering efficiency, storage, and combustion of nanoparticles. The particulate sampling and measuring system consist of three condensation particle counters (CPCs) calibrated to three different size classes (SPN4, SPN10, SPN23). The study revealed that all three aftertreatment technologies were effective in reducing PN from the motorcycle, although the standard OEM LS honeycomb is already below the passenger car Euro 6 particle emission limits [1]. However, the GPF with a three-way catalytic coating showed the highest filtering efficiency with a significant decrease in PN emissions, particularly SPN10 and above, compared to the baseline. The hybrid catalyst with a wire mesh filter was also effective with a slightly better reduction in PN emissions compared to the baseline, but it had better backpressure behavior than the GPF and a significantly robust design. The reduction efficiency of the TWC was consistent with prior research. Moreover, the study highlighted the importance of considering the size distribution of particles when assessing aftertreatment strategies. The GPF and the hybrid catalyst with a wire mesh filter demonstrated high filtering efficiencies across all size classes. The TWC with LS structure was less efficient, particularly for the larger size classes, as previously reported [2]. In conclusion, this study emphasizes the need to consider both the overall reduction of PN and the size-dependent filtering efficiency of different aftertreatment strategies when assessing their effectiveness in reducing emissions from motorcycle exhaust.
Schurl, Sebastian, Bonifer, Marcus, Schmidt, Stephan, Bretterklieber, Niko, Joshi, Pragati
Development of Detailed Surface Reaction Mechanism of CO/ NO/ O 2 System for Three Way Catalyst Based on Gaseous and Surface Species Analyses2023-32-01229/29/2023
In this study, we determined the detailed reaction mechanism of CO/NO/O2 for automotive three way catalysts. The N2O formation process obtained from measurements of the reaction properties and the formation process of adsorbed NCO species obtained from surface analysis of platinum group metals were added to a previous detailed surface reaction mechanism. The computational accuracy of the developed reaction mechanism was verified by the one-dimensional simulation software BOOST, and it was found to be sufficient for any combination of platinum group metals and gas concentrations.
Matsumoto, Yuhei, Shimokuri, Daisuke, Miyoshi, Akira, Hinokuma, Satoshi, Murakami, Hiroshi, Kawano, Michiharu
A Study of Multi-Functional Membrane Filters made of Fine Catalyst Particles2023-32-01259/29/2023
A multi-functional membrane filter was developed through deposition of agglomerated Three-Way Catalyst particles with a size of 1 ~ 2 microns on the conventional bare particulate filter. The filtration efficiency reaches almost 100 % from the beginning of soot trapping with a low pressure drop and both reductions of NO and CO emission were achieved.
Hanamura, Katsunori, Fujii, Shinpei, Teerapat, Suteerapongpun
Effects of Different Driving Behavior during Actual Road Driving on Ammonia Emissions from Gasoline Vehicles2023-32-00959/29/2023
Three-way catalysts are used in gasoline vehicles for simultaneous purifying nitrogen oxide, carbon monoxide, and hydrocarbon in recent years. However, the reduction of ammonia emission generated in the three-way catalyst is pressing issue. In EURO 7, ammonia will also be subject to the Real Driving Emissions regulation, and its emissions must be reduced. Previous studies have shown that ammonia emissions are higher under fuel-rich conditions, suggesting that differences in driving behavior have a significant impact on ammonia emissions in real-world driving, which includes various driving environments. In this study, driving tests were conducted on a direct- injection gasoline vehicle equipped with a three-way catalyst and Portable Emission Measurement System and Sensor-based Emission Measurement System to investigate the actual ammonia emissions on actual roads. Sensor-based Emission Measurement System includes the system that can measure ammonia and nitrogen monoxide concentrations independently with high accuracy. Two drivers were used to analyze the effects of different driving behaviors on ammonia emissions. The results showed that ammonia emissions in real world driving largely affected by the lean-rich conditions of three-way catalyst and increased for the driver who drove more aggressively because he/she entered, and fuel cut conditions and the rich condition more frequently during deceleration and acceleration.
Sato, Susumu, Chen, Jiaxin, Eang, Chanpaya, Tanaka, Kotaro, Tange, Takeshi
Potentials of Air Path Variabilities and Water Injection in HD Gas Engines2023-24-01208/28/2023
The transportation sector, and commercial vehicles in particular, play an important role in global CO2 emissions. For this reason, the EU recently decided to reduce CO2 emissions from commercial vehicles by 30% until 2030. One alternative to conventional diesel propulsion is the usage of stoichiometric natural gas combustion. Due to the lowered C/H ratio and the cost effective exhaust after treatment (EAT) in form of a three way catalyst (TWC), less CO2 is emitted and it is possible to comply even with most stringent NOX legislations. However, the stoichiometric combustion of natural gas has also disadvantages. In particular, the throttling and retarded 50 % mass fuel burned (MFB50) positions due to knocking lead to efficiency losses. One way to minimize these is the usage of exhaust gas re-circulation (EGR), Miller cycle and water injection. The reduced knocking tendency allows the geometric compression ratio to be increased further, which leads to an additional efficiency advantage. However, the above-mentioned measures in combination have not yet been investigated holistically on commercial vehicle engines. The aim of this project was therefore to evaluate the above-mentioned measures both experimentally and simulatively for future concepts. The experimental part was already been shown by the author in an earlier publication, in which experimental tests were carried out on a single-cylinder commercial vehicle engine. These results have now been used to calibrate a predictive combustion and knock model. Using a validated air path model of a commercial vehicle engine from MAN Truck & Bus, these three technologies are now transferred to a full engine and the effects with a realistic turbocharging system are investigated. The results with the reference turbocharger show, that Miller valve timing has a higher potential for increasing efficiency compared to EGR, which can be mainly attributed to improved utilization of the exhaust gas enthalpy and lowered unburned gas temperatures which reduces knocking. With a specially designed two-stage turbocharging system for Miller valve timing, the compression ratio could be increased which leads to an additional efficiency increase. Thus, an efficiency improvement of 4.8 % points compared to the reference natural gas engine configuration could be achieved. This corresponds to a CO2 reduction of 19 % compared to a conventional commercial vehicle diesel engine.
Betz, Marius, Eilts, Peter
Improvement of Post-Oxidation for Low-Emission Engines through 3D-CFD Virtual Development2023-24-01078/28/2023
There is a growing need for low-emissions concepts due to stricter emission regulations, more stringent homologation cycles, and the possibility of a ban on new engines by 2035. Of particular concern are the conditions during a cold start, when the Three-Way Catalyst is not yet heated to its light-off temperature. During this period, the catalyst remains inactive, thereby failing to convert pollutants. Reducing the time needed to reach this temperature is crucial to comply with the more stringent emissions standards. The post oxidation by means of secondary air injection, illustrated in this work, is a possible solution to reduce the time needed to reach the above-mentioned temperature. The strategy consists of injecting air into the exhaust manifold via secondary air injectors to oxidize unburned fuel that comes from a rich combustion within the cylinder. This strategy can be implemented without major modifications to the engine's hardware or control system, making it an attractive option for retrofitting older engines or incorporating into new designs. The investigation was conducted experimentally and numerically, with test bench measurements and 3D-CFD simulations. The test bench data were helpful for validating and calibrating the 3D-CFD simulations, which employ two interrelated approaches. The first approach utilizes a full-engine mesh, which includes a 0D turbocharger model, to extrapolate reliable boundary conditions. The second approach uses a detailed exhaust model that includes the mentioned accurate boundary conditions and a chemical reaction mechanism. This paper presents the effects of post oxidation in two different engine operating points. Various secondary air injection strategies, including different temperatures and mass flows, and an alternative exhaust manifold design, are evaluated to assess potential improvements in post oxidation by means of 3D-CFD virtual development.
Pipolo, Mario, Kulzer, Andre, Chiodi, Marco, Moriyoshi, Yasuo
Pre-investigations on Reactive Exhaust Gas Recirculation for a Naturally Aspirated Cogeneration Gas Engine2023-01-12126/26/2023
Given its ability to be combined with the three-way catalyst, the stoichiometric operation is significantly more attractive than the lean-burn process, when considering the increasingly severe NOx limit for cogeneration gas engines in Germany. However, the high temperature of the stoichiometric combustion results in increased wall heat losses, restricted combustion phasings (owing to knock tendency) and thus efficiency penalties. To lower the temperature of the stoichiometric combustion and thus improve the engine efficiency, exhaust gas recirculation (EGR) is one of the most effective means. Nevertheless, the dilution with EGR has much lower tolerance level than with excess air, which leads to a consequent drop in the thermal efficiency. In this regard, reducing the water vapor concentration in the recirculated exhaust gas and increasing the EGR reactivity are two potential measures that may extend the mixture dilution limit and result in engine efficiency benefits. Here, the reactive exhaust gas originates from a sub-stoichiometrically operated cylinder (of a multi-cylinder engine). In this work, the sub-stoichiometric (dedicated cylinder) as well as the stoichiometric (EGR-receiving cylinders) combustion processes with various EGR strategies are deeply analyzed. First, reaction kinetics simulations and engine experiments with comprehensive metrology were carried out to provide an accurate understanding of the sub-stoichiometric engine combustion process, the formation of the reactive species and the reactive exhaust gas properties. Among others, it was found that the increase in exhaust gas reactivity during mixture enrichment is associated with an increase in its specific heat capacity and hence in its diluting effect. Moreover, loss analysis has shown that the mixture enrichment results for near TDC combustion phasings in efficiency benefits associated with the reduced wall heat losses and suppressed real combustion losses. Second, the stoichiometric combustion process with various EGR characteristics, based on the outputs of the previous sub-stoichiometric investigations, was inspected relying on 1D flame simulations and engine trials with “artificially” reactive and variably dry EGR. “Artificially” reactive means that the reactive portion is provided by an external H2 supply into the intake path, while the inert portion (H2O, CO2, N2) is obtained from the recirculated λ = 1 exhaust gas. Here, the externally fed H2 represents all reactive species that would occur in the exhaust gas of a real sub-stoichiometric combustion (H2, CO, unburned HC). The results show that compared to the conventional EGR, the reactive and partially dry EGR provides an improved dilution tolerance, a decrease of wall heat losses and suppression of combustion losses, resulting in significant efficiency benefits.
Beltaifa, Youssef, Kettner, Maurice, Eilts, Peter, Ruchel, Bosse, Fröstl, Sebastian
Comparability of Hot-Wire Estimates of Liquid Water Content in SLD Conditions2023-01-14236/15/2023
Future compliance to FAA 14 CFR Part 25 and EASA CS-25 Appendix O conditions has required icing wind tunnels to expand their cloud simulation envelope, and demonstrate accurate calibration of liquid water content and droplet particle size distributions under these conditions. This has led to a renewed community interest in the accuracy of these calibrations, and the potential inter-facility bias due to the choice of instrumentation and processing methods. This article provides a comparison of the response of various hot-wire liquid water content instruments under Appendix C and supercooled large droplet conditions, after an independent similar analysis at other wind tunnel facilities. The instruments are being used, or are under consideration for use, by facilities collaborating in the ICE GENESIS program. For droplet median volume diameters (MVDs) between about 15 and 250 μm, cylindrical hot wire LWC sensors were found to consistently and increasingly under-read measurements from conical and trough TWC sensors as MVD increased, and were not considered further. Of the remaining TWC sensors, the specific instruments investigated were found to agree within about ± 20% of their average test point response for the range of conditions tested, but systematic scale differences between instruments were found to reach about a factor of 1.4. Sensitivity to increasing droplet MVD was concluded to be similar amongst different instruments given the uncertainties, except for two that exhibited notable roll-off with MVD relative to the others.
Esposito, Biagio M., Orchard, David, Lucke, Johannes, Nichman, Leonid, Bliankinshtein, Natalia, Lilie, Lyle, Catalano, Pietro, D'Aniello, Francesco, Strapp, J. Walter
Snow Particle Characterization. Part A: Statistics of Microphysical Properties of Snow Crystal Populations from Recent Observations Performed during the ICE GENESIS Project2023-01-14926/15/2023
Measurements in snow conditions performed in the past were rarely initiated and best suited for pure and extremely detailed quantification of microphysical properties of a series of microphysical parameters, needed for accretion modelling. Within the European ICE GENESIS project, a considerable effort of natural snow measurements has been made during winter 2020/21. Instrumental means, both in-situ and remote sensing were deployed on the ATR-42 aircraft, as well as on the ground (ground station at ‘Les Eplatures’ airport in the Swiss Jura Mountains with ATR-42 overflights). Snow clouds and precipitation in the atmospheric column were sampled with the aircraft, whereas ground based and airborne radar systems allowed extending the observations of snow properties beyond the flight level chosen for the in situ measurements. Overall, five flight missions have been performed at different numerous flight levels (related temperature range from -10°C to +2°C) beyond the ‘Les Eplatures’ airport. The manuscript focuses primarily on statistical retrievals of temperature dependent microphysical snow properties, with in particular, the total condensed water content (TWC), number and mass size distributions, the latter allowing to calculate the mass representative diameter proxy of the median mass diameter (MMD), ice crystal effective density, and a series of snow particle size dependent descriptors of morphological properties (3D volumetric diameter versus 2D image diameter, sphericity, crosswise sphericity, aspect ratio). In addition, snow properties from the ground based MASC imaging probe and complementary retrievals of snow properties from ground based and airborne radar observations are included in this study.
Jaffeux, Louis, Schwarzenboeck, Alfons, Coutris, Pierre, Febvre, Guy, Dezitter, Fabien, Aguilar, Boris, billault-Roux, Anne-claire, Grazioli, Jacopo, Berne, Alexis, Köbschall, Kilian, Jorquera, Susana, Delanoe, Julien
Analysis and Optimization of Metallic Based Substrates for After-Treatment System by Means of Full-Scale CFD Simulations and Experiments2023-01-03694/11/2023
The tightening trend of regulations on the levels of admitted pollutant emissions has given a great spur to the research work in the field of combustion and after-treatment devices. Despite the improvements that can be applied to the development of the combustion process, pollutant emissions cannot be reduced to zero; for this reason, the aftertreatment system will become a key component in the path to achieving near-zero emission levels. This study focuses on the numerical analysis and optimization of different metallic substrates, specifically developed for three-way catalyst (TWC) and Diesel oxidation catalyst (DOC) applications, to improve their thermal efficiency by reducing radial thermal losses through the outer mantle. The optimization process relies on computational fluid dynamics (CFD) simulations supported by experimental measurements to validate the numerical models carried out under uncoated conditions, where chemical reactions do not occur. Full-scale three-dimensional, multi-region models precisely describe the flow and temperature distributions allowing the evaluation of heat fluxes with the surrounding environment. A test cycle was designed to replicate the typical warm-up of a catalyst followed by a drop in the gas temperature and then a drop in the mass flow, replicating the engine switch-off condition. Different canning solutions and insulation strategies were considered at both numerical and experimental levels, and the results were compared. This allowed the validation of the numerical approach and identification of the best solution in terms of heat loss reduction and response time to heat up.
Sartirana, Andrea, Montenegro, Gianluca, Della Torre, Augusto, Onorati, Angelo, Pace, Lorenzo, Zaldua-Moreno, Naroa
Model-Free State Estimation Using Subspace Identification and Kalman Filter2023-01-03654/11/2023
The model-based design is very much prominent in the vehicle level control system design and state estimation algorithms. It gives the edge to understand and interpret the dynamic systems. Three-way catalytic converter is a thermo-chemical device to convert the toxic oxides into carbon dioxide and water vapor, during this conversion reactions it generates the heat over the catalyst surface. Detailed chemical and thermal model of the catalyst will be able to predict the conversion efficiency, state of stored oxygen (SoX) and oxygen storage capacity (OSC). As the catalyst get aged, the reaction rates of conversion reactions deteriorate, in results the temperature dynamics also varies which wanes the exothermic heat. In this work, a novel perspective is presented to capture the behavior of SoX and health of the catalytic converter using thermal model analysis of TWC. An equivalent second order multi input single output (MISO) linear sub-space model is identified for the complex detailed thermal model. A second order MISO system is obtained using measured temperature sensor signals across the device. Recursive least square method will be updating the system parameters online then Kalman filter is employed for state estimation. Joint estimation of the hidden state is tested and validated on urban drive cycle with differently aged catalytic converters.
Mandloi, Deepak, Sahu, Prachi, Bagade, Monika Jayprakash, Das, Himadri
Development of Three-Way Catalysts with Enhanced Cold Performance2023-01-03584/11/2023
Global focus on CO2 reduction and environmental protection is increasing. To comply with stricter exhaust gas regulations and reduce real world emissions, it is becoming increasingly important to improve the performance of three-way catalysts. Therefore, highly efficient conversion of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) is required. In general, the more active the precious metals used, the better the conversion performance. However, precious metals have supply risks, such as price fluctuation and the uneven distribution of production areas. Therefore, it is necessary to lower emissions while also lowering the amount of precious metals used. This paper focuses on how catalysts are used and describes the development of a new three-way catalyst for the purpose of strengthening cold conversion and decreasing the usage of precious metals.
Tojo, Takumi, Shirakawa, Shogo, Nakahigashi, Seiji, Hoshino, Sho, Onozuka, Takashi, Noguchi, Takahiro, Aikawa, Tomomasa
Experimental and Modeling Study on the Thermal Aging Impact on the Performance of the Natural Gas Three-Way Catalyst2023-01-03754/11/2023
The prediction accuracy of a three-way catalyst (TWC) model is highly associated with the ability of the model to incorporate the reaction kinetics of the emission process as a lambda function. In this study, we investigated the O2 and H2 concentration profiles of TWC reactions and used them as critical inputs for the development of a global TWC model. We presented the experimental data and global kinetic model showing the impact of thermal degradation on the performance of the TWC. The performance metrics investigated in this study included CH4, NOx, and CO conversions under lean, rich, and dithering light-off conditions to determine the kinetics of oxidation reactions and reduction/reforming/water-gas shift reactions as a function of thermal aging. The O2 and H2 concentrations were measured using mass spectrometry to track the change in the oxidation state of the catalyst and to determine the mechanism of the reactions under these light-off conditions. The experimental data indicate that the NOx and CH4 conversions were higher under rich lambda conditions, thereby generating more NH3 than that observed under lean lambda conditions. Conversely, the NH3 formation was mitigated under the dithering conditions resulting from the recovery of redox properties. The measured O2 and H2 concentration profiles indicated that the conversion of CH4 was attributed to its reaction with O2 until O2 was fully consumed. Further, it was converted through a reforming reaction that produced H2 when O2 was depleted. Consequently, dithering conditions with a substantial amount of O2 showed a delayed onset of reforming chemistry and NH3 formation than those observed under rich conditions. The global kinetic model was developed based on the O2 and H2 data obtained under lean and rich conditions as inputs. The model predicted the NOx reduction chemistry in the presence of CO and H2, steam reforming, and the total oxidation of methane reasonably well. We also discussed an approach to improve the model predictions for the partial oxidation reaction of methane.
Kim, Mi-Young, Dadi, Rama Krishna, Gong, Jian, Kamasamudram, Krishna
Real-Time Simulation of CNG Engine and After-Treatment System Cold Start. Part 2: Tail-Pipe Emissions Prediction Using a Detailed Chemistry Based MOC Model2023-01-03644/11/2023
In contrast to the currently primarily used liquid fuels (diesel and gasoline), methane (CH4) as a fuel offers a high potential for a significant reduction of greenhouse gas emissions (GHG). This advantage can only be used if tailpipe CH4 emissions are reduced to a minimum, since the GHG impact of CH4 in the atmosphere is higher than that of carbon dioxide (CO2). Three-way catalysts (TWC - stoichiometric combustion) and methane oxidation catalysts (MOC - lean combustion) can be used for post-engine CH4 oxidation. Both technologies allow for a nearly complete CH4 conversion to CO2 and water at sufficiently high exhaust temperatures (above the light-off temperature of the catalysts). However, CH4 combustion is facing a huge challenge with the planned introduction of Euro VII emissions standard, where stricter CH4 emission limits and a decrease of the cold start starting temperatures are discussed. The aim of the present study is to develop a reliable kinetic catalyst model for MOC conversion prediction in order to optimize the catalyst design in function of engine operation conditions, by combining the outputs from the predicted transient engine simulations as inputs to the catalyst model. Model development and training has been performed using experimental engine test bench data at stoichiometric conditions as well as engine simulation data and is able to reliably predict the major emissions under a broad range of operating conditions. Cold start (-7°C and +20°C) experiments were performed for a simplified worldwide light vehicle test procedure (WLTP) driving cycle using a prototype gas engine together with a MOC. For the catalyst simulations, a 1-D catalytic converter model was used. The model includes detailed gas and surface chemistry that are computed together with catalyst heat up. In a further step, a virtual transient engine cold start cycle is combined with the MOC model to predict tail-pipe emissions at transient operating conditions. This method allows to perform detailed emission investigations in an early stage of engine prototype development.
Leon de Syniawa, Larisa, Siddareddy, Reddy Babu, Oder, Johannes, Franken, Tim, Guenther, Vivien, Rottengruber, Hermann, Mauss, Fabian
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