Browse Topic: Diesel / compression ignition engines

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Design and Optimization of Diesel Engine Cold Start Heating System under Extreme Cold Conditions2026-99-08097/30/2026
With the goal of enhancing diesel engine adaptability to low-temperature environments and exploring cold-start potential at - 50 °C, this paper develops a one-dimensional simulation model for the cold-start system. The model is based on a method that utilizes a diesel heater to warm the coolant, which in turn heats the engine block and oil. The heating condition of coolant and oil of a 10-cylinder V-type engine within a specified time under a -50 °C environment is studied through simulation. We further optimized the cold-start process by enhancing the coolant flow distribution within each circulation circuit to improve overall thermal management and start-up efficiency. The results show that: at an ambient temperature of -50 °C, with a heating power of 80 kW, a total flow rate of 110 L/min, and an engine block flow rate of not less than 54 L/min, the diesel engine can raise the coolant temperature at the engine outlet to 40 °C and the oil temperature to -35 °C within 20 minutes. Through flow optimization, by maximizing the flow rate of the engine block heating circuit and reducing the flow diversion of the intercooler, the coolant temperature at the engine outlet can reach 40 °C in 18.9 minutes, while the oil is heated to -34.9 °C, and the final heating coolant temperature reaches 44.4 °C at 20 minutes. Compared to the situation without flow optimization, the time for the engine outlet coolant temperature to reach 40 °C was shortened by 0.55 minutes, and the final heating coolant temperature increased by 2.2 °C. Based on relevant experiments and the dynamic viscosity curve of 5 W engine oil, this paper holds that the starting conditions of a diesel engine can be met when the engine outlet coolant temperature reaches 40 °C, and the engine oil temperature reaches -35 °C.
Wang, Jingfei, Xie, Peng, Wang, Zhuo, Xia, Yingqiu, Zhang, Xiaodong, Chen, Ke, Wang, Guodong
2025 International Conference on Solid Mechanics and Materials2026-99-16007/24/2026
TOC
Tobolski, Sue
Fatigue Life Analysis of Diesel Engine Filter Seat under Random Vibration Condition2026-99-16567/24/2026
The filter seat of diesel engine fuel filters is a key load-bearing component in the engine fuel system. Its structural integrity directly affects the reliability and safety of fuel delivery. In actual operation, the filter seat is subjected to random vibration loads generated by engine operation and vehicle dynamics, which may cause fatigue failure over time, even when static stresses are below the yield strength. This study employs finite element modeling (FEM) to investigate the structural strength and fatigue life of the diesel engine filter seat under random vibration conditions. The CAD model is simplified and meshed to reflect the main load paths, and boundary conditions, including bolt preload, gravity, and measured vibration PSD spectra are applied. Modal and harmonic response analyses are performed using Abaqus, and the Tovo-Benasciutti frequency-domain method is used in fe-safe to predict fatigue life. The results identify the most fatigue-sensitive areas and reveal that the minimum fatigue life is 10^3.067 cycles under realistic conditions, with the most critical regions located near the bolt connection. The simulation methodology and results provide a reliable basis for structural optimization and life prediction of similar components under random vibration environments.
Gu, Kexuan, Zhu, Yi, Xie, Liang, Wang, Wei
Experimental and Computational Study on Combustion and Performance Characteristics of an Ammonia–Diesel Dual-Fuel Engine under Low Load Conditions2026-01-50627/22/2026
Ammonia is receiving heightened attention as a carbon-neutral and hydrogen energy carrier alternative fuel for compression ignition engines. However, replacing diesel with ammonia poses significant challenges due to its low reactivity and slow-burning nature, particularly at low-load conditions. This study investigated the effect of ammonia energy share (AES) on the combustion characteristics and performance of an ammonia–diesel dual-fuel (ADDF) compression ignition engine operating under low loads and at a constant speed of 1800 RPM. The experiments were conducted at three different loads: 6 Nm, 13.5 Nm, and 18 Nm, corresponding to 11%, 25%, and 33% of full load, respectively. At each load, the AES was incrementally increased, ranging from zero to its maximum limit, while maintaining the COV of IMEP below 3% to ensure stable combustion. Furthermore, CFD simulations were performed using a CONVERGE CFD model of the engine to analyze the in-cylinder thermal and chemical behavior, and the model was validated against the experimental data. The experimental results showed that the AES reached 40%, 58%, and 61% for engine loads of 6 Nm, 13.5 Nm, and 18 Nm, respectively. Increasing AES reduced the mean in-cylinder temperature and peak cylinder pressure, and shifted the peak pressure location toward the expansion stroke. Combustion phasing was delayed, and combustion duration increased with higher ammonia substitution. CFD analysis revealed weaker high-temperature and OH reaction zones, along with reduced OH and H radical activity, and increased persistence of NH2 and HO2 evolution at higher AES, indicating slower oxidation of the ammonia-containing mixture. The results highlight the challenges associated with high-ammonia operation at low loads and provide deeper insight into the combustion processes governing ADDF engine performance.
Sardar, Gobinda, Kishore, Kislay, Pradeep, P., Mittal, Mayank
Influence of Eccentric Chamfer Structure at Seat Ring Bottom Hole on Swirl Ratio and Flow Coefficient in Dual-Tangential Intake Ports2026-99-05247/10/2026
The airflow characteristics of engine intake ports significantly influence combustion efficiency and emission performance. This study investigates the effects of an eccentric chamfer structure at the seat ring bottom hole on the swirl ratio and flow coefficient in a dual-tangential intake port for a four-valve diesel engine. Computational fluid dynamics (CFD) simulations and steady flow experiments were conducted under valve lifts ranging from 1 mm to 9 mm. Results indicate that the eccentric chamfer structure enhances the swirl ratio by 39 times (from 0.12 to 4.73) at low valve lifts (<6 mm) without compromising the flow coefficient. At higher lifts (>6 mm), both chamfer designs exhibit negligible differences in performance. Experimental validation confirmed the CFD results, with errors below 3% for swirl ratio and 5% for flow coefficient. This work provides a practical approach to optimize low-speed engine performance through geometric modifications.
He, Shuchao, Li, Ying, Shi, Yanfei
Experimental Investigation into Port Water Injection on the Transient Behavior of a Heavy-Duty Hydrogen Engine2026-01-07437/1/2026
Hydrogen-fuelled internal combustion engines are a potential carbon-free propulsion solution for high-power applications such as construction machinery and heavy-duty commercial vehicles. However, compared to conventional diesel engines, hydrogen engines exhibit limitations in transient operation and at full load, primarily due to the high reactivity of hydrogen. In spark-ignited hydrogen engines, combustion anomalies represent the main constraint during performance-oriented operation, particularly during transient phases that require mixture enrichment to meet dynamic torque demands. Water injection is investigated in this study as a means to mitigate these limitations. The paper describes the implementation of a port water injection system on a heavy-duty commercial hydrogen engine and evaluates its influence on engine performance with a focus on transient operating conditions. A combustion anomaly evaluation method developed in-house is applied to quantify the effect of water injection on abnormal combustion behavior. The results show that water injection shifts the combustion anomaly limit toward richer air–fuel ratios, thereby enabling mixture enrichment up to stoichiometric conditions or under during transient load changes. Water is injected cyclically into each intake port to achieve a defined water-to-hydrogen ratio during load steps. Even at low water injection rates, a significant reduction in engine response time is observed, leading to transient torque response comparable to that of a diesel reference engine. Improved torque demand tracking is demonstrated in dynamic test cycles. In steady-state operation, the application of water injection also extends the achievable full-load operating range. Overall, the results indicate that port water injection is an effective measure for suppressing abnormal combustion in heavy-duty hydrogen engines and enables more aggressive yet stable engine calibration with minimal water consumption, contributing to diesel-like performance characteristics.
Schneider, David, Christoforetti, Paul, Kappacher, Peter, Kapeller, David, Schutting, Eberhard, Eichlseder, Helmut, Trapp, Christian
Experimental Investigation of Fuel Cutout Strategies in a Heavy-Duty Gasoline Compression Ignition Engine03-19-03-00156/26/2026
This study investigates Gasoline Compression Ignition (GCI), a family of advanced combustion strategies that can be used to achieve low engine-out criteria pollutant emissions in the heavy-duty transportation sector. In particular, high fuel stratification GCI (HFS-GCI) has been shown to have high thermal efficiencies while maintaining a highly controllable and responsive mixing-controlled combustion event. However, stable combustion at low loads has been shown to be the principal challenge to the implementation of HFS-GCI in production applications. It has also been observed that several strategies that achieve stable combustion at low loads result either in increased emissions or efficiency penalties. While the achievement and maintenance of high enough exhaust temperatures for efficient aftertreatment operation is a significant challenge at low loads even for traditional diesel engine operation, this challenge is exacerbated by the low reactivity and colder flame temperature of gasoline. In recent single-cylinder and 1D simulation studies, fuel cutout strategies have been proposed as an enabling strategy to simultaneously improve combustion stability at low loads and increase exhaust temperatures. In this study, fuel cutout strategies are studied in a prototype multicylinder heavy-duty GCI engine based on a Cummins ISX15 diesel engine. Steady-state engine studies are conducted at warm and cold idle conditions to identify combinations of cylinders that provide the most benefit. NOx and soot limits are set and the performance of cutout strategies are compared to a pre-optimized baseline. The most optimal strategies from steady-state testing are then implemented under transient test cycle conditions similar to those required under United States regulatory testing. The strategies were found to offer simultaneous improvements in stability, fuel consumption, criteria pollutants, and turbine outlet temperature. The choice of cylinders whose fuel supply was cut was seen to be important in realizing the observed benefits. The use of fuel cutout strategies offered optimal performance at all the conditions considered, offering an additional lever to improve the performance of HFS-GCI and highlighting a promising pathway to the use of gasoline-like fuels as alternatives to diesel in heavy-duty engines.
Viswanathan, Aravindh Babu, Zhang, Yu, Merritt, Brock
A Modeling and Experimental Study of the Argon Power Cycle Using Mixing-Controlled Combustion2026-01-50436/19/2026
The closed-cycle hydrogen-fueled argon power cycle is a zero emissions concept that combines a carbon-free fuel with argon as a diluent replacement for nitrogen. The lack of nitrogen in the argon power cycle results in zero NOx emissions on an internal combustion engine platform. There is also massive efficiency improvement because argon is monatomic and has a very high ratio of specific heats. However, this will also result in combustion temperatures and pressures exceeding those normally achieved on an air-standard engine platform. The literature shows conflict between modeling, which promises incredibly high efficiency gains, and experiment, which show more modest efficiency gains. This work combined thermodynamic modeling, literature analysis, and experiments to understand this discrepancy and ultimately understand what level of efficiency gain can be expected for the argon power cycle. It was found that while low compression ratio engines stand to see the largest relative efficiency improvement, high compression ratio engines are the ones that can ultimately achieve ~60%+ efficiency, corresponding to a 15–20% relative improvement in efficiency over an air-standard engine platform operating at or above 50% efficiency. The elevated temperatures and pressures of the cycle result in knock in spark ignition, so either a high compression ratio knock mitigation strategy or mixing-controlled operation is required. Experiments conducted using a diesel-fueled compression ignition engine showed that a 30% argon replacement resulted in ~6% and full nitrogen replacement with argon resulted in ~14% relative efficiency improvement at 8 bar gross indicated mean effective pressure (IMEPg) without intake boosting on a heavy-duty engine with a compression ratio of 20.0 and late intake valve closing, agreeing with modeling results. The key takeaway to match modeling and experimental trends is to accurately model heat transfer, which increases significantly for the argon power cycle.
Gainey, Brian, Ahrling, Christoffer, Tunestal, Per, Tuner, Martin
SAE Truck & Off-Highway Engineering: June 202626TOFHP066/11/2026
Hitting the road in the all-new VNR Volvo Trucks' revised VNR brings updated safety tech, improved fuel economy and driver comfort features to the regional haul segment. In fuel control How to ensure off-highway combustion systems operate with sufficient control to meet tightening emissions standards and evolving fuel landscapes without sacrificing reliability. Keeping industrial vehicles secure in a digital landscape OEMs, integrators and suppliers must continuously process, assess and identify platform vulnerabilities to prioritize and implement updates that protect systems from cyberattacks and data breaches. Editorial Diversification key for sustainable fleets ACT 2026: Uncertainty still exists over EPA 2027 NOx limit ZF bets big on hybrid transmissions Moog simplifies off-highway electrification Bosch shows off its first U.S. electrolyzer Microvision fast-tracks adoption of Luminar tech; eyes defense, industrial sectors Future-ready, customizable connectivity powers precision agriculture Kenworth's new C580 clocks in for work Harbinger extends its range of medium-duty EVs Kubota's SVL110-3 brings new tech and service features to CTL segment Product Briefs SPOTLIGHTS: Diesel Engines & Subsystems; Manufacturing Tools & Materials; Motors, Inverters & Gearboxes Q&A Volvo turns attention to vocational trucks
Development and Experimental Validation of a 1D Model for Performance and Emissions Analysis of Oxygenated Fuel Blends in a CI Engine2026-37-00286/9/2026
Emissions reduction remains a major concern for internal combustion engines in view of increasingly stringent environmental regulations. To address these challenges while maintaining acceptable engine performance, a wide range of alternative fuels and fuel blends have been investigated to ensure the continued viability of CI engines. This study reports the effects of blending the oxygenated fuel diethylene glycol diethyl ether (DGDE) with hydrotreated vegetable oil biodiesel (HVO) on engine performance and emissions. The investigation is conducted on a 2.3-liter, four-cylinder, common-rail diesel engine, equipped with a variable geometry turbocharger and a high-pressure exhaust gas recirculation system. The objectives of this study are achieved by developing a one-dimensional predictive engine model using the commercial GT-SUITE software. The engine model is developed and experimentally validated, at various operating conditions and HVO–DGDE fuel blends, to predict their effects on combustion characteristics and emissions formation. The validation is performed against measurements collected at the engine test bed. The results indicate that increasing the blending ratio of oxygenated fuel leads to improvements in indicated mean effective pressure and a more favorable Soot–NOx emissions trade-off compared with neat HVO operation. The findings highlight the potential of oxygenated fuel blends to enhance CI engine performance while reducing emissions. This study demonstrates the effectiveness of combining experimental and numerical approaches to evaluate biodiesel–oxygenated fuel blends and provides insights for future research aimed at minimizing CI engine emissions.
Arain, M Wajahat Rasool, Foglia, Antonio, Frasci, Emmanuele, Vitek, Oldrich, Pianese, Cesare, Arsie, Ivan
Investigation of Influential Parameters on the Integrated Hydrogen Argon Power Cycle2026-37-00126/9/2026
This study investigates hydrogen combustion in an argon–oxygen environment for argon power cycle application using computational fluid dynamics. The numerical framework, developed based on previously validated model, is applied to examine the influence of key operating parameters on combustion efficiency and indicated efficiency under constant cycle pressure conditions. A parametric analysis is conducted to evaluate the effects of excess oxygen ratio, argon rate, start of injection, and injector discharge coefficient on ignition characteristics, combustion efficiency, and engine performance. The results indicate that less fuel injection improves combustion efficiency but leads to a significant reduction in engine load. Increasing the argon rate enhances engine thermal efficiency, primarily due to the higher specific heat ratio of argon, which improves the thermodynamic efficiency of the cycle. However, elevated argon concentrations significantly reduce combustion efficiency because of limited oxygen availability, resulting in increased levels of unburned hydrogen. The analysis further demonstrates that higher injector flow rates improve both combustion and engine efficiency. Overall, unburned hydrogen is identified as a critical limitation for the practical implementation of compression ignition hydrogen engines operating in Ar–O₂ mixtures; however, unburned hydrogen levels up to approximately 8% can be tolerated without significant deterioration in combustion efficiency in next engine cycle. The results revealed that the combustion inefficiency arises due to tale combustion phase and is attributed to inappropriate mixing of fuel and oxidizer.
Chitsaz, Iman, Ahammed, Sajid, Kakoee PhD, Alireza, Salahi, Mohammad Mahdi, Andwari, Amin, Ahmad, Zeeshan, Hyvonen, Jari, Mikulski, Maciej
Development of a Diesel Combustion System for Next-Generation Heavy-Duty Engines Using a Synergistic Analysis-and-Testing Approach2026-37-00046/9/2026
Regulators and policymakers have introduced increasingly stringent limits on tailpipe CO₂ and pollutant emissions to accelerate the decarbonization of heavy-duty vehicle applications. The development of innovative propulsion technologies — such as advanced combustion systems, low-friction reciprocating components, and improved aftertreatment solutions — combined with hybridization and the adoption of alternative fuels (e.g., biogas, HVO, green hydrogen), is a key pathway for meeting future emission and GHG targets. In this study, advanced combustion systems were developed for a 13-liter diesel engine for heavy-duty truck applications, with the objective of meeting forthcoming Euro VII regulations while maximizing thermal efficiency. The combustion system architecture—including open-bowl geometry with high aspect ratio, injector nozzle with wider spray opening angle, and reduced swirl ratio—was optimized using a Machine Learning–algorithm trained on high-fidelity 3D CFD combustion data. The method enabled the identification of two optimized combustion-system “recipes”, one of which was evaluated through engine tests, which refined nozzle specifications and injection strategies, using a structured Design of Experiments (DoE) approach. Results were benchmarked against a MY24 baseline combustion system, assessing efficiency, NOx–soot trade-offs, and combustion behaviors. Based on 3D-CFD results, the advanced combustion concept achieved an improvement in Brake Thermal Efficiency (BTE) of up to +0.8% points and delivered substantial NOx reductions of up to 45%, while maintaining smoke emissions at or below baseline levels. The experimental results indicate that the advanced combustion system developments designed for next-generation heavy-duty engines can further increase BTE by up to ~1% relative to the baseline combustion system, without deteriorating the soot–NOx trade-off.
Belgiorno, Giacomo, Centini, Maria Pia, Pezza, Vincenzo, Cozza, Ivan F., Pesce, Francesco C., Vassallo, Alberto, Colombo, Giovanni, Gallo, Alessandro, Mirzaeian, Mohsen, Borg, Jonathan
An Open-Source Framework to Automate Virtual Optimization of Internal Combustion Engine Calibration Maps through Shape-Based Strategy2026-37-00016/9/2026
The automotive industry is facing increasingly stringent regulatory constraints, driving the need for faster and more efficient powertrain development. This results in higher systems complexity, making internal combustion engine calibration progressively more challenging to meet performance and emissions targets. This, combined with the manual nature of traditional calibration workflows, leads to a time-consuming process that heavily relies on human expertise. Although virtualization can reduce development time and costs, the overall workflow remains largely dependent on manual decision-making and iterative refinement. In this context, this work presents a virtual calibration framework based on a genetic algorithm, aimed at the automated optimization of engine calibration maps to satisfy performance and emissions constraints, while reducing manual effort. Each calibration map is represented through a polynomial parameterization. Specifically, a generic three-dimensional polynomial with map-specific order encodes the shape of each map, ensuring smoothness which directly impact on drivability. Accordingly, the calibration problem is reformulated as the optimization of a compact set of polynomial parameters that uniquely define the full set of calibration maps, rather than individual set-point. Each candidate solution is assessed by generating the corresponding calibration maps and simulating the engine behavior through a neural-network-based digital twin, providing predictions of operating conditions, hardware limits, performance metrics, and emissions. The proposed framework was validated on a passenger-car diesel engine, considering a reduced yet representative set of calibration maps, including main injection start of injection, air mass, boost pressure, and injection rail pressure. The objective of optimization was the minimization of brake mean fuel consumption, subject to an upper bound constraint on nitrogen oxides emissions. The global optimization process explored approximately 106 different calibration candidates within about 36 hours, leveraging parallel computation on a standard laptop. The results indicate that the procedure can deliver multiple near-optimal preliminary calibration solutions, providing an effective starting point for subsequent manual finetuning.
Romano, Gianvito, Aglietti, Filippo, Spedicato, Tonio, Cozza, Ivan Flaminio, Capra, Andrea
Investigation into Cooling Loss Reduction Associated with Changes in In-Cylinder Flame Distribution by Offset Orifice Nozzle2026-37-00036/9/2026
An increase in compression ratio has been widely recognized as one of the essential technologies for improving the thermal efficiency of heavy-duty diesel engines. However, a higher compression ratio tends to result in increased cooling loss, which could diminish the thermal efficiency gains. It was found that an offset orifice nozzle, in which the orifices are drilled with a small offset from the radial center of the nozzle, improves thermal efficiency and reduces cooling loss simultaneously. This study investigates the mechanism of cooling-loss reduction associated with changes in flame distribution when using an offset orifice nozzle, through in-cylinder combustion observations, two-color method image analysis, and local heat-flux measurements. High-speed combustion visualization was conducted to capture the growth of luminous flames. Radial profiles of the mean and standard deviation were computed at each crank angle to quantify spatial temperature non-uniformity. Furthermore, multiple thin-film thermocouples embedded in the piston were employed to measure transient surface temperature and to derive heat flux over the entire cycle. The results indicated that the luminous flame distribution with the offset orifice nozzle was significantly different from that with a conventional nozzle, leading to reduction in the spatial non-uniformity of high-temperature regions in the observed area. The piston surface temperature measured at multiple points suggested reduced spatial non-uniformity in surface temperature, with suppressed instantaneous heat flux. These findings confirm the hypothesis that cooling-loss reduction is achieved by suppressing localized hot spots on the piston surface through the altered flame distribution.
Mukayama, Tomoyuki, Enomoto, Yoshiteru, Mikami, Naotaka, Nomoto, Shigeru, Uchida, Noboru
On Natural Gas Combustion Split into Diesel Like Architecture of a Compression Ignition Engine Retrofitted for Spark Ignition Operation2026-37-00296/9/2026
In commercial areas that no longer favor diesel engines, such as Europe, it might be interesting to convert an existing compression ignition engine to the spark ignition operation and to use natural gas (NG) because of its advantages: availability of still abundant supplies worldwide and environmental benefits compared to conventional liquid fossil fuels. This paper first presents experimental results on NG combustion inside such a converted engine with diesel-like architecture dedicated to light-duty vehicles and passenger cars. Particularly, our study carried out at the engine test bed revealed that in certain operating points (low speed and load, stoichiometric mixture and rather high spark advance), the combustion is split into two distinct events (first, a fast combustion inside the cylinder and piston bowl and then, a slower combustion occurring outside the bowl-in combustion chamber, in other words, in the squish region), which is not specific to the standard spark ignition engine. This is clearly illustrated by a rate of heat release profile with two peaks. The explanations for such combustion event are also supported by a 3D CFD study showing the in-cylinder NG distribution. The combination of experimental and numerical investigations contributes to the understanding of NG combustion in the diesel like architecture of the converted CI engine when subjected to deliberately extreme conditions, namely non-optimal spark advance setting exceeding the maximum brake torque spark advance.
Clenci, Adrian F., Popa, Robert, Berquez, Julien, Iorga-Siman, Victor, Magheru, Catalin, Punov, Plamen, Niculescu, Rodica
Rapid Fuel Distribution Prediction in RCCI Marine Engines Using CFD-Informed, Active Learning Framework2026-37-00176/9/2026
Accurate prediction of in-cylinder fuel distribution (FD) is fundamental to reduced-order combustion modeling and emissions prediction yet remains computationally prohibitive with high-fidelity CFD alone. This work develops a CFD-informed machine-learning surrogate for spatial FD in a large-bore diesel engine, based on a Wärtsilä W20 injector and representative engine conditions. A fully coupled injector–spray–engine CFD framework under engine-like RCCI inert conditions determines the needle-lift profile and resolves the combined effects of injector geometry, needle dynamics, and operating conditions on in-cylinder flow, capturing physical phenomena not reproducible by isolated free-spray simulations. A high-fidelity database is generated using Latin Hypercube Sampling, from which FD is extracted at 15 CAD before top dead center within an annular multi-zone (MZ) representation consistent with reduced-order combustion models. A multi-output Random Forest (RF) surrogate, augmented with uncertainty-driven active learning, is trained to predict the complete spatial FD vector. Prediction errors are higher near the combustion chamber core than in liner-adjacent zones, reflecting stronger nonlinear coupling and localized data sparsity. To address this, four additional CFD samples are selected from regions of maximum predictive uncertainty and incorporated into the training dataset. This targeted enrichment markedly improves surrogate performance, reducing mean absolute error (MAE) under worst-case input conditions. Although localized error amplification persists in a few zones, these regions are systematically identified and can be mitigated through further adaptive sampling using candidates proposed by the updated surrogate. Convergence of the active-learning framework is assessed using mean MAE, worst-zone MAE, global L1 error, and ensemble-based predictive uncertainty, ensuring robust and consistent accuracy across the design space. The framework integrates CFD-resolved physics, machine-learning surrogates, uncertainty quantification, and adaptive sampling, providing a scalable and physically consistent approach for efficient FD prediction in advanced engines.
Moradi, Jamshid, Salahi, Mahdi, Heidarabadi, Shadab, Andwari, Amin, Konno, Juho, Wik, Christer, Mikulski, Maciej
Nitrogen-Based Emissions from Ammonia Combustion in a Heavy-Duty Spark Ignition Engine2026-37-00326/9/2026
Ammonia (NH3) is a carbon-free fuel with strong potential for spark-ignition (SI) engine applications. However, the engine can produce complex nitrogen-based emissions not adequately captured by conventional engine models. This study consolidated the results of experimental and numerical studies on the use of neat NH3 combustion in a heavy-duty compression-ignition engine converted to spark-ignition operation, first for a sweep of equivalence ratios (ϕ) from 0.7 to 1.0, and another from varying the energy substitution ratio of methane (CH4)– NH3 blends from neat CH4 to neat NH3 at constant ϕ = 0.8. Two 0-D two-zone SI engine models with detailed chemistry (called “original” and “extended”) predicted engine thermodynamics and emissions. While the original model reproduced in-cylinder pressure and combustion phasing, it failed to capture the effect of fuel composition or operating condition on NO trends, both under- and over-predicting them for neat NH3 and CH4-rich operations. An extension of the model incorporating a burned-zone batch reactor and two more reactors simulating the post-combustion oxidation of the mixture exiting crevices and the DeNOx processes during exhaust blowdown were implemented to address these limitations. Analysis of NO formation pathways highlighted the differences between modeling approaches. The equilibrium assumptions in the original model restricted NO formation primarily to thermal (Zeldovich) mechanisms. In contrast, the kinetics-driven model showed that non-thermal pathways dominate NO formation for all NH3-containing cases, which shows the limitations of conventional SI models developed for hydrocarbons when applied to nitrogen-containing fuels. Post-combustion homogeneous reactors for crevice-based oxidation and exhaust blowdown revealed significant NO and N2O formation after the end of combustion at moderate temperatures (850–1200 K), suggesting that N2O formation was dominated by secondary thermal processes. Therefore, the inclusion of post-combustion chemistry and more consistent models are essential for accurate emission prediction in NH3-fueled SI engines.
Trujillo Grisales, Juan, Saenz Prado, Stefany, Alvarez, Luis F., Akkerman, Vyacheslav, Dumitrescu, Cosmin E.
Investigation of the Combustion of Stearic Acid-Coated Pure Aluminum Powder as Additives in Biodiesel and Diesel Blends04-19-02-00106/8/2026
In the present study, research was conducted to increase the combustion efficiency in a diesel engine by adding 100 and 200 ppm aluminum powder to diesel and biodiesel (produced from 10% spent coffee ground oil and 90% waste cooking oil) blends. Aluminum powder is a flammable metal. Due to this feature, it has been used as an additive to liquid fuels in many studies in the literature. In general, it has been reported that thermal efficiency increases with the addition of aluminum particles. However, the high explosion sensitivity of aluminum can affect its stable combustion. In addition, Al is a metal that can be easily oxidized. Therefore, coating aluminum is considered a good solution. Stearic acid has been suggested in the literature as a suitable material for coating aluminum. In this study, stearic acid, a saturated fatty acid, was used to coat aluminum particles. Stearic acid is a good surfactant, hydrophobic substance, and plasticizer. It is also a more environmentally friendly substance compared to its counterparts. In this study, aluminum particles were coated with stearic acid to increase the combustion efficiency of Al particles. To make the coating, stearic acid was dissolved in ethanol and mixed with Al particles. Then, the stearic acid coating was achieved by self-assembly using the evaporation technique. As a result of experiments conducted by adding aluminum and stearic acid-coated aluminum to diesel and biodiesel blends, the thermal efficiencies of DAl200, DAl100, and DSA@Al100 fuels were 2.99%, 3.21%, and 4.59% higher than that of standard diesel fuel, respectively. Likewise, the thermal efficiencies of B10D90Al200, B10D90Al100, and B10D90SA@Al100 fuels were 2.73%, 2.99%, and 3.62% higher than that of standard diesel fuel, respectively.
Kül, Volkan Sabri, Akansu, Selahaddin Orhan, Sarıtaş, Mehmet
Experimental Investigation of Diesel, Aqueous Ammonia, and Compressed Natural Gas Mixtures on Performance and Emissions in a Compression Ignition Engine04-19-03-00115/30/2026
Abstract This study investigates and evaluates systematically the combustion, performance, and emissions characteristics of heavy-duty diesel engines fueled by diesel–ammonia–compressed natural gas triple blends. While dual-fuel systems are well-documented, the interactive effects of ammonia and CNG within a single compression ignition (CI) engine remain largely unexplored. Experiments were conducted on a 300 Nm, 660 rpm diesel engine by testing pure diesel, diesel–ammonia blends (10–20 wt.% aqueous ammonia), and triple-fuel mixtures containing 10% of the total energy from compressed natural gas. Pure diesel was first tested to provide baseline data, and subsequently blends were tested for a comparative study. The primary contribution of this work is the identification of a synergistic effect of the fuel triple blends on engine performance and emissions. Results indicate that all fuel blends improve thermal efficiency and reduce fuel consumption compared to conventional diesel. The blend containing 20% aqueous ammonia, 80% diesel, and 10% of the total fuel energy supplied by compressed natural gas achieved the highest thermal efficiency of 39.7% (7% higher than diesel) and the lowest brake specific fuel consumption of 211.22 g/kWh. Furthermore, emissions analysis revealed that carbon dioxide and nitrogen oxide emissions were significantly reduced with this triple blend. The blend decreased carbon dioxide by 26.6% and nitrogen oxide emissions by 32.1%, while hydrocarbon emissions were also lowered by up to 29.2%. Carbon monoxide emissions increased slightly for the triple blends, reaching a maximum value of 3.9028 g/kWh for the A20D80CNG10 mixture, compared to diesel operation. The slight increase in carbon monoxide emissions for triple blends highlights a trade-off in emission behavior. These findings address the combined utilization of diesel–ammonia–compressed natural gas triple-fuel mixtures in heavy-duty engines, demonstrating that strategic blending can simultaneously improve efficiency while mitigating environmental impact. Graphical Abstract
Sinkala, Happy, Sarıtaş, Mehmet, Kül, Volkan Sabri, Akansu, Selahaddin Orhan, Ünalan, Sebahattin
Effect of Burning Biomass Fuel Cyclohexanol on Diesel Engine Performance2026-99-17085/22/2026
Against the backdrop of growing global demands for energy sustainability and stricter emission regulations for diesel engines, this study investigates the performance implications of incorporating cyclohexanol—a renewable oxygenated fuel—into diesel fuel blends. Using a marine medium-speed diesel engine as the experimental platform, the research systematically evaluates engine performance and emission characteristics across a range of cyclohexanol-diesel blend ratios under low, medium, and high load conditions. Experimental findings reveal multifaceted effects of cyclohexanol blending on engine operation. Combustion of the blended fuels enhances the engine’s dynamic performance, particularly under medium and high loads, where the maximum in-cylinder burst pressure exhibits a noticeable increase. This improvement is attributed to cyclohexanol’s oxygen-carrying capacity, which promotes more vigorous and sustained combustion reactions. In terms of emissions, increasing the proportion of cyclohexanol in the fuel blend leads to significant reductions in soot and carbon monoxide (CO) emissions, reflecting the cleaner-burning properties of the oxygenated component. However, this is accompanied by an uptick in nitrogen oxide (NOx) emissions, likely due to the elevated combustion temperatures generated by the more efficient fuel oxidation process. From an economic perspective, cyclohexanol blending at consistent load levels induces a postponement in the crank angle at which peak heat release occurs during combustion. This temporal shift prolongs the effective combustion duration, enabling more complete fuel utilization within the cylinder. Consequently, fuel consumption rates decrease, and overall engine efficiency improves, highlighting the potential of cyclohexanol blends to enhance operational economy in marine propulsion systems. In summary, this study underscores the complex trade-offs associated with cyclohexanol-diesel blends: while they offer tangible benefits in power output, fuel efficiency, and reduced particulate emissions, managing the increase in NOx emissions remains a critical challenge. The results provide a foundational framework for advancing biofuel applications in marine engines, emphasizing the need for integrated emission control strategies to optimize the balance between performance and environmental sustainability.
Chen, Ke, Yang, Chenxi, Wang, Yibin, Fan, Jinyu, Liu, Yuchen, Ye, Zixiao, Huang, Jialiang
Effect of EGR Rate on Cyclohexanol-Diesel Dual-fuel Engines2026-99-17095/22/2026
To reduce high NOx emissions from diesel-cyclohexanol blends, this study employed a marine medium-speed diesel engine as the experimental platform. An in-cylinder combustion model was developed and meshed using AVL - FIRE software, with model validity validated against experimental data. Tests were conducted at four load conditions (25%, 50%, 75%, and 100% load) with a 30% cyclohexanol blend (C30) and four EGR rates (0%, 7.5%, 10%, and 12.5%) to analyze combustion characteristics, emissions, and fuel economy. The results showed that the introduction of EGR had a striking inhibitory effect on NOx emissions. At 100% load with 12.5% EGR rate, NOx emissions were substantially reduced compared to baseline operation without EGR. However, EGR implementation led to delayed ignition timing, reduced in-cylinder pressure, and worsened fuel economy. Therefore, an appropriately calibrated EGR strategy can effectively reduce NOx emissions, though it requires optimization to mitigate adverse effects on combustion performance and efficiency.
Liu, Yuchen, Yang, Chenxi, Fan, Jinyu, Chen, Ke, Ye, Zixiao, Huang, Jialiang
Development of a Variable Interface Finite Volume Method for Simulating One- and Three-Dimensional Unsteady Gas Flow and Performances of Underwater Marine Diesel Engines03-19-03-00125/6/2026
Diesel engines used for the main power supplier of submarine normally run in high back pressure and low intake pressure, causing unstable performances. Furthermore, when a submarine runs under the sea the exhaust pipe of the diesel engine is under the seawater. Once the lowest pressure in the exhaust pipe is not sufficient to push all the water out, the water will flow into the exhaust pipe and damage the diesel engine. Modeling can provide a useful guide for designing diesel engines, intake and exhaust pipes, and turbocharging systems to avoid water flowing into diesel engine. However, existing simulation methods cannot well simulate the exhaust system of an underwater diesel engine, in which the interface between the liquid water and the exhaust gas is variable. To overcome the drawbacks of existing simulation methods in handling the variable interface between the two phases, a variable interface finite volume method (FVM) is proposed, and a corresponding model is developed in this work. This is the major contribution of this work. A detailed model description and numerical treatment of governing equations are given. The new model is validated using the experiment conducted in this work on the procedure of gas pushing water in a pipe. The validation results show that the variable interface FVM is effective and reliable. Due to the complexity of the exhaust gas flow at the tailpipe, three-dimensional (3D) flow at the exit of exhaust pipe under different exhaust gas speeds is studied. Results show that, when the exhaust gas speed is below 20 m/s, after the bubble leaves the exit, a part of seawater will flow into the exhaust pipe and flow down along the pipe wall under gravity. With the increase in speed, this phenomenon disappears. Using the newly developed one-dimensional (1D) and 3D model, the 16V-MTU396SE84 underwater diesel engine’s performance was simulated under different back pressures. Also, the effect of silencer’s volume on the stability of diesel engine’s exhaust system was studied. Simulation results show that, with the increase in exhaust back pressure, the excess air factor becomes smaller, combustion turns worse, combustion pressure and maximum in-cylinder pressure become lower, the combustion temperature, maximum temperature, and brake specific fuel consumption go up. In addition, silencer’s volume is very important to the stability of engine performance. The bigger the silencer, the more stable the exhaust system. The flow in the 16V-MTU396SE84 diesel engine’s exhaust pipe under the seawater was also calculated. Simulation results are consistent with engine tests showing that when the engine runs under full load the exhaust gas pressure and the pushing water speed in the exhaust pipe are high, whereas in the part load, the exhaust gas pressure and the water speed become a little lower. The correct results of these simulated performances of underwater marine diesel engines indicate that the models newly developed in this work are reliable.
Guo, Dongshao, Zhang, Licheng, Yang, Shiyou, Sun, Yong, Abidin, Zainal, Lin, Shujun
TOC99-08-02-0TOC4/13/2026
TOC
Tobolski, Sue
Technical Outlook on the Potential of HVO and Biodiesel Blends for Cleaner Combustion2026-01-03164/7/2026
The increasing need to decarbonize the transport sector is accelerating the adoption of renewable and low-carbon fuels such as Hydrotreated Vegetable Oil (HVO) and biodiesel as sustainable substitutes for fossil diesel. These fuels are evaluated as drop-in solutions requiring no engine recalibration, enabling immediate GHG emission reduction in existing diesel fleets. This study experimentally investigates the combustion, performance, and emission characteristics of a turbocharged common-rail two-cylinder diesel engine (Kohler LWD 442 CRS) operated with conventional fossil Diesel, pure HVO (Hydrotreated Vegetable Oil), and an HVOB20 blend (80% HVO and 20% biodiesel produced from waste cooking oil and animal fats). Tests were carried out under steady-state conditions at the DIIEM Engine Laboratory of Roma Tre University. The analysis focused on in-cylinder pressure evolution, brake power, brake specific fuel consumption (BSFC), and both regulated and unregulated emissions. Regulated species include carbon monoxide (CO), nitrogen oxides (NOₓ) and particulate number concentration (PNC > 23 nm, PMP-compliant), while unregulated emissions cover non-methane hydrocarbons (NMHC), formaldehyde (HCHO), nitrous oxide (N₂O). CO and NMHC are key indicators of incomplete combustion: CO results from partial oxidation of carbon during fuel burning, and NMHC represents the fraction of unburned hydrocarbons excluding methane. Both pollutants decreased markedly with renewable fuels, indicating a more complete oxidation process promoted by HVO’s paraffinic composition and FAME’s oxygenated nature. Experimental results show that HVO and HVOB20 slightly increase brake torque and reduce BSFC compared with fossil diesel, despite their lower density and heating value. Combustion remained stable across all operating conditions, with negligible variations in ignition delay and pressure rise rate. NOₓ emissions were comparable or marginally higher at medium engine speeds, likely due to faster ignition and elevated combustion temperatures. Unregulated species such as HCHO and N₂O decreased or remained negligible with increasing renewable content, while PNC and count mean diameter (CMD) were significantly reduced, confirming cleaner combustion and reduced soot formation. Overall, both HVO and HVOB20 demonstrated improved combustion efficiency and emission performance while ensuring full engine operability without calibration adjustments. These findings confirm the technical viability of renewable diesel fuels as immediate, drop-in solutions for reducing GHG emissions.
Zaccai, Martina, Chiavola, Ornella, Palmieri, Fulvio, Verdoliva, Francesco
1D System Evaluations for Efficiency Trade-Offs for a Heavy-Duty H2ICE Concept2026-01-02744/7/2026
Lean H2 combustion strategies have shown promising gross thermal efficiency and ultra-low engine-out NOx emissions for H2-fuel based internal combustion engines (H2ICE) in heavy-duty (HD) transport. Implementing lean combustion strategies require excessive air flow demand that further increases with the engine load increase. To meet such air flow demands efficiently across a wide engine operating region, a detailed system optimization is warranted including next generation turbocharging systems. In this 1D system analysis campaign, a detailed study of various air-system configurations was conducted for a modified HD, direct-injection (DI), H2ICE concept based-off a Cummins heavy-duty 15L engine. The concept engine configuration had a geometric compression ratio of 10.4 and no external exhaust gas recirculation (EGR) was implemented. First, a calibrated 1D engine model representing the H2ICE concept was developed. Using the 1D model, a detailed system-level analysis was conducted at five operating conditions from the heavy-duty SET cycle: A75, A100, B75, B100, and C100. A wide range of lambda levels, valve phasing, miller strategies were characterized by the gross engine performance improvements. Subsequently, different air-system configurations were evaluated for closed-cycle efficiency vs pumping losses trade-offs, while meeting the air flow targets. For next-generation turbocharging, both single stage (1S) and two-stage (2S) boost systems were simulated. Air versus external EGR dilution strategies were also studied at boost-limited engine operating conditions. From the results, high lambda levels reflected the benefits of lean combustion operation. Implementing millerization and cam phasing further elevated these benefits, at the expense of high boost pressure demands. The 1S boost system, with advantages of low-complexity and post-turbine thermal performance, incurred rapidly deteriorating turbocharger performance from the choke and the surge limits for lambda levels beyond 2.2. A 2S boost system achieved higher lambda levels without risking compressors choke or surge limits. Irrespective of turbocharging, the required intake charge cooling was noted ~2-3x times of the conventional diesel engine levels, depending on the targeted lambda levels. A detailed fuel-energy balance analysis was conducted to highlight system trade-offs between the 1S and the 2S based H2ICE configurations.
Kumar, Praveen, Sari, Rafael, Merritt, Brock, Popuri, Sriram
Simultaneous Reduction of NOx and Fuel Consumption for Off-Road Powertrains2026-01-02964/7/2026
Simultaneously reducing criteria pollutants and fuel consumption is important for clean air and improving vehicle total cost of ownership. The goal of this effort was focused on a 90% NOx reduction and 10% fuel savings for an off-road 407 kW diesel engine. The baseline was a production Fiat Powertrain 13L engine and aftertreatment system meeting 0.4 g/kW-hr NOx. The baseline system was quantified over the NRTC, RMC, new low load cycle and five field cycles. A next generation engine was built incorporating several fuel-efficient design features, including a higher compression ratio, increased fuel-rail pressure, low-friction piston rings, and a high-efficiency variable-geometry turbocharger. Cylinder deactivation and EGR pump technologies were added to this engine as well. The combination was optimized prior to adding advanced aftertreatment systems, showing the trade-off of engine out NOx and exhaust temperature. Two next-generation catalyst technologies were employed into a LO-SCR plus main SCR system, both with and without an electric heater upstream of the LO-SCR. These catalysts were hydrothermally aged to simulate significant field use. Dual SCR dosing with newly developed controls played a critical role in achieving the proper split between the upstream LO-SCR and the downstream main SCR. Adding a next generation mixer for the downstream SCR proved essential in obtaining the final results. The optimal configuration required adding an electric heater to elevate the exhaust temperature at the LO-SCR for early cycle NOx reduction. The final results showed a 94.8% NOx reduction and 15.7% fuel savings on the composite NRTC.
McCarthy, Jr.,, James, Wine, Jonathan, Bradley, Ryan, Hasseman, Andy, Prikhodko, Vitaly, Howell, Thomas
Challenges of Mixture Formation in Methanol Port Fuel Injection Engines2026-01-03374/7/2026
Port fuel injection (PFI) is an attractive strategy for methanol adoption in both spark-ignition and dual-fuel compression-ignition engines due to its lower cost and simpler hardware compared to direct-injection. However, methanol PFI mixture formation can be challenging due to methanol’s high heat of vaporization, low volatility at cold conditions and high tendency to wall wetting. Understanding and addressing these challenges is critical to ensure robust engine operation. In this study, the effects of injector geometry, coolant temperature, intake temperature and fueling rate on mixture formation of methanol PFI have been investigated for anhydrous methanol and for a blend of 90%vol methanol plus 10%vol water in an optical engine. Mie scattering and infrared imaging were applied to assess the liquid and vapor methanol distribution in the cylinder. For a high-flow injector compatible with methanol, significant amounts of liquid were detected in the cylinder at all conditions tested, leading to poor mixing and high fuel stratification during the compression stroke. This effect was mitigated by using a multi-hole injector that promoted better atomization, indicating that high atomization is preferred over high flow for methanol PFI. The probability of detecting liquid in the cylinder decreased as the coolant temperature or the intake temperature increased or if the fueling rate decreased, with coolant temperature being the dominant parameter to control methanol vaporization. Liquid probability increased with water addition mainly because of the high heat capacity of water. Liquid methanol accumulated in the intake port, decreasing the effective engine intake temperature and limiting fuel vaporization. This accumulation led to a delay of the system response to changes in the PFI settings, with injected fuel requiring one cycle to reach the cylinder and additional 50 cycles required to completely flush the fuel accumulated in the port. Finally, the operating envelope for liquid-free operation was defined.
Lee, Sanguk, Narayanan, Abhinandhan
Improving Transient Diesel Performance with E-Supercharging and Multiple-Input Multiple-Output Controls2026-01-04444/7/2026
Torque transients are challenging for turbocharged diesel engines. Engine torque response is limited by the lag in air flow, restricting the rate at which fuel can be delivered to avoid high engine-out soot emissions. Electrified forced induction systems (EFIS) offer a solution to address this challenge. In this study, an electrified supercharger (e-supercharger) is utilized in addition to the stock turbocharger on a 4.5-L 4-cylinder diesel engine to create a two-stage boosting system. Two control strategies were studied for e-supercharger control during engine transients, a model-based single-input single-output (SISO) controller and a model-based robust multiple-input multiple-output (MIMO) controller. Constant speed load acceptance (CSLA) experiments and emulated drive-cycles were performed to evaluate the performance of each control method. In-cylinder pressure measurements were acquired and apparent heat release calculations were performed and analyzed to better understand the transient engine response. The e-supercharged two-stage boosted engine demonstrated significant improvements over the baseline engine when using both control approaches. The rate of transient power generation was improved by as much as 59.4% resulting in reduced engine speed droop and decreased engine speed recovery time. Transient engine-out soot emissions were also reduced. Although both control approaches improved transient response relative to the baseline engine, the MIMO controller showed the greatest potential for future improvements.
Vang, Nicholas, Rothamer, David, Ghandhi, Jaal, Ashta, Shubham, Qiu, Weijin, Rayasam, Sree Harsha, Shaver, Greg, Frushour, Bryan, Dou, Danan
Model-Based Development of a Heavy-Duty H 2 -ICE and Integrated, Turbogeneration, Electrification, and Supercharging (ITES) System2026-01-04264/7/2026
Changing global economic conditions and efforts to reduce greenhouse gas emissions are driving the need to develop efficient, near-term, alternative propulsion system technologies for heavy-duty vehicles. This study combines a hydrogen internal combustion engine (H2-ICE) with electrically assisted turbocharging, exhaust energy recovery, and mild hybridization to maximize propulsion system efficiency and reduce NOx emissions. To reduce cost and packaging impact of integration of these technologies on an engine, the study presents a model-based development and optimization of an Integrated Turbogeneration, Electrification, and Supercharging (ITES) system that combines the enabling components into a single compact unit. In the first phase of this study, a H2-ICE and aftertreatment concept for a MY2027 7.7L medium heavy-duty on-road engine was developed and evaluated through 1D simulation. The concept was to convert a diesel engine by changing the cylinder head to implement a port fuel injection (PFI) lean H2 SI combustion system with two-stage turbocharging and no external EGR. The concept was optimized for compression ratio, valve lift profiles, turbocharging, aftertreatment size/specification, and calibration using 1D system simulation in GT-SUITE. In the second phase of this study, the H2-ICE concept performance was further improved by integrating the ITES system and evaluated through 1D simulation. The ITES system replaces the conventional low-pressure stage of the boosting system and adds the capability of electrically assisted turbocharging, turbogeneration from exhaust energy, and P1 mild-hybridization. Applying a model-based approach, the H2-ICE & ITES component sizes were optimized for the best performance and emissions benefit. Using 1D simulation of validated models, the efficiency benefit of the ITES system on engine and vehicle level system was predicted. Finally, a vehicle level simulation was conducted comparing the fuel consumption between a conventional advanced boosting system H2-ICE concept and H2-ICE+ITES concept for Class 6-7 medium heavy duty truck application.
Bustamante, Oscar, Correia Garcia, Bruno, Joshi, Satyum, Franke, Michael
Effect of Ignition Timing on Combustion Characteristics in Ammonia-Hydrogen Blended Fuel Engine with Passive Pre-Chamber2026-01-03234/7/2026
Against the backdrop of energy structure transformation and upgraded environmental protection requirements, ammonia has been gaining significant traction for its potential application as a zero-carbon fuel. However, it faces challenges such as difficult ignition, slow combustion rate, and low heating value. Thus, researching efficient combustion strategies suitable for ammonia as a fuel holds great significance. In this study, a two-cylinder diesel engine was modified into an ammonia-hydrogen blended fuel engine. Experimental study coupled with numerical simulations were carried out to investigate the effects of varying ignition timing on the combustion characteristics employed a passive pre-chamber ammonia-hydrogen fuel engine. The results show that the peak in-cylinder pressure exhibits a "first increase then decrease" trend as the ignition timing is retarded, reaching a maximum value of 7.42 MPa at the ignition timing of -27.5°CA ATDC. When the ignition timing is retarded beyond -15°CA ATDC, a double-peak phenomenon appears in the in-cylinder pressure curve. The peak heat release rate (HRR) gradually increases with the retardation of ignition timing, but excessively retarded ignition diminishes the proportion of constant-volume combustion in the combustion process. The combustion rate is the fastest when the ignition timing is -20°CA ATDC under the operating conditions of an engine speed of 1800 r·min-1, a hydrogen energy fraction (HEF) of 11.6%, and a λ of 1.0, with the shortest combustion duration (CA10~CA90) of 22.5°CA, which leads to the highest indicated thermal efficiency of 42.5%.
Deng, Jun, Luo, Mingyu, Shang, Quanbo, Tang, Yongjian, Qin, Jie, Li, Liguang
Effects of the Spark Location and Timing in a Heavy-Duty Hydrogen-Fueled Engine2026-01-03314/7/2026
The use of hydrogen in internal combustion engines offers a promising route to lower-carbon propulsion in heavy-duty transportation. However, its distinct combustion characteristics as high flame speed, wide flammability limits, and susceptibility to abnormal combustion, necessitate careful engine and ignition system design. This study numerically investigates the combined effects of spark plug (SP) location and ignition timing on the performance of a heavy-duty diesel engine converted to spark-ignition and operated with hydrogen as fuel at reduced compression ratio. The numerical study aims to guide engine design. Three-dimensional computational fluid dynamics simulations with detailed hydrogen chemistry were conducted to evaluate flame development, and relevant combustion metrics under different loads. Model validation against engine combustion data and hydrogen injection from a low-pressure, high-mass-flow direct injector are also presented. The results demonstrate that SP placement is pivotal to control for combustion stability and efficiency due to the complex in-cylinder mixing and stratification associated with direct hydrogen injection. For each load, optimal ignition timings were identified. Highlights demonstrate the feasibility of installing the SP close to the jet-forming cap (injector tip) to exploit local enrichment and enhance flame propagation.
Menaca, Rafael, Shakeel, Mohammad Raghib, Panithasan, Mebin, Liu, Xinlei, Qahtani, Yasser, AlRamadan, Abdullah, Cenker, Emre, Silva, Mickael, Pei, Yuanjiang, Turner, James, Im, Hong
Accelerometer Location Study for Non-Intrusive Start of Combustion (SOC) Detection in Compression-Ignition Engines2026-01-02884/7/2026
This study investigates the impact of sensor location on accelerometer-based sensing of combustion phasing for compression-ignition engines. Ten accelerometer locations were studied on a light-duty compression-ignition engine for a set of conditions with variations in engine load, speed, injection timing, and injection strategy. Start of combustion (SOC) was identified from the filtered acceleration signal using a previously developed approach. Each location was assessed using both signal-based metrics, including magnitude squared coherence (MSC) between block surface acceleration and in-cylinder pressure, as well as SOC outcome-based metrics, such as detection success rate. Results demonstrate that the mounting location has a significant impact on the ability to extract combustion phasing information from the accelerometer signal. Sensors mounted on the front face of the engine produced the strongest signals for an individual cylinder. For multi-cylinder sensing, side-mounted locations delivered the most reliable performance, with SOC detection success above 98 percent, defined as correctly identifying the acceleration peak most closely aligned with the corresponding pressure-derived SOC for each cycle. This work outlines a practical framework for selecting and evaluating accelerometer mounting locations, enabling broader use of accelerometers in engine platforms operating on a range of combustion approaches.
Hegge, Graydon, Hanson, Reed, Kim, Kenneth, Rothamer, David
A Quantitative Approach for Mapping and Assessing Diesel Particulate Filter Regeneration Events in Diesel Engines2026-01-03774/7/2026
Regeneration of diesel particulate filters (DPFs) is crucial for maintaining the performance of diesel engines and minimizing harmful particulate matter (PM) emissions from exhaust. However, conventional regeneration strategies often suffer from incomplete soot removal and inefficient monitoring. These issues lead to increased exhaust back pressure, reducing engine efficiency, and potentially damaging the particulate filter. In this paper, an approach is proposed for mapping and quantifying the real-world DPF regeneration process for diesel engines complying with the stringent emission standards. We introduce a novel metric, the differential pressure drop percentage (DPDP), to detect regeneration events and quantify soot burn quality. The proposed method utilizes real-time sensor data obtained through the vehicle’s On-Board Diagnostics (OBD) system. The algorithm processes sensor data and robustly maps the regeneration quality. The performance of regeneration event detection and soot burn quality has been validated based on diagnostic trouble codes (DTCs) raised by the engine control unit (ECU). Our proposed method demonstrates that predictive maintenance can be used to manage strategies for diesel exhaust after-treatment systems, which can effectively reduce increased maintenance costs and operational downtime.
Bagga, Harleen Kaur, Nagare, Mukund B., Patil, Bhushan D., Ravishankar, Hariharan, Melapudi, Vikram, Vanderheide, Craig, Patil, Abhijit
Ultra-Low NOx Technologies for Heavy-Duty Applications with Reduced Total Cost of Ownership2026-01-02944/7/2026
The utilization of gasoline engines in heavy-duty vehicles for the purpose of continental transportation is in direct competition with conventional diesel engines. It’s imperative that the operating performance of the gasoline engine is equivalent to the diesel engine, and that the gasoline engine shows efficiency benefit to both cost segments, the product manufacturing costs and total cost of ownership (TCO). The 11.6-liter gasoline engine developed has been designed and applicated in such a way that it operates at a stoichiometric combustion air ratio (λ = 1) across the entire engine map range without exception. In combination with external exhaust gas recirculation (EGR) this strategy does not result in a substantial decrease in the absolute NOx concentration in raw emissions compared to the diesel engine with 15.0-liter displacement, but it facilitates the cost-efficient utilization of the three-way catalyzer as the main exhaust aftertreatment system, thereby reducing NOx emissions to the detection limit. This reduction is necessary for adherence to the stringent future emission standards for heavy trucks that are being established by the U.S. regulatory authorities (EPA; CARB) for model years commencing in 2027. In addition to the stoichiometric operating strategy, the engine features an innovative combustion chamber geometry, including a high compression ratio, high EGR compatibility within the real engine operating range, and an optimized crankshaft drive. This already tested technology package is now being applied to heavy-duty engines, proving its scalability and effectiveness. Its application to heavy-duty engines not only promises significant production cost savings but also ensures compliance with future emission regulations. By integrating high EGR rates and high compression ratio, the engine achieves optimal combustion efficiency, thereby minimizing emissions without compromising performance. The engine efficiency is demonstrated by its brake thermal efficiency of 43.1% and an extended map range with a specific consumption of less than 200 g/kWh. In a real heavy-duty driving cycle, the average consumption is 228 g/kWh (vs. 217.5 g/kWh), resulting in a significant reduction in total operating costs on the American market using gasoline as fuel.
Medicke, Mario, Arnold, Thomas, Bohme, Jan, Krause, Matthias, Leesch, Mirko
The Influence of Split Injection Ratio on Efficiency and NO x Emissions in a Pilot Diesel-Ignited Hydrogen Direct Injection Engine2026-01-03294/7/2026
This study investigates the impact of the hydrogen split injection ratio on the combustion of pilot diesel-ignited hydrogen direct-injection engines, which is expected to affect hydrogen-air mixture conditions and thus flame propagation and diffusion flame developments. Experiments were conducted on a 1-litre single-cylinder diesel engine equipped with an additional hydrogen injector operating at 35 MPa. Hydrogen accounting for 95% of total input energy was injected at 150 and 60 °CA bTDC for the first and second pulses, which were selected as high-efficiency injection timings from previous equal-split injection tests. The 5% diesel energy was injected near TDC to control CA50 at 10 °CA aTDC. While varying the split ratio between the two hydrogen injections, in-cylinder pressure/aHRR profiles, engine efficiency/power output and engine-out emissions of NOx and CO2 were evaluated. Results showed that the hydrogen split ratio does not significantly affect IMEP/efficiency, which consistently achieved a 17.2% increase over the diesel baseline. While CO2 emissions remained at a very low level due to high substitution of hydrogen energy, they showed no dependency on the split ratio. By contrast, NOx emissions were highly sensitive to the hydrogen injection split ratio. Increasing the first hydrogen injection fraction to 30% reduced NOx, attributed to decreased locally rich mixtures formed by late second hydrogen injection and increased lean mixture homogeneity from early first hydrogen injection, leading to a slower burning effect. However, further increasing the first injection fraction led to higher NOₓ emissions due to increased hydrogen compression, which raised TDC and combustion pressure.
Zhao, Yifan, Chan, Qing Nian, Kook, Sanghoon
Enhancing the Understanding of a State-of-the-Art Fe/zeolite Selective Catalytic Reduction Catalyst2026-01-03624/7/2026
Fe/zeolite selective catalytic reduction (SCR) catalysts are commercially used for NOx emissions reduction from diesel engines. In comparison to Cu/zeolite, these catalysts are widely reported to form less N2O as a byproduct of the SCR reactions. However, Fe/zeolite SCR is less active than Cu/zeolite for low temperature NOx conversion under standard SCR conditions. In this study, a state-of-the-art Fe/zeolite SCR catalyst is probed with a combination of N2 physisorption, SEM/EDX, reactor-based performance and active site quantification. Measurements investigate the impact of degreening, mild and extreme hydrothermal aging. In a degreened condition, the impact of water vapor on standard and fast SCR and isothermal desorption of NH3 is assessed. The Fe/zeolite catalyst’s hydrothermal durability is studied following hydrothermal aging at temperatures from 550°C up to 950°C. NH3 adsorption and temperature programmed desorption (TPD) and NO2 adsorption and TPD experiments are used to quantify the surface acidity and active Fe sites of the catalysts, respectively. Kinetic analysis of the standard SCR data is conducted to elucidate the mechanisms responsible for SCR activity loss upon hydrothermal aging. The authors believe the results presented herein can support the industry wide efforts to continue to improve diesel emissions control.
Ottinger, Nathan, Xi, Yuanzhou, Liu, Z. Gerald
Advanced Multifunctional Catalysts for Emission Control in Hydrogen and Diesel Engines2026-01-03674/7/2026
As hydrogen internal combustion engines (H2-ICE) gain traction, optimizing exhaust aftertreatment technologies for nitrogen oxide (NOx) control has become increasingly critical. While selective catalytic reduction (SCR) systems remain the primary approach for NOx mitigation, oxidation catalysts are also being explored to facilitate hydrogen oxidation and improve overall exhaust treatment efficiency. This work presents a multifunctional catalyst (MFC) concept that combines supported Pd and Cu-zeolite to enable simultaneous NOx reduction and hydrogen oxidation within a single catalytic unit. Preliminary results show that hydrogen oxidation on supported Pd occurs above 300 °C, while Cu-zeolite achieves nearly complete NOx conversion. Experiments on individual components indicate that supported Pd initiates ammonia oxidation only after hydrogen is depleted. In the presence of hydrogen, ammonia conversion remains below 20%, indicating that hydrogen availability suppresses ammonia oxidation, which is favorable for SCR operation. The MFC can be configured either on a substrate or as an on-filter catalyst (MFCoF), providing simultaneous chemical conversion and urea-derived particulate filtration. In addition to hydrogen engines, the MFCoF concept can be applied to diesel and biodiesel engines, enabling effective filtration of soot particles while maintaining NOx reduction performance along with hydrocarbon oxidation capability. By combining NOx reduction, hydrogen/hydrocarbon oxidation, and particulate filtration in one unit, the MFCoF approach provides a promising pathway for next-generation exhaust systems across diverse engine platforms.
Danghyan, Vardan, Becker, Jan Martin, Hünnekes, Edgar, Patchett, Joseph
Technology Development of Novel Aftertreatment High Pressure Diesel Delivery Unit to Meet Future Emission Regulations for Medium-Heavy Duty Diesel Engines2026-01-03584/7/2026
Future emission regulations (Euro VII, LEV IV, Tier V, China VII, etc.) will impose more stringent requirements both in terms of regulated pollutants emissions and CO2 for On-Road and Off-Road Diesel applications. The higher regulatory stringency will require more complex Aftertreatment Systems (ATS) architectures. Among the innovative technologies that will be introduced, the Diesel Dosing Unit (DDU) in the exhaust is emerging as one of the enablers for overall compliance. Currently available DDUs work at low pressure (LP) fuel supply around 5 bar and often require a mixer downstream in the exhaust line to ensure the right level of fuel atomization, evaporation and mixing. The usage of high pressure (HP) fuel supply at around 200 bar, together with component design enhancement and dedicated spray targeting generates advantages in terms of CO2 both during Diesel Particulate Filter (DPF) regeneration and normal modes and on pollutant emissions in regeneration mode. To quantify the advantages, steady state and transient tests were executed on a state of the art 6.6 L Diesel engine where the HP-DDU was assessed in comparison with LP-DDU which was part of the baseline ATS. The comparison between the two technologies was made by installing the HP-DDU in two ATS layouts: nominal mixing length (as baseline) and reduced mixing length. For both HP-DDU ATS layouts, the mixers present in the baseline LP-DDU were removed. During DPF regeneration, both layouts assessed showed benefit in THC (up to 20%), CO (up to 95% at low flow, 50% at medium flow), and BSFC (up to 1.5-2.0%). Additionally, DPF regeneration tests in transient conditions highlighted better temperature control and higher residual O2 (after fuel oxidation over the DOC), leading to shorter DPF regeneration duration. In normal mode, a reduced back pressure due to the mixer removal resulted in an estimated CO2 saving up to 10% at rated power. Considering all the measured benefits, the Dumarey developed HP-DDU technology is considered promising for compliance with upcoming CO2 and emission regulations worldwide.
Ciaravino, Claudio, Belgiorno, Giacomo, Negro, Cosma, Cosseddu, Cinzia, Gallo, Giovanni, Gestri, Luca, Soriani, Matteo, Cipriani, Massimiliano, Cibella, Marco, Giannantoni, Lorenzo, Di Nieri, Aldo, Mital, Rahul
Evaluation of Current and Next-Gen Diesel Particulate Filter Performance for US EPA MY27+ LD/MD Particulate Mass Emissions Regulation2026-01-03694/7/2026
Diesel particulate filters (DPF) have been part of vehicle after-treatment solutions in the US since being adopted in 2007 as the “go-to” solution for meeting particulate mass (PM) standards as set by the EPA for HD diesel engines. Within the highly popular LD/MD truck segment, defined as trucks weighing between 8501lb-14000lb, these limits have seen additional reduction in PM levels to 8 or 10 mg/mile as these vehicles have transitioned mostly over to chassis-based certification since 2014-2017. However, these reductions in PM requirements have been relatively minor, allowing for DPF technology used on these platforms to remain mostly unchanged over the same time period. With the finalization of MY27+ LD/MD vehicle emissions standards; PM limits are now set to make significant reductions down to 0.5 mg/mile, with phase-in to be completed by MY31. While the new limits present significant challenges for gasoline vehicles and most likely will require the use of gasoline particulate filter (GPF), this additional reduction of up to 95% for diesel vehicles may also require technology advancements of the DPF in order to meet compliance targets. The goal of this study was to evaluate the capability of current DPF technology along with other state-of-the-art DPF technologies to meet the new Tier 4 limits. Test conditions were run under both normal operation and active-regeneration certification-cycle conditions to be able to properly calculate a final PM result with IRAF (infrequent regeneration adjustment factor), as both test conditions have a tremendous impact on the final reported result. A combination of engine-based and vehicle-based (modern T3B170 HDV diesel truck) test measurements were used to complete the initial assessment for this evaluation. This report will show that advanced DPFs can deliver high PM filtration efficiency along with other system level improvements, positioning them well as one solution to meet the upcoming US EPA 0.5 mg/mile PM limit.
Warkins, Jason, Sadek, Ghadi, He, Suhao
Optimizing Custom Hybrid Solutions for Low-Volume Specialist Equipment2026-01-04794/7/2026
Off-road vehicles are typically powered by diesel engines, sized to cover the highest peak loads in their dutycycles. Such applications can be designed with downsized engines, using hybridization to supplement engine power with electrical power for short periods. However, many applications are low-volume and specialized, making it impractical to deploy heavy engineering resources to optimize each one. For this reason, manufacturers tend to produce maid-of-all-work vehicles to cover every situation. This paper demonstrates the benefits of custom hybridization for specialist applications, and addresses the lack of accessible software tools for evaluating such opportunities. Analysis is applied with a fast, low-cost, Concept-based software tool named “ePOP Concept”, suited to original equipment manufacturers (OEMs) who seek to provide custom low-volume vehicles. It allows many different powertrain architectures to be evaluated rapidly at the product planning stage, and can be quickly set up and used by non-specialists in simulation. Agricultural load cases are analyzed, showing the benefits of adding hybridization through electric motors and stored energy, supplementing engine power for demand peaks to enable engine downsizing. Use cases for four Fendt diesel tractors were taken from a dataset generated by Götz et al, at the agricultural facilities of the Technical University of Munich, which has been made publicly available by the authors to address the absence of standard load cycle data for the analysis of tractor electrification. The results show benefits for a customizable hybridization architecture to accommodate specific use cases, and the benefits of quick, accessible analysis methods for small engineering teams, to support early product decisions and what-if analyses.
De Salis, Rupert, Fons, Daniel
Experimental Analysis and Numerical Simulation of the Performance Parameters of Tire Pyrolytic Oil in a Compression Ignition Engine2026-01-03454/7/2026
The search for alternative solutions for non-fossil fuels has led to several studies worldwide. This study focuses on environmentally responsible solutions to accelerate tire degradation, focusing on the transformation of these residues into fuel for diesel engines. The objective of this study was to experimentally evaluate, through numerical simulation, the performance of a compression ignition engine operating with pure diesel S10 fuel, crude and refined tire pyrolytic oil, and mixtures in proportions of 20, 40, 60, 80 and 100% with diesel oil. The experimental tests were performed on a single-cylinder engine coupled to a dynamometer bench, and the numerical simulation was performed using the Diesel Engine RK software. The experimental results indicated that increasing the proportion of refined pyrolytic oil in diesel slightly improves engine performance up to approximately 2750 RPM, after which the performance is reduced compared to pure Diesel. The addition of crude pyrolytic oil slightly improves engine performance throughout the engine operating range compared to pure diesel. The simulation results revealed performances similar to those obtained experimentally, with a highlight on the 20% blend ratio, which behaved similarly to Diesel. The research is relevant because valuable results were obtained in the search for more sustainable alternatives in the context of compression ignition internal combustion engines.
Santana, Claudio Marcio, Prudente, Lucas Rhuan, Leal, Elisangela M, Rocha, Ana Maura, Peixoto, Claudio
Influence of Lubrication Oil on Hydrogen Fuel-Share Combustion in a Conventional Medium-Speed Marine Diesel Engine2026-01-50142/23/2026
Carbon-free fuels present a potential solution for achieving climate-neutral operation of marine engines. However, their availability is minimal at the moment, though a steady increase can be expected in the coming years. During this transition phase, engine concepts that offer conventional diesel operation and a partial blending of alternative fuels to substitute diesel become interesting. This can be achieved, for example, by blending hydrogen in the intake air of a diesel engine, known as hydrogen fuel-share. Due to the high reactivity of hydrogen, its use in engines is limited by abnormal combustion phenomena (e.g., pre-ignition, knocking combustion), which current research on pure gas engines has shown to be strongly promoted by lube oil reactivity. Building on these fundamental investigations, this paper examines the influence of lubricating oil on the combustion characteristics of a H2 fuel-share medium-speed diesel engine and quantifies the potential to increase the hydrogen share using a less reactive engine oil. For this purpose, single-cylinder engine tests were conducted and supported by 0D/1D simulations with GT-Power and Cantera. The engine was configured as a conventional medium-speed marine diesel, equipped with a hydrogen port fuel injection (PFI) system on the cylinder head. A thermally stable ester-based gas engine oil was used for reducing reactivity compared to a state-of-the-art mineral diesel engine oil. The results show reduced auto-ignition tendency during compression and a mitigation of backfire. An increase in average effective CO2 reduction of up to 17 percentage points is demonstrated, resulting in a total CO2 reduction of 39% on a standard load profile for main propulsion engines. These findings highlight that the choice of lubricating oil can play a key role in increasing the hydrogen share in H2 fuel-share diesel engines, thereby supporting the transition toward climate-neutral propulsion concepts.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
CFD Simulation of Combustion and Emission Characteristics of Pure Spirulina Microalgae Biodiesel in a Single-Cylinder DI Diesel Engine2026-28-00432/12/2026
In this study, the combustion and emission characteristics of a single-cylinder direct injection (DI) diesel engine fueled with Spirulina biodiesel along with diesel blends were examined using a combined CFD and thermodynamic simulation framework. Three test fuels, including pure diesel (D100), Spirulina biodiesel blends (B20 and B40), and pure Spirulina biodiesel (B100), were analysed at 1500 rpm under full load. In the first stage, CFD simulations were performed in ANSYS Fluent, where the Discrete Phase Model (DPM) was applied to capture spray atomization and droplet evaporation, while a non-premixed combustion model coupled with the RNG k-ε turbulence model was employed to resolve in-cylinder flow and heat release dynamics. Subsequently, the Diesel-RK software was utilised to predict engine performance and exhaust emissions based on compression ratios (18.5) and injection timings. Results from the CFD analysis revealed faster atomization and reduced ignition delay for biodiesel blends compared with pure diesel, supported by enhanced cylinder pressure development. Diesel-RK simulations indicated that Spirulina biodiesel blends (B20) generally improved brake thermal efficiency at higher compression ratios while increasing brake specific fuel consumption due to their lower calorific value. Emission analysis showed consistent reductions in CO, HC, and smoke capacity with higher biodiesel content, while NOx emissions exhibited a rising trend. The findings confirm Spirulina biodiesel (B20) as a viable renewable fuel and highlight simulation-driven strategies for optimising compression ratio and injection timing in CI engines..
Kumar, B Varun
Alternate Catalyst for DOC in a Catalytic Converter2026-28-00162/12/2026
Emission norms have become much more stringent to reduce emissions from vehicles. Diesel engines in particular are the predominant contributors to higher emissions. Diesel Oxidation Catalyst (DOC) in diesel engine catalytic converter systems is the crucial component in reducing harmful emissions such as Carbon Monoxide (CO) and unburnt Hydrocarbons (HC). DOCs often rely on expensive noble metals like platinum, palladium, and rhodium as catalyst materials. This significantly raises the cost of emission control units. The proposed idea is to explore MnO2-CeO₂ (Manganese Oxide, Cerium Oxide) as an alternative catalyst to traditional DOC materials. The goal is to deliver effective oxidation performance while reducing overall system cost. MnO2-CeO₂ catalysts are promising because of their good low-temperature activity, oxygen storage capacity, and redox behavior. These features are helpful for diesel engines that operate under various conditions. They improve the oxidation of CO and HC, even during cold starts or at lower exhaust temperatures. The catalyst was successfully synthesized and applied to a honeycomb substrate, resulting in a fabricated catalytic converter prototype. Quantitatively, the fabricated MnO₂–CeO₂ coated prototype demonstrated a 43% reduction in CO, 47% reduction in HC, 27% reduction in NOx, and 41% reduction in PM during low-temperature exhaust testing (150 – 400 °C) during testing on a 1.5 L diesel engine. The results were based on repeated experimental runs using an uncoated substrate as baseline. The work also focuses on material accessibility and environmental sustainability by using non-noble, widely available metal oxides. The hypothesis of this study is that a MnO₂–CeO₂ catalyst synthesized via co-precipitation can deliver meaningful low-temperature oxidation performance at significantly lower cost compared to PGM-based DOCs. Thus, the project contributes a significant step toward developing more accessible and sustainable emission control technologies for the automotive industry.
C, Jegadheesan, T, Karthi, Rajendran, Pawan, Muruganantham, Kowshiik, S, Vaitheeshwaran
Optimized Design, Analysis, and Validation of a Tractor Muffler for Enhanced Back-Pressure Control and Cost Efficiency2026-28-00042/12/2026
Internal combustion engines generate intense acoustic pulses during combustion, necessitating the use of exhaust mufflers to suppress noise emissions. With evolving regulations on permissible noise levels and the automotive industry's drive toward lightweight, high-performance vehicles, muffler designs must balance effective sound attenuation, minimal back pressure, and reduced mass. This study presents a comparative analysis of three muffler configurations serpentine, rectangular, and zigzag designed using Solid Works for a light commercial vehicle (LCV) diesel engine. The models were evaluated using computational fluid dynamics (CFD) simulations to assess their acoustic and flow performance. Each design incorporated internal baffle arrangements to enhance sound absorption while aiming to minimize back pressure. The serpentine model featured a perforated baffle layout that promoted multiple reflections and dissipated acoustic energy more efficiently. Simulation results indicated that the serpentine muffler achieved a pressure drop reduction of up to 18% compared to the rectangular model and 12% lower back pressure than the zigzag design under identical engine output conditions. Additionally, the serpentine configuration demonstrated superior sound attenuation in the 200–800 Hz frequency range, which is critical for diesel engine noise suppression. While reducing muffler wall thickness and overall volume contributed to weight savings, these modifications were carefully balanced against the risk of increased back pressure. The optimized serpentine muffler maintained structural integrity and met regulatory noise standards without compromising engine performance. This study highlights that advanced internal geometry, particularly the use of perforated baffles in a serpentine path, is effective for achieving both noise reduction and low back pressure in modern automotive mufflers.
Deepan Kumar, Sadhasivam, Palaniselvam, Senthil Kumar, D, Ashokkumar, R, Krishnamoorthy, Mahendran, M, Pasupuleti, Thejasree, G, Dhayanithi, L, Boopalan
Enhancing Combustion, Performance and Emission Profiles Using Kapok Methyl Ester Blends with Hydrogen2026-28-00582/12/2026
This study investigates the potential of using a dual green alternative fuel combination, the one is hydrogen fuel and another one is biodiesel for enhancing the Performance, combustion and emission profile of a compression ignition engine. The kapok oil biodiesel was blended with Diesel in proportions of 20% (K20) and 40% (K40) by volume. The hydrogen gas was supplied at a constant flow of 4 liter per minute (LPM). The experimental fuels are neat diesel D100, K20 (80% Diesel and 20 % kapok methyl ester), K40 (60% Diesel + 40 % Kapok methyl ester), K20 + H4L (K20 with 4 LPM hydrogen) and K40+H4L (K40 with 4 LPM hydrogen). These test blends are investigated in a single cylinder direct injection CI engine under 0% to 100% load conditions at a fixed speed of 1500 rpm combustion, and emissions characteristic were evaluated and compared with base fuel. The outcomes indicated that the use of B20 and B40 blends without hydrogen led to reduced BTE because of their lower cetane number and calorific value. Additionally, higher viscosity of the blends resulted in increased BFSC. However, the introduction of hydrogen and the K20H fuel blend demonstrated notable emission improvements compared to conventional diesel, achieving reductions of 9–11% in unburned hydrocarbons, 5.3% in carbon monoxide, and approximately 8% in nitrogen oxides (NOₓ). These findings highlight the potential of K20H as a cleaner alternative fuel.
Anbarasan, B, M, Kumaresan, Balamurugan, S, Rajesh, Munnusamy
TOC99-08-01-0TOC2/11/2026
TOC
Tobolski, Sue
Potential of a Hydrogen Fuel-Share Combustion Concept for a Conventional Medium-Speed Marine Diesel Engine2026-01-50072/2/2026
To meet the International Maritime Organization’s (IMO) short-term greenhouse gas (GHG) reduction targets, partial decarbonization of the existing fleet, often powered by medium-speed diesel engines, is required. One approach for reducing CO2 emissions is to enrich the charge air with hydrogen to substitute diesel. However, hydrogen’s high reactivity can lead to combustion abnormalities such as backfire, pre-ignition, and knocking, thus limiting the feasible admixture rates. These challenges are particularly relevant in medium-speed diesel engines designed for high power output and efficiency at low rpm. While hydrogen fuel-share has previously been tested in small-bore engines at moderate loads, this study investigates the influence on combustion and achievable hydrogen admixture rates in a medium-speed, 4-stroke diesel engine operating with up to 30 bar net indicated mean effective pressure (net IMEP). To minimize retrofitting efforts and to preserve diesel performance, the investigations were conducted on a single-cylinder engine with representative design features of a conventional diesel engine: a high compression ratio, Miller valve timing, valve overlap, and a piston with deep valve pockets. The piston ring system is suited for heavy fuel oil (HFO) operation. Hydrogen was supplied via a port fuel injection (PFI) system. 0D/1D process simulations supplement the experimental data. Findings indicate that energetic hydrogen admixture rates of up to 43% are achievable at low loads, limited by an advancing start of combustion, and up to 15% hydrogen share at high loads, constrained by backfire. This results in an average CO2 reduction of ~22% on the E2 cycle for constant-speed main propulsion engines. Due to rising NOx emissions, the results are only applicable when meeting IMO Tier II limits with selective catalytic reduction (SCR). The results demonstrate that conventional medium-speed diesel engines are suited for hydrogen fuel-share operation and that CO2 reductions comparable to liquid natural gas (LNG) conversions are feasible.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Research on Characterization Parameters for Engine Valve Clearance Based on Vibration Signals2026-01-50052/2/2026
To address mechanical faults caused by abnormal engine valve clearance, this study investigates the extraction methods of vibration signal feature parameters. A six-cylinder diesel engine test bench was established to collect cylinder head vibration signals under varying rotational speeds, torque loads, and valve clearance conditions. Four time–domain parameters, including peak-to-peak values, rectified average values, standard deviations, and root mean square amplitude, were extracted alongside the energy distribution of frequency bands obtained through wavelet packet decomposition. The correlations between these parameters and valve clearance states were systematically analyzed. The results demonstrated that all parameters exhibited significant increasing trends with elevated rotational speeds, whereas torque variations exerted minimal influence. Abnormal valve clearance induces significant amplitude increases in time–domain parameters. The energy within frequency bands 5–8 (6–12 kHz) derived from wavelet packet decomposition demonstrates marked sensitivity to valve clearance variations. These findings provide effective technical support for online monitoring of engine valve clearance and early fault warning systems.
Ji, Shaobo, Dong, Yiming, Yue, Yuanhang, Pan, Chi, Liao, Guoliang, Lu, Yueqi
Performance and Emission Characteristics of a Lean-Boosted Direct Injection Hydrogen Combustion System for Retrofitting Heavy Duty Diesel Engines2026-26-02681/16/2026
To address the imperative for decarbonizing the heavy-duty transport sector and advancing sustainable energy solutions, this paper presents a novel lean-boosted Direct Injection (DI) Hydrogen Internal Combustion Engine (H2 ICE) combustion system. This system is developed to retrofit existing flat-deck Diesel engines, offering a viable pathway towards drastically reduced emissions. Building on consolidated expertise from prior production-oriented Port Fuel Injection H2 engine development (DUMAREY 6.6ℓ V8), this research focuses on leveraging the distinct advantages of DI for hydrogen. An experimental assessment, supported by 1D and 3D-CFD analyses, demonstrates the system's capability to achieve highly efficient operation in Spark Ignition (SI) mode under ultra-lean and EGR-diluted conditions. The study confirms the elimination of combustion anomalies such as backfiring, pre-ignition, and knock, while achieving ultra-low engine-out NOx emissions and near-zero CO2, HC, CO, and PM. The authors discuss the optimization of key combustion drivers and the beneficial effects of dilution strategies. The findings reveal the significant potential of this DI H2 system, particularly when applied to the swirling cylinder head designs typical of common Diesel engines, to facilitate a rapid and cost-effective transition to cleaner freight mobility. Additionally, a specific flat-deck based tumble motion design has been investigated as a mixing improver versus swirl design, showing further margin for enhancing efficiency and effectiveness of the combustion process.
Gessaroli, Davide, Golisano, Roberto, Pesce, Francesco, Boretto, Gianmarco, Accurso, Francesco
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