Browse Topic: Synthetic fuels

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Combustion Characterization of Hydroprocessed Esters and Fatty Acids (HEFA) as an Alternative Fuel for Use in IC Engines2026-01-03174/7/2026
In the endeavors to reduce reliance on fossil fuels and reduce greenhouse gas emissions, synthetic fuels from less carbon intensive feedstocks have emerged as a promising alternative to conventional fuels. These synthetic fuels have gained traction in the aviation industry as sustainable aviation fuels (SAFs). One such fuel is a synthetic paraffinic kerosene derived from hydroprocessed esters and fatty acids (HEFA). Preliminary research has also suggested that this fuel may also be favorable for use in IC engines. This investigation will explore the combustion characteristics of HEFA in an IC engine in more detail. The thermophysical properties of HEFA were investigated and found comparable to or improving upon those of ULSD. Spray atomization analysis revealed more than 25% smaller SMD compared to ULSD, and lower span factor indicating a more uniform spray which can promote faster formation of a homogenous mixture. A tribological analysis using a pin-on-disk tribometer revealed comparable lubricity compared to ULSD, without requiring any additives. A CVCC was used to investigate the autoignition characteristics of the fuels. HEFA was found to have a DCN of 58 compared to ULSD at 48. Resultingly, the ignition delay for HEFA was notably shorter compared to the baseline of ULSD. Fired engine testing was conducted using a single-cylinder CRDI experimental engine. Emissions were measured using a FTIR and Microsoot sensor. Combustion characteristics such as ignition delay, LTHR, pressure rise rate, peak pressure, ringing intensity, CA50, and combustion duration were compared to ULSD at matched operating modes. HEFA was observed to have a shorter ignition delay and smaller premixed combustion event, releasing more of its energy in mixing controlled combustion. This caused CA50 and overall combustion duration to be extended compared to ULSD. The combustion behavior of HEFA contributed to significant reductions in NOx and Soot emissions compared to ULSD. Cycle variability was reduced by half for HEFA, indicating smoother engine operation and combustion stability. These results showcase the versatility of this SAF to be used in IC engines with conventional combustion strategies.
Soloiu, Valentin, Willis, James, Norton, Coleman, Davis, Zachary, Peralta Lopez, Guillermo, Rahman, Mosfequr
The Effects of Ethanol on Combustion in a Super-Lean-Burn Engine2026-01-03034/7/2026
To mitigate global warming, many countries are working toward carbon neutrality. Reducing CO₂ emissions from vehicles requires electrification technologies in hybrid and plug-in hybrid electric vehicles (HEVs, PHEVs) and improving thermal efficiency of internal combustion engines (ICEs). Lean-burn combustion is one approach to improving ICE thermal efficiency. Biofuels and synthetic fuels can also reduce CO₂ emissions in existing vehicles. Ethanol, a bio-derived fuel, is widely used in varying contents worldwide, and its further utilization is anticipated. This study examines the effects of ethanol blending on emissions, thermal efficiency, knocking, and combustion speed in a super-lean-burn engine. Gasoline surrogates with varying ethanol contents were tested at an excess air ratio (λ) of 2.5. Higher ethanol content reduced nitrogen oxides (NOx) emissions due to lower adiabatic flame temperature. Total hydrocarbon (THC) emissions measured by a Flame Ionization Detector (FID) showed a decreasing trend; however, after correction for low sensitivity to ethanol and aldehydes, no significant differences were observed. Thermal efficiency increased with ethanol content, due to reduced cooling losses. Knocking was mitigated by the higher Research Octane Number (RON) from ethanol blending; however, the extent was smaller than in the production engine operating at λ = 1. This mechanism was examined through ignition delay calculations. At λ = 2.5 and in-cylinder pressures above 9 MPa, the 50–90% combustion duration was prolonged, attributable to suppressed ethyl radical formation under lean conditions and a greater influence of the reaction in which methyl radicals consume hydrogen atoms to produce methane under high-pressure conditions.
Sugata, Kenji, Matsubara, Naoyoshi, Yamada, Ryota, Kitano, Koji
The Impact of Mid-Level Ethanol Blends on Reliability, Performance and Emissions in Gasoline Engine2026-01-03024/7/2026
To reduce CO₂ emissions from automobiles, it is essential to improve system efficiency through the electrification of vehicles with internal combustion engines (ICEs), such as hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), as well as through enhancements in ICE thermal efficiency. Additionally, biofuels and synthetic fuels are gaining attention as promising options to reduce CO₂ emissions from existing vehicles. Among these alternative fuels, ethanol, a bio-derived fuel, is already used at varying concentrations in many countries, and its further adoption is expected. Expanding the fleet of flex-fuel vehicles (FFVs) capable of running on high ethanol blends is one approach; however, increasing ethanol content in conventional gasoline, which is more widely used, is considered to have a greater impact on CO₂ reduction. A key issue is how existing vehicles adapt to increased ethanol concentrations such as E20, E30, and E40. This study focuses on turbocharged engines typically found in heavier passenger vehicles, which are less likely to be electrified, to assess the effects of varying ethanol concentrations on performance, efficiency, emissions, and reliability. The evaluation showed that increasing ethanol concentration from E0 to E40 in a fixed Blend stock for Oxygenate Blending (BOB) resulted in comparable or slightly improved torque and thermal efficiency, with emissions remaining similar and abnormal combustion tendencies suppressed. No reliability issues were observed in endurance testing. Furthermore, advancing ignition timing to take advantage of ethanol’s knock resistance within the constraints of mass-produced engines revealed that medium ethanol concentrations are sufficient to realize these benefits. Therefore, to improve output and thermal efficiency across a wider range of vehicles using the same ethanol volume, medium concentrations may be more advantageous than higher concentrations.
Matsubara, Naoyoshi, Sugata, Kenji, Koyama, Takashi, Ochi, Yuta, Aoki, Mizuki, Hashima, Takashi, Kodama, Kohei, Tomoda, Keiju, Kojima, Masakiyo
Fuel Effects on EGR Tolerance of Synthetic Gasoline Fuels in a DISI Engine2026-01-03054/7/2026
Drop-in synthetic gasoline fuels are an attractive alternative to traditional fossil fuels for transportation due to their high energy density, compatibility with the existing fleet and potential to decrease carbon intensity. Despite of meeting gasoline standards, the composition of these fuels can vary depending on the feedstock used for production and the production process, which has been shown to affect engine performance and emissions. This study investigated the effects of synthetic fuel composition on combustion in a direct-injection spark-ignition engine. Spark timing sweeps from the stability limit to the knock limit were performed with three different bio-fuels, methanol-to-gasoline, ethanol-to-gasoline and hydrotreated-biomass gasoline, at different exhaust gas recirculation (EGR) rates, and results were compared against a research-grade E10 (10%vol ethanol) regular gasoline representative of petroleum gasoline available in the US. Octane index analyses showed that knock resistance differences between fuels cannot be explained by their octane rating when EGR is added. Results demonstrated that adding EGR at medium loads is a very effective approach to increase efficiency despite of increasing burn duration because higher EGR rates led to lower pumping loses and lower heat transfer, while keeping combustion efficiency constant. The impact of EGR on combustion has shown to be very sensitive to fuel composition, and the knock resistance of fuels with strong low-temperature chemistry increased more with EGR addition that that of fuels with mild low-temperature chemistry. Similarly, the early flame propagation of fuels with strong low-temperature chemistry is more affected by EGR, limiting retardability and EGR tolerance. Results from this study indicated that, despite being considered drop-in, composition variability of synthetic fuels can be leveraged to improve engine performance.
MacDonald, James, Narayanan, Abhinandhan, Lopez Pintor, Dario, Matsubara, Naoyoshi, Kitano, Koji, Yamada, Ryota, Sugata, Kenji
Review of Comprehensive Evaluation and Comparative Analysis of Approaches for Capturing Atmospheric CO₂ and Converting It into Sustainable eFuels2026-26-01151/16/2026
As atmospheric CO₂ concentrations continue to rise at unprecedented rates, the urgent need for breakthrough technologies that can efficiently capture carbon directly from the air and convert it into sustainable synthetic fuels has never been clearer. While numerous capture and conversion methods have been propose, many remain at an early stage of development, facing significant challenges such as low energy efficiency, limited scalability, and high operational costs. This lack of technological maturity underscores a vast, largely untapped potential for innovation and transformative advancement. In response to this gap, the present study compiles and critically examines a wide spectrum of emerging capture and conversion technologies. Through a detailed exploration of their functionalities, potentials, advantages, and challenges, the paper accumulates a comprehensive and well-informed dataset. This holistic understanding not only reveals key bottlenecks but also identifies promising pathways to overcome them, offering a valuable foundation for future research and practical implementation. At its core, the study explores how strategic integration and optimization of capture and conversion systems can significantly enhance overall energy efficiency potentially more than doubling current benchmarks. Through this hypothesis-driven approach, it uncovers new possibilities for elevating technology readiness and achieving commercially viable solutions. Serving as a vital resource for researchers, industry stakeholders, and policymakers, this work advances scientific understanding and offers a clear roadmap to accelerate innovation and investment. The insights presented hold the promise to revolutionize sustainable fuel production, facilitate the global reduction of carbon emissions, and catalyze the transition toward a resilient, circular carbon economy that benefits both society and the environment.
Jain, Gaurav, Premlal, P, Pathak, Rahul, Gore, Pandurang
Letter from the Guest Editors04-19-01-000112/10/2025
Letter from the Guest Editors
Assanis, Dimitris, Cho, Seokwon, Lawler, Benjamin, Pintor, Dario Lopez
Multi-Objective Optimization of Oxyfuel Gas Engine Using Stochastic Engine Model and Detailed Chemistry2025-01-052911/25/2025
The energy transition initiatives in Germany’s renown coal mining region Lusatia have driven research into Power-to-X-to-Power technologies, where synthetic fuel is produced from renewably sourced hydrogen and captured CO2, and converted to electricity and heat through oxyfuel combustion. This work investigates the multi-objective optimization of oxyfuel gas engine using a stochastic engine model and detailed chemistry. Exhaust gas recirculation (EGR) rate, initial cylinder temperature and pressure, spark timing, piston bowl radius and depth are selected as design parameters to minimize the exhaust temperature at exhaust valve opening and indicated specific fuel consumption (ISFC) corresponding to oxyfuel operation with different dry and wet EGR rates. The optimization problem is solved for a dry EGR and four wet EGR cases with various CO2/H2O fractions, aiming to achieve comparable performance as in conventional natural gas / air operation, and energy-efficient carbon capture. The case with the lowest humidity (T10deg) had the lowest temperature of 1537 K, while the one with the highest vapor fraction (T70deg) attained the minimum 260 g/kWh ISFC. The superiority of the T10deg case is offset by much higher cooling demand (3.06 kW) for CO2 separation than that for T70deg case (0.81 kW). The constraint for combustion efficiency (>65%) limited the solution space towards high ISFC values, while the constraint for low indicated mean effective pressure (IMEP) (>7 bar) and the constraint for high IMEP (<8 bar) limited the solution space in between the two distinct clusters of feasible designs, and towards high exhaust temperature, respectively. The optimized designs from all the cases could outperform the reference case in terms of IMEP, nevertheless they fell below 31% indicated efficiency, which is associated with stoichiometric combustion.
Asgarzade, Rufat, Franken, Tim, Mauss, Fabian
Development of a Comprehensive Predictive QD Knock Simulation Model for Hydrogen, Methanol, and an Ammonia–Hydrogen Blend2025-01-052811/25/2025
To support the transition toward climate-neutral mobility and power generation, internal combustion engines (ICEs) must operate efficiently on renewable, carbon-neutral fuels. Hydrogen, methanol, and ammonia-hydrogen blends are promising candidates due to their favorable production pathways and combustion properties. However, their knock behavior differs significantly from conventional fuels, requiring dedicated simulation tools. This work presents a modeling framework based on quasi-dimensional (QD) engine simulation, including two separate knock prediction models. The first model predicts the knock boundary of a given operating point and combines an auto-ignition model with a knock criterion. The overall methodology was originally developed for gasoline and is here adapted to hydrogen, methanol, and ammonia-hydrogen blends. For this purpose, the relevant fuel properties were incorporated into the auto-ignition model, and a suitable knock criterion was identified that applies to all investigated fuels. The model was validated using experimental data from single-cylinder engine tests. In addition, two entirely new modeling approaches were developed to predict statistical knock values, specifically knock frequency and knock intensity. Each model was calibrated once per fuel and subsequently validated across a wide range of conditions. The results show that the adapted knock boundary model and the new statistical model accurately capture the knock behavior of hydrogen, methanol, and ammonia-hydrogen blends. The methodology enables predictive knock analysis using QD simulation and supports the development of robust, high-efficiency ICEs for future carbon-neutral applications.
Benzinger, Steffen, Yang, Qirui, Grill, Michael, Kulzer, Andre Casal, Plum, Lukas, Hermsen, Philipp, Günther, Marco, Pischinger, Stefan, Hurault, Florian, Foucher, Fabrice, Rousselle, Christine
In-Flight Evaluation of Sustainable Hydrocarbon Fuels in Compression Ignition Aircraft Engines2025-01-053311/25/2025
As global air traffic is expected to increase significantly in the coming decades, reducing the associated climate impact requires scalable solutions. While alternative propulsion technologies such as electric and hybrid-electric systems might offer long-term potential, their current applicability remains limited due to low energy density, limited range and scalability, and system complexity. Consequently, thermodynamic propulsion systems – such as gas turbines and piston engines – are expected to remain dominant in the medium term. In this context, sustainable hydrocarbon-based aviation fuels represent a practical and necessary solution. Certified sustainable aviation fuel (SAF) pathways are currently approved exclusively for use in gas turbines, with certification standards tailored to turbine-specific requirements. Consequently, fuel properties such as cetane number and evaporation behavior are not included in existing specifications. However, when SAF-kerosene blends are used in compression ignition engines, the impact of these properties on ignition quality, combustion behavior, and emissions must be specifically evaluated. For this purpose, a flight test campaign was conducted using a fully instrumented Diamond DA42 aircraft, configured as a flying laboratory and equipped with serial-production piston engines. Two synthetic fuel variants were evaluated: one certified according to ASTM D7566-23a Annex A2 (HEFA SPK) and a second, Tall Oil derived fuel with a distinctly different molecular composition – characterized by an increased content of cycloparaffins and low aromatics content. The aircraft as a flying air lab was equipped with special engine measurement technology including high-pressure in-cylinder indication to analyze the impact of these differing fuel compositions on engine efficiency and combustion characteristics, including ignition delay and peak pressure. Furthermore, a mobile emission and particle number measurement system enabled the assessment of environmental performance under real flight conditions. Both fuels demonstrated significant reductions in thermal NOx formation due to their low aromatics content. However, no clear benefit was observed in total particle number (PN), likely due to a shift in the particle size distribution towards the nanoparticle regime.
Kleissner, Florian, Hofmann, Peter, Vogd, Philipp, Vauhkonen, Ville, Käkölä, Jaana, Greve, Alina
Study on Combustion Detection of a Spark-Ignition Engine with Fuel Variation Using Various Sensors2025-32-005211/3/2025
The use of alternative fuels, such as biofuels and synthetic fuels in small mobility engines has become more common these days. Although these fuels contribute to the carbon neutrality, it is known that they do not have a certain fuel composition, which significantly affects the combustion characteristics of an engine, such as knocking and combustion duration. Therefore, to get the most out of these sustainable fuels, it is necessary to develop engine systems that are highly robust to variations in fuel composition. To achieve this goal, a method to sense fuel characteristics onboard using sensors already widespread in use or can be installed inexpensively is required. Although in-cylinder piezoelectric pressure sensors are useful for research in the laboratory, it is not suitable for the use in commercial engines because of its high cost. Therefore, the use of other sensors should be considered. The purpose of this study is to experimentally analyze what information related to combustion and fuel can be obtained from multiple cost-effective sensors mounted on an engine. For that goal, a linear multiple regression model and Neural Network (NN) model was developed to estimate fuel’s Lower Heating Value (LHV) and combustion duration. Experiments were conducted on a 4-cylinder spark ignition (SI) engine, and combustion characteristics of multiple fuels were investigated while varying engine operating conditions. In addition to gasoline, CH4 gas was introduced into cylinders to simulate the change in fuel composition. Sensors used in this study include intake and exhaust pressure sensors, thermocouples, and in-cylinder ion current sensor. Selection of input variables (sensors) for the regression models were done based on the results of the experiment, and linear multiple regression model and NN model were developed. The prediction errors (RMSE) for LHV were 0.54 MJ/kg with linear regression model and 0.95 MJ/kg with NN model. For CA10-90, prediction errors were 6.15 deg with linear regression model and 14.48 deg for NN model. Since the accuracy of the models were not high enough, hyperparameter tuning was done using Bayesian optimization, and prediction accuracies were improved. However, further work, such as building physical model,increasing sample size, or adding extra sensors, must be done to use these models for engine control.
Hayashi, Kohei, Kim, Jihoon, Yamasaki, Yudai
Study on CO 2 Absorption via Atomization Utilizing Surface Texturing and Surface Energy for Small Engine Applications2025-32-007611/3/2025
In response to the stringent CO2 regulations set to be enforced in Europe in 2030, there is a global demand for innovative technologies to significantly reduce CO2 emissions from internal combustion engines used in trucks, ships, and other applications. For this reason, future power sources are anticipated to adopt a three-pronged approach: electrification; hydrogen fuel used in fuel cells or internal combustion engines; and synthetic fuels (e-fuels) produced from renewable energy-sourced hydrogen, as approved by the European Commission (EC), and from raw materials that capture CO₂ directly from the atmosphere via the Direct Air Capture (DAC) method, combined with internal combustion engines. In this study, we aimed to absorb and capture “Green” CO₂ emissions from e-fuel and carbon-neutral (CN) fuels combined with internal combustion engines by investigating a method that atomizes a CO₂-absorbing solution. This approach involved spraying the solution and impingement the droplets within the exhaust pipe to promote surface absorption reactions with CO₂ in the gas flow. By spraying an amine-based CO2 absorbent onto an impingement plate that has been especially surface textured and further treated with heating, we were able to enhance the surface area and control the surface energy of the CO2 absorbent. This approach opens up new possibilities for improved CO2 absorption reactions.
Nohara, Tetsuo, Nara, Shotaro, Kawamoto, Yuki, Fukushima, Naoya, Ochiai, Masayuki
Model-Based Optimization of Diesel/OMEx Fuelled CI Engine under Multiple Blending Conditions2025-24-00389/7/2025
The search for alternative solutions for vehicle electrification, while reducing the carbon footprint during the transition to green mobility, leads to the investigation of electro-fuels (e-fuels) in conventional internal combustion engines. Leveraging previous research, the present study focuses on the optimisation of a Compression Ignition (CI) engine combustion control in response to the use of the Oxymethylene Dimethyl Ethers (OMEx) blended with conventional diesel. The selected e-fuel is the OME3, which is expected to be used as a drop-in solution and to easily achieve a reduction in soot emissions due to both its high oxygen content and lack of direct carbon bonds in its molecular structure. To verify its potential, a 1D single-cylinder CI multi-zone engine model has been exploited to simulate various diesel/OME3 blends in a wide engine operating range. The first step deals with the evaluation of performance and emissions to demonstrate the differences, particularly in terms of emissions reduction compared to the baseline standard configuration. Each operating condition is then optimized to minimize the energy losses associated with fuel substitution while maintaining the beneficial emission reductions. The model parameters identification and the optimisation of the different blends for each engine operating point are carried out using the software GT-Suite. This approach aims to provide an assessment of the methodology to design new control strategies along with the analysis of the potential impact of using such blends. On the basis of these results, a further optimization was carried out to assess, for each optimized operating point, which blending ratio guarantees the best performance both in terms of emissions and fuel consumption.
Foglia, Antonio, Cervone, Davide, Frasci, Emmanuele, Arsie, Ivan, Polverino, Pierpaolo, Pianese, Cesare
Investigation of the Combustion Process of a Thermally Conditioned Active Prechamber in Monovalent Operation with Ammonia2025-24-00289/7/2025
The debate over synthetic fuels is intense especially in sectors with a high energy demand like maritime [1, 2]. Hydrogen production from renewable sources is growing, but immediate measures for decarbonization are needed [3, 4]. In this context, the project MethMag was funded, and a gas engine for methane combustion with an innovative cooling concept and a purged prechamber (PC) spark plug was virtually developed [5, 6]. Validation with data from the test bench demonstrates that the simulations accurately represent the operating conditions [7, 8]. This combustion process is adapted for ammonia, which is being considered as a climate-friendly fuel of the future, particularly in maritime transportation [4, 9]. This fuel faces significant combustion challenges and is therefore mostly considered in complex, bivalent systems [10]. In particular, the prechamber is examined regarding the ignitability of ammonia. The overarching objective is to eliminate the necessity for a secondary fuel system, thereby reducing system complexity and associated costs. The transition to ammonia highlights the need for further adjustments. The geometry of the PC cap significantly affects turbulence and mixture formation in the prechamber [11]. While swirl caps generate high turbulence, the mixture formation is inadequate. Tumble caps, on the other hand, provide advantages in mixture formation by achieving an earlier increase in turbulence, even though the maximum turbulence is lower. For ammonia combustion, PC wall conditioning is not essential, given the inherently low combustion temperatures. However, conditioning can improve cold-start behavior by accelerating PC combustion and offering greater flexibility in ignition timing [12]. Direct injection into the prechamber enhances fuel mixing and reduces sensitivity to ignition timing adjustments. This leads to higher efficiency and better combustion characteristics, particularly at lean air-fuel ratios [13, 14]. Operating with a lean ammonia-air mixture is challenging but offers benefits for non-selective catalytic reduction (non-SCR) of nitrogen oxides. Simulations show that operation with λ = 1.2 and λ = 1.4 is feasible, although efficiency decreases at leaner mixtures [15].
Rothe, Paul, Bikas, Georgios, Mauss, Fabian
Drop-In Performance of Propyl- and Butyl-Terminated Oxymethylene Ethers in a Compression Ignition Engine04-19-01-00037/16/2025
Oxymethylene ethers (OMEs) have been proposed for use in diesel engines as a high-reactivity fuel with reduced soot emission. Historically, the focus on methyl-terminated OMEs has limited drop-in applicability. In this work, a set of extended-alkyl OMEs with methyl, propyl, and butyl terminations are tested in an unmodified 4.5L Deere diesel engine, neat and in various blends with ultra-low-sulfur diesel (ULSD). Engine operability and emissions data are collected for the various fuel blends. External laboratory testing against the ASTM D975 standard demonstrates that a blend of 30% butyl-terminated OMEs with ULSD meets all ASTM standard requirements except lubricity. It is shown that the OMEs and OME–diesel blends demonstrate shorter combustion durations, as defined by the 10%–90% heat release timing, than the ULSD control. Engine brake efficiency is unaffected by OME usage, while specific fuel consumption increases in proportion to the reduced heating values of OMEs. Particulate emissions are reduced to a greater extent for all OMEs and OME blends than the blend ratio would suggest when using the yield sooting index as an estimator. NOx emissions from the OMEs and OME blends are increased with respect to ULSD; however, the increase in NOx is much lower than the decrease in particulates, indicating a possible improvement in the soot/NOx tradeoff seen in combustion engines. Two observed downsides are increases in unburned hydrocarbon and formaldehyde emissions. Overall, butyl-terminated OMEs are recommended for future study as the ideal diesel blendstock studied in this work, with good balance of matching properties and improved emissions performance.
Lucas, Stephen P., Zdanowicz, Andrew, Wolff, Wyatt W., Windom, Bret
Prediction of Pre-Ignition Borderline on Supercharged SI Engine by Livengood-Wu Integral2024-32-00084/18/2025
The LSPI (Low Speed Pre-Ignition) is one of the consecutive abnormal combustion cycles of supercharged SI engine with direct injection fuel supply system [1]. The LSPI occurs when the engine is running at low speed and high load condition. It is important for the SI engine to control essentially with alternative fuel, e-fuel and hydrogen in the future. It is considered that the LSPI would be caused by the autoignition of the deposit, the lubricating oil from ring crevice, the lubricating oil from piston crown and so on [2, 3, 4, 5]. Among of these causes, this research focuses on the scattering lubricating oil from piston crown. The previous our research has reported on the two points. One is about the frequency and quantity of the lubricating oil scattering from piston crown [6]. Another is about the frequency of abnormal combustion by the engine test [7]. As the result, it has been cleared that the frequency of abnormal combustion is 1/10 of scattering frequency of the lubricating oil from piston crown. Moreover, it has been evaluated in-cylinder condition by the Livengood-Wu integral when the autoignition occurred. The LSPI would occur suddenly, continue several cycles and return to the normal combustion cycle again. However, it is difficult to find the borderline that the LSPI would occur or not for each engine and operating condition. This research will try to define the borderline of the occurring LSPI or not. The experimental data show the autoignition timing has three patterns. The autoignition timing advances from ATDC to BTDC when the consecutive abnormal combustion cycles proceed, it delays from BTDC to ATDC and all abnormal combustion cycles appear at ATDC. It is proposed that the borderline of LSPI is defined by the analysis of those autoignition with the Livengood-Wu integral.
Omori, Takaya, Tanaka, Junya
Comprehensive Investigation of Combustion Characteristics, Emissions, and Tribological Properties of Synthetic Kerosene (S8) in a CVCC and CRDI Research Engine2025-01-84434/1/2025
There is a need to reduce both the greenhouse gas emissions of internal combustion engines, and the reliance on traditional fossil fuels like Ultra Low Sulfur Diesel (ULSD). In this research, a synthetic paraffinic kerosene fuel, designated S8 and created from natural gas feedstocks using the Fischer-Tropsch process was investigated to determine its autoignition and combustion characteristics, emissions, and tribological properties. This fuel, S8, was found to have a Derived Cetane Number (DCN) of 62, which reflects a shorter Ignition Delay (ID), and Combustion Delay (CD) compared to ULSD, which has a DCN of 48. However, due to the chemical properties of S8, it lacks sufficient lubrication qualities in comparison to ULSD, so addition of 3% methyl oleate by mass was used to improve lubricity. The shorter ignition delay of S8, initially observed in a Constant Volume Combustion Chamber (CVCC) and confirmed in a fired Common Rail Direct Injection (CRDI) experimental engine. Investigations with Mie scattering He-Ne laser instrument, revealed the superior atomization of S8, which resulted in a Sauter Mean Diameter (SMD) of 19.2 μm, 8% smaller than that of ULSD. The combined effect of the superior atomization and shorter ID of S8 resulted in a reduction of the premixed combustion event for S8, with smoother engine operation due to the greater proportion of mixing-controlled combustion. This characteristic was also reflected in the comparison of the Low Temperature Heat Release (LTHR) region of S8 with that of ULSD. In LTHR, S8 released more energy during the low temperature cool flame formation region and entered High Temperature Heat Release (HTHR) sooner than ULSD. Analysis of the emissions of the CRDI engine when operated with S8 was conducted with the engine under a sustained load at 5.4 bar Indicated Mean Effective Pressure (IMEP), and the results were compared with identical operating parameters using ULSD. A 14% reduction in NOx emissions and a 33% reduction in soot was achieved compared to ULSD.
Soloiu, Valentin, Willis, James, Norton, Coleman, Davis, Zachary, Graham, Tristan, Nobis, Austin
Automotive Engineering: March 202525AUTP033/6/2025
Hydrogen won't accept 'no' for an answer From automakers to companies in the wider mobility industry, hydrogen power is seeing no shortage of investment and research even as some remain unconvinced of its future. Advanced silicones for ADAS in light vehicles Material solutions for thermal management, protection and assembly. Editorial Wrecking Ball Supplier Eye Cooler heads should prevail The international fight over eFuels, internal combustion's would-be savior Hydrogen storage: Not everything need look like a sausage Power over Coaxial: a simplified path to advanced vehicle systems Lighter, recyclable body seal wins SAA award Enhancing E-motor design, thermal efficiency with advanced cooling Mercedes proposes "in-drive brakes" for better EVs Product Briefs Spotlight: ADAS/AV sensors & simulation Interview Mercedes CEO talks software-defined vehicles and 30 years in Silicon Valley
The international fight over eFuels, internal combustion's would-be savior25AUTP03_053/1/2025
Efuels, synthetic gasolines made from captured carbon dioxide and renewable energy (usually wind and solar power), are “a valuable part of the solution,” said Aston Martin CEO Adrian Hallmark at a press briefing in New York on January 31. He described the process of creating the fuel as “really clean,” but also cited a rather off-putting price: $31 a gallon in the U.S. Still, Hallmark thinks eFuels could be a way for Aston to continue producing at least a few V12-powered cars in the coming electric future. Other automakers agree, but the battle over eFuels has by no means reached a cease-fire.
Motavalli, Jim
Jet-Induced Compression Ignition (JICI)—Application of Spark-Assisted Compression Ignition (SACI) in a Combustion System with Active Pre-Chamber03-18-01-00091/17/2025
The application of short burn durations at lean engine operation has the potential to increase the efficiency of spark-ignition engines. To achieve short burn durations, spark-assisted compression ignition (SACI) as well as active pre-chamber (PC) combustion systems are suitable technologies. Since a combination of these two combustion concepts has the potential to achieve shorter burn durations than the application of only one of these concepts, the concept of jet-induced compression ignition (JICI) was investigated in this study. With the JICI, the fuel is ignited in the PC, and the combustion products igniting the charge in the main combustion chamber (MC) triggered the autoignition of the MC charge. A conventional gasoline fuel (RON 95 E10) and a Porsche synthetic fuel (POSYN) were investigated to assess the fuel influence on the JICI. Variations of the relative air/fuel ratio in the exhaust gas (λex) were performed to evaluate both the occurrence of the JICI and the dilution capability. To assess the sensitivity of the JICI, variations of the engine speed and the engine load were performed. When using RON 95 E10, a shift from a conventional PC combustion to the JICI was observed between λex = 2.3 and λex = 2.5. The variations of the engine speed and the engine load revealed an increased JICI intensity when the engine speed decreased and when the engine load increased. When using POSYN, no JICI was observed. The occurrence of the JICI was correlated to the knock resistances of the fuels, i.e., the lower knock resistance of RON 95 E10 yielded the JICI, whereas the higher one of POSYN did not. At λex = 2.8, applying POSYN resulted in an increase of the burn duration of 5.5°CA, which was a relative increase of 41%, compared to the use of RON 95 E10 due to the absence of the JICI in case of POSYN. However, the application of POSYN resulted in the highest net indicated efficiency (ηi,net). In particular, the application of RON 95 E10 yielded a maximum of ηi,net = 41.5% at λex = 2.6, whereas using POSYN resulted in a maximum of ηi,net = 42.6% at λex = 2.2 due to the higher knock resistance of POSYN.
Burkardt, Patrick, Günther, Marco, Villforth, Jonas, Pischinger, Stefan
Sustainable Aviation Fuel – An Effective Tool for Complying with the Aviation’s Global Environmental Commitment2024-36-006612/20/2024
The (commercial) aviation sector (passenger and freight), which is strongly engaged with the world efforts to mitigate the carbon emissions and their inherent climate change effects, has accounted in 2018 for 2.4 % of global carbon dioxide (CO2) emissions (pre-pandemic levels). Despite the reductions in air travel demand during the 2020 pandemic, with a reduction of up to 80% in passenger travel during the peak pandemic period, the air travel demand has already recovered to around 80% of the pre-pandemic level, with aviation emissions in 2022 reaching around 800 Mt CO2, accounting for 2% of the global energy related CO2 emissions. Moreover, the demand for air travel is expected to double by 2040, growing at an annual average rate of 3.4%, which means that. despite the efficiency improvement trend (average 2%/year), will almost double the aviation’s greenhouse (GHG) emissions, with a significant increase in its relative GHG share, compared to the other transport modes. Meanwhile the aviation sector is one of the hardest to decarbonize, with few and costly pathways available. Zero emissions technologies, such hydrogen fuel and electric batteries are currently far from commercially ready for aviation use in the short to medium term, due to the technical challenges, such as aircraft onboard liquid hydrogen storage difficulties, as well as battery weight and volume, and are unlikely ever to be able to power large or long-haul flights. In this scenario, the so called sustainable aviation fuel (SAF), a drop-in fuel concept, already available in modest amounts on a commercial scale, are seen as a promising short to medium term alternative to tackle aviation emissions, by using existing aircraft designs and infrastructure. As a drop-in fuel, the SAF enables the replacement for the fossil jet fuel by using the existing fuel delivery and storage infrastructure and existing aircraft engines, with lifespan that still ranges from 20 to 30 years. From a chemical perspective, the SAF is the liquid aviation fuel derived from non fossil carbon resources, such as biomass or organic derived waste feedstocks, as well as synthetic fuels produced from carbon capture and renewable energy sources. They might be currently used in blends with fossil jet fuel, with current blending limits ranging from 5% to 50%, depending on the feedstock and production pathway. It is estimated from the International Air Transport Association (IATA) that to reach the net zero emission commitment, by 2050, around 65% of emission reductions should be reached by replacing conventional jet fuel with SAF. Despite its important role in the aviation decarbonization, the SAF share currently makes up only 0.1% of aviation fuel demand, which requires a huge increase in the production capacity, which might face challenges, such as feedstock availability, fuel sustainability and cost competitiveness. This work presents a review of the SAF technology, with a focus on the production pathways and their environmental footprint, their use on current aircraft engines and the associated required blends, as well as the challenges associated with SAF production increase and cost reductions, still required to make it a realistic aviation decarbonization tool.
Barbosa, Fábio Coelho
Toyota, Mazda, Subaru agree carbon is ‘the enemy’ with new internal combustion engine announcement24AUTP08_108/1/2024
Toyota, Mazda and Subaru announced a new technological effort to create new internal combustion engines and ways to use them in the electrification era, specifically for hybrid and plug-in hybrid vehicles. The companies said at a joint press conference in Japan that they would encourage increased use of petroleum alternatives like biofuels and eFuels in their effort to create carbon-neutral vehicles. A joint statement from the three OEMs claims this push for new and better ICEs comes with a focus on “carbon as the enemy” as they develop engines that can better work with electric motors, batteries, and other electric drive units. Toyota, Mazda and Subaru made clear they are not getting rid of EV-only vehicle plans. Here's how each company will approach the new ICE+EV era (quotes provided in English by on-site interpreters).
Blanco, Sebastian
How Can a Sustainable Energy Infrastructure Based on Renewable Fuels Contribute to Global Carbon Neutrality?2024-01-30237/2/2024
With the COP28 decisions the world is thriving for a future net-zero-CO2 society and the and current regulation acts, the energy infrastructure is changing in direction of renewables in energy production. All industry sectors will extend their share of direct or indirect electrification. The question might arise if the build-up of the renewables in energy production is fast enough. Demand and supply might not match in the short- and mid-term. The paper will discuss the roadmaps, directions and legislative boundary parameter in the regenerative energy landscape and their regional differences. National funding on renewables will gain an increasing importance to accelerate the energy transformation. The are often competing in attracting the same know-how on a global scale. In addition the paper includes details about energy conversion, efficiency as well as potential transport scenarios from production to the end consumer. Technologies are compared in respect of their TLR level and maturity for the market application. Furthermore the need for energy buffering on molecule or electron basis, availability and technical options will be evaluated. Finally the paper concludes with scenario calculations considering technology readiness and TCO for production, transport and infrastructure. Comparing all electricity based scenarios including molecules – respectively hydrogen and e-fuel are part of the evaluation.
Rothbart, Martin
Numerical Study of a Six-Stroke Gasoline Compression Ignition (6S-GCI) Engine Combustion with Oxygenated Fuels2024-01-23734/9/2024
A numerical investigation of a six-stroke direct injection compression ignition engine operation in a low temperature combustion (LTC) regime is presented. The fuel employed is a gasoline-like oxygenated fuel consisting of 90% isobutanol and 10% diethyl ether (DEE) by volume to match the reactivity of conventional gasoline with octane number 87. The computational simulations of the in-cylinder processes were performed using a high-fidelity multidimensional in-house 3D CFD code (MTU-MRNT) with improved spray-sub models and CHEMKIN library. The combustion chemistry was described using a two-component (isobutanol and DEE) fuel model whose oxidation pathways were given by a reaction mechanism with 177 species and 796 reactions. The key advantage of six-stroke engine operation is the ability to switch the combustion mode among kinetical controlled mode (KCM), kinetically-driven mixing control mode (K-MCM) and mixing controlled mode (MCM) in the second power stroke (PS2) providing a wider range of combustion control. The K-MCM mode operation has shown to reduce both soot and NOx emissions substantially at low load (around 7bar IMEP) engine operations. The current work focuses on 6S-GCI engine operation using synthetic fuels at high load engine operation with the constraints on pressure rise rate (<10bar/deg), combustion efficiency (>90%), soot and NOx emissions (<1g/kg fuel). With the constraints met, engine operating conditions at 15 bar IMEP and 2000 rpm were identified as a function of fuel split ratio and injection timings. Parametric study was also performed by varying fuel injection pressure, initial gas temperature at IVC, boost pressure and exhaust gas recirculation ratio. Engine performance and emissions characteristics of parametric variation are presented as well.
Purushothaman, Ashwin Karthik, Ra, Youngchul, Ha, Kyoung Pyo, Zhu, Shengrong, Ullal, Ankith
Demonstration of Low Criteria Pollutant and Greenhouse Gas Emissions: Synergizing Vehicle Emission Reduction Technology and Lower Carbon Fuels2024-01-21214/9/2024
This study focuses on evaluation of various fuels within a conventional gasoline internal combustion engine (ICE) vehicle and the implementation of advanced emissions reduction technology. It shows the robustness of the implemented technology packages for achieving ultra-low tailpipe emissions to different market fuels and demonstrates the potential of future GHG neutral powertrains enabled by drop-in lower carbon fuels (LCF). An ultra-low emission (ULE) sedan vehicle was set up using state-of-the-art engine technology, with advanced vehicle control and exhaust gas aftertreatment system including a prototype rapid catalyst heating (RCH) unit. Currently regulated criteria pollutant emission species were measured at both engine-out and tailpipe locations. Vehicle was run on three different drive cycles at the chassis dynamometer: two standard cycles (WLTC and TfL) at 20°C, and a real driving emission (RDE) cycle at -7°C. Several EN228 compliant fuels, including lower-carbon fuel candidate, were tested. Fuels were formulated representing the distribution of volatility, C9 and higher aromatics (A9+), and C11 and higher aromatics (A11+) currently in the European market. The results show that with ULE technology, a significant reduction in tailpipe emissions is achievable across various test cycles and conditions. It was found that fuel property effects on tailpipe emissions are mitigated by the ULE test vehicle. However, the engine-out total hydrocarbon (THC) and particle number (PN) emission showed sensitivity to fuel formulation. Fuel mid-distillation range was a good general predictor of engine-out THC emissions. Engine-out PN emissions were not consistently correlated with any fuel properties. However, Yield Sooting Index (YSI) in combination with back-end volatility was correlated with PN emissions on two of three test cycles on this vehicle.
Storch, Michael, Singh, Ripudaman, Haubold, Sven, Voice, Alexander
Automotive Engineering: April 202424AUTP044/4/2024
eFuels: An Alternative to the Alternative Synthetic fuels promise low-carbon alternatives, but can they deliver? WCX 2024: Come for the AI, stay for the optimism AI top of mind at SAE's annual technical mobility conference. A Peek at Electrify America's Charging Station Future Twenty DC fast chargers and amenities are available, but the most important detail is that everything works. Full speed ahead for second-generation Indy autonomous racers Major hardware and software upgrades underpin the Indy Autonomous Challenge racecar for 2024, proving self-driving vehicle capabilities at triple-digit speeds. Editorial The future is back Supplier Eye New keys to success Sumitomo Sensing Core: a sensor-free smart tire Neural Propulsion Systems claims significant radar breakthrough Porsche study: Europe missing out on tooling battery gigafactories All-electric Nissan Ariya handles ultra-cold temps on pole-to-pole trek Introducing new Concept CLA, Mercedes says Europe, North America charging to rapidly get better 2025 Kia Carnival MPV Hybrid brings unplugged PHEV power Spotlight: Simulation and analysis tools Q&A Owl AI making better ADAS systems with help from drones
eFuels: An Alternative to the Alternative24AUTP04_014/1/2024
Low-carbon fuels promise greener alternatives, but can they deliver? Even as electric vehicles dominate today's alternative powertrain market for passenger cars, the future of how we will all someday drive without burning petroleum is cloudier than ever. To decarbonize transportation, governments and companies around the world are promoting various future technologies, including hydrogen and synthetic fuels, as alternatives to the alternative. In the U.S., the road to a hydrogen future recently hit a few road-blocks. In February 2024, Shell announced it would dramatically scale back its H2 refueling station plans in California and close some of its few stations. This dealt a blow to local H2-vehicle drivers as well as the state's plans for a robust hydrogen infrastructure. When Hyundai announced in October 2021 that it would support Shell's plans to add 48 additional H2 refueling stations in California, it said that “hydrogen refueling infrastructure growth is critical to rapidly increase consumer adoption of zero-emission fuel cell vehicles.”
Blanco, Sebastian
EDITORIAL: The future is back24AUTP04_054/1/2024
As I was working on this issue's cover story - a look at the current state of low- and no-carbon fuels and the potential they hold - the cyclical nature of life made itself readily apparent (once again). I will warn those of you who were involved in the automotive industry a decade or two ago that you might experience similar flashbacks when you read about how eFuels could, if everything works the way it's supposed to, provide a way for much of today's internal combustion engines to power legitimately zero-new-emission vehicles, especially in regions of the world where EVs don't yet make sense. That's great. Well, it sounds great, at least. The many promises made by producers and researchers of synthetic fuels sound strikingly similar to what the companies supporting biofuels were saying back when George W. Bush was still president. The fuel is cleaner, they said. We can keep (some of) the same infrastructure, or just modify it slightly, they said. This will work with EVs to make the whole future brighter. That was the message. Obviously, ethanol and biodiesel have not taken over the world's gas stations. Just ask the Coskatas, BioWillies and Solazymes of the era. There are, of course, notable technical differences between those biofuels and the next-gen eFuels that some automakers and oil companies are researching today. I'm not trying to compare them directly to find out which is better. The point is, things often move in cycles. As different as the auto industry is from where it was in decades past, certain ideas just cycle their way in and then back out before returning.
Blanco, Sebastian
Decarbonization Routes for Global Road Mobility and Regional ChallengesEPR202302510/26/2023
The importance of decarbonizing mobility to slow climate change is already a common goal worldwide. However, there is a lack of alignment on which technological routes to take. While the electrification of mobility assumes dominance in some markets, it is essential to consider specificities of each region so that different applications of transport modes can be concretely evaluated. Decarbonization Routes for Global Road Mobility and Regional Challenges discusses regional approaches, such as those from Brazil and India, that can offer more representative participation in global decarbonization processes. These routes leverage these countries’ domestic talent and regional potential instead of simply copying the solutions coming from developed countries. Biofuels, biomass, and green hydrogen can be very effective ways of reducing global warming for these countries and others with similar economic characteristics, bringing more opportunities for market development and competitive advantages for various economic sectors. Click here to access the full SAE EDGETM Research Report portfolio.
Adas, Camilo Abduch
Potential for Particulate Reduction by Use of eFuels in MPFI Engines2023-01-184810/24/2023
Currently, emission regulations for the LVs using standard spark ignited ICEs considering only gaseous pollutants, just as CO, HC and NOx. Following the upcoming legislation for personal vehicles sector, the LVs might also include limits of PN and PM. Regarding fuel injection strategies, the MPFI which was previously excluded from particulate control will be incorporated into the new regulation [1]. In terms of social harm, there will be a necessity to reduce engine particulate emissions, as they are known for being carcinogenic substances [2, 3, 4]. Generally, the smaller the particulate diameter, the more critical are the damages for human health therefore, the correct determination of PN and particulate diameter is essential. Beside future challenges for reducing and controlling particulates, the reduction of fossil fuel usage is also an imminent target, being the replacement by eFuels one of the most promising alternatives. Therefore, the particulate generation behavior of eFuels and the influence of their novel fuel composition need to be researched. Hence, gas chromatography of five different eFuel blends was carried out in order to identify precisely the fuel composition and subsequentially correlate it with particulate emission behavior. Thereafter, the impacts of eFuel functional groups on PM/PN were studied using a motorcycle equipped with a two-cylinder engine by two different experiments. First, the standard homologation test cycle WMTC was selected for evaluating the total PM/PN emitted. Then, particulate size distribution at steady state condition was investigated to determine soot composition at two different operational load points of the vehicle, utilizing a scanning mobility particulate sizer (SMPS). By adopting this approach, it becomes possible to develop strategies for reducing particulate emissions by taking into account fuel composition and a comprehensive analysis of particle size distribution.
Schurl, Sebastian, Batalha, Guilherme, Kupper, Martin, Schmidt, Stephan, Krasa, Helmut
Impacts of eFuels on Solid and Gaseous Emissions of Powersport Two-Wheelers2023-01-183810/24/2023
As alternative to electrification or carbon free fuels such as hydrogen, CO2-neutral fuels have been researched aiming to decrease the impact of fossil energy sources on the environment. Despite the potential benefit of capturing CO2 emission after combustion for own fuel production, the so-called eFuels also benefit by using a green source of energy during their fabrication. Among all the possibilities for eFuels, alcohols, ethers (such as MTBE and ETBE) and alternative hydrocarbons have shown positive impacts regarding emission reduction and performance when compared to standard gasoline. Previously in [1] and [2], synthetic fuels and methanol blends were tested at steady state conditions in order to verify advantages and drawbacks relative to gasoline, for power-sport motorcycles. However, for real-world operation, transient behavior must be investigated addressing critical topics such as emissions during engine / aftertreatment warm-up, catalyst light-off and its interaction with eFuels. Therefore, for assessing eFuels impacts on raw / tail-pipe emissions, as well on solid particulate emissions, WMTC measurements were performed whereas engine parameters were adapted to e-fuel operation. Further, targeting at an optimum operation with a selected eFuel, novel catalysts structures and coating strategies were tested aiming to reduce gaseous and solid tail-pipe emissions in the WMTC cycle.
Batalha, Guilherme Pellizzaro, Schurl, Sebastian, Schmidt, Stephan, Bonifer, Marcus
Cold Start Performance of Sustainable Oxygenated Spark Ignition Fuels2023-32-01669/29/2023
The objective of this study was to reduce pollutant emissions during cold start conditions in a spark-ignited direct injection engine, by exploring the potential of oxygenated fuels. With their high oxygen content and lack of direct C-C bonds, they effectively reduce particle number (PN) and NOx emissions under normal conditions. Methanol was chosen due to its wide availability. As methanol is toxic to humans and associated with cold-start issues, a second promising synthetic fuel was selected to be benchmarked against gasoline, comprising 65 vol% of dimethyl carbonate and 35 vol% of methyl formate (C65F5). Currently, there is a lack of detailed investigations on the cold start performance for both oxygenated fuels utilizing today’s injector capabilities. Spray measurements were caried out in a constant volume chamber to assess the spray of C65F35. Reduced fuel temperature increased spray-penetration length and compromised fast vaporization. Therefore, the injection strategy becomes crucial to avoid spray-liner interaction and improve mixture formation. This was evaluated in a single-cylinder research engine, with the engine’s coolant water temperature maintained at -5°C. Compared to gasoline’s optimal single injection at 7 bar indicated mean effective pressure, C65F35 achieved a ten-fold reduction in PN emissions. Simultaneously, fuel-losses were reduced by ~10% as blow-by was effectively avoided. For both oxygenated fuels, a single late compression stroke injection was found to be effective while maintaining reasonable combustion stability. Delayed injection timing during the compression stroke resulted in lower NOx emissions, but increased emissions of CO, CH4, and CH2O due to reduced homogenization time.
Kraus, Christoph, Fellner, Felix, Miyamoto, Akiyasu, Sauerland, Henning, Härtl, Martin, Jaensch, Malte
Study on Combustion and Exhaust Emissions Characteristics of Oxymethylene Dimethyl Ether Blends with Fischer-Tropsch Fuels in Diesel Engines2023-32-01679/29/2023
Synthetic fuels (e-fuels) synthesized from H2 and CO by renewable electricity are expected as the next- generation diesel fuels and two types of e-fuels have received extensive attention: Fischer-Tropsch (FT) fuel and Oxymethylene dimethyl ether (OME). In this study the effects of OME blending ratios with 0 to 50 vol.% in FT fuels on combustion, emissions and spray characteristics in diesel engines are investigated. The results suggest that the OME blends to FT fuels suppressed the deterioration in combustion efficiency under low intake oxygen concentration conditions. The smoke emissions of FT fuels and OME blended fuels were both lower than those of diesel fuel and decreased with the increase in the OME blend ratio, and the soot-NOx trade-off relation in diesel engines can be improved.
Yuan, Haoyu, Tsukuda, Takuma, Nishino, Jumpei, Shibata, Gen, Ogawa, Hideyuki
Automated Kinetic Mechanism Evaluation for e-Fuels Using SciExpeM: The Case of Oxymethylene Ethers2023-24-00928/28/2023
In the rapidly changing scenario of the energy transition, data-driven tools for kinetic mechanism development and testing can greatly support the evaluation of the combustion properties of new potential e-fuels. Despite the effectiveness of kinetic mechanism generation and optimization procedures and the increased availability of experimental data, integrated methodologies combining data analysis, kinetic simulations, chemical lumping, and kinetic mechanism optimization are still lacking. This paper presents an integrated workflow that combines recently developed automated tools for kinetic mechanism development and testing, from data collection to kinetic model reduction and optimization. The proposed methodology is applied to build a consistent, efficient, and well-performing kinetic mechanism for the combustion of oxymethylene ethers (OMEs), which are promising synthetic e-fuels for transportation. In fact, OMEs are easily mixed with conventional fuels and share similar ignition propensity, and are therefore potential drop-in fuels. Additionally, their oxygenated nature significantly reduces soot emissions. The proposed workflow extends our recently developed kinetic mechanism for OME1 (dimethoxymethane – DMM) to OME2-4: the model is derived from state-of-the-art detailed literature mechanisms, updated according to a reaction class-based approach, and simplified according to chemical lumping. Then, the model is reduced to two different skeletal versions using DRGEP method. An extensive database of ~80 datasets for kinetic mechanism testing is collected, covering different reactor types and experimental conditions. The selected datasets are uploaded to SciExpeM, a recently developed data ecosystem that allows automated kinetic mechanism performance evaluation through a multi-index approach. The performance obtained from SciExpeM shows that the lumped mechanism reproduces well the selected experimental data, and both skeletal mechanisms, well-suited to CFD and engine simulations, show equally good performance. Some minor model deficiencies identified for OME2 and OME3 are finally recovered via data-driven kinetic modeling optimization, which relies on the same multi-index approach adopted in SciExpeM for the kinetic model evaluation.
Dinelli, Timoteo, Pratali Maffei, Luna, Pegurri, Alessandro, Puri, Amedeo, Stagni, Alessandro, Faravelli, Tiziano
Experimental and 3D-CFD Analysis of Synthetic Fuel Properties on Combustion and Exhaust Gas Emission Characteristics in Heavy-Duty Diesel Engines2023-24-00528/28/2023
Synthetic fuels can significantly improve the combustion and emission characteristics of heavy-duty diesel engines toward decarbonizing heavy-duty propulsion systems. This work analyzes the effects of engine operating conditions and synthetic fuel properties on spray, combustion, and emissions (soot, NOx) using a supercharging single-cylinder engine experiment and KIVA-4 code combined with CHEMKIN-II and in-house phenomenological soot model. The blended fuel ratio is fixed at 80% diesel and 20% n-paraffin by volume (hereafter DP). Diesel, DP1 (diesel with n-pentane C5H12), DP2 (diesel with n-hexane C6H14), and DP3 (diesel with n-heptane C7H16) are used in engine-like-condition constant volume chamber (CVC) and engine experiments. Boosted engine experiments (1080 rpm, common-rail injection pressure 160 MPa, multi-pulse injection) are performed using the same DP fuel groups under various main injection timings, pulse-injection intervals, and EGR = 0-40%. Once the 3D-CFD model is validated with the CVC and experimental engine data, in-cylinder combustion and emissions are analyzed. The CVC experiments show that DP2 and DP3 liquid penetrations are shorter than diesel oil. In engine tests, NOx did not change much for all DP fuels for the same engine operating condition. However, shorter-penetrated DP2 and DP3 reduce soot emissions by more than 60% and CO without worsening brake-specific fuel consumption compared to diesel oil. The 3D-CFD results show that n-hexane shifts the penetration of the high-carbon number to the low-carbon fuel. Vapor penetrations are found to be shortened by blending low-volatility fuels with diesel oil. Visualizations of the in-cylinder confirmed a decrease in the amount of soot formation near the wall for DP2 and DP3 fuels. In addition, equivalence ratio – temperature (phi-T) maps of these fuels indicate that at 40% EGR, soot emissions are reduced at lower equivalence ratios than diesel oil.
Shimizu, Kunihiro, Narushima, Tomoki, Sok, Ratnak, Kusaka, Jin
Evaluation of Different Gasoline Formulations on a High-Performance Engine2023-24-00388/28/2023
The future of the combustion engine will to some extent depend on the use of CO2-neutral eFuels to avoid further fossil CO2 emissions. Also, the use of synthetic fuels offers the possibility to improve various engine properties, such as thermodynamics, EGR compatibility or emissions, through targeted influence on specific fuel properties. To this end, a methodology was generated to attribute various engine effects to particular fuel properties. Therefore, the Chair of Combustion Engines (LVAS) at the TU Dresden developed a fully automated testbed for motorcycle engines, including clutch and gear switching mechanisms. Hitherto, emissions measurements for motorcycles were done mostly on chassis dynamometers, with the disadvantage of a large spread of results. Due to the lack of consistency the analysis of fuel properties was not possible. To prove the developed methodology, a test campaign including 15 different gasoline fuels was elaborated in cooperation with KTM R&D GmbH. Before measuring over 200 WTMC cycles on this new engine test stand, a fast conditioning system was devised for the coolant, engine oil and catalyst. This allows for cycle times of just over an hour with subsequent cold start. The experiments demonstrate the detailed effects of the fuel on engine behaviour. The highly dynamic engine test stand showed a much better reproducibility and a massively decreased test interval, compared to the conventional dyno testing. During the evaluation of engine measurement data, differences between fuels were established regarding various characteristics. These include starting behaviour, CO2 emissions and fuel consumption in correlation with varying C-H-O ratios, CO and NOx as well as particle emissions. Recommendations for future engine application and adaptation for synthetic fuels can be drawn from the findings.
Graßmeyer, Marius, Atzler, Frank
Efficiency Optimized Engine Operation with CO 2 Neutral Fuels through Thermodynamic Loss Calculation and Model-Based Fuel Detection2023-24-00968/28/2023
Global efforts to reduce anthropogenic carbon dioxide (CO2) emissions require innovative measures in the field of vehicle drives to present solutions in all areas of the transportation sector in the future. Synthetic fuels, that can be used in conventional combustion engines, show promising potentials. An increasing amount of synthetic fuels will be found in the off-highway sector, which is characterized by a high power and work density. The properties of synthetic fuels can differ depending on their chemical structure. In particular, the calorific value (LHV) and the stoichiometric air-fuel-ratio (AFRst) have a direct influence on the performance and emission characteristics of an engine. In addition to providing optimal fuel-specific engine operation, fuel detection can ensure that the engine is only operated with regenerative energy carriers in future. In this paper, the methodical approach for optimizing fuel-specific engine operation on the basis of thermodynamic loss calculation and model-based fuel detection is presented using the example of the synthetic fuel oxymethylene ether (OME). In this context, quantities of the engine control unit (ECU) represent the input values of the fuel detection system. Based on this, neural networks are built to detect the regenerative share in the fuel. By calculating the thermodynamic losses, the fuel-specific losses can be quantified to derive optimization potentials. These are evaluated using steady-state operating points and cycles. The combination of fuel detection, loss quantification and optimization enables the flex-fuel operation of series engines for an optimal use of CO2-neutral fuels.
Demel, Philipp, Knost, Friedemar, Obée, Alexander, Beidl, Christian
Experimental and Numerical Investigation of Combustion and Noise, Vibrations, and Harshness Emissions in a Drone Jet Engine Fueled with Synthetic Paraffinic Kerosene01-17-01-00068/14/2023
Emissions and effects of climate change have prompted study into fuels that reduce global dependence on traditional fuels. This study seeks to investigate engine performance, thermochemical properties, emissions, and perform NVH analysis of Jet-A and S8 using a single-stage turbojet engine at three engine speeds. Experimental Jet-A results were used to validate a CFX simulation of the engine. Engine performance was quantified using thermocouples, pressure sensors, tachometers, flow meters, and load cells fitted to the engine. Emissions results were collected using an MKS Multigas Emissions Analyzer that examined CO, CO₂, H₂O, NOx, and THC. NVH analysis was conducted using a multifield, free-field microphone, and triaxial accelerometer. This study found that Jet-A operates at higher temperatures and pressures than S8, and S8 requires higher fuel flow rates than Jet-A, leading to poorer efficiency and thrust. S8 produced stronger vibrations over 5 kHz compared to Jet-A. S8 showed a decrease in all measured emissions. The CFD model was validated, showing an increase in temperature, pressure, and gas velocity as speed increased. The swirl effect of combustion was examined, improving atomization. Emissions contours were validated by experimental results, showing increases in CO₂, H₂O, and NOx, and a decrease in CO as speed increases.
Soloiu, Valentin, Mcafee, John, Ilie, Marcel, Rowell, Aidan, Willis, James, Dillon, Nicholas
Decarbonized Fuel Options for Civil AviationEPR20230126/13/2023
Drop-in replacement biofuels and electrofuels can provide net-zero CO2 emissions with dramatic reductions in contrail formation. Biofuels must transition to second-generation cellulosic feedstocks while improving land and soil management. Electrofuels, or "e-fuels,” require aggressive cost reduction in hydrogen production, carbon capture, and fuel synthesis. Hydrogen has great potential for energy efficiency, cost reduction, and emissions reduction; however, its low density (even in liquid form) combined with it’s extremely low boiling temperature mean that bulky spherical tanks will consume considerable fuselage volume. Still, emerging direct-kerosene fuel cells may ultimately provide a superior zero-emission, energy-dense solution. Decarbonized Power Options for Civil Aviation discusses the current challenges with these power options and explores the economic incentives and levers vital to decarbonization. Until common and enforceable global carbon pricing arrives, targeted national measures (e.g., mandates, price support, and finance) will be required. Click here to access the full SAE EDGETM Research Report portfolio.
Muelaner, Jody E.
Numerical Validation and Optical Study of Injection of Different Oxymethylene Ether Fuels for Heavy-Duty Application04-17-01-00046/5/2023
A reliable toolchain for the validation and evaluation of numerical spray break-up simulation for the potentially carbon-neutral fuels polyoxymethylene dimethylether (POMDME, or short OME) is developed and presented. The numerical investigation is based on three-dimensional computational fluid dynamics (3D-CFD) with the commercial code STAR-CD v2019.1 using a Reynolds-averaged Navier-Stokes (RANS) equations approach. Fuel properties of the representatives OME1 and OME3 are implemented into the software and with that the fuels are investigated numerically. For validation purposes, optical experimental results in a heated spray chamber with inert nitrogen-pressurized atmosphere are presented. The measurement data are based on Mie scattering of the liquid phase and Schlieren imaging of the vapor phase. Solely experimental results are shown for OME1b and OME3–6 to assess if the knowledge from the numerical modeling with OME1 and OME3 can also be transferred to the corresponding multicomponent fuels. While the results for a match between OME3 and OME3–6 are close, the measurement for OME1b exceeds the result of OME1 in the liquid penetration significantly. This is explained by the molecular structure of the low-volatile additive in OME1b based on long-chained polyglycol ethers. For the numerically modeled operating conditions, the fuel injection rate with the corresponding fuel is measured. Two atomization and spray break-up approaches are investigated in simulation, based on Reitz-Diwakar (RD) models and a combination using Huh’s atomization and the Kelvin-Helmholtz Rayleigh-Taylor (KHRT) spray break-up models. A holistic parameter study in a single operating point with the fuel OME1 helps to determine the sensitivities of the models. Adjustments to the spray momentum by a variation of the parameter for the nozzle hole diameter are used to get results closely aligned with measurement data. The transfer of the calibrated RD model to a validation study with OME3 at different operating conditions matches well to measurement with no further adjustments necessary.
Gaukel, Kai, Pélerin, Dominik, Dworschak, Patrick, Härtl, Martin, Jaensch, Malte
Effects of Pre-spark Heat Release of Ethanol-Blended Gasoline Surrogate Fuels on Engine Combustion Behavior04-17-01-00035/2/2023
Regulations limiting greenhouse gas (GHG) emissions in the transport sector have become more restrictive in recent years, drawing interest to synthetic fuels such as e-fuels and biofuels that could “decarbonize” existing vehicles. This study focuses on the potential to increase the thermal efficiency of spark-ignition (SI) engines using ethanol as a renewable fuel, which requires a deep understanding of the effects of ethanol on combustion behavior with high compression ratios (CRs). An important phenomenon in this condition is pre-spark heat release (PSHR), which occurs in engines with high CRs in boosted conditions and changes the fuel reactivity, leading to changes in the burning velocity. Fuel blends containing ethanol display high octane sensitivity (OS) and limited low-temperature heat release (LTHR). Consequently, their burning velocities with PSHR may differ from that of gasoline. This study therefore aimed to clarify the effects of ethanol on SI combustion behavior under PSHR conditions. Combustion behavior was studied by performing single-cylinder engine experiments and chemical kinetics simulations. The experimental measurements were performed to characterize the relationship between the occurrence of PSHR and the main combustion duration. Analysis of this relationship showed that the ethanol-blended fuel has a lesser PSHR and a longer combustion duration than the non-ethanol fuel by approximately 5% in high engine load conditions. Simulations using input data from the experiments revealed that the ethanol-blended fuel has a lower laminar burning velocity due to the lower temperature in the unburned mixture caused by its PSHR. Additional simulations examining the chemical effect of partially oxidized reactants caused by PSHR on the laminar burning velocity showed that partially oxidized reactants increase the laminar burning velocity of the ethanol-blended fuel but decrease that of a reference fuel without ethanol. A large number of fuel radicals and oxides of the ethanol-blended fuel enhances chain-branching reactions in the pre-flame zone and possibly increases its laminar burning velocity. However, the thermodynamic effect of PSHR on laminar burning velocity exceeds the chemical effect, and thus the ethanol-blended fuel has a lower turbulent burning velocity in the PSHR conditions.
Yoshimura, Kei, Isobe, Kohei, Kawashima, Mitsutaka, Yamaguchi, Kyohei, Sok, Ratnak, Tokuhara, Satoshi, Kusaka, Jin
E-fueling for the future23AUTD05_045/1/2023
The development of carbon-neutral e-fuels enjoyed a major boost from European regulators, but production cost and scale remain issues. Synthetic and bio-based liquid “e-fuels” have in various forms enjoyed fits and starts of industry attention and R&D investment in recent years. They got the most significant boost ever in March 2023 when a politically charged deal between the European Union and Germany brokered an exemption in the EU's mandate for sales only of EVs starting in 2035. The agreement allows manufacturers to continue selling internal-combustion models after the 2035 deadline - but only if they run on carbon-neutral e-fuels. In an instant, e-fuels were guaranteed a market all to themselves. It remains to be seen whether e-fuels - at least in their current state of technology - can answer the call. But as some supporters enthused after the EU's escort of e-fuels into the post-EV landscape, developers have more than a decade to address technical challenges and concerns about production cost and scale.
Visnic, Bill
Europe steps back from 2035 ICE ban23AUTD05_125/1/2023
In a surprising move that paves the way for the European Union's adoption of a mandate to eliminate vehicle CO2 emissions, on March 25 the EU reached an agreement with Germany to step back from a complete ban of combustion-engine vehicles starting in 2035. The EU agreed to permit sales and registration of IC-engine models after the 2035 deadline - provided those vehicles operate only on carbon-neutral fuels, often generically referred to as ‘e-fuels.’ With a significant portion of its economy related to the historically ICE-based automotive industry, Germany had resisted the EU's total ban, although its Parliament's Green Party supported the forced sunsetting of ICE passenger vehicles. Reuters reported German Transport Minister Volker Wissing as tweeting, “We secure opportunities for Europe by preserving important options for climate-neutral and affordable mobility.” In another Twitter post, Wissing reportedly added, “Vehicles with internal combustion engines can still be newly registered after 2035 if they fill up exclusively with CO2-neutral fuels.”
Visnic, Bill
Fuels to transition the global legacy fleet23AUTD05_055/1/2023
The EV bandwagon has obscured potential solutions for decarbonizing the enormous global ICE legacy fleet. Put the promise of mass vehicle electrification and its myriad challenges aside for a moment, and consider: What if most IC-engine vehicle owners don't switch to EVs as the industry and regulators hope they will? And how long will it take to alter the existing global vehicle parc, estimated at more than one billion mostly ICE-powered vehicles, to the extent its greenhouse-gas emissions are insignificant in the crusade to achieve net-zero (and thwart global warming) by 2050?
Brooke, Lindsay
Development of 50% Thermal Efficiency S.I. Engine to Contribute Realization of Carbon Neutrality2023-01-02414/11/2023
To prevent global warming, many countries are making efforts to reduce CO2 emissions toward achieving 2050 carbon neutrality. In order to reduce CO2 concentration quickly, in addition to spread of renewable energy and expansion of BEV, it is also important to reduce CO2 emissions by improving thermal efficiency of ICE (internal combustion engine) and utilizing carbon neutral fuels such as synthetic fuels and biofuels. It is well known that lean burn is an effective technology to increase thermal efficiency of engine highly. However, since NOx emission from lean burn engine cannot be reduced with three-way catalyst, there have been issues such as complicated system configuration due to the addition of NOx reduction catalyst or limiting lean operation to narrow engine speed and load in order to meet emission regulation of each country. This paper introduces super lean burn engine with over lambda 2.5 that achieves both high thermal efficiency and significantly low NOx emission in order to solve the issues of conventional lean burn engine. Key technologies for combustion such as ignition, flame propagation, and unburned HC reduction are described firstly, and then the possibility of further improvement of thermal efficiency and combustion effect by applying ethanol as CN (Carbon neural) fuel to the super lean burn engine is indicated.
Kimura, Koshiro, SAKAI, Hiroyuki, Omura, Tetsuo, Takahashi, Daishi
Ignition and Combustion Characteristics of OME 3-5 and N-Dodecane: A Comparison Based on CFD Engine Simulations and Optical Experiments2023-01-03054/11/2023
Synthetic fuels derived from renewable power sources, so-called e-fuels, will play a crucial role in achieving climate-neutral future mobility because they can be used in the existing fleets and in hard-to-decarbonize applications. In particular e-fuels that contain oxygen in their chemical structure can also burn more cleanly in terms of soot formation. For compression-ignition engines, polyoxymethylene dimethyl ethers (PODEs or OMEs) are among the most promising candidates for such oxygenated e-fuels. Here, we investigated the characteristics of injection and combustion of OME3-5 mixture compared to n-dodecane, a reference diesel-like fuel. Both single and multi-injection, comprising a short pilot injection, is used. Experiments were performed in a single-cylinder optically accessible Bowditch-type engine, injecting with 1500 bar pressure with a 3-hole injector (Spray B of the Engine Combustion Network). Liquid and vapor penetration were measured by imaging the spray illuminated by a pulsed light-emitting diode (LED). Ignition delay, lift-off length and flame morphology were investigated based on multi-spectral high-speed imaging of chemiluminescence. For simulations, a 3D CFD engine model was developed. The combustion simulation was performed on a 120° sector mesh onto which flow and turbulence fields from a gas exchange simulation are mapped prior to fuel injection. The model accounts for piston-ring blow-by. For the combustion of both fuels, detailed reaction mechanisms were used. In general, quite good agreement between model predictions and experimental results was achieved. In particular the consideration of blow-by losses by the CFD model produced a realistic behavior during the high-pressure cycle. Both CFD simulation and optical experiments, reveal significant differences between the two fuels. For OME, the liquid phase penetrates further into the combustion chamber, the ignition delay is shorter compared to n-dodecane and the equivalence ratio of OME during combustion is significantly leaner.
Wiesmann, Frederik, Bauer, Esra, Kaiser, Sebastian A., Lauer, Thomas
Injector Design and Fuel Pressure Variation for Oxygenated Spark Ignition Fuels2023-01-03064/11/2023
This study provides an overview of injector design adaptations and fuel pressure variations for oxygenated synthetic fuels, benchmarked against gasoline. The promising oxygenated fuels exhibited reduced emissions, especially with respect to particles. In gasoline engines, high fuel pressures are needed to keep the particle emissions below the permitted level. In oxygenated fuels, high fuel pressures are required to compensate for the lower volumetric energy density when used with non-adapted injectors. This study demonstrates that an adapted injector design enables engine operation with a fuel pressure reduction from 35 MPa to 10 MPa, without emission drawbacks. The fuel investigated contained dimethyl carbonate (DMC) and methyl formate (MeFo). The fuel mass contained around 50% oxygen. A relatively high percentage of 35 vol.% MeFo was chosen because of its high vapor pressure, thus providing fast mixture formation and enabling very late compression stroke injections. The basic design adaptations are expected to be transferable to other oxygenated synthetic fuels, e.g., containing methanol (MeOH) and MeFo. The main tests were conducted on a single cylinder research engine, based on a four-cylinder automotive engine. The exhaust gas composition was measured using an FTIR equipped with a fuel-tailored evaluation method, several standard exhaust gas analyzers, and a solid particle counting system with 10 and 23 nm cut-off sizes. The spray from both the two synthetic fuel injectors and the standard injector was further investigated at a spray chamber by means of a high-speed camera. Given a standard injector the spray pattern of 65vol% DMC+ 35vol%MeFo, and 85vol%MeOH+15 vol% MeFo were compared to the pattern of G100. All of the injectors were further investigated at an injection rate analyzer in order to provide necessary information about the injected fuel mass.
Kraus, Christoph, Fellner, Felix, Miyamoto, Akiyasu, Sauerland, Henning, Härtl, Martin, Jaensch, Malte
Highly Efficient and Clean Combustion Engine for Synthetic Fuels2023-01-02234/11/2023
This paper provides an overview of possible engine design optimizations by utilizing highly knock-resistant potential greenhouse gas (GHG) neutral synthetic fuels. Historically the internal combustion engine was tailored to and highly optimized for fossil fuels. For future engine generations one of the main objectives is to achieve GHG neutrality. This means that either carbon-free fuels such as hydrogen or potential greenhouse gas neutral fuels are utilized. The properties of hydrogen make its use challenging for mobile application as it is very diffusive, not liquid under standard temperature/pressure and has a low volumetric energy density. C1-based oxygenated fuels such as methanol (MeOH), dimethyl carbonate (DMC) and methyl formate (MeFo) have properties like conventional gasoline but offer various advantages. Firstly, these fuels can be produced with renewable energy and carbon capture technologies to be GHG neutral. Secondly, the C1-based fuels burn with significantly less pollutant emissions. A third advantage is the high knock resistance of those fuels. This inherits a drastic efficiency potential for spark ignition engines as the compression ratio and therefore the potential thermal efficiency can be directly increased. In the single cylinder engine, a compression ratio (CR) of ~20:1 is investigated proving the high knock resistance as well as the efficiency potential of MeOH and a mixture containing 65 vol% DMC and 35 vol% MeFo (C65F35). Special attention is paid to the direct injection strategy, which utilizes up to quadruple injections and 35MPa fuel pressure. Later on, a more moderate CR increase to 15:1 with a CFD optimized piston design is investigated at a state of the art four-cylinder engine (4CE) utilizing C65F35. The whole engine map is presented proving the real-world usability and efficiency potential of this fuel type in combination with the optimized piston. WLTC and RDE tests were performed, underling both the practicality and the efficiency potential in dynamic conditions. The 4CE tests are rounded off by showcasing the potential of lean operation with two different high-energy ignition systems (Corona and passive pre-chamber ignition). The performance investigation on both engines is accompanied by emission measurements utilizing standard exhaust analyzers, an FTIR-device and particle number counting systems.
Kraus, Christoph, Thamm, Fabian, Retzlaff, Mario, Gadomski, Bartosch, Fitz, Patrick, Härtl, Martin, Hoppe, Steffen, Jaensch, Malte
A Numerical Approach for the Analysis of Hydrotreated Vegetable Oil and Dimethoxy Methane Blends as Low-Carbon Alternative Fuel in Compression Ignition Engines2023-01-03384/11/2023
Despite recent advances towards powertrain electrification as a solution to mitigate pollutant emissions from road transport, synthetic fuels (especially e- fuels) still have a major role to play in applications where electrification will not be viable in short-medium term. Among e-fuels, oxymethylene ethers are getting serious interest within the scientific community and industry. Dimethoxy methane (OME1) is the smaller molecule among this group, which is of special interest due to its low soot formation. However, its application is still limited mainly due to its low lower heating value. In contrast, other fuel alternatives like hydrogenated vegetable oil (HVO) are considered as drop-in solutions thanks to their very similar properties and molecular composition to that of fossil diesel. However, their pollutant emission improvement is limited. This work proposes the combination of OME1 and HVO as an alternative to fossil diesel, to achieve noticeable soot emission reductions while compensating for the different properties of the first fuel. The aim of this work is to provide insight into the combustion characteristics of blends of these two fuels. For this purpose, experimental and numerical studies are combined. In this context, n-dodecane is proposed as a surrogate for HVO simulation based on the high similarities experimentally observed between both fuels. Then, a compact kinetic mechanism is developed and validated, combining individual OME1 and n-dodecane mechanisms. Results confirm that the numerical approach followed was able to capture the experimental behavior of these blends in terms of heat release rate, in-cylinder pressure and soot formation. An increase of the OME1 content in the blend greatly influences the combustion process. The ignition delay, as well as the premixed combustion phase peak, increase with the OME1 percentage in the blend. However, HVO helps on limiting this effect while remarkable soot formation reductions are still achieved thanks to OME1.
Garcia-Oliver, Jose M, Novella, Ricardo, Lopez Pintor, Dario, Micó, Carlos, Bin-Khalid, Usama
Combustion Characteristics of Low DCN Synthetic Aviation Fuel, IPK, in a High Compression Ignition Indirect Injection Research Engine2023-01-02724/11/2023
The Coal-To-Liquid (CTL) synthetic aviation fuel, Iso-Paraffinic Kerosene (IPK), was studied for ignition delay, combustion delay, pressure trace, pressure rise rate, apparent heat release rate in an experimental single cylinder indirect injection (IDI) compression ignition engine and a constant volume combustion chamber (CVCC). Autoignition characteristics for neat IPK, neat Ultra-Low Sulfur Diesel (ULSD), and a blend of 50%IPK and 50% ULSD were determined in the CVCC and the effects of the autoignition quality of each fuel were determined also in an IDI engine. ULSD was found to have a Derived Cetane Number (DCN) of 47 for the batch used in this experimentation. IPK was found to have a DCN of 25.9 indicating that is has a lower affinity for autoignition, and the blend fell between the two at 37.5. Additionally, it was found that the ignition delay for IPK in the CVCC was 5.3 ms and ULSD was 3.56 ms. This increase in ignition delay allowed the accumulation of fuel in the combustion chamber when running with IPK that resulted in detonation of the premixed air and fuel found to cause high levels of Ringing Intensity (RI) when running neat IPK indicated by the 60% increase in Peak Pressure Rise Rate (PPRR) when compared to ULSD at the same load. An emissions analysis was conducted at 7 bar Indicated Mean Effective Pressure (IMEP) for ULSD and the blend of 50% ULSD and 50% IPK. With the addition of 50% IPK by mass, there was found to be a reduction in the NOx, CO2, with a slight increase in the CO in g/kWh.
Soloiu, Valentin, Weaver, Amanda, Smith, Richard, Rowell, Aidan, Mcafee, John, Willis, James
Prediction of Spray Vapor Tip Penetration of Diesel, Biodiesel and Synthetic Fuels Using Artificial Neural Networks with Confidence Intervals2023-01-03154/11/2023
Fuel spray and atomization processes affect the combustion and emissions characteristics of fuels in internal combustion engines. Biodiesel and synthetic fuels such as oxymethylene dimethyl ethers (OME) show great promise as alternative fuels and are complementary in terms of reproducing the fluid properties of conventional diesel fuels through blending, for instance. Averaged experimental results, empirical correlations and Computational Fluid Dynamics (CFD) have typically been used to evaluate and predict fuel spray liquid and vapor penetration values so as to better design internal combustion engines. Lately, Machine Learning (ML) is being applied to these investigations. Typically, ML spray studies use averaged experimental data and then over-trained neural networks on the limited available data. By contrast, in this study we present spray vapor tip penetration predictions using artificial neural networks with systematic treatment of uncertainties arising from experimental variability and limitations in the neural network training process. This has not been presented previously, and it allows the calculation of confidence intervals on the spray penetration predictions produced by neural networks. Using the present method, we evaluate four different diesel, biodiesel and OME fuel blends under four fuel injection conditions each and predict spray vapor tip penetration values with a correlation coefficient of 0.999. Across all fuel variants and injection conditions, one standard deviation represented less than 1.5 mm spray tip penetration (circa 2% of spray tip penetration) 1 ms from the start of injection. Despite this precision, a 95% confidence interval on neural network predictions encompassed the experimental fuel penetration data across all fuel variants, injection conditions and time steps. By calculating the confidence intervals on neural network predictions, we enable internal combustion engine designers to better quantify the applicability of neural networks in predicting spray characteristics.
Richards, Bryn, Emekwuru, Nwabueze
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