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    <title>Transport Research International Documentation (TRID)</title>
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    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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    <item>
      <title>Combustion Characteristics of High-Energy Syngas in Internal Combustion Engines under Constant Co2 and N2 Conditions</title>
      <link>https://trid.trb.org/View/2694418</link>
      <description><![CDATA[Within the framework of promoting circular economy strategies and expanding the portfolio of renewable energy sources, synthesis gases (syngas) produced from the gasification of municipal and plastic waste constitute a promising alternative fuel. This research investigates five high-energy syngas compositions, each maintaining constant inert gas proportions (10% CO2 and 5% N2), focusing on their combustion behavior in a spark-ignition internal combustion engine designed for cogeneration applications. This analysis focuses on the characterization of in-cylinder pressures, the indicated mean effective pressure (IMEP), heat release dynamics, and the duration of the combustion process. Experimental results demonstrate that elevated hydrogen proportion in fuel mixtures accelerates combustion, evidenced by reduced burn duration. However, hydrogen content did not exhibit a direct correlation with peak in-cylinder pressure. The maximum peak pressure was achieved by a mixture containing moderate hydrogen and elevated carbon monoxide content. A hydrogen-rich mixture displayed the shortest burn duration yet produced the lowest maximum pressure, attributed to spark timing positioned near top dead center (TDC). Methane concentration directly influenced the volumetric lower heating value (LHV), subsequently affecting both IMEP and torque output. Relative to methane operation, engine torque output decreased by 6% to 13.4%, while hourly fuel consumption increased from 1.55 kg.h-1 to 3.88 kg.h-1 depending on mixture composition.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:14:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/2694418</guid>
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    <item>
      <title>Project EcoFuel: Renewable Electricity-Based, Cyclic and Economic Production of Fuel</title>
      <link>https://trid.trb.org/View/2581577</link>
      <description><![CDATA[E-fuels, produced from CO₂ using renewable electricity, currently suffer from low energy efficiency, hence high energy demand, related high cost and are therefore not yet produced at industrial scale. To be commercially viable, e-fuels production pathways require the availability of vast amounts of low-cost electricity. The Horizon 2020 project EcoFuel, with the aim of overcoming these deficiencies, develops and demonstrates a novel process chain that significantly improves the energy efficiency for production of synthetic fuel out of CO₂ and water using renewable energy. The process chain comprises (a) the supply of CO₂ from the atmosphere via a novel direct air capture (DAC) approach, (b) direct electro-catalytic reduction of CO₂ to C2/C3 hydrocarbons at close to ambient temperatures, and (c) thermo-catalytic liquefaction of alkenes, upgrading and fractionation into transport fuels. The direct electro-catalytic CO₂ reduction to hydrocarbons offers greatly enhanced efficiency potentials compared to Power-to-X technologies downstream of water electrolysis and at the same time, reduces process pathway steps. Overarching objectives of EcoFuel are to reduce primary energy demand, to enhance resource and cost efficiency of production, minimize the environmental footprint of the process, and to demonstrate the ecological and economic advantage.]]></description>
      <pubDate>Fri, 05 Jun 2026 16:39:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/2581577</guid>
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    <item>
      <title>Fuel Effects on EGR Tolerance of Synthetic Gasoline Fuels in a DISI Engine</title>
      <link>https://trid.trb.org/View/2692289</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692289</guid>
    </item>
    <item>
      <title>The Impact of Mid-Level Ethanol Blends on Reliability, Performance and Emissions in Gasoline Engine</title>
      <link>https://trid.trb.org/View/2692271</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692271</guid>
    </item>
    <item>
      <title>The Effects of Ethanol on Combustion in a Super-Lean-Burn Engine</title>
      <link>https://trid.trb.org/View/2692269</link>
      <description><![CDATA[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 (?) 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 ? = 1. This mechanism was examined through ignition delay calculations. At ? = 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.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692269</guid>
    </item>
    <item>
      <title>Combustion Characterization of Hydroprocessed Esters and Fatty Acids (HEFA) as an Alternative Fuel for Use in IC Engines</title>
      <link>https://trid.trb.org/View/2692266</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692266</guid>
    </item>
    <item>
      <title>Elucidating the Effects of Lower Boiling Point Fuel Blends on the Performance of a Heavy-Duty Diesel Engine</title>
      <link>https://trid.trb.org/View/2646089</link>
      <description><![CDATA[This study investigates the impact of synthetic fuel properties on improving the combustion and emissions of high-compression-ratio (CR) heavy-duty diesel engines. Diesel, DP2b (diesel + C₆H₁₄: 6:4 vol%), and DP3b (diesel + nC₇H₁₆: 6:4 vol%) fuels are tested in a single-cylinder CR=23 engine. A 3D-CFD model was calculated using CHEM-KIVA4 and Waseda’s phenomenological soot model. The results showed that the use of mixed fuels reduced Soot under each operating conditions. Comparison between experiments and calculations confirms that the reasons why soot is reduced with mixtures fuels are promotion of spray atomization and suppressing for soot particle nucleation and surface growth processes.]]></description>
      <pubDate>Fri, 20 Mar 2026 14:47:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2646089</guid>
    </item>
    <item>
      <title>A Study on the Effect of Synthetic Fuels with Different Properties on Combustion and Exhaust Emission Characteristics of a Heavy-Duty Compression-Ignition Engines</title>
      <link>https://trid.trb.org/View/2646087</link>
      <description><![CDATA[Appropriate fuel properties can be expected to further improve thermal efficiency and exhaust gas emissions, compared to conventional diesel fuel. However, the effects of each fuel property on compression ignition combustion and emission characteristics have not yet been revealed, since each fuel property interacts with others, resulting in the difficulty of identifying them separately. Evaluating the independent effects of each fuel property could help in designing preferable fuels for a future carbon-neutral society. This study investigates the effects of synthetic fuels with different properties on combustion characteristics and exhaust emissions.]]></description>
      <pubDate>Fri, 20 Mar 2026 14:47:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2646087</guid>
    </item>
    <item>
      <title>Aviation e-fuel mandates: balancing average and minimum requirements for emission reduction</title>
      <link>https://trid.trb.org/View/2616270</link>
      <description><![CDATA[This paper examines a policy design to regulate the airline industry’s use of e-fuel, a type of sustainable aviation fuel (SAF). We compare three policy approaches: an average policy that regulates only the average e-fuel usage; a minimum policy that mandates only the minimum e-fuel usage per sub-period; and a dual policy that enforces both average e-fuel usage over a period and minimum e-fuel usage in each sub-period. Using a two-period model, we evaluate these policies in terms of emission reduction and their impact on aviation outputs and e-fuel utilization. Our findings reveal that the average and minimum policies are equivalent in emission reduction efficiency (ERE), defined as the ratio of emission reduction under these policies to that under the dual policy. The ERE is influenced by market fluctuations, with larger fluctuations reducing the ERE to a minimum of 50%. We also explore the implications of incomplete information on policy design. When the government lacks information about future market growth, average e-fuel usage increases under low growth scenarios, though the minimum e-fuel requirement under the dual policy remains unaffected. Interestingly, under incomplete market information, the average or minimum policy may outperform the dual policy in emission reduction. Furthermore, even with incomplete information on e-fuel costs, the first-best outcomes achievable under complete information can still be realized, even when e-fuel costs are high. Our theoretical findings are validated through model calibrations, which provide actionable insights for policymakers aiming to optimize e-fuel mandates for emission reduction.]]></description>
      <pubDate>Mon, 09 Feb 2026 08:53:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2616270</guid>
    </item>
    <item>
      <title>E-fuels in IC engines: A key solution for a future decarbonized transport</title>
      <link>https://trid.trb.org/View/2612381</link>
      <description><![CDATA[This editorial piece emphasizes the importance of low-carbon, synthetic electro-fuels (e-fuels) in decarbonizing transport, which complements other decarbonization measures, including efficiency improvements, vehicle electrification and hybridization, as well as bio-based renewable fuels. Given the stringency of the emissions legislations worldwide, and the desire for many countries to achieve net-zero CO₂ emissions by 2050, synthetic electro-fuels, produced using renewable electricity, water and captured CO₂, has the potential to deliver significant CO₂ reductions. When e-fuels are designed to be chemically similar to conventional fuels, they can be compatible with existing vehicles and infrastructure. Therefore, e-fuels can be a drop-in solution to facilitate an accelerated decarbonization of the existing legacy fleet as well as next generation IC engines. Furthermore, e-fuels could unlock greater penetration of renewable electricity into the transport sector by enabling international trade of renewable electricity in the form of liquid energy carriers. This is particularly useful for matching lower cost renewable electricity producers from regions with high solar irradiation and wind potential, with existing and growing energy demand centers globally that have limited renewable electricity generation potentials. The paper highlights the potential of several e-fuels: hydrogen, ammonia, e-gasoline, alcohols, DMC, paraffinic fuels, OMEx (DME), and their use in internal combustion engines, considering both spark-ignition and compression-ignition combustion, with an insight on dual-fuel and reactivity-controlled CI combustion modes. Advantages in terms of combustion efficiency and pollutant emissions are also comprehensively discussed, together with the challenges related to their use and production. Finally, the paper remarks the importance of Life-Cycle-Assessment (LCA) to assess the climate change mitigation potential of alternative fuels and powertrains. LCA studies reveal that there is no silver-bullet to decarbonizing transport, neither fuels nor powertrain technologies, since the CO₂ reduction potential of these technologies is highly dependent on how they are produced and operated throughout their entire life cycles.]]></description>
      <pubDate>Mon, 29 Dec 2025 09:37:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2612381</guid>
    </item>
    <item>
      <title>In-Flight Evaluation of Sustainable Hydrocarbon Fuels in Compression Ignition Aircraft Engines</title>
      <link>https://trid.trb.org/View/2639321</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Wed, 10 Dec 2025 16:10:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/2639321</guid>
    </item>
    <item>
      <title>Multi-Objective Optimization of Oxyfuel Gas Engine Using Stochastic Engine Model and Detailed Chemistry</title>
      <link>https://trid.trb.org/View/2639301</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Wed, 10 Dec 2025 16:10:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/2639301</guid>
    </item>
    <item>
      <title>Study on CO2 Absorption via Atomization Utilizing Surface Texturing and Surface Energy for Small Engine Applications</title>
      <link>https://trid.trb.org/View/2623949</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:12:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2623949</guid>
    </item>
    <item>
      <title>Study on Combustion Detection of a Spark-Ignition Engine with Fuel Variation Using Various Sensors</title>
      <link>https://trid.trb.org/View/2623933</link>
      <description><![CDATA[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.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:12:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2623933</guid>
    </item>
    <item>
      <title>Investigation of the Combustion Process of a Thermally Conditioned Active Prechamber in Monovalent Operation with Ammonia</title>
      <link>https://trid.trb.org/View/2600394</link>
      <description><![CDATA[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 ? = 1.2 and ? = 1.4 is feasible, although efficiency decreases at leaner mixtures [15].]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600394</guid>
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