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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=PHNlYXJjaD48cGFyYW1zPjxwYXJhbSBuYW1lPSJkYXRlaW4iIHZhbHVlPSJhbGwiIC8+PHBhcmFtIG5hbWU9InN1YmplY3Rsb2dpYyIgdmFsdWU9Im9yIiAvPjxwYXJhbSBuYW1lPSJ0ZXJtc2xvZ2ljIiB2YWx1ZT0ib3IiIC8+PHBhcmFtIG5hbWU9ImxvY2F0aW9uIiB2YWx1ZT0iMCIgLz48L3BhcmFtcz48ZmlsdGVycz48ZmlsdGVyIGZpZWxkPSJpbmRleHRlcm1zIiB2YWx1ZT0iJnF1b3Q7SWduaXRpb24gc3lzdGVtcyZxdW90OyIgb3JpZ2luYWxfdmFsdWU9IiZxdW90O0lnbml0aW9uIHN5c3RlbXMmcXVvdDsiIC8+PC9maWx0ZXJzPjxyYW5nZXMgLz48c29ydHM+PHNvcnQgZmllbGQ9InB1Ymxpc2hlZCIgb3JkZXI9ImRlc2MiIC8+PC9zb3J0cz48cGVyc2lzdHM+PHBlcnNpc3QgbmFtZT0icmFuZ2V0eXBlIiB2YWx1ZT0icHVibGlzaGVkZGF0ZSIgLz48L3BlcnNpc3RzPjwvc2VhcmNoPg==" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <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>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Comprehensive Engine Testing Methodologies for Hydrogen Internal Combustion Engine Validation with Combustion &amp; Performance Evaluation Techniques</title>
      <link>https://trid.trb.org/View/2761873</link>
      <description><![CDATA[Validation of hydrogen-fuelled internal combustion engine (H2 ICE) is critical to assess its feasibility as sustainable transportation with zero carbon emissions. This experimental analysis conducted on Ashok Leyland’s 6cylinder 2V engine to evaluate the engine performance & durability with hydrogen fuel. Combustion behaviour of hydrogen ICE needs to be closely monitored during continuous operation of validation testing, due to its unique properties compared to other conventional fuels. During engine run, a pre-ignition source can cause knock event leading to instant failure of critical parts like piston assembly, spark plug, liner, valves & cylinder head. Also, hotspots inside IMF leads to backfire affecting the air intake & fuel injection assembly. This study emphasizes the significance of precise instrumentation of thermocouples across engine on cylinder head, intake manifold & exhaust manifold, to detect performance detoriation and combustion abnormalities causing knocking & backfire. Crankcase ventilation system design plays a critical role in evacuating the blowby gas from engine block. This paper explains methodology to measure the moisture condensation from blowby gas, as it leads to oil emulsification. Experimental data shows variation in inlet manifold air temperature directly impacts engine power as H2 ICE operates at higher stoichiometric ratio. Increase in air intake temperature from turbo compressor out is a result of barometric temperature and pressure variation. This measurement is critical to understand the engine performance variation in real-time operating condition. Hence validation of H2 ICE necessitates a specialized instrumentation during testing to monitor the performance parameters and hardware detoriation. This research provides critical insights into the procedural adaptations required for H2 ICE testing and validation by integrating frugal instrumentation with experimental analysis. This study offers a robust framework for assessing engine performance, reducing operational risks, and ensuring test results reliability. These findings contribute to the design & development of hydrogen-fuelled engines, facilitating their adoption as a sustainable alternative for transportation while addressing durability, emissions, and regulatory compliance challenges.]]></description>
      <pubDate>Wed, 19 Aug 2026 13:48:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/2761873</guid>
    </item>
    <item>
      <title>Misfires Detection in Bi-Fuel Engines – A Brief Note</title>
      <link>https://trid.trb.org/View/2761775</link>
      <description><![CDATA[With the expansion of compressed natural gas (CNG) filling station in India, bi-fuel vehicles are gaining popularity in recent times. Bi-fuel engine runs on more than one fuel, say in both CNG and petrol. Hence, the engine must be optimized in both the fuel modes for performance and emissions. However, due to the inherent differences in combustion characteristics: ignition dynamics and fuel properties, they pose a significant challenge in case of detection of misfires. Misfires are caused because of faulty injection systems and ignition systems and incorrect fuel mixture. Accurate detection is essential as misfires deteriorate the catalysts performance and may impacts emission. Misfires (or engine roughness) is calculated from engine crankshaft speed signal. In this study, the effectiveness of crankshaft-based misfires detection method, comparison of misfire signals magnitude in bi-fuel modes and practices developed for accurate detection of misfires is presented.]]></description>
      <pubDate>Wed, 19 Aug 2026 13:48:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/2761775</guid>
    </item>
    <item>
      <title>Development of High BMEP Natural Gas Engine with Knock Mitigation</title>
      <link>https://trid.trb.org/View/2761771</link>
      <description><![CDATA[The stringent emission norms over the past few years have driven the need to use low-carbon fuels and after treatment technology. Natural gas is a suitable alternative to diesel heavy-duty engines for power generation and transportation sectors. Stoichiometric combustion offers the advantages of complete combustion and low carbon dioxide emissions. Turbocharging and cooled exhaust gas recirculation (EGR) technology enhances the power density along with reduced exhaust emissions. However, there are several constraints in the operation of natural gas spark ignition engine such as exhaust gas temperature limit of 780 °C, sufficient before turbine pressure for EGR drivability, boost pressure, peak cylinder pressure limit and knocking. These limits coulld restrict the engine BMEP (brake mean effective pressure). In the present study, tests were conducted on a V12, 24 liters, heavy duty natural gas fuelled spark ignition engine (600 HP) with different EGR and turbocharger configurations to achieve 16 bar BMEP without abnormal combustion. Considering the maximum exhaust temperature limit of 780 °C of exhaust system, minimal engine hardware changes were done to ensure less complexity, cost-effective engine development with robust design. The turbine trim was decreased from 89% to 84% to avoid excessive high before turbine backpressure, backflow of residual gases into cylinder and knock possibility. EGR system optimization with mixer enhanced EGR mixing and distribution in all cylinders that improved BSFC by 3%. During knock calibration, the offset to base ignition timing was used for individual cylinders to mitigate knock. Endurance trial of 100 hours was carried out to validate the reliability of engine design and calibration, and no issues were detected. The developed engine is the highest BMEP V12 engine in its segment in India using stoichiometric combustion with cooled EGR and three-way catalyst. The engine is certified with latest Indian CPCB IV+ emissions norms.]]></description>
      <pubDate>Wed, 19 Aug 2026 13:48:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2761771</guid>
    </item>
    <item>
      <title>Technologies and Strategies for High Brake Thermal Efficiency Gasoline Engine to Meet the Future CO2 Emission Targets in India</title>
      <link>https://trid.trb.org/View/2761765</link>
      <description><![CDATA[The Indian automobile industry is experiencing a significant shift, propelled by environmental necessities and national climate obligations set at the CoP26 summit, aiming for a 45% decrease in CO2 emissions by 2030 and reaching carbon neutrality by 2070 [1]. Transportation continues to be a significant source of air pollution; consequently, India is enhancing its regulatory frameworks with BS VI Stage 2 regulations, CAFE Phase III norms set for 2027, and CAFE Phase IV by 2032 [2]. Furthermore, the transition from MIDC to WLTP driving cycle is meant to increase the accuracy of the efficiency and emissions assessments [2]. To comply to these upcoming regulations, the automotive industry is moving toward producing high efficiency engines in India. A naturally aspirated (NA) 1.5L, 4-cylinder inline gasoline engine was selected from Indian market for this study. Maximum Brake Thermal Efficiency (BTE) of this engine is around 37%. Assessment of new technologies were performed by implementing them stepwise to see the impact on BTE. A well calibrated 1D GT-SUITE model was considered from FEV database to perform the simulation-based approach to increase the BTE by improving the stroke/bore (s/B) ratio, increasing the compression ratio, implementing Atkinson cycle with variable valve timing (VVT) / variable valve lift (VVL) optimization, and charge motion refinement for optimal in-cylinder combustion. Low temperature cooled EGR (TEGR < 70°C) and pre-catalyst pick-up distributed EGR strategies were simulated to improve the combustion stability and pumping loss for BTE improvement. Friction losses were further minimized by implementing the polished surfaces, electrification of auxiliary components, and other advanced surface treatments. Advanced technologies including Dual Port Fuel Injection (Dual PFI) system, high energy ignition system with thermal swing coatings, and system designed to operate with highly diluted mixture are required to achieve maximum BTE. These technologies would also be explored in this study. This paper also covers the rivals' restrictions put on engine geometry and number of cylinders concerning possible max. BTE level with which the engine can achieve. With the completed study, the efficiency step walk document indicated BTE improvement from each technology step to achieve a target max. BTE for the engine.]]></description>
      <pubDate>Wed, 19 Aug 2026 13:48:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2761765</guid>
    </item>
    <item>
      <title>Performance Optimization of 2 Cylinder Flex Fuel Engine for Small Commercial Vehicle – A STEP TOWARDS SUSTAINABILITY</title>
      <link>https://trid.trb.org/View/2761766</link>
      <description><![CDATA[Increasing ethanol blending in gasoline is significant from both financial (reducing dependency on crude oil) and sustainability (overall CO2 reduction) points of view. Flex Fuel is an ethanol-gasoline blend containing ethanol ranging from 20% to 85%. Flex Fuel emerges as an exceptionally advantageous solution, adeptly addressing the shortcomings associated with both gasoline and ethanol. Performance optimization of Flex Fuel is a major challenge as fuel properties like knocking tendency, calorific value, vapour pressure, latent heat, and stoichiometric air-fuel ratio change with varying ethanol content. This paper elaborates on the experimental results of trials conducted for optimizing engine performance with Flex Fuel for a 2-cylinder engine used in a small commercial vehicle. To derive maximum benefit from the higher octane rating of E85, the compression ratio is increased, while ignition timing is optimized to avoid knocking with E20 fuel. For intermediate blends, ignition timing is suitably interpolated. Fuel injection pressure is increased to address the higher fuel flow requirement, and a fuel heater is added to address cold starts with E85 fuel. Ethanol content detection is done through software, and by suitable interpolation, fuelling and ignition timing are optimized for the entire range of Flex Fuel in a single calibration file. Engine performance with E20 & E93 fuel is optimized considering all mechanical and thermal limits of the engine through various iterations. The experimental results are analysed using the first principle method.]]></description>
      <pubDate>Wed, 19 Aug 2026 13:48:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2761766</guid>
    </item>
    <item>
      <title>NOx Formation Characteristics of Lean Hydrogen Combustion: From 0D Analysis to Comprehensive 3D-CFD Engine Investigations</title>
      <link>https://trid.trb.org/View/2724703</link>
      <description><![CDATA[The transition toward climate-neutral transportation requires powertrain concepts that combine high efficiency with low pollutant emissions. In this context, hydrogen-fueled internal combustion engines represent a promising solution when hydrogen is produced from renewable energy sources. Owing to its specific molecular properties, hydrogen offers new possibilities for influencing and optimizing the combustion process and reducing the emission formation. This paper presents a numerical approach for characterizing the NOx formation in a single-cylinder research engine equipped with port fuel injection and a passive pre-chamber ignition system. The single-cylinder is operated over a wide range of engine loads and speeds, covering air-to-fuel ratios from ?=1.5 to 2.5 and achieving up to 23 bar indicated mean effective pressure. The study focuses on the influence of engine load and mixture composition on NOx emissions. A dedicated look-up table approach in combination with several reaction parameters based on the extended Zeldovich mechanism are evaluated through comparison with experimental data. Furthermore, multiple sampling positions within the CFD mesh are examined. The simulations reproduce measured trends across variations in load and air-to-fuel ratio with good accuracy. At high load and ?=1.5, NOx emissions of up to 6000 ppm are produced, decreasing exponentially with increasing excess air. Finally, potential NOx reduction strategies for the single-cylinder are examined. While influencing the mixture homogenization shows limited effectiveness, temperature-based actions prove to be more effective. Among the investigated approaches, a Miller intake valve strategy yields the largest benefit, achieving approximately 10% NOx reduction by lowering end-of-compression temperatures and increasing residual gas dilution under otherwise identical operating conditions.]]></description>
      <pubDate>Tue, 21 Jul 2026 11:41:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2724703</guid>
    </item>
    <item>
      <title>Study on Diesel-Methanol Non-Premixed Combustion Characteristics of a Marine Dual-Fuel Engine at Different Methanol Substitution Rate</title>
      <link>https://trid.trb.org/View/2732223</link>
      <description><![CDATA[Methanol use in marine engines has the potential to reduce nitrogen oxide                     emissions, particulates, and greenhouse gas emissions. A turbocharged                     four-stroke marine diesel powerplant was converted to run as a double-DI (direct                     injection) diesel-methanol hybrid engine. Experimental studies using a                     non-premixed combustion scheme showed that higher methanol substitution ratios                     (MSR) led to increased peak heat release rates. The combustion process displayed                     distinctive two-phase behaviors. Increasing MSR caused retarded ignition timing,                     shortened combustion duration, and improved thermal efficiency. Combustion                     stability was significantly improved at higher MSR. Emissions results showed                         NOX and HC were increased in proportion to MSR, whilst                     particulate emissions and CO concentrations were inversely reduced. Methanol                     enrichment was found to enhance NOX and HC formation processes but                     also accelerate soot particulate decomposition and CO oxidation mechanisms.]]></description>
      <pubDate>Tue, 21 Jul 2026 11:36:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2732223</guid>
    </item>
    <item>
      <title>Effects of Engine Geometries on the Combustion Characteristics of a Heavy-Duty Hydrogen Spark-Ignition Engine</title>
      <link>https://trid.trb.org/View/2717287</link>
      <description><![CDATA[For heavy-duty applications, hydrogen (H2) internal combustion engines offer a practical solution for future transportation. However, the influence of cylinder head flow characteristics and piston geometry on lean H2 combustion remains insufficiently understood. This study presents a comprehensive computational investigation of three engine configurations characterized by distinct in-cylinder flow dynamics: mild swirl and tumble (Engine a), strong tumble (Engine b), and strong swirl (Engine c). High-fidelity three-dimensional computational fluid dynamics simulations were performed for both port-fuel injection (PFI) and direct injection (DI) strategies. The impact of piston geometry was evaluated by comparing the baseline piston with a flat piston, while the spark timing was optimized to achieve favorable combustion phasing. Combustion and NOx formation were modeled using a G-equation-based combustion framework incorporating diffusive-thermal instability effects and a validated in-house H2 chemical mechanism. Turbulence-flame interactions were further characterized using Borghi-Peters diagrams. Under PFI operation, the strong-tumble configuration (Engine b) generated the highest turbulent kinetic energy (TKE), resulting in faster flame propagation, more advanced combustion phasing, and improved thermal efficiency. The flat piston further enhanced efficiency by reducing mixture confinement within piston-induced recirculation zones. Under DI operation, H2 injection significantly increased turbulence intensity, and a flat piston promoted higher TKE near spark timing in Engines b and c by reducing mixture-wall interaction, leading to faster combustion compared with the baseline piston. In contrast, the original piston produced higher TKE within the piston bowl in Engine a due to stronger recirculation. Additionally, the strong-tumble configuration achieved the most homogeneous mixture distribution under DI conditions. These results demonstrate that in-cylinder flow structure, piston geometry, and DI injection strongly affect turbulence generation, mixture formation, and combustion performance. The strong-tumble configuration shows the greatest potential for achieving high thermal efficiency with controlled emissions in lean H2 spark ignition engines.]]></description>
      <pubDate>Tue, 23 Jun 2026 10:34:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2717287</guid>
    </item>
    <item>
      <title>Predictive Modelling of NOx and Unburned Hydrogen Emissions in a Direct-Injection Hydrogen Spark-Ignition Engine</title>
      <link>https://trid.trb.org/View/2717249</link>
      <description><![CDATA[Hydrogen is emerging as a compelling energy carrier for future transportation due to its potential to enable fully decarbonised operation and near-zero tailpipe pollutant emissions. Realising this potential in reciprocating internal combustion engines requires a detailed understanding of the complex interactions governing hydrogen combustion and emissions formation. In this context, physics-based reduced-order emission predictive modelling offers a powerful means to accelerate the development and optimisation of hydrogen-fuelled engines by enabling rapid evaluation of operating strategies without the need for extensive experimental campaigns. This study investigates the simulation of nitrogen oxides (NOx) and unburned hydrogen (uH2) emissions from a 0.5L spark-ignition direct injection single-cylinder research engine within a 1D-0D simulation approach. For NOx prediction, a simplified kinetic mechanism is coupled with both a 0D two-zone combustion model and a thermal multi-zone in-cylinder representation, enabling assessment of the need to account for temperature stratification for accurate prediction. For uH2 emissions, phenomenological sub-models describing flame wall quenching and top-land crevice mechanisms are implemented and calibrated to capture the dominant sources of hydrogen escape during combustion.The models are validated against an experimental dataset spanning a wide range of engine conditions, including variations in engine load, relative air–fuel ratio from stoichiometric to ultra-lean combustion, dilution via exhaust gas recirculation, and spark timing. The comparison highlights the models' ability to reproduce observed physical trends across different engine operating conditions for both NOx and uH2. Regarding NOx emissions, the accounting of temperature stratification with the multi-zone model enables more accurate predictions of trends and absolute values. The uH2 model provides fundamental insights into hydrogen engine flame propagation by highlighting the need for flame propagation in the top-land crevice at richer ? to reproduce observed trends. Overall, the study provides insights into both hydrogen-specific emission mechanisms and key modelling requirements for accurate pollutant simulation in hydrogen engines.]]></description>
      <pubDate>Tue, 23 Jun 2026 10:34:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2717249</guid>
    </item>
    <item>
      <title>A Holistic CFD Methodology for Full- and Multi-Cycle Simulation of Hydrogen Direct-Injection Internal Combustion Engines</title>
      <link>https://trid.trb.org/View/2717244</link>
      <description><![CDATA[Hydrogen is emerging as a viable energy carrier for the decarbonization of internal combustion engines (ICEs), representing a necessary step toward the long-term sustainability of this technology. In particular, hydrogen direct injection (DI) operation is receiving increased attention due to its inherent advantages over port fuel injection (PFI), such as reduced risks of abnormal combustion, higher specific power, and improved thermal efficiency. However, the mixture preparation process in DI operation generally leads to a stratified charge, especially under intermediate-to-late injection strategies, which in turn strongly affects ignition, combustion performance, and engine-out emissions. Therefore, investigating mixture formation, its key influencing parameters, and the resulting effects on the combustion process is essential for the proper design and optimization of hydrogen-fuelled DI ICEs. In this context, computational fluid dynamics (CFD) emerges as a powerful tool to address this research gap. Nevertheless, the numerical simulation of hydrogen DI ICEs presents several challenges, mainly related to the high pressure ratios across the injector nozzle, which generate under-expanded hydrogen jets with complex shock structures, as well as to the combustion behaviour of lean air–hydrogen mixtures characterized by thermo-diffusive instabilities. Consequently, the development of a high-fidelity and computationally efficient CFD methodology is a key requirement. In this work, a retrofitted single-cylinder engine (SCE) equipped with a hollow-cone injector is simulated over the entire engine cycle, considering operation under a moderately late DI strategy. First, the proposed 3D-CFD methodology is validated against the engine experimental data to assess its predictivity. The same operating condition is then investigated through multi-cycle simulations to evaluate numerical stability and analyse convergence behaviour. The results show that the air–hydrogen mixture is highly stratified at ignition timing, yet the methodology accurately captures the in-cylinder pressure and heat release rate evolution, also across multiple engine cycles.]]></description>
      <pubDate>Tue, 23 Jun 2026 10:34:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2717244</guid>
    </item>
    <item>
      <title>Effect of Pre-Chamber Geometry on Methanol Cold-Start Combustion in an SI Engine</title>
      <link>https://trid.trb.org/View/2701251</link>
      <description><![CDATA[Vehicle pollutant emissions are a major challenge in the development of internal combustion engines. To meet increasingly strict regulations, the automotive sector is exploring alternative fuels and lean-burn strategies. Methanol is gaining importance as a carbon-neutral fuel due to advances in green production technologies. Methanol, despite its potential for renewable production, faces severe limitations due to its inherent poor cold-start performance with conventional ignition systems. In this context, the present study aims to investigate the influence of pre-chamber ignition on cold-start combustion by using high-speed optical diagnostics to visualize flame propagation while simultaneously measuring in-cylinder pressure and engine performance. A major result concerns the significant cyclic variability of conventional spark ignition (SI) under cold-start conditions, which exhibits significant cyclic variability. Instead, passive pre-chamber ignition significantly enhances cold-start combustion stability, lowering CoV IMEP to below 3% at ? = 1.0 and sustaining stability under 5% even in ultra-lean conditions (? = 1.6), where conventional SI operation fails. Flame visualization quantitatively confirms that this stability stems from distributed, multi-point ignition, which accelerates initial flame propagation by 3-4x compared to SI. These findings demonstrate that pre-chamber ignition can effectively overcome the traditional "cold-start" problem for methanol, enabling stable combustion from the first cycles. This provides an invaluable dataset for CFD model validation, as it captures a highly stable combustion process largely independent of the adverse thermal boundary conditions typical of cold start, thereby simplifying the modeling challenge.]]></description>
      <pubDate>Tue, 12 May 2026 09:23:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/2701251</guid>
    </item>
    <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>Investigation of In-Cylinder Cycle-to-Cycle Variation Using PIV, LIF and RANS Simulation</title>
      <link>https://trid.trb.org/View/2692282</link>
      <description><![CDATA[Cycle-to-cycle variation (CCV) of combustion is an issue that inevitably arises in internal combustion engines. There is a need to clarify and improve the situation, as well as predict it using computational fluid dynamics (CFD). This study involved carrying out experimental analyses of the factors that cause combustion cycle fluctuations, as well as predicting the CCV of gas flow using RANS. To elucidate the CCV in gas flow and combustion within gasoline engine, simultaneous TR-PIV, PLIF and direct-photography of flame propagation were performed using an optical single-cylinder engine, CCV prediction model for gas flow using RANS was verified. The results revealed the following: The variation in the equivalence ratio per cycle has little effect on initial combustion but does influence IMEP. Evaluating the laminar flame speed, SL and turbulent flame speed, ST as factors determining initial combustion revealed almost no correlation with SL, while moderate correlations were observed between ST and CA10. The position of the tumble vortex center at ignition timing was found to be critical; the vortex center position most favorable for advancing combustion timing was located to diagonally below the spark plug. The angular velocity at the center of the tumble vortex in the ensemble averaged flow significantly affected the turbulence kinetic energy (TKE) at the ignition timing, initial flame propagation speed, and CA10 phase. A model predicting cycle fluctuations during non-combustion was developed and verified against experiments. The CCV predicted using the spatial-based model reproduced the experimental CCV trends.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692282</guid>
    </item>
    <item>
      <title>A Comparative Study of Combustion Stability Improvement via Prolonged Discharge Duration under Engine Idling Conditions</title>
      <link>https://trid.trb.org/View/2692272</link>
      <description><![CDATA[Proper control over combustion and emission characteristics under engine idling conditions remains to be challenging, especially when engine block temperature is low. A specially designed common-coil pack was demonstrated to improve engine idling stability in previous SAE congress. In this paper, the progress on further development of the ignition system was reported with improved system stability and enhanced ignition performances. The impact of the prolonged discharge duration on the combustion stability was investigated on a turbocharged 4-cylinder production engine, with special attention to cylinder-by-cylinder variation under cold and hot engine block temperatures. It is observed that a prolonged discharge duration can reduce both cycle-to-cycle and cylinder-to-cylinder variations significantly. Especially under cold engine block temperature conditions, prolonged discharge duration together with advanced spark timing can increase engine load and reduce carbon monoxide emissions effectively. Then, the total energy consumption of the ignition system under various operation conditions were calculated and compared with the engine power gained by the ignition system.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692272</guid>
    </item>
    <item>
      <title>The Impact of Various Renewable Hydrocarbons on Performance and Emissions in a Super Lean Burn Engine</title>
      <link>https://trid.trb.org/View/2692268</link>
      <description><![CDATA[Compared to regular fuels, biofuels can play a key role as low-carbon transitional energy sources for ICE vehicles as the fleet moves towards increasing electrification. Blending of ethanol plays a key role in enhancing the anti-knock properties of the fuel and also allows renewable hydrocarbons (such as bio-naphtha) to be incorporated into the blend whilst maintaining an acceptable overall fuel quality.Super lean burn ICE technology with ? between 2 and 3 can lead to enhanced fuel economy and reduced NOx emissions. The Toyota prototype engine used to generate data for this project injects most of the fuel in PFI mode to generate a homogeneous super-lean charge in the cylinder, but just before spark ignition the DI injector sprays a small amount of fuel towards the spark plug to create a richer charge near the spark plug to promote flame kernel development.Various fuel formulations with high biofuel content were tested in both conventional and super lean burn engines. Certain fuel compositions were formulated with faster burning components such as ethyl benzene. The super lean burn engine showed a clear link between faster combustion and minimization of unburned fuel losses, thereby resulting in a further efficiency benefit. The effect of fuel composition on particulate emissions was more complex: although the conventional engine emitted higher particulate numbers (PN) when operating on fuels with a higher content of heavier aromatics (as might be predicted from standard particulate index approaches), the super lean burn engine suggests that additional factors are at play which are discussed in the paper.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692268</guid>
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