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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=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" rel="self" type="application/rss+xml" />
    <description></description>
    <language>en-us</language>
    <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>
    <image>
      <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>Combustion characteristics optimization and thermal efficiency enhancement by stratified charge of hydrogen direct injection for argon power cycle hydrogen engine</title>
      <link>https://trid.trb.org/View/2417571</link>
      <description><![CDATA[Argon power cycle hydrogen engine is a novel approach to increasing the thermal efficiency of hydrogen engines while achieving zero CO₂ emissions. This paper presents a combination of experiments and simulations used to examine the effects of hydrogen direct injection on the combustion characteristics and thermal efficiency of argon power cycle engines. The results of the study indicate that, in comparison to port hydrogen injection, hydrogen direct injection produces a delay of CA50 exceeding 12.36°CA at an engine speed of 1000 r/min. This delay optimizes combustion and diminishes knock intensity to below 0.1 MPa by creating a stratified mixture, which in turn decelerates the combustion rate. Through adjusting hydrogen direct injection timing and incorporating super lean combustion, a maximum gross indicated thermal efficiency of 53.72% is achieved. By optimizing the first injection timing, the second injection timing, and the second injection ratio, dual hydrogen direct injection can significantly suppress knock and increase thermal efficiency compared with original single hydrogen injection conditions.]]></description>
      <pubDate>Wed, 09 Oct 2024 15:17:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/2417571</guid>
    </item>
    <item>
      <title>Combustion in Direct Injection Diesel in Comparison with Controlled Combustion Stratified Charge Engines</title>
      <link>https://trid.trb.org/View/1786469</link>
      <description><![CDATA[Controlled combustion in direct injection stratified charge engines can be achieved by the use of impinging jets for injection as well as for ignition, in association with a close-loop, electronic control system. Upon the description of the method of approach required for the design of a control strategy, illustrated by application to a conventional diesel engine, salient features of novel concepts for direct injection stratified charge engines are presented.]]></description>
      <pubDate>Sun, 06 Oct 2024 16:36:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1786469</guid>
    </item>
    <item>
      <title>Analysis of a Stratified Charging Concept for High-Performance Two-Stroke Engines</title>
      <link>https://trid.trb.org/View/1786570</link>
      <description><![CDATA[This paper presents the results and conclusions from a conceptual design study for a stratified charging concept. The stratified charging engine has a displacement of 64 cm³ and a four-port design with reed valves at two ports to control the bypass air. During the intake stroke of the engine, bypass air is sucked into the transfer ports to purge the air-fuel mixture present in the ports from the previous stroke back into the crankcase. This fills the transfer ports near the exhaust with pure air at the beginning of the scavenging stroke. During scavenging, the bypass air is ejected in the cylinder, shielding the exhaust against the fresh mixture coming from the ports on the intake side. This allows the hydrocarbon emissions to be reduced by over 40%. The conceptual design study is based on an analysis of the mixture short-circuiting mechanisms and CFD investigations of the scavenging flow with charge stratification.]]></description>
      <pubDate>Sun, 06 Oct 2024 16:36:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/1786570</guid>
    </item>
    <item>
      <title>The Influence of Dilution Composition and Temperature Upon a Stratified Charge Spark Ignition Engine</title>
      <link>https://trid.trb.org/View/1788000</link>
      <description><![CDATA[A thermodynamic model has been utilised in the analysis of a SI engine operating with a divided charge stratification system. Such a charge stratification system divides the cylinder charge into two distinct regions: a combustible charge around the spark plug and a dilution charge beyond this. The model has been utilised to reveal differing effects of both dilution charge composition (EGR or air) and temperature upon the performance and emissions of such a stratified charge engine.]]></description>
      <pubDate>Sun, 30 Jun 2024 16:02:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1788000</guid>
    </item>
    <item>
      <title>Multiple-objective optimization of direct dual fuel stratification (DDFS) combustion at different loads</title>
      <link>https://trid.trb.org/View/2344481</link>
      <description><![CDATA[The operating parameters of the direct dual fuel stratification (DDFS) strategy in a heavy-duty engine are optimized across a full load range by utilizing a combination of three-dimensional computational fluid dynamics simulation and genetic algorithm. After obtaining the optimized results, sensitivity analyses were conducted on the operating parameters at various loads using the Pearson method. The results show that the DDFS strategy can attain stable and efficient combustion across the entire full-load range after optimization. At low-to-medium loads, the engine’s performance is predominantly influenced by initial operating parameters, while both initial and injection parameters play critical roles at high loads. The sensitivities of operating parameters increase as load increases, with the operating parameters having higher sensitivities having more concentrated distributions, while those with lower sensitivities have more dispersed distributions. The optimal conditions for low-to-medium load combustion generally involve a premixed-dominated combustion regime with some degree of reactivity stratification, which is strongly influenced by charge thermodynamics. Increasing the proportion of high-reactivity diesel fuel can improve combustion efficiency and stability, particularly under low-load conditions. Under high-load conditions, the optimal combustion strategy involves using a significant amount of direct-injected gasoline to achieve a more distinct stratified and diffusion combustion regime, which helps mitigate excessive heat release rates. However, this approach may result in reduced fuel economy compared to the optimal strategy for low-to-medium loads. As a consequence, the role of charge thermodynamics becomes less significant while the injection strategy becomes more critical for achieving optimal combustion at high loads.]]></description>
      <pubDate>Mon, 15 Apr 2024 08:38:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2344481</guid>
    </item>
    <item>
      <title>Effects of Fuel Properties on the Mixture Formation under the Stratified-Charge Combustion Condition of Direct-Injection Gasoline Engine</title>
      <link>https://trid.trb.org/View/1791641</link>
      <description><![CDATA[In order to clarify the effects of fuel properties on the mixture formation under the stratified-charge combustion condition in a direct-injection gasoline engine, fuel concentration measurement in the vicinity of the ignition plug was established using a fast response flame Ionization detector (FID). A single-cylinder direct-injection gasoline engine, for which a Toyota D-4 engine was modified, was used. Paraffin, olefin, naphthene and ether having a boiling point of approximately 50°C, and paraffin, olefin and an aromatic compound having a boiling point of approximately 100°C were used as candidate fuels. As a result, the effect of boiling point on the mixture formation was clarified.]]></description>
      <pubDate>Thu, 07 Dec 2023 14:00:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1791641</guid>
    </item>
    <item>
      <title>Effects of Octane Number on Stratified Charge Combustion in a Direct Injection Gasoline Engine</title>
      <link>https://trid.trb.org/View/1790878</link>
      <description><![CDATA[The effects of octane number on stratified charge combustion were investigated with single cylinder direct injection gasoline engine. Two tests were conducted. First, combustion characteristics of stratified charge combustion were studied by changing fuel octane number. Second, auto-ignition characteristics of stratified charge combustion were compared with that of homogeneous charge combustion by changing fuel component. Three types of fuels were used to change octane number and fuel component. They were single-component fuel, multi-component fuel and refinery feedstock, Unique combustion characteristics concerning octane number was found on stratified charge combustion. The increase of indicated thermal efficiency and decrease of unburned hydrocarbon were observed as octane number decreased. The difference of octane number influence between stratified charge combustion and homogeneous charge combustion was discussed.]]></description>
      <pubDate>Thu, 22 Jun 2023 09:49:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1790878</guid>
    </item>
    <item>
      <title>Optical characterization of stratified-premixed natural gas direct-injection combustion regimes</title>
      <link>https://trid.trb.org/View/2157307</link>
      <description><![CDATA[Gaseous fuels for heavy-duty internal combustion engines provide inherent advantages for reducing CO₂, particulate matter (PM), and NOₓ emissions. Pilot-ignited direct-injected NG (PIDING) combustion uses a small pilot injection of diesel to ignite a late-cycle main direct injection of NG, resulting in significant reduction of unburned CH₄ emissions relative to port-injected NG. Previous works have identified NG premixing as a critical parameter establishing indicated efficiency and emissions performance. To this end, a recent experimental investigation using a metal engine identified six general regimes of PIDING heat release and emissions behavior arising from variation of NG stratification through control of relative injection timing (RIT) of the NG with respect to the pilot diesel. The objective of the current work is to provide comprehensive description of in-cylinder fuel mixing of direct injected gaseous fuel and its impacts on combustion and pollutant formation processes for stratified PIDING combustion. In-cylinder imaging of OH*-chemiluminescence (OH*-CL) and PM (700 nm), and measurement of local concentration of fuel is considered for 11 different RIT, representing 5 regimes of stratified PIDING combustion (performed with Pᵢₙⱼ = 22.0 MPa and ϕ=0.63). The magnitude and cyclic variability of premixed fuel concentration near the bowl wall provides direct experimental validation of thermodynamic metrics (RITₚᵣₑₘᵢₓ, SOIng,trans, RIT*) that describe the fuel-air mixture state of all 5 regimes of PIDING combustion. The local fuel concentration develops non-monotonically and is a function of RIT. High indicated efficiency and low CH₄ emissions previously observed for stratified-premixed PIDING combustion in previous (non-optical) investigations are due to: (i) very rapid reaction zone growth (>45 m/s) and (ii) more distributed early reaction zones when overlapping pilot and NG injections cause partial pilot quenching. These results connect and extend the findings of previous investigations and guide the future strategic implementation of NG stratification for improved combustion and emissions performance.]]></description>
      <pubDate>Thu, 01 Jun 2023 09:32:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/2157307</guid>
    </item>
    <item>
      <title>Effects of stratification and charge cooling on combustion in a gasoline direct-injection compression ignition (GDCI) engine</title>
      <link>https://trid.trb.org/View/2120686</link>
      <description><![CDATA[With the development of low temperature engine combustion strategies, performance of gasoline-type fuels under compression ignition conditions has attracted extensive research interest. Meanwhile, for the sake of co-optimization of engines and fuels for future ground transportation, identification and evaluation of general fuel properties should be a core research priority instead of endless testing of specific fuels. In this study, the roles of fuel octane sensitivity in characterizing the ignition performance of gasoline surrogates have been systematically investigated under typical gasoline direct ignition compression ignition (GDCI) engine conditions using 3D combustion CFD simulation, especially considering the subsequent in-cylinder charge stratification and charge cooling. Two different operating conditions, high boost pressure low boost temperature (beyond-RON) case and low boost pressure high boost temperature (beyond-MON) case, were considered. By comparing with the previous zero-dimensional chemical kinetic study of gasoline surrogates in advanced compression ignition (ACI) engines, the effects of stratification and charge cooling on the combustion processes are investigated. It is found that different fuel octane sensitivities lead to slight difference in equivalence ratio stratification and charge cooling due to differences in volatility. However, fuel reactivity is still the more dominant factor than the stratification and charge cooling effects in determining combustion phasing. The present results help to justify the P-T domain framework for engine autoignition analysis of overlapping pressure-temperature trajectory with ignition delay iso-contour. The results also provide useful guidance to the understanding of GCI combustion process, and to the evaluation of controlling fuel properties and the selection of alternative fuels in GCI engines.]]></description>
      <pubDate>Mon, 27 Mar 2023 15:10:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/2120686</guid>
    </item>
    <item>
      <title>Heat release rate and emissions regimes of stratified pilot-ignited direct-injection natural gas combustion</title>
      <link>https://trid.trb.org/View/2108002</link>
      <description><![CDATA[Natural gas (NG) is an attractive fuel for heavy-duty internal combustion engines because of its potential for reduced CO₂, particulate, and NOₓ emissions and lower cost of ownership. Pilot-ignited direct-injected NG (PIDING) combustion uses a small pilot injection of diesel to ignite a main direct injection of NG. Recent studies have demonstrated that increased NG premixing is a viable strategy to increase PIDING indicated efficiency and further reduce particulate and CO emissions while maintaining low CH₄ emissions. However, it is unclear how the combustion strategies relate to one another, or where they fit within the continuum of NG stratification. The objective of this work is to present a systematic evaluation of pilot combustion, NG combustion, and emissions behavior of stratified-premixed PIDING combustion modes that span from fully-premixed to non-premixed conditions. A sweep of the relative injection timing, RIT, of NG and pilot diesel was performed in a heavy-duty PIDING engine with Pᵢₙⱼ = 140–220 bar, ϕg = 0.47–0.71, and a constant NG energy fraction of 94%. Apparent heat release rate and emissions analyses identified interactions between the pilot fuel and NG, and qualitatively characterized the impact of NG stratification on combustion and emissions. Changes in the RIT resulted in six distinct PIDING combustion regimes, for all considered injection pressures and equivalence ratios: (i) RIT-insensitive premixed, (ii) stratified-premixed (early-cycle injection), (iii) NG jet impingement transition, (iv) stratified-premixed (late-cycle injection), (v) variable premixed fraction, and (vi) minimally-premixed. Parametric definitions for the bounds of each regime of combustion were valid for the wide range of Pᵢₙⱼ and ϕg investigated, and are expected to be relevant for other PIDING engines, as previously identified regimes agree with those identified here. This conceptual framework encompasses and validates the findings of previous stratified PIDING investigations, including optimal ranges of operation that provide significantly increased efficiency and lower emissions of incomplete combustion products.]]></description>
      <pubDate>Thu, 23 Mar 2023 10:20:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/2108002</guid>
    </item>
    <item>
      <title>Investigations into the Effects of Thermal and Compositional Stratification on HCCI Combustion – Part I: Metal Engine Results</title>
      <link>https://trid.trb.org/View/1818058</link>
      <description><![CDATA[This study utilized a 4-valve engine under HCCI combustion conditions. Each side of the split intake port was fed independently with different temperatures and reactant compositions. Therefore, two stratification approaches were enabled: thermal stratification and compositional stratification. Argon was used as a diluent to achieve higher temperatures and stratify the in-cylinder temperature indirectly via a stratification of the ratio of specific heats (γ = cₚ/cᵥ). Tests covered five operating conditions (including two values of A/F and two loads) and four stratification cases (including one homogeneous and three with varied temperature and composition). Stratifications of the reactants were expected to affect the combustion control and upper load limit through the combustion phasing and duration, respectively. The two approaches to stratification both affect thermal unmixedness. Since argon has a high γ, it reached higher temperatures through the compression stroke [1]. Therefore, the result of the stratified composition cases was an indirect thermal stratification. Over all test conditions, the direct thermal stratification had no noticeable effect on the combustion duration or phasing within the limits of the experiment (a thermal difference of 45°C in the reactant gas mixtures, measured at the valve stems). However, the argon stratification case produced indirect thermal stratifications of sufficient magnitude to keep a constant combustion phasing with a mass-averaged intake temperature up to 14°C lower than the fully homogeneous case. For a given combustion phasing, it also increased the combustion duration by approximately 2°CA (and thereby decreased the maximum pressure rise rate by 20 – 40%). The combined thermally and compositionally stratified case had the same combustion phasing effect (to a smaller degree), and the same combustion duration effect (to a slightly larger degree).]]></description>
      <pubDate>Mon, 24 Oct 2022 10:22:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1818058</guid>
    </item>
    <item>
      <title>A comparative study of gasoline skeletal mechanisms under partial fuel stratification conditions using large eddy simulations</title>
      <link>https://trid.trb.org/View/2017395</link>
      <description><![CDATA[Partial fuel stratification (PFS) is a low temperature combustion strategy that can alleviate high heat release rates of traditional low temperature combustion strategies by introducing compositional stratification in the combustion chamber using a split fuel injection strategy. In this study, a three-dimensional computational fluid dynamics (CFD) model with large eddy simulations and reduced detailed chemistry was used to model partial fuel stratification at three different stratified conditions. The double direct injection strategy injects 80% of the total fuel mass at −300 CAD aTDC and the remaining 20% of the fuel mass is injected at three different timings of −160, −50, −35 CAD to create low, medium, and high levels of compositional stratification, respectively. The PFS simulations were validated using experiments performed at Sandia National Laboratories on a single-cylinder research engine that operates on RD5-87, a research-grade E10 gasoline. The objective of this study is to compare the performance of three different reduced chemical kinetic mechanisms, namely SKM1, SKM2, and SKM3, at the three compositional stratification levels and identify the most suitable mechanism to reproduce the experimental data. Zero-dimensional chemical kinetic simulations were also performed to further understand differences in performance of the three reduced chemical kinetic mechanisms to explain variations in CFD derived heat release profiles. The modeling results indicate that SKM3 is the most suitable mechanism for partial fuel stratification modeling of research-grade gasoline. The results also show that the autoignition event progresses from the richer to the leaner compositional regions in the combustion chamber. Notably, the leaner regions that have less mass per unit volume, can contribute disproportionately more toward heat release as there are more cells at leaner equivalence ratio ranges. Overall, this study illuminates the underlying compositional stratification phenomena that control the heat release process in PFS combustion.]]></description>
      <pubDate>Mon, 24 Oct 2022 10:22:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2017395</guid>
    </item>
    <item>
      <title>Effect of Octane Rating and Charge Stratification on Combustion and Operating Range with DI PCCI Operation</title>
      <link>https://trid.trb.org/View/1810676</link>
      <description><![CDATA[A single cylinder engine has been run with direct-injection premixed charge compression ignition (PCCI) operation. The operation is fueled with primary reference fuels for a wide variety of injection timing and equivalence ratio to investigate the effect of charge stratification and octane rating on PCCI combustion. The test results showed that although the change of the injection timing can gain the high combustion efficiency for a wide range of equivalence ratio, the combustion phasing where the high combustion efficiency is accomplished is not varied only by changing the injection timings. Therefore, the only change of injection timings does not improve the thermal efficiency which is influenced by the combustion phasing. On the other hand, at the fixed compression ratio, inlet air temperature and so on, the octane rating is useful in altering the combustion phasing. The experiments in which the octane rating was changed demonstrated that for the lean air-fuel mixture which produces low NOₓ emission without EGR, the combustion phasing must be advanced to gain the better combustion efficiency at low load. By contrast, higher equivalence ratio allows the combustion phasing to be retarded with keeping high combustion efficiency.]]></description>
      <pubDate>Mon, 03 Oct 2022 09:16:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/1810676</guid>
    </item>
    <item>
      <title>Frozen Equilibrium and EGR Effects on Radical-Initiated H₂ Combustion Kinetics in Low-Compression D.I. Engines Using Pistons with Micro-Chambers</title>
      <link>https://trid.trb.org/View/1797463</link>
      <description><![CDATA[Using hydrogen as a fuel, this chemical-kinetics study qualitatively examines the phenomenon of “frozen equilibrium” in Stratified Charge Radical Ignition (SCRI) engines with direct injection (DI) and exhaust gas recirculation (EGR). In such engines, this phenomenon is believed to preserve select highly reactive species formed in the side chambers (called micro-chambers) embedded inside the piston bowl so that these species can be carried-over to enhance autoignition in the next engine cycle. In turn this enhancement makes possible ignition and combustion at compression ratios that are markedly lower than those considered “standard” (for a given fuel), resulting in reduced emissions. Analysis is based on a detailed chemical-kinetics mechanism that includes NOₓ production and makes use of up to 19 species and 58 reactions. Along with detailed versions of the momentum and energy equations, this mechanism is simultaneously solved within the two separate but interactively connected open systems representing the individual main chamber and micro-chamber combustion processes. Part of the aim of the present study is to identify several of the engine processes and dominant chemical-kinetics sub-mechanisms responsible for the much lower compression ratios and reduced NOₓ emissions in SCRI-DI engines with EGR.]]></description>
      <pubDate>Mon, 26 Sep 2022 09:12:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1797463</guid>
    </item>
    <item>
      <title>Effects of Fuel Properties on the Stratified-Charge Combustion of Direct-Injection Gasoline Engine with EGR</title>
      <link>https://trid.trb.org/View/1797224</link>
      <description><![CDATA[The objective of this study is to clarify the effects of fuel properties on the stratified-charge combustion of direct-injection gasoline engine with EGR. A single-cylinder direct-injection gasoline engine, based on a Toyota D-4 engine, was used. First, the effects of EGR on the stratified-charge combustion of direct-injection gasoline engine were investigated under various conditions. As a result, 20% EGR can drastically reduce NOₓ emission without reducing the IMEP under the stratified-charge combustion. Next, paraffin, olefin, naphthene and ether having a boiling point of approximately 50 °C and paraffin, olefin and aromatic compounds having a boiling point of approximately 100°C were used for fuel to investigate the effects of fuel properties on the stratified-charge combustion of a direct-injection gasoline engine with EGR. As a result, the effects of fuel properties on the stratified-charge combustion of direct-injection gasoline engine were maintained by the use of EGR. Paraffins and olefins having a lower boiling point had a higher IMEP under the stratified-charge combustion with EGR.]]></description>
      <pubDate>Mon, 26 Sep 2022 09:12:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1797224</guid>
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