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    <title>Transport Research International Documentation (TRID)</title>
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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>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Study on Modeling of Combustion Chamber Deposits in High-Efficiency Gasoline Spark-Ignition Engines (First report)</title>
      <link>https://trid.trb.org/View/2695907</link>
      <description><![CDATA[During the operation of a SI engine, combustion chamber deposits (CCD) form inside the engine combustion chamber. The formation of CCD causes unstable combustion, resulting in adverse effects on thermal efficiency and emissions. In this study, acceleration generation experiments of CCD were conducted using a spark ignition engine, and the time profiles of CCD thickness were obtained. Timeline observations of the CCD surface and detailed observations using SEM were also conducted. As a result, the CCD thickness increased significantly at the beginning of operation and then remained stable, and the formation process and detailed structure of the CCD differed depending on the operating conditions.]]></description>
      <pubDate>Fri, 31 Jul 2026 09:23:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2695907</guid>
    </item>
    <item>
      <title>Study on Modeling of Combustion Chamber Deposits in High-efficiency Gasoline Spark-Ignition Engines (Second Report)</title>
      <link>https://trid.trb.org/View/2684141</link>
      <description><![CDATA[In the pursuit of improved thermal efficiency and reduced CO₂ emissions in passenger vehicles, various technological approaches are being explored. However, the formation of combustion chamber deposits (CCDs) can have adverse effects, such as engine knocking. This study aims to elucidate the mechanisms behind CCD formation, establish effective suppression methods, and develop predictive models. To achieve these goals, both experimentally simulated deposits and actual engine-derived samples were analyzed to identify and evaluate the key factors influencing deposit formation.]]></description>
      <pubDate>Tue, 23 Jun 2026 13:53:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2684141</guid>
    </item>
    <item>
      <title>Hardening Mechanism of Gasoline Deposits</title>
      <link>https://trid.trb.org/View/2646092</link>
      <description><![CDATA[In our previous research, we discovered that gasoline-derived deposits hardened at room temperature when formed at temperatures exceeding 110 ℃. In this study, we found that repeated heating and cooling between 100 ℃ and room temperature also led to hardening, accompanied by a gradual increase in molecular weight. Chemical analysis revealed that the deposits mainly consisted of hydrocarbons containing hydroxyl and carboxyl groups. However, no significant compositional changes were observed before and after thermal cycling. We identified the strong polarity and intermolecular forces of these functional groups as key factors contributing to the hardening behavior.]]></description>
      <pubDate>Fri, 20 Mar 2026 14:47:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2646092</guid>
    </item>
    <item>
      <title>Development of Evaluation Method to Quantify the Effect of Fuels and Lubricants on Gasoline Engines</title>
      <link>https://trid.trb.org/View/2582075</link>
      <description><![CDATA[A method to quantitatively evaluate the deposit effects of fuels and lubricants in various usage environments of direct-injection gasoline engines has been investigated. TG-DTA and Autoclave were selected as test methods that could simulate all the operating environments in the engine and calculate the deposit generation rate. The experimental test conditions that can quantitatively generate deposit for the selected evaluation method are reported.]]></description>
      <pubDate>Fri, 26 Sep 2025 13:39:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2582075</guid>
    </item>
    <item>
      <title>Experimental study of vegetable oil droplets vaporization under low temperature conditions such as those found in diesel engine cold parts</title>
      <link>https://trid.trb.org/View/2548007</link>
      <description><![CDATA[This paper presents an analysis of three vegetable oil droplets vaporization process in the range temperature from 473 to 723 K corresponding to low temperature conditions found in diesel engine cold parts. This process is analyzed for a droplet evaporating in a hot environment at atmospheric pressure using the fiber-suspended droplet technique well used in the literature, and analyzing the droplet normalized square diameter and temperature evolution surrounding the droplet when vaporizing. The main difference between those already studied in literature is the range temperature which varies between 473 and 723 K in which vegetable oils vaporizing problems leading to deposits formation in the cold regions of diesel engines especially in direct injection. This presents a scientific challenge for resolving deposit formation. The findings reveal that vegetable oil droplets experience expansion and heating for temperatures below 623 K: no other changes are observed. Between temperatures of 623 and 683 K, an increase in temperature, expansion, and an inconsistent vaporization is observed. This is followed by a phase of low and constant vaporization. From 683 K, vegetable oils experience an initial stage of heating and expansion, which is accompanied by a phenomenon of puffing and bursting. Finally, in the last phase, residue formation occurs. Puffing and bursting phenomena manifest once the temperature reaches 683 K, indicating the emergence of substantial quantities of light compounds including carboxylic acids, aromatics, acrolein, ketene, and fatty acids. These compounds are formed through the thermal degradation and polymerization of vegetable oils. This process causes deposits to form in the colder areas of diesel engines.]]></description>
      <pubDate>Fri, 13 Jun 2025 09:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2548007</guid>
    </item>
    <item>
      <title>Study on Clarification of Formation Factors of Deposits on Air-fuel Ratio Sensors</title>
      <link>https://trid.trb.org/View/2535988</link>
      <description><![CDATA[Deposits form on the air-fuel ratio sensor used for air-fuel ratio control in direct-injection gasoline spark-ignition (DISI) engines. They affect the signal response of the sensor, which provides the problems of the control of air-fuel ratio. In this study, the formation mechanism of deposits on the air-fuel ratio sensors was investigated using a gasoline DISI engine and the factors that affect the response of the air-fuel ratio sensor were clarified. As a result, it is found that the influence of PN concentration, gas flow rate, and gas flow speed have a large influence on the response time of the signals of the air-fuel sensors.]]></description>
      <pubDate>Mon, 14 Apr 2025 09:35:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2535988</guid>
    </item>
    <item>
      <title>Development of a Method for Quantifying the Cause of Carbon Deposit in Gasoline Engines</title>
      <link>https://trid.trb.org/View/2444740</link>
      <description><![CDATA[The carbon deposit in gasoline engines have various influences on engine performance and hinder long-term operation. They are generated from carbon in fuel oils and lubricating oils. It is important to classify the cause of carbon deposit broadly in research & development and investigate the countermeasures to reduce them at an early stage. In this study, the authors report on the development of a method to quantitatively indicate the specific causes in gasoline engines for all deposit that affect engine performance.]]></description>
      <pubDate>Mon, 11 Nov 2024 09:41:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2444740</guid>
    </item>
    <item>
      <title>Effect of Soot Layer on Catalyzed Gasoline Particulate Filter（2nd report）</title>
      <link>https://trid.trb.org/View/2408132</link>
      <description><![CDATA[In the case of hybrid cars with both an internal combustion engine and a battery-powered electric motor, less space in the engine room is available. Then, one needs the aftertreatment system of a gasoline particulate filter (GPF) combined with a three-way catalyst (TWC). However, deposited soot inside the filter may degrade catalytic activity. In this study, by using a lattice Boltzmann method (LBM), the authors conducted numerical simulations of catalyzed GPF to discuss the effect of soot layer on the conversion rate of TWC. They investigated the effects of the deposited soot mass, the exhaust gas component and the filter length on the catalyst performance. Results show that as the deposited mass is increased, the conversion rates of CO, HC and NO are generally decreased. The concentrations of CO, HC and NO largely affect these conversion rates. When the filter length is larger, these conversion rates do not change much.]]></description>
      <pubDate>Mon, 26 Aug 2024 11:19:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2408132</guid>
    </item>
    <item>
      <title>Study on the Formation Mechanism of Deposits on Air-Fuel Ratio Sensors</title>
      <link>https://trid.trb.org/View/2387110</link>
      <description><![CDATA[There is a problem that deposits formed on the air-fuel ratio (A/F) sensor affect A/F control. To solve the problems, the mechanism of deposit formation and reduction method of the deposits are required to be investigated. In this study, the engine experiments for generating the deposits on the A/F sensor were conducted and the formation mechanism of the deposits on the A/F sensor was evaluated. As a result, the amount of the deposit increased with increasing the difference of the exhaust gas temperature and the surface temperature of the A/F sensors, suggesting that the deposit was generated by thermophoresis.]]></description>
      <pubDate>Thu, 11 Jul 2024 13:53:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/2387110</guid>
    </item>
    <item>
      <title>An original nondestructive sampling method to study the effect of gravity on the deposition of micron-sized large particles in exhaust gas recirculation (EGR) cooler fouling</title>
      <link>https://trid.trb.org/View/2371152</link>
      <description><![CDATA[Fouling is one of the barriers to developing more efficient and near-zero emission internal combustion engines. The micron-sized particulate matter is one of the roots of this fouling phenomenon in exhaust gas recirculation (EGR) coolers. This fouling is inadequately evaluated quantitatively, and its deposition mechanism is unknown. To investigate the effect of gravity on the deposition of micron-sized particles, an original nondestructive sampling fouling method and experiment apparatus have been developed to effectively obtain the upper and lower bottom fouling in the cooler in the direction of airflow, and the area proportion, count, and diameter of large particles in the fouling using image processing software. It was found that (i) the area proportion of large particles in the lower bottom fouling was almost 2.5 times higher than the upper bottom fouling; (ii) the count of large particles in the lower bottom fouling was higher, and the maximum diameter was larger, up to 639 μm; (iii) the mass of the lower bottom fouling was 1.5 times higher than the upper bottom fouling; (iv) gravity can significantly promote the deposition of micron-sized particles and should be considered in the design and arrangement of the EGR cooler to prevent fouling.]]></description>
      <pubDate>Thu, 30 May 2024 13:56:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2371152</guid>
    </item>
    <item>
      <title>ASTM Unwashed Gum and the Propensity of a Fuel to Form Combustion Chamber Deposits</title>
      <link>https://trid.trb.org/View/1787906</link>
      <description><![CDATA[An investigative group set up under the auspices of the Coordinating European Council collected data on combustion chamber deposits (CCD), ASTM unwashed gum results and the thermogravimetric analysis  of these gums for different fuels from many different sources. The analysis of this data shows that unwashed gum cannot and does not predict CCD. It is not possible to use unwashed gum or any aspect of its behavior in the thermogravimetric analysis to assess the CCD-forming tendency of randomly chosen fuels.]]></description>
      <pubDate>Mon, 20 May 2024 14:02:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1787906</guid>
    </item>
    <item>
      <title>Study on the Formation Mechanism of Deposits Generated from Exhaust Gas of Gasoline Spark-Ignition Engines.</title>
      <link>https://trid.trb.org/View/2359095</link>
      <description><![CDATA[The use of exhaust gas recirculation (EGR) is necessary to improve the thermal efficiency of spark-ignition engines. However, deposits formed in the EGR valve or cooler cause valve sticking and reduced heat exchange performance of the cooler, which are serious problems. In this study, the formation mechanism of EGR deposits was investigated using the gasoline engine exhaust and an EGR deposit model was constructed. As a result, it was found that the deposit was formed under the conditions where the wall temperature was below 200 ℃, and the amount of the deposit increased with decreasing the wall temperature between 80 and 200 ℃. The developed model predicted the experimental results well.]]></description>
      <pubDate>Tue, 30 Apr 2024 09:23:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/2359095</guid>
    </item>
    <item>
      <title>Influence of Spray-Wall Interaction and Fuel Films on Cold Starting in Direct Injection Diesel Engines</title>
      <link>https://trid.trb.org/View/1782344</link>
      <description><![CDATA[Various single and split injection schemes are studied to provide a better understanding of fuel distribution during cold starting in DI diesel engines. Improved spray-wall interaction, fuel film and multicomponent vaporization models are used to analyze the combustion processes. Better combustion characteristics are obtained for the split injection schemes than with a single injection. An analysis of the fuel impingement processes identifies the mechanisms involved in producing the differences in vaporization and combustion of the fuel. A greater amount of splashing occurred for the split injections compared to a single injection. This behavior is attributed to the decreased film thickness (less dissipation of impingement energy), the decreased impingement area (obtained by increasing the impingement Weber number), and most importantly, the reduced frequency of drop impingement. In comparison, the single injection scheme resulted in an impingement time between drops (i.e., drop frequency) that was considerably smaller than the time required for splashing. Thus, subsequent impinging drops interfered with the splashing process, resulting in a greater quantity of adhered fuel on the walls. The increased splashing for the split injection schemes reduced the overall droplet size, which further aided vaporization and combustion. The partitioning of the injected fuel and the dwell between injection pulses have shown to provide better combustion characteristics for cold starting. One common approach to improve startability is to increase the amount of fuel injected. This type of strategy was also modeled. However, the results indicate that better combustion characteristics may be achieved through the optimization of the injection scheme as an alternative to overfueling.]]></description>
      <pubDate>Wed, 07 Feb 2024 16:53:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1782344</guid>
    </item>
    <item>
      <title>A Technique to Measure Thermal Diffusivity and Thickness of Combustion Chamber Deposits In-Situ</title>
      <link>https://trid.trb.org/View/1782299</link>
      <description><![CDATA[A “thermal pulse” technique has been used to measure thermal diffusivity and thickness of combustion chamber deposits continuously during engine operation. The technique uses a fast-response thermocouple junction at the combustion chamber wall surface and a simplified model which describes the effect of the deposit on the measured temperature cycle. Results from 13 tests using four different fuels and three different commercial additive packages are discussed in the paper. Thermal diffusivity values in the range of 0.85 - 4.2 x 10-7 m2s-1 were measured. Deposit growth is normally a continuous process. However, occasionally deposit flaking events characterized by a sudden significant decrease in deposit thickness were observed.]]></description>
      <pubDate>Wed, 07 Feb 2024 16:52:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/1782299</guid>
    </item>
    <item>
      <title>Effect of Soot Loading on the Thermal Characteristics of Diesel Engine Oils</title>
      <link>https://trid.trb.org/View/1790789</link>
      <description><![CDATA[When compared with new oil, used diesel engine oils exhibited thermal conductivity that increases as the concentration of soot increases. The magnitude of the effect depends on the oil composition, and on the size and dispersion of the soot particles. Although soot in engine oil is generally deleterious to engine performance from the standpoint of wear and deposits, no negative effects were observed on the thermal performance of the oil itself; indeed, even slight positive effects are expected for oils that maintain soot in stable dispersion. Therefore, the thermal challenge for engine oils in diesel engines that use exhaust gas recirculation will be to prevent soot deposition on engine surfaces.]]></description>
      <pubDate>Thu, 21 Dec 2023 13:51:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1790789</guid>
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