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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>
    <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>Back-Pressure-Based Traffic Signal and Discretized Trajectory Joint Control for Low CAV Penetration Rate Environment</title>
      <link>https://trid.trb.org/View/2598846</link>
      <description><![CDATA[This paper presents an innovative joint traffic signal and trajectory control (JSTC) model for a mixed traffic environment with a low penetration rate of connected autonomous vehicles (CAVs). The JSTC model integrates a back-pressure (BP) signal controller that comprehensively considers the right-of-way with traffic modes and the person-based traffic demand, which aims to enhance intersection throughput and improve the probability of arrival on green (PAOG) of CAVs. Additionally, this paper provides a theoretical stability proof of the control system by deviating the upper bound of the Lyapunov drift penalty function. Furthermore, it simultaneously introduces a discretized CAV trajectory control model by discretizing continuous time variables with vehicle-to-infrastructure (V2I) communication periods for smooth and safe travelling. Simulation results demonstrate that the JSTC model exhibits excellent responsiveness and achieves the lowest convergence value of cycle maximum queue length across various flow-based traffic demand levels. The smoothness of the Lyapunov function values validates the ability to stabilize the control system. Two months of connected transit buses (CTB) operation data shows that substantial progress has achieved. These include the elimination of unnecessary stops, an over 20 km/h increase in daily average speed, a 17% reduction in weekly average delay, and at least 10% reduction in weekday travel time.]]></description>
      <pubDate>Mon, 22 Dec 2025 16:07:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2598846</guid>
    </item>
    <item>
      <title>An experimental and computational analysis of backfire initiation and propagation in a single-cylinder hydrogen port-fuel-injection engine</title>
      <link>https://trid.trb.org/View/2640607</link>
      <description><![CDATA[The global push for defossilization necessitates the advancement of hydrogen internal combustion engines as a key solution for the heavy-duty transport sector. However, the distinct combustion properties of hydrogen, particularly its high reactivity, introduce operational challenges for port-fuel-injected (PFI) engines, most critically the risk of backfire—the uncontrolled ignition in the intake system. This phenomenon not only makes the engine potentially unsafe for operation but also severely limits the achievable power density and combustion stability. Addressing this barrier requires a comprehensive understanding of the complex interactions between various engine control parameters. This study presents a coordinated experimental and computational fluid dynamics (CFD) investigation focusing on strategies to mitigate backfire in a single-cylinder, heavy-duty hydrogen PFI engine. The influence of engine parameters such as injector location, start of injection (SOI) timing, backpressure, engine valve timing and injection pressure and duration on mixture formation, and backfire onset were also analyzed. The findings establish critical guidelines for defining the stable operating window, demonstrating how the tuning of key control variables can effectively promote mixture preparation, reduce backfire instances and potentially increase engine efficiency. This research provides an essential framework for the reliable, safe and efficient deployment of hydrogen PFI technology in future low-carbon transportation applications.]]></description>
      <pubDate>Mon, 15 Dec 2025 10:33:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2640607</guid>
    </item>
    <item>
      <title>Coupled Engine/Cooling System Simulation and its Application to Engine Warm-up</title>
      <link>https://trid.trb.org/View/1804388</link>
      <description><![CDATA[Coupled system modeling is increasingly advantageous as the consideration for vehicle system interactions intensifies. Significant interactions can occur between an engine and cooling system. Vehicle cooling systems can be coupled to the vehicle powertrain in many locations, including the cylinder structure, oil cooler, mechanical coolant pump, mechanical fan, EGR cooler, and charge-air-cooler. To enable the analysis of coupled systems, a linking capability was added to a cooling system simulation tool, GT-COOL, to tie it into an engine simulation tool. The paper describes the linkage methodology and its application. This coupled simulation was applied to the study of a new concept, where the engine exhaust back pressure (and thus engine load) was artificially increased, in order to speed up the engine warm-up. The simulation was used to predict the effect of this concept on the rate of warm-up of the coolant and of the cylinder structure.]]></description>
      <pubDate>Fri, 22 Dec 2023 11:19:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1804388</guid>
    </item>
    <item>
      <title>A comparative analysis of moving average filter and Kalman filter for large diesel engine test cell back-pressure control</title>
      <link>https://trid.trb.org/View/2226116</link>
      <description><![CDATA[Diesel engine combustion releases many harmful components, thus there are continuous efforts into improving the efficiency of these engines and reducing the harmful gasses and particulates to meet the emission authorities targets. To develop and sell new engine-related products, these engines are required to run and to be audited in diesel engine test cells. A critical measurement for benchmark testing is the exhaust back-pressure, which is the resultant exhaust flow from the engine and a product of the air and fuel consumed. The back-pressure is controlled by restricting the flow of the exhaust using a butterfly valve and this pressure must be set to the defined limits to ensure engine compliance. Setting this limit takes time and consumes large volumes of fuel, which causes additional emissions. Therefore, a feedback control solution to regulate this back-pressure is desirable. In current practice, a moving average filter is used on two commercial standard engine softwares – SGS CyFlex® and AVL Puma 2® Data Acquisition and Control Systems to provide a useful signal for feedback control. Considering the presence of erratic noise associated with the back-pressure measurement, a Kalman Filter with tunable measurement uncertainty and process noise gains is also considered. By modifying the script in SGS CyFlex® and AVL PUMA 2®, a Kalman Filter is implemented for the first time on diesel engine test cells and a comparative analysis between the performance of the two filters is provided. Both filters effectively reduce the noise of the system, with the Kalman Filter showing a closer tracking to the desired system response. This demonstrates the potential of applying the Kalman Filter to provide the feedback signal for improved back-pressure control that could reduce the fuel consumption during testing, thereby makes testing process more economical and environment friendly. The script and results presented in this work will open up the opportunities of applying Kalman filtering method’s in various engine testing functions, which will have broader impact in the current industrial practice.]]></description>
      <pubDate>Fri, 22 Sep 2023 09:08:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/2226116</guid>
    </item>
    <item>
      <title>Using Valve Timing and Exhaust Back Pressure to Improve Catalyst Warm-Up Time</title>
      <link>https://trid.trb.org/View/1829284</link>
      <description><![CDATA[This work examines the effects of valve timing and back pressure on the engine out enthalpy flow which is critical to the light off of the catalyst. The engine behavior is observed under fast-idle condition using a turbocharged production direct injection spark ignition engine with variable cam phasing that could shift both the intake and exhaust valve timing by 50 deg. crank angle. The back pressure is adjusted by throttling the exhaust. The engine operates at a constant net indicated mean effective pressure of 2 bar. The valve timing effect is largely governed by the residual gas trapped. With increasing valve overlap, the exhaust enthalpy flow increases because of the increase in exhaust temperature due to a slower combustion, and of the increase in air and fuel flow to compensate for the lower efficiency due to the slower combustion. When the back pressure is increased, the engine through flow has to increase to compensate for the larger pumping loss. The exhaust temperature also increases because there is less expansion for the charge in the blow-down process. Both effects contribute to a higher enthalpy flow to the catalyst and facilitate the light off process.]]></description>
      <pubDate>Fri, 21 Apr 2023 09:49:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/1829284</guid>
    </item>
    <item>
      <title>Predicting Running Vehicle Exhaust Back Pressure in a Laboratory Using Air Flowing at Room Temperature and Spreadsheet Calculations</title>
      <link>https://trid.trb.org/View/1818099</link>
      <description><![CDATA[In today’s highly competitive automotive environment people are always looking to develop processes that are fast, efficient, and effective. Moving testing from expensive prototype vehicles into the laboratory is an approach being implemented for many different vehicle subsystems. Specifically a process has recently been developed at General Motors that predicts exhaust back pressure performance for a running vehicle using laboratory testing and spreadsheet calculations. This paper describes the laboratory facility and procedure, the theory behind the calculations, and the correlation between vehicle test and laboratory based results. It also comments on the benefits of the process with respect to reduction in design iterations, quicker availability of results, and money savings.]]></description>
      <pubDate>Mon, 24 Oct 2022 10:22:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1818099</guid>
    </item>
    <item>
      <title>The Effect of the Back-Pressure Changes in an Exhaust System on Vibration When Attaching a Variable Device during Idling</title>
      <link>https://trid.trb.org/View/1985156</link>
      <description><![CDATA[The vibration of the ignition frequency component of the engine during idling causes driver discomfort. To minimize this, an optimal exhaust system with a variable device that can exert optimal pressure is required. In this study, the geometry of the variable device was designed in orifice and cylinder types. Next, the designed variable devices were implemented in a conventional exhaust system with an X chamber. A comparative analysis was conducted to propose an optimal geometry through back-pressure and vibration measurements. During the experiment, the orifice geometry exhibited higher back pressure than the conventional geometry and a large difference in back pressure before and at the exhaust gas merging position. Furthermore, the orifice geometry showed a 2.56% increase in the vibration of the 1X component in the Y-axis direction. By contrast, the cylinder geometry exhibited slightly higher back pressure than the conventional geometry and the smallest difference in back pressure before and at the exhaust gas merging position. The cylinder geometry showed a 2.45% reduction in the vibration of the 1X component in the Y-axis direction.]]></description>
      <pubDate>Mon, 27 Jun 2022 17:17:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1985156</guid>
    </item>
    <item>
      <title>Optical screening investigations of backfire in a large bore medium speed hydrogen engine</title>
      <link>https://trid.trb.org/View/1941747</link>
      <description><![CDATA[Further improvement of hydrogen combustion in port fuel injection engines is limited by backfire. To overcome this drawback of hydrogen port fuel injection engines it is essential to locate and understand the reasons for the inflammation of a backfiring cycle. To contribute to this understanding a minimal invasive lateral optical access was developed for a medium speed large bore engine. The access uses a UV enhanced endoscope to investigate the OH radical’s natural chemiluminescence to locate the inflammation of a backfiring cycle in the combustion chamber. The investigations are carried out at high engine load. The optical investigations were based on a thermodynamic screening. This included the variation of the start of the hydrogen port fuel injection and the engine’s backpressure. These experiments prove the influence of exhaust backpressure and the start of injection on the probability of backfire. As higher backpressure leads to an increased probability of backfire, the SoI strategy has also a decisive influence. An optimum start of injection timing with less backfire under high backpressure was experimentally determined at 300°CA with respect to 720°CA as FTDC. The conducted optical investigations show that backfire starts by ignition by hot residual gasses during the first cycle located under the exhaust valves. Furthermore, the results show ongoing combustion in the intake manifold leading to serious damage of the engine if not prohibited.]]></description>
      <pubDate>Fri, 24 Jun 2022 17:07:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1941747</guid>
    </item>
    <item>
      <title>Arrival-Based Backpressure Traffic Signal Control</title>
      <link>https://trid.trb.org/View/1941721</link>
      <description><![CDATA[Fluctuations in arrival rates significantly affect the performance of traffic signal controls. In this paper, we propose an arrival-based distributed control algorithm based on the backpressure control framework, and show that this arrival-based backpressure (ABP) algorithm preserves the attractive features of backpressure control, including queue mitigation and global stability. Moreover, numerical results show that the ABP algorithm outperforms the fixed, actuated, and original backpressure signal controllers in low, medium, and heavy loading demand levels in increasing throughput, reducing queue length and waiting time.The benefits are evident under periodic traffic scenarios.]]></description>
      <pubDate>Fri, 15 Apr 2022 17:15:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1941721</guid>
    </item>
    <item>
      <title>Effects of Exhaust Backpressure Increment on the Performance and Exhaust Emissions of a Single Cylinder Diesel Engine</title>
      <link>https://trid.trb.org/View/1902715</link>
      <description><![CDATA[Exhaust gas aftertreatment systems and exhaust gas waste heat recovery systems are main solutions to decrease the environmental impact and increase the efficiency of diesel engines. However, any system installed on the exhaust pipe of diesel engines is a source of exhaust backpressure. Moreover, increasing the exhaust backpressure has negative effects on the performance and environmental impact of diesel engines. The study aims to investigate the negative impacts of exhaust backpressure increment on performance indicators, fuel consumption and exhaust emissions of a diesel engine. The experimental study was performed on a test bench comprising a single cylinder diesel engine, a dynamometer and various measurement equipment. The backpressure was increased by adding various sized orifices on the exhaust pipe of the test engine and the test engine was run under six different engine loads at an engine speed of 1600 rpm. Subsequently, the impacts of backpressure increment on the brake specific fuel consumption (BSFC), brake thermal efficiency, volumetric efficiency, mean effective pressures, mechanical efficiency, and exhaust emissions were determined. The study results showed that backpressure increment causes retarding of combustion phases up to a crank angle of 4°, decrease in the indicated mean effective pressure, and decrease in the peak cylinder pressure from 78.36 to 70.7 bar at the maximum available engine load. From fuel consumption perspective, backpressure increment caused an increase in the BSFC approximately up to 3.29% at 24.66 kPa backpressure. On the other hand, the results showed that increasing the backpressure caused a significant increment in the pumping mean effective pressure and a remarkable decrease in the volumetric efficiency. The findings of this study have significant implications for evaluating the negative impacts of any system installed on the exhaust pipe of a diesel engine.]]></description>
      <pubDate>Fri, 25 Feb 2022 08:58:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/1902715</guid>
    </item>
    <item>
      <title>Method for design and evaluation of ICE exhaust silencers</title>
      <link>https://trid.trb.org/View/1850503</link>
      <description><![CDATA[The noise levels generated by an unmuffled engine exhaust system can be identified as the loudest vehicle noise source. The muffler or silencer is an essential component of the internal combustion engine exhaust system. Its main function is to reduce the exhaust-generated noise to an acceptably low level. Its design development is a complex process affecting the engine efficiency and thus fuel consumption, emissions and overall noise generation. This paper focuses on the design development of a muffler for a single-cylinder engine application. A 1D GT-Power model of a single valve engine was developed. Additionally, an analytical muffler preliminary design methodology was introduced. The methodology provides guidelines for muffler grade selection, sizing of different components, and calculation of backpressure as a function of the exhaust gas flow rate. Two custom mufflers design concepts were developed for the single-cylinder engine based on the introduced analytical methodology. Two commercial single-cylinder engine muffler designs available from Yanmar and Loncin were considered for the engine performance evaluation simulation. The presented combination of analytical and numerical modelling procedures can reduce the overall length of the muffler development stage by eliminating faulty design concepts and refining the muffler's performance parameters.]]></description>
      <pubDate>Tue, 16 Nov 2021 11:12:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1850503</guid>
    </item>
    <item>
      <title>Backpressure control with estimated queue lengths for urban network traffic</title>
      <link>https://trid.trb.org/View/1868842</link>
      <description><![CDATA[Backpressure (BP) control was originally used for packet routing in communications networks. Since its first application to network traffic control, it has undergone different modifications to tailor it to traffic problems with promising results. Most of these BP variants are based on an assumption of perfect knowledge of traffic conditions throughout the network at all times, specifically the queue lengths (more accurately, the traffic volumes). However, it has been well established that accurate queue length information at signalized intersections is never available except in fully connected environments. Although connected vehicle technologies are developing quickly, a fully connected environment in the real world is still far. This paper tests the effectiveness of BP control when incomplete or imperfect knowledge about traffic conditions is available. BP control is combined with a speed/density field estimation module suitable for a partially connected environment. The proposed system is referred to as a BP with estimated queue lengths (BP-EQ). The robustness of BP-EQ is tested to varying levels of connected vehicle penetration, and BP-EQ is compared with the original BP (i.e. assuming accurate knowledge of traffic conditions), a real-world adaptive signal controller, and optimized fixed timing control using microscopic traffic simulation with field calibrated data. These results show that with a connected vehicle penetration rate as little as 10%, BP-EQ can outperform the adaptive controller and the fixed timing controller in terms of average delay, throughput, and maximum stopped queue lengths under high demand scenarios.]]></description>
      <pubDate>Thu, 29 Jul 2021 12:00:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/1868842</guid>
    </item>
    <item>
      <title>Investigation on the unsteadiness of centrifugal compressor exposed to pulsating backpressure</title>
      <link>https://trid.trb.org/View/1854786</link>
      <description><![CDATA[Centrifugal compressor is exposed to pulsating backpressure due to the movement of intake valves in internal combustion engine. The performance of compressor deviates from the steady performance map, which affects the matching between turbocharger and engine. The behavior of compressor system at pulsation conditions are investigated via an in-house developed 1D unsteady code validated by experimental results. The influence of pulse frequency, magnitude and compressor characteristic curve on the compressor transient responses, including filling-emptying effect and wave dynamics, are analyzed. Results show that the strength of wave dynamics grows stronger with the increasing of pulse frequency, while the strength of filling-emptying effect increases first then decreases. The rise of pulse magnitude results in an almost linearly increasing of filling-emptying effect, while it can hardly affect the wave dynamics. Furthermore, the influence of pulsation magnitude and frequency represents the influence of local pressure gradient, and a correlation as quadratic curve can be evaluated between the pressure gradient and compressor unsteadiness. On the other hand, the influence of operating point, including the average mass flow rate and the slope of characteristic curve, is confirmed to be evidently smaller, comparing to the influence of pulsation frequency and magnitude. This study is helpful to estimate the behavior of compressor and the discrepancy of performance when operating at unsteady environment or matched with engine.]]></description>
      <pubDate>Fri, 23 Jul 2021 15:25:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/1854786</guid>
    </item>
    <item>
      <title>Experimental and computational investigation on comparison of micro-scale open rotor and shrouded rotor hovering in ground effect</title>
      <link>https://trid.trb.org/View/1846463</link>
      <description><![CDATA[Various investigations on open rotor (OR) hovering in-ground effect (IGE) are carried out, but few papers report shrouded rotor (SR) hovering IGE. This paper compares aerodynamic performance and flowfield characteristics of OR and SR hovering IGE by both experimental measurements and computational fluid dynamic (CFD) simulations. Experimental results reveal that in IGE flight, the aerodynamic performance of SR is more sensitive than that of OR. And at constant power, SR offers more thrust than OR at the same ground distance. Ground has a great influence on thrust for OR below 2.2 rotor radius distance, while for SR it shows obvious effect below 1.5 rotor radius distance. It is also shown that normalized aerodynamic coefficients of OR and SR are independent on rotor speed. In addition, for OR the rotor thrust coefficient changes nearly linearly with the logarithmic distance from ground, while for SR it changes nonlinearly. Flowfield analysis by CFD shows that shroud changes the tip flow features and expands the slipstream area of SR. When ground distance gets small, back pressure below the rotor-disk plane increases, which is more obvious for SR than OR. Furthermore, shroud thrust of SR decreases because of tip leakage flow and flow separation.]]></description>
      <pubDate>Thu, 27 May 2021 12:39:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1846463</guid>
    </item>
    <item>
      <title>Mechanism for pressure drop variation caused by filtration of diesel particulates</title>
      <link>https://trid.trb.org/View/1763360</link>
      <description><![CDATA[Diesel engines have better fuel consumption efficiency than gasoline engines. To reduce the particle emission in the diesel exhaust, a ceramic filter, called diesel particulate filter, has been developed. Unfortunately, the pressure drop (filter backpressure) continues to increase, resulting in an increase in fuel conversion rate as well as available torque. In order to develop the filter with lower pressure drop, the filter structure is strategically optimized in the design of the filter product. To do so, the information on phenomena during the filtration is needed. This article sets out numerically to study the variation in the pressure drop when the particulates are trapped inside the porous walls of diesel particulate filter. To discuss the flow dynamics and pressure drop caused by the soot deposition, the numerical simulation is purposely conducted in two-dimensional coordinate. This is because the variation in flow channel through pores during the filtration can be visualized easily. Here, eight filters were tested systematically. Utilizing these simulation results, the authors try to explain the main factors for the pressure drop variation during the filtration. Based on the presented results, it is shown that the flow field is gradually varied during the filtration. The knowledge regarding the well-known pressure drop variation observed in the stage from the depth filtration to the surface filtration is provided.]]></description>
      <pubDate>Mon, 22 Feb 2021 10:22:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1763360</guid>
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