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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" />
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    <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>
    </image>
    <item>
      <title>1D System Evaluations for Efficiency Trade-Offs for a Heavy-Duty H2ICE Concept</title>
      <link>https://trid.trb.org/View/2691985</link>
      <description><![CDATA[Lean H2 combustion strategies have shown promising gross thermal efficiency and ultra-low engine-out NOx emissions for H2-fuel based internal combustion engines (H2ICE) in heavy-duty (HD) transport. Implementing lean combustion strategies require excessive air flow demand that further increases with the engine load increase. To meet such air flow demands efficiently across a wide engine operating region, a detailed system optimization is warranted including next generation turbocharging systems.In this 1D system analysis campaign, a detailed study of various air-system configurations was conducted for a modified HD, direct-injection (DI), H2ICE concept based-off a Cummins heavy-duty 15L engine. The concept engine configuration had a geometric compression ratio of 10.4 and no external exhaust gas recirculation (EGR) was implemented.First, a calibrated 1D engine model representing the H2ICE concept was developed. Using the 1D model, a detailed system-level analysis was conducted at five operating conditions from the heavy-duty SET cycle: A75, A100, B75, B100, and C100. A wide range of lambda levels, valve phasing, miller strategies were characterized by the gross engine performance improvements. Subsequently, different air-system configurations were evaluated for closed-cycle efficiency vs pumping losses trade-offs, while meeting the air flow targets. For next-generation turbocharging, both single stage (1S) and two-stage (2S) boost systems were simulated. Air versus external EGR dilution strategies were also studied at boost-limited engine operating conditions.From the results, high lambda levels reflected the benefits of lean combustion operation. Implementing millerization and cam phasing further elevated these benefits, at the expense of high boost pressure demands. The 1S boost system, with advantages of low-complexity and post-turbine thermal performance, incurred rapidly deteriorating turbocharger performance from the choke and the surge limits for lambda levels beyond 2.2. A 2S boost system achieved higher lambda levels without risking compressors choke or surge limits. Irrespective of turbocharging, the required intake charge cooling was noted ~2-3x times of the conventional diesel engine levels, depending on the targeted lambda levels. A detailed fuel-energy balance analysis was conducted to highlight system trade-offs between the 1S and the 2S based H2ICE configurations.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2691985</guid>
    </item>
    <item>
      <title>Optimization of a Positive Displacement Type Supercharger Using Response Surface Modeling (RSM)</title>
      <link>https://trid.trb.org/View/2663504</link>
      <description><![CDATA[Air suction in a naturally aspirated engine is a crucial influencing parameter to dictate the specific fuel consumption and emissions. For a multi-cylinder engine, a turbocharger can well address this issue. However, due to the lack of availability of continuous exhaust energy pulses, in a single or two-cylinder engine, the usage of turbocharger is not recommended. A supercharger solution comes handy in this regard for a single or two-cylinder engine. In this exercise, we explore the possibility of the usage of a positive displacement type supercharger, to enhance the air flow rate of a single cylinder, naturally aspirated, diesel engine for genset application, operating at 1500 rpm. The supercharger parametric 3D CAD model has been prepared in Creo, with three design parameters i.e. (a) Generating radius, (b) depth of blower and (c) clearance between lobes & lobe and casing. The optimum roots blower design is expected to fulfil the target boost pressure, power consumption and hydraulic efficiency requirements. The baseline DoE using Sobol algorithm generates 28 designs, which has been simulated using the Ansys CFX software via modeFRONTIER process automation. A sensitivity analysis of the input variables on the response variables establishes that generating radius is the most dominant parameter influencing the pressure, efficiency and power consumption. A detailed Response Surface analysis using 12 different algorithms showed that, Anisotropic Kriging captures the pressure variable accurately, while Gaussian Process captures the efficiency and power consumption with the best accuracy as per R-squared comparison. A virtual optimization conducted using the favorite RSMs using the MOGA algorithm generated an optimum roots blower design which complies all the constraints for pressure, efficiency and power. RSM optimized design is further validated in the CFX software, and the results for response variables are accurate within 6% error margin.]]></description>
      <pubDate>Mon, 02 Feb 2026 16:36:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663504</guid>
    </item>
    <item>
      <title>Improving Late Pilot Injection Strategy in Dual-Fuel Diesel/Methane
                    Engines through Supercharging and Hydrogen Enrichment</title>
      <link>https://trid.trb.org/View/2656987</link>
      <description><![CDATA[
                
                In this study, a novel dual-fuel combustion strategy is investigated, employing
                    late pilot injection in diesel–methane engines to improve performance and reduce
                    emissions. The engine was first tested with conventional diesel and methane,
                    exploring a wide range of pilot injection timings, injection pressures, and
                    intake boost pressures. Subsequently, experiments were repeated using a
                    methane/hydrogen blend to assess the influence of hydrogen addition. Results
                    show that, when using only methane, delayed pilot injections have minimal
                    effects on engine performance. In naturally aspirated operation, unburned
                    hydrocarbons and carbon monoxide are reduced, while in supercharged conditions,
                    emissions increase; however, they remain within acceptable limits. Nitrogen
                    oxides and particulate matter reach their lowest levels with delayed injection.
                    Introducing hydrogen reduces engine performance and hydrocarbons and carbon
                    monoxide emissions; notably, it suppresses the typical nitrogen oxides increase
                    associated with hydrogen, while also lowering particulate matter. These findings
                    demonstrate that combining late pilot injections with hydrogen addition and
                    supercharging is a promising strategy for improving dual-fuel engine efficiency
                    and emissions, offering a potential pathway toward cleaner combustion.
            ]]></description>
      <pubDate>Fri, 23 Jan 2026 16:42:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2656987</guid>
    </item>
    <item>
      <title>Diagnostics Methodology for Turbocharger System Using Data Driven Models</title>
      <link>https://trid.trb.org/View/2623802</link>
      <description><![CDATA[In a conventional powertrain driven by Internal combustion (IC) engines, turbocharger (TC) is a key component for enhancing performance and efficiency. Predominantly turbochargers are used to serve multiple purposes of downsizing, increased power, better fuel efficiency, reduced emissions, and improved performance at high altitudes. TC is responsible for fulfilling the air mass requirement of the engine at different operating conditions. Failure of TC system leads to abnormal engine operation. If the TC hardware is beyond repair, the associated replacement cost is very high. Ultimately, a predictive diagnostics approach is required to identify the issue with TC so that the failure of TC could be avoided.The proposed methodology uses advanced artificial intelligence technique called recurrent neural network (RNN) and long short-term memory (LSTM) network for predicting faults in a typical TC system. In this study, actual values of TC speed and boost pressure are obtained from physical sensors present on the vehicle whereas estimated values of TC speed and boost pressure are obtained from data driven models. To enable predictive diagnostic of TC, a fault detection unit is incorporated which differentiates between the various fault conditions such as TC hardware fault or sensor fault.For initial validation, this methodology was applied to a healthy TC system to ensure that fault conditions were not getting active. For further validation, a faulty TC system was selected. Using the proposed approach, degradation in the boost pressure and TC speed for faulty TC was successfully identified. Various fault conditions and steps involved in the fault detection are clearly described.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:26:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2623802</guid>
    </item>
    <item>
      <title>Effective Power Management on Diesel Engine Using Electrified Turbocharger</title>
      <link>https://trid.trb.org/View/2624027</link>
      <description><![CDATA[The growing demand for improved fuel efficiency and reduced emissions in diesel engines has led to significant advancements in power management technologies. This paper presents a dual-mode functional strategy that integrates electrified turbochargers to enhance engine performance, provide boost and generate electrical power. This helps in optimizing the overall engine efficiency. The engine performance is enhanced with boosting mode where the electric motor accelerates the turbocharger independent of exhaust flow, effectively reducing turbo lag and provides immediate boost at low engine speeds. This feature also improves high altitude performance of the engine. Conversely, in generating mode, the electric turbocharger recovers or harvest energy from exhaust gases depending on engine operating conditions, converting it into electrical energy for battery recharging purpose. Advanced control systems enable real-time adjustments to boost pressure and airflow in response to dynamic driving conditions, maximizing engine efficiency. Simulation studies and engine testing validate the expected benefits, demonstrating that the electrified turbocharger can significantly facilitate engine downsizing, reduce fuel consumption, and lower emissions through precise power management. These advancements align with global sustainability goals, presenting a viable solution to meet stringent environmental regulations while maintaining robust engine performance. The integration of electrified turbochargers represents a critical step towards the next generation of eco-friendly diesel engines, supporting both environmental sustainability and economic efficiency.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:07:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2624027</guid>
    </item>
    <item>
      <title>Using Turbogenerators for Energy Recovery in Turbocharged Hybrid Powertrains</title>
      <link>https://trid.trb.org/View/2600534</link>
      <description><![CDATA[The widespread adoption of battery electric vehicles (BEVs) is progressing more slowly than anticipated, making hybridization crucial for improving efficiency through load point shifting, running the engine at its most efficient operating points and kinetic energy recovery. As the world continues to use fossil fuels, enhancing powertrain efficiency is critical to reducing CO2 emissions. Improved efficiency will also increase the share of renewable e-fuels in the energy mix, supporting the transition to low-carbon mobility.A significant portion of energy in ICEs is lost through exhaust heat, which is a high-grate energy source that can be converted into electricity in hybrid systems. Conventional turbochargers, widely used to enhance volumetric efficiency and drivability, typically incorporate a wastegate (WG) to regulate boost pressure. However, this results in the intentional dumping of excess valuable exhaust energy leading to energy loss.This paper investigates the replacement of conventional wastegate-based turbocharging systems with energy recovery technologies—specifically a turbogenerator and an electrically assisted turbocharger (e-turbocharger)—in a light-duty spark-ignition (LD SI) engine. A fully validated 1D GT-Power simulation model of a production 2.0 L turbocharged engine is used to assess system-level trade-offs in energy recovery, exhaust backpressure, and engine performance. The turbogenerator features a downsized variable geometry turbine (VGT) operating in parallel to the main turbocharger, while the e-turbocharger replaces the conventional turbo system entirely. Parametric simulations evaluate the impact of turbine sizing, mass flow variations, and shaft inertia. Results indicate a maximum recoverable power of up to 21 kW, with realistic net recovery after generator losses in the range of ~ 9–11% of crankshaft power. These findings support the technical feasibility of wastegate-free turbocharging architectures to enhance hybrid powertrain efficiency.Simulation results show that by eliminating WG and implementing a turbogenerator or an e-turbocharger, up to 11.3% of the original crankshaft power – previously lost through WG exhaust can be recovered at high engine loads. This recovered energy can be stored in a battery and reused, contribution to lower CO2 emissions. The findings demonstrate the protentional of such systems to replace conventional turbocharging strategies and pave the way for more energy efficient hybrid vehicle architecture.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600534</guid>
    </item>
    <item>
      <title>Influence of Gas Pressure Levels on Injection Timing, Combustion Anomalies, and Emissions of a Hydrogen Gas Engine</title>
      <link>https://trid.trb.org/View/2600505</link>
      <description><![CDATA[A former diesel heavy-duty engine was retrofitted to hydrogen operation to simultaneously facilitate the shift from fossil to renewable fuels and maximize the quantity of reusable engine parts. Simply changing the fuel in this case does not make a properly working engine; the burning process needs to be realized in a premixed flame regime, rather than a diffusional flame regime. Therefore, an additional ignition source is necessary. A well-known characteristic of hydrogen is the low need for ignition energy and the wide range of ignitable air/ fuel ratios. Both must be considered to reach a diesel engine equivalent performance.Port fuel injection (PFI) and direct injection (DI) are commonly used in spark-ignited internal combustion engines. Some disadvantages, such as weak volumetric efficiency and combustion abnormal phenomena like backfire, are connected to PFI. To further improve the volumetric efficiency, high boost pressures are needed. To maximize volumetric efficiency with DI, injection timing after intake valve closure is mandatory.With a high-pressure level for hydrogen injection, a new field of application possibilities is generated regarding the degree of freedom in the injection timing. Furthermore, combustion anomalies can be prevented or their effects mitigated. The influence of pressure on the mixture formation mechanisms and time scales regarding engine load and speed variation was investigated. Simultaneously, the exhaust gas was analyzed concerning the common emissions, nitrogen oxide (NOx), and hydrogen slip (H2 slip).Investigations were carried out on a single-cylinder research engine in two experimental setups. A low-pressure direct injection setup with pressure levels up to 30 bar and a high-pressure direct injection setup with up to 200 bar pressure. While varying the hydrogen injection pressure, two novel injectors were in use. The single-cylinder research engine’s displacement is representative of heavy-duty applications such as trucks, buses, and excavators. In a series application in a four-cylinder diesel engine setup, the following data is representative of the employed engine type: ]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600505</guid>
    </item>
    <item>
      <title>Waste Heat Recovery in Hydrogen Fueled Internal Combustion Engines</title>
      <link>https://trid.trb.org/View/2600442</link>
      <description><![CDATA[Waste Heat Recovery is one of the most investigated and promising technologies for energy efficiency in the transportation sector. It consents to maintain the high-level technology of the present propulsion systems, based on Internal Combustion Engines, while increasing the overall engine and vehicle system efficiency. At the same time, the use of alternative fuels, like hydrogen, has the same crucial role to reduce harmful and greenhouse emissions, without overturn the existing mature technology.A hydrogen-fueled Internal Combustion Engine is proposed in this paper, equipped with waste heat recovery consisting in an additional radial turbine downstream the turbocharger of the engine (Turbo-Compound). The aim is to have a reduction of the specific consumption in most of the operating points of the engine, considering the effect of the recovery and the engine equilibrium rearrangement. The use of hydrogen increases recoverable enthalpy at the engine exhaust, which is intended to be recovered through an expansion of the gases inside the additional turbine. When this secondary turbine is installed downstream of the turbocharger, the overall engine backpressure increases. This alters the turbocharger's operating point, which in turn shifts the engine’s operating conditions. Ultimately, this has a counterproductive effect on the engine efficiency: it faces higher backpressure at exhaust valve opening, leading to an increase in specific fuel consumption.This paper examines the modifications to the engine’s exhaust line resulting from the conversion of waste heat into mechanical energy via a Turbo-Compound system. It discusses the conditions under which the system yields a net positive effect, primarily by compensating for the increased back pressure it introduces. Changes in key engine parameters—such as Variable Geometry Turbocharger control, boost pressure, air/fuel mass flow rate, and equivalence ratio—are analyzed, along with their influence on in-cylinder pressure. Furthermore, the paper identifies the operating range in which the Turbo-Compound system provides a net performance benefit.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600442</guid>
    </item>
    <item>
      <title>Experimental Study of the Lubricating Oil Impact on the Unsteady Performance of an Automotive Turbocharger</title>
      <link>https://trid.trb.org/View/2600440</link>
      <description><![CDATA[Turbocharging technique is a key technology for the development of hydrogen engines, allowing high lambda values to reach low NOx emissions. In ultra-lean mixture conditions, the thermal management of the lubricating oil and its cold condition becomes a crucial aspect that cannot be neglected. Accordingly, the impact of different lubricating oils and different lubricant thermal conditions is highlighted referring to the performance of a turbocharging system for automotive application.To this aim, an experimental campaign is conducted at the test bench for components of propulsion systems of the University of Genoa. Tests are performed on a turbocharger equipped with a variable geometry turbine under both steady and unsteady flow conditions, considering different positions of the turbine regulating device. A 4-cylinder engine head was coupled to the turbocharger in order to reproduce the pulsating flow related to the opening and closing of the engine valves.The influence of the lubricants on the assessment of turbine thermo-mechanical efficiency is analyzed under steady flow conditions considering different lubricating oils.The study reports the effects of the oil temperature on instantaneous turbine power and turbocharger efficiency under unsteady flow conditions. This analysis aims to provide a comprehensive understanding of turbocharger performance during the engine warm-up phase. The effects of heat transfer between turbocharger components are taken into account, along with the impact of different oil temperatures on friction losses and their effects on the instantaneous rotational speed of the turbocharger.The aim of this work is to provide valuable information on the actual performance of the turbocharger under unsteady flow condition with reference to the impact of the lubricating oil characteristic on the boost pressure provided to the engine.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600440</guid>
    </item>
    <item>
      <title>Characterization of Exhaust Gas Recirculation Effects in a Hydrogen-Fueled 4-Cylinder Engine with Direct Injection</title>
      <link>https://trid.trb.org/View/2600425</link>
      <description><![CDATA[The increasing importance of hydrogen as alternative energy source to reduce CO2 emissions in the transport sector makes its adoption in spark-ignited engines an attractive and cost-efficient alternative to fuel cell-powered vehicles. Lean combustion is the preferred operating strategy for H2-engines in order to achieve performance targets, enhance efficiency and at the same time avoid critical knocking and pre-ignition phenomena. Additionally, an effective approach to lower cylinder temperatures, relevant engine-out NOx emissions and boost pressure requirements at the same time, is an external exhaust gas recirculation (EGR) system. The aim of this work is to analyze and compare the effects of exhaust gas recirculation on the combustion of a lean hydrogen mixture in a turbocharged 4-cylinder H2-ICE with direct injection. For this investigation a load point at 18 bar BMEP and 4000 rpm is selected with and without the utilization of additional external EGR. In this case, a BTE of 38 % is achieved at lambda 1.8 with an 11 % EGR rate. Under these conditions, the NOx emissions are also reduced by 80 % while the efficiency rises by 0.7 %pt., compared to the case without exhaust gas recirculation. Several experiments at the test bench were carried out and used to calibrate a 3D-CFD engine model, in which the complete 4-cylinder engine is virtually reproduced, including high-pressure injection and detailed chemistry for combustion and knock modeling in a single simulation. By investigating the impact of a varying residual gas concentration and air-to-fuel ratio on the mixture formation and the combustion properties, consequences for NOx emissions and abnormal combustion events are derived. A sensitivity study regarding the EGR temperature was additionally performed by means of 3D-CFD simulation to analyze the effects of 80 °C, 160 °C and 240 °C hot external EGR on the combustion process.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600425</guid>
    </item>
    <item>
      <title>Experimental Analysis of Enhanced Scavenging Efficiency in Hydrogen-Powered Internal Combustion Engines for Heavy-Duty Applications</title>
      <link>https://trid.trb.org/View/2600417</link>
      <description><![CDATA[The purpose of this work is to highlight the benefits of improved scavenging efficiency for premixed, lean-burn, spark-ignited heavy-duty engines fueled by hydrogen. Scavenging efficiency measures the effectiveness of replacing exhaust gases with fresh air (or an air-fuel mixture) within the cylinder of an internal combustion engine. Enhanced scavenging efficiency reduces residual gas content and increases the proportion of fresh air, resulting in a cooler local mixture temperature. Additionally, it improves heat dissipation within the combustion chamber, cooling potential hotspots and allowing for earlier injections with fewer restrictions due to combustion anomalies, particularly pre-ignitions. To increase scavenging efficiency in a 4-stroke internal combustion engine, valve timing adjustments were made by introducing a valve lift profile with greater overlap of the exhaust valve closing and the inlet valve opening sequences. Additionally, a high-efficiency turbocharger was used to reduce backpressure and thereby increase the pressure gradient across the engine and promote scavenging. A test campaign was conducted on a 12.9-liter inline 6-cylinder heavy-duty engine to determine the impact of increased scavenging efficiency. The benefits were quantified using indicators such as intake and exhaust manifold pressures and maximum power output. In addition to an engine map and a full-load performance study, start-of-injection trade-offs were made at various engine speeds, loads, and different lambda targets. The test results confirmed the anticipated improvements. The increased valve overlap, and the high-efficiency turbocharger led to enhanced volumetric efficiency and a greater negative pressure differential between the intake and exhaust manifolds. These enhancements were particularly beneficial in the high-load area, where high boost pressure is essential to achieve the desired lambda value. At lower loads, where the engine typically operates in throttled conditions with a positive pressure gradient, no deterioration was observed. In summary, implementing the scavenging concept enabled the engine to operate more stable and achieve on average approximately 15 % higher performance without experiencing pre-ignition. Additionally, the lower local mixture temperature reduced thermal stress on the combustion chamber hardware, which helps mitigate wear and potential engine damage.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600417</guid>
    </item>
    <item>
      <title>Experimental Measurement of Dynamometer Homologation Cycles in a Dual-Fuel Medium-Duty Engine</title>
      <link>https://trid.trb.org/View/2600407</link>
      <description><![CDATA[Dual-fuel engines employing alternative combustion concepts have shown promising results in meeting significant emission reductions while maintaining engine performance. In the medium and heavy-duty transport sectors, where electrification remains challenging, developing low-temperature combustion is still a technological solution for reducing carbon impact. However, most of the results in this research field have been presented under stationary conditions, which still positions the transient operation as a challenge. One of the main reasons has been the lack of a dedicated control system to manage the load transitions and the inoperability of stock turbochargers to satisfy the EGR dilution ratios and boost pressure to sustain dual-fuel combustion. This study employs a modified 7.7 L dual-fuel engine for its operation in transient conditions by incorporating a prototype turbocharger system. The study addresses the recalibration of the engine to introduce modifications to the injection and air management strategies, allowing for a smoother transition between fully premixed and diffusive combustion modes while maintaining low emissions and similar performance. The study identified the transition from 50% to 75% as the most challenging transition from moving from a fully premixed zone with pressure gradients near the physical limits to a more diffusive combustion region in the engine map. After refining the calibration to allow smooth transitions between loads, transient cycle performance under the World Harmonized Stationary Cycle (WHSC) is experimentally measured, progressively increasing load from 50% to 100%. The results under transient tests confirmed that the recalibration successfully enables full-load operation while mitigating combustion instability and excessive emissions. This research advances the understanding of dual-fuel combustion strategies and highlights the potential of dual-fuel engines as a technological solution for its implementation under real-world vehicle applications in the freight transport sector.]]></description>
      <pubDate>Tue, 16 Sep 2025 11:12:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2600407</guid>
    </item>
    <item>
      <title>Hydrogen Operation Strategies in a Turbocharged SI Engine: Challenges
                    and Solutions</title>
      <link>https://trid.trb.org/View/2562998</link>
      <description><![CDATA[
                
                Hydrogen is a promising fuel for internal combustion engines, offering the
                    potential for efficient, environmentally friendly, and reliable operation. With
                    a large number of technical challenges, there is currently no mass production of
                    hydrogen-powered engines despite great efforts. One of the key challenges is the
                    complexity of optimizing hydrogen combustion and its control. Despite the
                    variety of proposed operation strategies, questions regarding their comparative
                    efficiency, interrelation, and mutual influence remain open, particularly in
                    turbocharged engines with direct multi-injection. To explore various hydrogen
                    operation strategies, a mathematical simulation of a turbocharged
                    hydrogen-powered engine was performed over its full range of loads and speeds.
                    This study employed a modified mathematical model based on Wiebe functions,
                    which describes the combustion of a premixed mixture in the flame front,
                    diffusion combustion, and relatively slow combustion occurring behind the flame
                    front, in lean mixture zones, and near-wall regions. The results revealed that
                    in hydrogen engines, the use of well-known mixture formation strategies in
                    combination with early direct injection, spark timing, and boost control
                    presents significant challenges. These challenges include an increased risk of
                    abnormal combustion, reduced maximum engine power, higher NOx emissions, and
                    increased mechanical stress on engine components. The study identified the
                    operating conditions under which these issues are most likely to occur. To
                    mitigate these problems and improve engine efficiency, the focus was placed on
                    implementing a late injection strategy in conjunction with dual injection (two
                    injections of hydrogen during a single engine cycle). A methodology for
                    selecting the optimal dual injection and ignition parameters was developed and
                    the engine power cycle under these strategies was simulated. The research
                    results showed that the proposed approach leads to an increase in engine power,
                    a lower probability of abnormal combustion, reduced peak cylinder pressures, and
                    decreased nitrogen oxide emissions.
            ]]></description>
      <pubDate>Tue, 24 Jun 2025 10:25:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2562998</guid>
    </item>
    <item>
      <title>Saw-Tooth Ramps for the Suppression of Flow-Acoustic Coupling in a High-Frequency Silencer for Turbocharger Compressors</title>
      <link>https://trid.trb.org/View/2552102</link>
      <description><![CDATA[The ported shroud casing treatment for turbocharger compressors is desirable for mitigating broadband/whoosh noise and enhancing boost pressures at low to mid flow rates. Yet, it is accompanied by elevated narrowband noise at the blade-pass frequency (BPF). Compressor BPF noise occurs at high frequencies where wave propagation is often multi-dimensional, rendering traditional planar wave silencers invalid. An earlier work introduced a novel reflective high-frequency silencer (baseline) targeting BPF noise in the 8-12 kHz range using an “acoustic straightener” that promoted planar wave propagation along arrays of quarter-wave resonators (QWRs). The design, however, faced challenges with high-amplitude tonal noise generation at specific flow conditions due to flow-acoustic coupling at the opening of the QWRs, thereby compromising the noise attenuation. The current study explores two QWR interface geometries that weaken the coupling, including linear and saw-tooth ramps on the upstream edge of each QWR. Computational fluid dynamics is utilized to study the mechanism of flow-acoustic coupling and assess the effectiveness of these modified interface geometries. Prototypes of the improved designs fabricated by additive manufacturing are then experimentally evaluated on a flow bench against the baseline silencer. The saw-tooth ramps prove particularly effective, achieving superior suppression of flow-acoustic coupling with lower flow restriction relative to the linear ramps. Next, the insertion loss of the baseline silencer and that with the saw-tooth ramps are determined on a turbocharger gas stand equipped with a rotating inlet duct. This unique setup is utilized to calculate the transmitted sound power upstream of the configurations with and without the silencer and therefore its insertion loss. The sharp valleys of negative insertion loss indicating tonal noise due to flow-acoustic coupling in the baseline silencer are eliminated by the saw-tooth ramps, therefore enhancing the overall noise attenuation.]]></description>
      <pubDate>Tue, 13 May 2025 10:11:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/2552102</guid>
    </item>
    <item>
      <title>DoE-Based Numerical Optimization of Intake and Exhaust Port Geometry of a Small Opposed-Piston 2-Stroke (OP2S) Hydrogen Engine</title>
      <link>https://trid.trb.org/View/2547855</link>
      <description><![CDATA[The future potential of an opposed-piston two-stroke (OP2S) engine has attracted the attention of researchers worldwide as it offers a high thermal efficiency and power-to-weight ratio with a simple engine configuration. This engine can be used with low-carbon fuels and hydrogen to reduce greenhouse gas emissions. However, the two-stroke operation has always been limited by its low scavenging efficiency and short-circuit of fresh charge. The current work is focused on optimizing scavenging efficiency and short-circuit in a small 200 cc single-cylinder OP2S SI engine using 3-D computational fluid dynamic (CFD) simulations. The effect of four parameters, namely, area of intake ports, area of exhaust ports, and angular orientations of intake ports (swirl and tilt) on scavenging efficiency and short-circuit, has been assessed and optimized. A Latin-hypercube based Design of Experiments (DoE) methodology is used to sample the design space spanning over a range of four parameters. A response surface is generated using the Kriging method, and the geometry of intake and exhaust ports have been optimized for maximum scavenging efficiency and minimum short-circuit using a genetic algorithm on the response surface. The results show that the scavenging efficiency improves with the increase in exhaust port area, but it also increases the short circuit of fresh air. The Intake port swirl angle significantly impacts scavenging efficiency and short-circuit. The current optimization process achieved a scavenging efficiency of 85% (percentage of the total mass in the cylinder) and a short circuit of 12% (percentage of trapped fresh air). Apart from the geometric parameters, the effect of intake boost pressure and the engine speed on scavenging efficiency and short-circuit has also been evaluated.]]></description>
      <pubDate>Tue, 29 Apr 2025 15:53:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2547855</guid>
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