<div>Hydrogen-fueled reciprocating engines typically feature reasonable efficiencies and low engine-out emissions but low power density, compromising their utility and economics. Previous hydrogen engine research has found efficiency and anti-knock benefits when using either Miller cycles or water injection. This article therefore studies, for the first time, a directly injected (DI), spark-ignited, heavy-duty, turbocharged and hydrogen-fueled engine operated with both Miller cycles and water injection. Miller cycles, with either early or late intake valve closure, and water injection combine to achieve high engine efficiencies approaching 50%, which is significantly higher than the same engine with standard valve timing. The increased susceptibility of hydrogen autoignition in these Miller cycles is overcome by water injection, which simultaneously increases the charge density, counteracting both lean-burn hydrogen’s and Miller cycles’ commonly observed power loss. This demonstrates that the combination of DI, Miller cycles, and water injection is a pathway toward highly efficient, low-emission, hydrogen-fueled engines with power densities that are comparable to conventional engines.</div>

<div>Air pollution is a significant long-term public health issue, with on-road traffic emissions being a primary contributor, especially in urban areas. Remote emission sensing (RES) is an innovative method for large-scale monitoring of vehicle emissions. It not only enables accurate detection of pollutants from vehicles under real-world driving conditions but also offers actionable insights to optimize engine performance. The point sampling-based RES technique involves sampling the vehicle exhaust plume along the roadside with a sampling line and using exhaust analyzers. In this method, the sampling line is placed alongside the road for sample extraction. Thus, the sampling position and knowledge regarding the spread of the exhaust plumes are crucial. Other modern RES systems utilize laser absorption spectroscopy to measure the pollutants in vehicle exhaust. For accurate absorption measurements, the laser’s height must align with the height of the exhaust plume, and the absorption length must be known. In this work, we present a gas density Schlieren imaging sensor (GDSIS) system designed to visually capture, quantitatively analyze, and reconstruct the density fields of exhaust plumes from category L-vehicles. By analyzing the density fields, we can pinpoint the location of the highest density within the exhaust plume. This information indicates the ideal height for positioning sampling lines and lasers used in RES systems. Identifying this ideal height can enhance the efficiency and capture rate of RES systems while also helping to detect engine inefficiencies that can negatively affect performance and increase emissions. Moreover, emission patterns can inform engine calibration or maintenance schedules, which helps optimize fuel consumption and engine response. The performance of the GDSIS system in both laboratory settings with controlled gas flows and on the road with L-vehicles during emissions measurement campaigns is evaluated.</div>

<div>The present study aims to simulate the non-reacting flow within the cylinder of a two-stroke spark ignition internal combustion engine (SIE) utilizing gasoline direct injection (GDI). A computational fluid dynamics (CFD) analysis was employed to forecast the turbulence levels of the in-cylinder flow, including the root-mean-square (RMS) turbulent velocity. The three-dimensional model was developed using ANSYS-FLUENT. The investigation examined the intake manifold inclination angles of 0°, 10°, 20°, 30°, and 40° for two different types of single-intake port engines (I and II) and a single-type double-intake port engines, that are presented at an engine speed of 1500 rpm. The findings revealed that the highest RMS turbulent velocities occurred at a 30° inclination for the double-intake engine, while the single-intake engines (I) and (II) showed peak velocities at 0° and 10°, respectively. Furthermore, in single-intake engine (I), the RMS turbulent velocity was found to be 38.7% greater than that of the double-intake engine, and single-intake engine (II) exhibited a 35% increase compared to single-intake port (I).</div>

<div>The growing number of automobiles on the road has raised awareness about environmental sustainability and transportation alternatives, sparking ideas about future transportation. Few short-term alternatives meet consumer needs and enable mass production. Because they do not accurately reflect real-world driving. Current models are unable to estimate vehicle emissions. However, the purpose of this research is to present an application of an adaptive neuro-fuzzy inference system for managing the various factors contributing to vehicle gasoline engine exhaust emissions. It examines how well the three known standardized driving cycles (DSCs). Accurately reflect real-world driving and evaluate the impact of real-world driving on vehicle emissions. Indirect emissions are inversely proportional to the vehicle’s fuel consumption. The methodology used is Eco-score methodology to calculate indirect emissions of light vehicles. Expected emission charge estimates for different using styles. Emission rates range substantially between battery classes. The vehicle’s gasoline efficiency is four times better than a similar automobile, but neither mass nor charge multiplied appreciably. The range of this car is not restrained by the battery length, which increases driver comfort, while automobile meets customer expectations in addition to environmental worries and advantages. Despite the fact that they continue to be affordable, they offer a possibility for mass manufacturing reducing overall environmental effects. In keeping with the consequences, the adaptive neuro-fuzzy inference system works nicely to simulate and regulate vehicle engine exhaust emissions.</div> <div>However, the final objective of a regulatory-oriented studies software that focuses on air pollution from mobile sources is to identify and quantify any outcomes that the emissions may have on human fitness.</div> <div>However, before we invest highbrow and economic sources, we need to first recognize the restrictions of modern information and methodologies that preclude accurate estimates of risk to human health. Destiny research packages should be justified by way of their promise to triumph over these boundaries. The goal of this extent, then, is to identify troubles and pick out a studies schedule with a purpose to be only in advancing our potential to quantify the fitness dangers related to air pollution.</div>

<div>Ammonia-fired reciprocating engines have emerged as a promising technology in the maritime and power generation sector at medium-to-large scale (1–80 MW). The use of “on-the-fly” partial ammonia decomposition to produce a relatively small amount of hydrogen that can be used as combustion promoter, replacing fossil fuels in this function, enables this technology to provide carbon-free propulsion and power generation. In this context, it is envisioned that a hydrogen-fired prechamber ignition strategy offers significant advantages by accelerating the ammonia ignition and complete combustion process, increasing its reliability and robustness while still aiming to achieve low NO<i> <sub>x</sub> </i>, N<sub>2</sub>O, and NH<sub>3</sub> emissions. This study exploits an OpenFOAM-based Large Eddy Simulation (LES) numerical modeling framework to investigate the ignition and combustion behavior of an ammonia main charge ignited by a hydrogen-fired prechamber. First, a conventional port-injection premixed configuration for the ammonia main charge is considered whereas the hydrogen-fired prechamber is found to provide a sufficiently strong ignition source for all ammonia–air mixtures investigated. The effect of the main charge equivalence ratio and the wall temperature on combustion efficiency and emissions formation is evaluated. Second, considering a non-premixed configuration for comparison, an identically configured hydrogen-fired prechamber is used to study the ignition and combustion process for ammonia main charges directly injected as liquid sprays and modeled as Lagrangian particle tracking (LPT) in conjunction with the LES model. The LES results suggest that the relative timing and angle of injection between the liquid sprays and the hydrogen jet flames emerging from the prechamber play a major role in controlling the ignition and combustion process. Finally, the non-premixed ammonia main charge configuration is found to significantly reduce the formation of pollutants and extend the operating range to leaner global equivalence ratios, compared to the premixed ammonia main charge configuration.</div>

<div>The combustion timing of auto-ignited combustion is determined by composition, temperature, and pressure of cylinder charge. Thus, for a successful auto-ignition, those key variables must be controlled within tight target ranges, which is challenging due to (i) nature of coupling between those variables, and (ii) complexity of managing multiple actuators in the engine. In this article, a control strategy that manages multiple actuators of a boosted homogeneous charge compression ignition (HCCI) engine is developed to maintain robust auto-ignited combustion. The HCCI engine being considered is equipped with multiple boosting devices including a supercharger and a turbocharger in addition to conventional actuators and sensors. Since each boosting device has its own pros and cons, harmonizing those boosting devices is crucial for successful transient operation. To address the multi-variable transient control problem, speed-gradient control methodology is applied to minimize coupling between boosting devices. Simulation results show that the control strategy overcomes turbo lag by utilizing the supercharger during transient. The controller developed is still appliable to manage multiple boosting devices with conventional engines as well as HCCI engine.</div>

<div>Biogas (60% methane–40% CO<sub>2</sub> approximately) can be used in the reactivity-controlled compression ignition (RCCI) mode along with a high-reactivity fuel (HRF). In this work dimethyl ether (DME) that can also be produced from renewable sources was used as the HRF as a move toward sustainable power generation. The two-cylinder turbocharged diesel engine modified to work in the DME–biogas RCCI (DMB-RCCI) mode was studied under different proportions of methane (45–95%) in biogas since the quality of this fuel can vary depending on the feedstock and production method. Only a narrow range of biogas to DME ratios could be tolerated in this mode at each output without misfire or knock. Detailed experiments were conducted at brake mean effective pressures (BMEPs) of 3 and 5 bar at a speed of 1500 rpm and comparisons were made with the diesel–biogas dual-fuel and diesel–biogas RCCI modes under similar methane flow rates while the proportion of CO<sub>2</sub> was varied. The DMB-RCCI mode exhibited superior brake thermal efficiency (25.3% as against 22% and 31.5% as against 29% at the BMEPs of 3 and 5 bar) as compared to the other modes and was not sensitive to the concentration of methane. The NOx and soot emissions were also negligible and the lowest CH<sub>4</sub> emission levels were also attained. The cyclic fluctuations in IMEP were lower than 5% in this mode. Thus, DME can be used along with biogas to enhance its reactivity for sustainable power generation in the RCCI mode.</div>

<div>The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage. One such fluid is the condensed water in the low-pressure exhaust gas recirculation channel (LP-EGR) formulated at cold starts and low-speed high load conditions. This kind of design has been developed to reduce nitrogen oxide emissions and is used in both gasoline and diesel engines. This article presents a state-of-the-art review of this WDE process, focusing on the formation of the condensed water before the compressor wheel, summarizing the influencing factors of WDE and the effects of the damage including using component testbench experiences and simulation methodologies. Inspection possibilities such as high-speed camera measurement and vibration analysis are also an important part of the document.</div>

<div>At present, it is generally considered in the analysis of the secondary motion of engine piston that the piston skirt–cylinder liner friction pair is fully lubricated in an engine operating cycle. However, in practice, when the piston moves upward, the amount of lubricating oil at the inlet may not ensure that the friction pair is fully lubricated. In this article, the secondary motion of piston is studied when the transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair. The secondary motion of piston is solved based on the combined piston motion model, hydrodynamic lubrication model, asperity contact model, and lubricating oil flow model. The secondary motion equation of piston is solved by the Broyden method. The hydrodynamic lubrication equation is solved by the finite difference method. The asperity contact between piston skirt and cylinder liner is calculated by the Greenwood model. The flow of lubricating oil is analyzed based on the theory of fluid mechanics. The results indicate that, when the actual transport of lubricating oil is considered to determine the lubrication condition of piston skirt–cylinder liner friction pair, the secondary motion of piston is remarkably different from that in which the flooded lubrication is assumed in an engine operating cycle. Therefore, it is helpful to improve the accuracy and make the analysis closer to the actual engine operating situation that the transport of lubricating oil is considered in the analysis of the secondary motion of engine piston.</div>

<div>This study investigates the behavior of pre-chamber knock in comparison to traditional spark ignition engine knock, using a modified constant-volume gasoline engine with an optically accessible piston. The aim is to provide a deeper understanding of pre-chamber knock combustion and its potential for mitigating knock. Five passive pre-chambers with different nozzle diameters, volumes, and nozzle numbers were tested, and nitrogen dilution was varied from 0% to 10%. The stochastic nature of knock behavior necessitates the use of statistical methods, leading to the proposal of a high-frequency band-pass filter (37–43 kHz) as an alternative pre-chamber knock metric. Pre-chamber knock combustion was found to exhibit fewer strong knock cycles compared to SI engines, indicating its potential for mitigating knock intensity. High-speed images revealed pre-chamber knock primarily occurs near the liner, where end-gas knock is typically exhibited. The study identified that increasing pre-chamber nozzle diameter resulted in a larger dispersion of knock cycles and more severe knock intensity, likely due to shorter jet penetration depth requiring more time for end-gas consumption. Strategies for mitigating knock in pre-chamber combustion systems include reducing the pre-chamber volume for a fixed A/V ratio and increasing dilution level. The results of this study offer valuable insights for developing effective knock mitigation approaches in pre-chamber combustion systems, contributing to the advancement of more efficient and reliable engines.</div>