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Combustion visualizations were carried out in a constant volume vessel to study the partially premixed combustion of a gasoline-like fuel using high speed imaging. The test fuel (G80H20) is composed by volume 80% commercial gasoline and 20% n-heptane. The effects of ambient gas composition, ambient temperature and injection pressure on G80H20 combustion characteristics were analyzed. Meanwhile, a comparison of the EGR effect on combustion process between G80H20 and diesel was made. Four ambient gas conditions that represent the in-cylinder gas compositions of a heavy-duty diesel engine with EGR ratios of 0%, 20%, 40% and 60% were used to simulate EGR conditions. Variables also include two ambient temperature (910K and 870K) and two injection pressure (20 MPa and 50 MPa) conditions.

The large amount of controllable fuel injection parameters of Diesel engine equipped with high pressure common-rail fuel injection system makes the control of combustion more flexible, and also makes the workload of calibration and optimization much heavier. For higher efficiency, model-based approaches are presented and researched. This contribution presents a new method for modeling which is constituted by Neural Network and Adaptive Network-based Fussy Inference System (ANFIS). The experiment is carried out on a 6-cylinder common rail diesel engine. The analysis and experiment show that effective modeling can be achieved using this method.

This paper presents an investigation of drivability issue of engine start-stop. Hybrid vehicles provide excellent benefits regarding fuel efficiency and emission. However, vibration results from constant engine start and stop events generate drivability issues, thus compromising driving comfort. This paper has designed a high speed torque sensor to capture instantaneous torque at the engine shaft. Its consequences help to find out the most suitable index of vibration severity. This paper is organized in four sections. The first section introduces the powertrain to be studied. The second section introduces development of a specially designed torque sensor. The torque sensor is installed between the engine and ISG (Integrated Starter Generator), alongside with an encoder. The torque sensor is utilized to collect the instantaneous shaft torque on occasion of engine start. In the third section, this paper has performed two experiments.

A plateau self-adapted turbocharging system based on variable geometry turbocharger (VGT) technology is proposed to solve the problem of diesel engine operating at plateau. The control strategy of the plateau self-adapted turbocharging system is studied using a GT-Power engine model. The control strategy is based on the optimization of the VGT nozzle vane position at various engine operating conditions and various altitudes. Simulation results show that by optimizing the matching and controlling the VGT, the performance of the engine matched with VGT can be improved significantly compared with the one matched with FGT (fixed geometry turbocharger) at various altitudes. Surge and overspeed phenomena of the turbocharger can also be avoided.

Presently, urban transportation highly depends on the fossil fuels, but its rapid fluctuating economic issues and environmental consequences impose the variegation of energy sources. Hydrogen enriched compressed natural gas (HCNG) engines offer the potential of higher brake thermal efficiency with low emissions, which also satisfies the strict pollutant emission standards. The two-zone turbulent entrainment quasi-dimensional combustion model is developed to predict the combustion process of spark-ignited hydrogen enriched compressed natural gas-fueled engines. The fundamentals of thermodynamic process, turbulent flame propagation model and other sub-models like laminar burning velocity, adiabatic temperature and ignition lag model are introduced for the better accuracy. The experiments have been conducted for three different fuels; pure CNG, 20% HCNG, and 40% HCNG blends under MAP of 105 kPa for various excess air ratios (λ) and ignition timing (θi).

Atomization of fuel sprays is a key factor in controlling the combustion quality in the direct-injection engines. In this present work, the effect of saturation ratio (Rs) on the near nozzle spray patterns of ethanol was investigated using an ultra-high speed imaging technique. The Rs range covered both flash-boiling and non-flash boiling regions. Ethanol was injected from a single-hole injector into an optically accessible constant volume chamber at a fixed injection pressure of 40 MPa with different fuel temperatures and back pressures. High-speed imaging was performed using an ultrahigh speed camera (1 million fps) coupled with a long-distance microscope. Under non-flash boiling conditions, the effect of Rs on fuel development was small but observable. Clear fuel collision can be observed at Rs=1.5 and 1.0. Under the flash boiling conditions, near-nozzle spray patterns were significant different from the non-flash boiling ones.

Advanced exhaust after-treatment technology is required for heavy-duty diesel vehicles to achieve stringent Euro VI emission standards. Diesel particulate filter (DPF) is the most efficient system that is used to trap the particulate matter (PM), and particulate number (PN) emissions form diesel engines. The after-treatment system used in this study is catalyzed DPF (CDPF) downstream of diesel oxidation catalyst (DOC) with secondary fuel injection. Additional fuel is injected upstream of DOC to enhance exothermal heat which is needed to raise the CDPF temperature during the active regeneration process. The objective of this research is to numerically investigate soot loading and active regeneration of a CDPF on a heavy-duty diesel engine. In order to improve the active regeneration performance of CDPF, several factors are investigated in the study such as the effect of catalytic in filter wall, soot distribution form along filter wall, and soot loads.

Turbulent jet ignition (TJI) combustion using pre-chamber ignition can accelerate the combustion speed in the cylinder and has garnered growing interest in recent years. However, it is complicated for the optimization of the pre-chamber structure and combustion system. This study investigated the effects of the pre-chamber structure and the intake ports on the combustion characteristics of a gasoline engine through CFD simulation. Spark ignition (SI) combustion simulation was also conducted for comparison. The results showed that the design of the pre-chamber that causes the jet flame colliding with walls severely worsen the combustion, increasing the knocking intendency, and decrease the thermal efficiency. Compared with SI combustion mode, the TJI combustion mode has the higher heat transfer loss and lower unburned loss. The well-optimized pre-chamber can accelerate the flame propagation with knock suppression.

The strategy for emission reduction in the P2.5 hybrid system involves the optimization of engine torque, engine speed, catalyst heat duration, and motor torque regulation in a coordinated manner. In addition to employing traditional engine control methods used in HEV models, unique approaches can be utilized to effectively manage emissions. The primary principle is to ensure that the engine operates predominantly under steady-state conditions or limits its load to regulate emissions levels. The main contributions of this paper are as follows: The first is the optimization of catalyst heating stage. During the catalyst heating stage, the system divides it into one or two stages. In the first stage, the vehicle is driven by the motor while keeping the engine idle. This approach stabilizes catalyst heating and prevents fluctuations in air-fuel ratio caused by speed and load changes that could potentially worsen emissions performance.

In this paper, a hybrid combustion mode in four-stroke gasoline direct injection engines was studied. Switching cam profiles and injection strategies simultaneously was adopted to obtain a rapid and smooth switch between SI mode and HCCI mode. Based on the continuous pressure traces and corresponding emissions, HCCI steady operation, HCCI transient process (combustion phase adjustment, SI-HCCI, HCCI-SI, HCCI cold start) were studied. In HCCI mode, HCCI combustion phase can be adjusted rapidly by changing the split injection ratio. The HCCI control strategies had been demonstrated in a Chery GDI2.0 engine. The HCCI engine simulation results show that, oxygen and active radicals are stored due to negative valve overlap and split fuel injection under learn burn condition. This reduces the HCCI sensitivity on inlet boundary conditions, such as intake charge and intake temperature. The engine can be run from 1500rpm to 4000rpm in HCCI mode without spark ignition.

A conceptual approach to help understand and simulate droplet induced pre-ignition is presented. The complex phenomenon of oil-fuel droplet induced pre-ignition has been decomposed to its elementary processes. This approach helps identify the key fluid properties and engine parameters that affect the pre-ignition phenomenon, and could be used to control LSPI. Based on the conceptual model, a 3D CFD engine simulation has been developed which is able to realistically model all of the elementary processes involved in droplet induced pre-ignition. The simulation was successfully able to predict droplet induced pre-ignition at conditions where the phenomenon has been experimentally observed. The simulation has been able to help explain the observation of pre-ignition advancement relative to injection timing as experimentally observed in a previous study [6].

Polyoxymethylene dimethyl ethers (PODEn) are promising alternative fuel candidates for diesel engines because they present advantages in soot reduction. This study uses a PODEn mixture (contains PODE3-6) from mass production to provide oxygen component in blend fuels. The spray combustion of PODEn-diesel bend fuels in a constant volume vessel was studied using high speed imaging, PLII-LEM and OH* chemiluminescence. Fuels of several blend ratios are compared with pure diesel. Flame luminance data show a near linear decrease tendency with the blend ratio increasing. The OH* images reveal that the ignition positions of all the cases have small differences, which indicates that using a low PODEn blend ratio of no more than 30% does not need significant adjustment in engine combustion control strategies. It is found that 30% PODEn blended with diesel (P30) can effectively reduce the total soot by approximately 68% in comparison with pure diesel.

A computational fluid dynamics (CFD) guided design optimization was conducted for the piston bowl geometry for a heavy-duty diesel engine. The optimization goal was to minimize engine-out NOx emissions without sacrificing engine peak power and thermal efficiency. The CFD model was validated with experiments and the combustion system optimization was conducted under three selected operating conditions representing low speed, maximum torque, and rated power. A hundred piston bowl shapes were generated, of which 32 shapes with 3 spray angles for each shape were numerically analyzed and one optimized design of piston bowl geometry with spray angle was selected. On average, the optimized combustion system decreased nitrogen oxide (NOx) emissions by 17% and soot emissions by 41% without compromising maximum engine power and fuel economy.

Ammonia shows promise as an alternative fuel for internal combustion engines (ICEs) in reducing CO2 emissions due to its carbon-free nature and well-established infrastructure. However, certain drawbacks, such as the high ignition energy, the narrow flammability range, and the extremely low laminar flame speed, limit its widespread application. The dual fuel (DF) mode is an appealing approach to enhance ammonia combustion. The combustion characteristics of ammonia-diesel dual fuel mode and ammonia-PODE3 dual fuel mode were experimentally studied using a full-view optical engine and the high-speed photography method. The ammonia energy ratio (ERa) was varied from 40% to 60%, and the main injection energy ratio (ERInj1) and the main injection time (SOI1) were also varied in ammonia-PODE3 mode.

Both ammonia and hydrogen, as zero-carbon fuels for internal combustion engines, are received growing attention. However, ammonia faces a challenge of low flame propagation velocity. Through injecting hydrogen into active pre-chamber, its jet flame ignition can accelerate the flame propagation velocity of ammonia. The influence of different pre-chamber structures on engine combustion characteristics is significant. In this paper, numerical studies were conducted to assess the impact of various pre-chamber structures and hydrogen injection strategy on the combustion characteristics of ammonia/hydrogen engines while maintaining the equivalent ratio of 1.0. The results indicate that the jet angle significantly affects the position of jet flame and the followed main combustion. The in-cylinder combustion pressure peaks at jet angle of 150°. Meanwhile, the combustion duration of 150° is shortened by 74.3% compared with that of 60°.

Homogeneous Charge Induced Ignition (HCII) combustion is believed to be a promising approach to achieve clean and high efficiency combustion. HCII can be realized by using port-injection of the high-volatile fuel (gasoline) to prepare in-cylinder homogeneous charge and direct injection of the high-ignitable fuel (diesel) near the top dead center to control the start of combustion. In the current study, a numerical study was carried out to understand the mixing and auto-ignition process in HCII combustion. A multicomponent chemical kinetic mechanism for gasoline and diesel, consisting of n-heptane, iso-octane, ethanol, toluene, diisobutylene and n-decane, has been developed for predicting their ignition and oxidation. The final mechanism consists of 104 species and 398 reactions. This mechanism was validated with the experimental data of ignition delay times and laminar flame speeds for each component and real transportation fuels.

2, 5-Dimethylfuran (DMF) has been receiving increasing interest as a potential alternative fuel to fossil fuels, owing to the recent development of new production technology. However, the influence of DMF properties on the in-cylinder fuel spray and its evaporation, subsequent combustion processes as well as emission formation in current gasoline direct injection (GDI) engines is still not well understood, due to the lack of comprehensive understanding of its physical and chemical characteristics. To better understand the spray characteristics of DMF and its application to the IC engine, the fuel sprays of DMF and gasoline were investigated by experimental and computational methods. The shadowgraph and Phase Doppler Particle Analyzer (PDPA) techniques were used for measuring spray penetration, droplet velocity and size distribution of both fuels.

Ammonia (NH3), a zero-carbon fuel, has great potential for internal combustion engine development. However, its high ignition energy, low laminar burning velocity, narrow range of flammability limits, and high latent heat of vaporization are not conducive for engine application. This paper numerically investigates the feasibility of utilizing ammonia in a heavy-duty diesel engine, specifically through low-pressure direct injection (LP-DI) of hydrogen to ignite ammonia combustion. Due to the lack of a well-corresponding mechanism for the operating conditions of ammonia-hydrogen engines, this study serves only as a trend-oriented prediction. The paper compares the engine's combustion and emission performance by optimizing four critical parameters: excess air ratio, hydrogen energy ratio, ignition timing, and hydrogen injection timing. The results reveal that excessively high hydrogen energy ratios lead to an advanced combustion phase, reducing indicated thermal efficiency.

Spray atomization, spray-wall impingement, and mixture formation are key factors in affecting the particulate matter (PM) emission in gasoline direct injection (GDI) engines. Current knowledge of wall-wetting phenomenon and mixture formation are mostly based on the studies that the fuel is injected at ordinary temperature and various ambient conditions. In the real GDI engine, the fuel pipe and injector are always heated up by the pump and the engine body, especially at hot engine conditions, thus the fuel temperature is always higher than the ordinary temperature, and the relevant research is still limited. The aim of this study is to numerically investigate the spray, spray-wall impingement, and mixture formation characteristics under different fuel temperature conditions, so as to provide theoretical support in optimizing the combustion performance and further reducing the PM emission of GDI engines.

Diesel particulate filter (DPF) is necessary for diesel engines to meet the increasingly stringent emission regulations. Many studies have demonstrated that the lubricant derived ash has a significant effect on DPF pressure drop and engine fuel economy, and this effect becomes more and more severe with the increasing of operating hours of the DPF because the ash accumulated in the DPF cannot be removed by regeneration. It is reported that most of the DPFs operated with more ash than soot in the filter for more than three quarters of the time during its lifetime [1]. In order to mitigate this problem, the original engine manufacturers (OEM) tend to use an oversized DPF for the engine. However, it will increase the costs of the DPF and reduce the compactness of the engine aftertreatment system.