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In order to improve the ignition capacity and burning rate for spark-ignited engines, pre-chamber jet ignition is a promising technique to achieve fast premixed combustion and low pollutant emissions. However, few studies focus on the interaction between multiple reacting (i.e. flamelet) or reacted (i.e. radical) jets, its effect on ignition, exotherm and flow behaviors also remain to be revealed. This paper investigated two types of jet interaction under different pre-chamber structures, including the jet-crossing and unequal nozzle designs. Optical experiments under different conditions were conducted in a constant volume combustion chamber with CH4 as fuel, using simultaneous high speed schlieren and OH* chemiluminescence method. Meanwhile, computational fluid dynamics (CFD) simulations with CH4 and NH3/CH4 blend fuels were carried out using Converge software to provide further insights of turbulent flow and ignition process.

Ethanol fuel blends with gasoline for spark ignition (SI) internal combustion engines are widely used on account of their advantages in terms of fuel economy and emissions reduction potential. The focus of this paper is to study the effects of these blends on combustion characteristics such as in-cylinder pressure profiles, gas-phase emissions (e.g., unburned hydrocarbons, NOx) and particulates (e.g., particulate matter and particle number) using both measurement campaigns and digital engineering workflows. Nineteen load-speed operating points in a 1L 3-cylinder GDI SI engine were measured and modelled. The measurements for in-cylinder pressure and emissions were repeated at each operating point for three types of fuel: gasoline (E0, 0% by volume of ethanol blend), E10 (10 % by volume of ethanol blend) and E20 (20% by volume of ethanol blend).

Due to the rapid development of road infrastructure and vehicle population in China, the fuel consumption and emission of on-road vehicles tested in China World Transient Vehicle Cycle (C-WTVC) cannot indicate the real driving results. But the test results in China Heavy-duty Commercial Vehicle Test Cycle-Coach (CHTC-C) based on the road driving conditions in China are closer to the actual driving data. In this paper, the model for predicting the performance of heavy-duty vehicles is established and validated. The fuel consumption and NOx emission of a Euro VI heavy-duty coach under C-WTVC and CHTC-C tests are calculated by employing the developed model. Furthermore, the fuel consumption of the test coach is optimized and its sensitivity to the driving factors is analyzed.

The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere.

In this paper, the differences between multi-hole and single-hole spray contour under the same conditions were compared by using high-speed photography. The difference between the contour area of multi-hole and that of single-hole spray was used as a parameter to describe the degree of spray collapse. Three dimensionless parameters (i.e. degree of superheat, degree of undercooling, and nozzle pressure ratio) were applied to characterize inside-nozzle thermodynamic, outside-nozzle thermodynamic and kinetic factors, respectively. In addition, the relationship between the three dimensionless parameters and the spray collapse was analyzed. A semi-empirical equation was proposed for evaluation of the degree of collapse based on dimensionless parameters of flash and non-flash boiling sprays respectively.

Gasoline Direct Injection (GDI) engines show advantages in reducing fuel consumption and gaseous pollution emissions when compared to Port Fuel Injection (PFI) engines. However, particulate matter emissions are an essential issue for GDI engine development due to increasingly stringent worldwide emission regulations. Previous studies have shown that gasoline fuel compositions, as well as deposits formed in GDI fuel injectors, can affect emissions in the GDI engine. In this work, the impact of gasoline fuel properties on forming injector deposits and the resulting effect on particulate emissions were investigated using a modern Chinese GDI engine. Six test fuels with different properties involving changes in olefins, aromatics, heavy (C9/C9+) aromatics, T90 and deposit control additive (DCA) were prepared based on the gasoline survey results from the Chinese gasoline fuel market and the China 6 gasoline fuel standard limits.

Water management, particularly in the gas diffusion layers (GDL), plays an important role in the performance and reliability of the proton exchange membrane fuel cells (PEMFCs). In this study, a two-phase multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) is employed to simulate water transport in a reconstructed GDL and the effect of perforation shapes is investigated. The revised pseudopotential multiphase model is adopted to realize high-density ratio, good thermodynamic consistency, adjustable surface tension and high contact angle. The transport characteristics are analyzed in both vertical and horizontal transport directions. The LBM simulation provides detailed results in mesoscale and indicates that the surface tension dominates the process of water transport in the perforated GDL, which exhibits unexpectedly similarities in the vertical and horizontal transport.

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.

An experiment was carried out to investigate the effect of single and double-deck pre-chamber on the combustion characteristics of premixed CH4/air in a constant volume vessel using schlieren method. A special design was proposed for the visualization of the pre-chamber. Combustion with different initial temperatures (300 K, 400 K, 500 K) were observed at stoichiometric ratio to lean-burn limit. Although single-deck pre-chamber has advantages over double-deck pre-chamber in both initial flame development duration and main combustion duration, the latter could extend the lean-burn limit by up to 0.3 and promote the stability of ignition. It is also found that extensive distribution of active species in main chamber before ignition can accelerate speed of flame propagation enormously.

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 indispensable for diesel engines to meet the increasingly stringent emission regulations. Both the peak temperature and the maximum temperature gradient of the DPF during active regeneration should be well controlled in order to enhance the reliability and durability of the filter. In this paper, the temperature field of the DPF during active regeneration with hydrocarbon (HC) injection was investigated with engine bench tests and numerical simulation. For the experimental study, 24 thermocouples were inserted into the DPF channels to measure the inner temperature of the filter to capture its temperature field, and the circumferential, axial and radial distribution of the filter temperature was analyzed to understand the DPF temperature field behavior during active regeneration.

Polyoxymethylene Dimethyl Ether (PODEn) is a promising green additive to diesel fuel, owing to the unique chemical structure (CH3O[CH2O]nCH3, n≥2) and high cetane number. Together with the general wide-distillation fuel (WDF), which has an attractive potential to reduce the cost of production of vehicle fuel, the oxygenated WDF with PODEn can help achieve a high efficiency and low emissions of soot, NOx, HC, and CO simultaneously. In this paper, the first detailed reaction mechanism (225 species, 1082 reactions) which can describe the ignition characteristics of PODE1 and PODE3 at low temperature was developed.

This study compared the combustion and emission characteristics of Homogeneous Charge Compression Ignition (HCCI) and Direct Injection Compression Ignition (DICI) modes in a boosted and high compression ratio (17) engine fueled with gasoline and gasoline/diesel blend (80% gasoline by volume, denoted as G80). The injection strategy was adjusted to achieve the highest thermal efficiency at different intake pressures. The results showed that Low Temperature Heat Release (LTHR) was not observed in gasoline HCCI. However, 20% additional diesel could lower down the octane number and improve the autoignition reactivity of G80, which contributed to a weak LTHR, accounting for approximately 5% of total released heat. The combustion efficiency in gasoline DICI was higher than those in gasoline HCCI and G80 HCCI, while the exhaust loss and heat transfer loss in DICI mode were higher than those in HCCI mode.

The demand for more efficient and clean engines have prompted the research and development of new engine technologies. Automotive engines expected to run with leaner mixtures and higher compression ratios. Lean burn is effective to increase fuel economy whilst reducing emissions but unreliable ignition of the lean mixtures by the conventional spark plug is one of the problems which causes concerns to the engine designers. Laser ignition is a promising technology and holds many benefits over the spark ignition because it can extend the ignitability of lean mixtures with flexibility of the ignition location and absence of electrode degradation for improved engine performance with lean burn. In this study, high-speed photography is used to investigate the flame kernel growth and propagation in an optical direct injection engine using laser ignition by an Nd:YAG laser.

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.

Gasoline direct injection (GDI) engine technology is now widely used due to its high fuel efficiency and low CO2 emissions. However, particulate emissions pose one challenge to GDI technology, particularly in the presence of fuel injector deposits. In this paper, a 4-cylinder turbocharged GDI engine in the Chinese market was selected and operated at 2000rpm and 3bar BMEP condition for 55 hours to accumulate injector deposits. The engine spark timing, cylinder pressure, combustion duration, brake specific fuel consumption (BSFC), gaseous pollutants which include total hydro carbon (THC), NOx (NO and NO2) and carbon dioxide (CO), and particulate emissions were measured before and after the injector fouling test at eight different operating conditions. Test results indicated that mild injector fouling can result in an effect on engine combustion and emissions despite a small change in injector flow rate and pulse width.

An experimental study of particulate matter and volatile organic compounds (VOCs) emissions was conducted on a direct injection gasoline (DIG) engine and a port fuel injection (PFI) engine which both were produced by Chinese original equipment manufacturers (OEMs) to investigate the impact of fuel properties from Chinese market on particulate and VOCs emissions from modern gasoline vehicles. The study in this paper is just the first step of the work which is to investigate the impact of gasoline fuel properties and light duty vehicle technologies on the primary and secondary emissions, which are the sources of particulate matter 2.5 (PM2.5) in the atmosphere in China. It is expected through the whole work to provide some suggestions and guidelines on how to improve air quality and mediate severe haze pollution in China through fuel quality control and vehicle technology advances.

Wide Distillation Fuel (WDF) refers to the fuels with a distillation range from Initial Boiling Point (IBP) of gasoline to Final Boiling Point (FBP) of diesel. Polyoxymethylene Dimethyl Ethers (PODEn) have high oxygen content and cetane number, are promising green additive to diesel fuel. In this paper, WDF was prepared by blending diesel and gasoline at ratio of 1:1, by volume; the mass distribution of oligomers in the PODE3-4 product was 88.9% of PODE3 and 8.46% of PODE4. Diesel fuel (Diesel), WDF (G50D50) and WDF (80%)-PODE3-4 (20%) (G40D40P20) were tested in a light-duty single-cylinder diesel engine, combustion characteristic, fuel consumption and exhaust emissions were measured. The results showed that: at idling condition, G40D40P20 has better combustion stability, higher heat release rate, higher thermal efficiency compared with G50D50.

Stoichiometric dual-fuel compression ignition (SDCI) combustion has superior potential in both emission control and thermal efficiency. Split injection of diesel reportedly shows superiority in optimizing combustion phase control and increasing flexibility in fuel selection. This study focuses on split injection strategies in SDCI mode. The effects of main injection timing and pilot-to-total ratio are examined. Combustion phasing is found to be retarded in split injection when overmixing occurs as a result of early main injection timing. Furthermore, an optimised split injection timing can avoid extremely high pressure rise rate without great loss in indicated thermal efficiency while maintaining soot emission at an acceptable level. A higher pilot-to-total ratio always results in lower soot emission, higher combustion efficiency, and relatively superior ITE, but improvements are not significant with increased pilot-to-total ratio up to approximately 0.65.

The design and optimization of a modern spray-guided gasoline direct injection engine require a thorough understanding of the fuel spray characteristics and atomization process. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics, and as a consequence, to drastically reduce experimental work during the engine development process. For this reason, an accurate numerical simulation of the spray evolution process is imperative. Different models based on aerodynamically-induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effect of turbulence from the injector nozzle is recently being concerned increasingly by engine researchers. In this study, a turbulence-induced primary breakup model coupled with aerodynamic instability is developed.