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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).

Gasoline Direct Injection (GDI) vehicles now make up the majority of European new car sales and a significant share of the existing car parc. Despite delivering measurable engine efficiency benefits, GDI fuel systems are not without issues. Fuel injectors are susceptible to the formation of deposits in and around the injector nozzles holes. It is widely reported that these deposits can affect engine performance and that different fuels can alleviate the buildup of those deposits. This project aims to understand the underlying mechanisms of how deposit formation ultimately leads to a reduction in vehicle performance. Ten GDI fuel injectors, with differing levels of coking were taken from engine testing and consumer vehicles and compared using a range of imaging and engine tests. At the time of writing, a new GDI engine test is being developed by the Co-ordinating European Council (CEC) to be used by the fuel and fuel additive industry.

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.

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.

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.

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.

Diesel engines are the versatile power source and is widely used in passenger car and commercial vehicle applications. Environmental temperature conditions, fuel quality, fuel injection strategies and lubricant have influence on cold start performance of the diesel engines. Strategies to overcome the cold start problem at very low ambient temperature include preheating of intake air, coolant, cylinder block. The present research work investigates the effect of coolant temperatures on passenger car diesel engine’s performance and exhaust emission characteristics during the cold start at cold ambient temperature conditions. The engine is soaked in the -7°C environment for 6 hours. The engine coolant is preheated to the desired coolant temperatures of 10 and 20°C by an external heater and the start ability tests were performed.

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.

There is an increasing recognition of injector deposit (ID) formation in fuel injection equipment as direct injection spark ignition (DISI) engine technologies advance to meet increasingly stringent emission legislation and fuel economy requirements. While it is known that the phenomena of ID in DISI engines can be influenced by changes in fuel composition, including increasing usage of aliphatic alcohols and additive chemistries to enhance fuel performance, there is however still a great deal of uncertainty regarding the physical and chemical structure of these deposits, and the mechanisms of deposit formation. In this study, a mechanical cracking sample preparation technique was developed to assess the deposits across DISI injectors fuelled with gasoline and blends of 85% ethanol (E85).

The combustion timing, work output and in-cylinder peak pressure for HCCI engines often converge to a stable equilibrium point, which implies that the HCCI combustion may have a self-stabilization feature. It is thought that this behavior is due to the competing residual-induced heating and dilution of the reactant gas. As one of the most important features of HCCI combustion, the self-stabilization behavior can give great guidance to people for designing controller for HCCI engine control. The self-stabilization features of HCCI combustion had been observed by many researchers and mentioned in some publications. However, there is no report to experimentally analyze this phenomenon individually. Due to the fuel injection normally ending during the NVO process and the spark plug is turned off for HCCI engines, there is no direct control approach between the Intake Valve Close (IVC) and the start of combustion.

An experimental study of particulate matter (PM) emission was conducted on four cars from Chinese market. Three cars were powered by gasoline direct injection (GDI) engines and one car was powered by a port fuel injection (PFI) engine. Particulate mass, number and size distribution were measured based on a chassis dynamometer over new European driving cycle (NEDC). The particulate emission behaviors during cold start and hot start NEDCs were compared to understand how the running conditions influence particulate emission. Three kinds of gasoline with RON 91.9, 94.0 and 97.4 were tested to find the impact of RON on particulate emission. Because of time and facilities constraints, only one cold/hot start NEDC was conducted for every vehicle fueled with every fuel. The test results showed that more particles were emitted during cold start condition (first 200s in NEDC). Compared with cold start NEDC, the particulate mass and number of hot start NEDC decreased by a wide margin.

This paper studied the knock combustion process in gasoline HCCI engines. The complex chemical kinetics was implemented into the three-dimensional CFD code with LES (Large eddy simulation) to study the origin of the knock phenomena in HCCI combustion process. The model was validated using the experimental data from the cylinder pressure measurement. 3D-CFD with LES method gives detailed turbulence, species, temperature and pressure distribution during the gasoline HCCI combustion process. The simulation results indicate that HCCI engine knock originates from the random multipoint auto-ignition in the combustion chamber due to the slight inhomogeneity. It is induced by the significantly different heat release rate of high temperature oxidation (HTO) and low temperature oxidation (LTO) and their interactions.

Fuel spray atomization process is known to play a key role in affecting mixture formation, combustion efficiency and soot emissions in direct injection engines. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics such as penetration, droplet size and droplet velocity, 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 approaches and various models based on aerodynamically induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effects of turbulence and cavitation from the injector nozzle is recently being concerned increasingly by engine researchers. In this study, an enhanced turbulence and cavitation induced primary breakup model combining aerodynamic breakup mechanism is developed.

The cold start performance of a diesel engine has been receiving more attention as the European Commission emission regulations directed to include cold start emissions in the legislative emission driving cycles. The cold start performance of diesel engines is influenced by the ambient temperature conditions, engine design, fuel, lubricant and engine operating conditions. The present research work investigates the effect of cold ambient conditions on the diesel engine's performance and the exhaust emission (gaseous and particulate emissions) characteristics during the cold start and followed by idle. The engine startability and idling tests were carried out on the latest generation of diesel engine in a cold cell at various ambient temperatures ranging between +20°C and −20°C. Higher fuel consumption and peak speed were observed at very cold ambient compared to those at normal ambient during the cold start.

Dieseline combustion as a concept combines the advantages of gasoline and diesel by offline or online blending the two fuels. Dieseline has become an attractive new compression ignition combustion concept in recent years and furthermore an approach to a full-boiling-range fuel. High speed imaging with near-parallel backlit light was used to investigate the spray characteristics of dieseline and pure fuels with a common rail diesel injection system in a constant volume vessel. The results were acquired at different blend ratios, and at different temperatures and back pressures at an injection pressure of 100MPa. The penetrations and the evaporation states were compared with those of gasoline and diesel. The spray profile was analyzed in both area and shape with statistical methods. The effect of gasoline percentage on the evaporation in the fuel spray was evaluated.

Using EGR instead of throttle to control the load of a stoichiometric dual-fuel dieseline (diesel and gasoline) compression ignition (SDCI) engine with three-way catalyst (TWC) aftertreatment is considered a promising technology to address the challenges of fuel consumption and emissions in future internal combustion engines. High-speed imaging is used to record the flame signal in a single-cylinder optical engine with a PFI+DI dual injection system. The premixed blue flame is identified and separated using green and blue channels in RGB images. The effects of injection timing on SDCI combustion are studied. An earlier injection strategy is found to be ideal for soot reduction; however, the ignition-injection decoupling problem results in difficulties in combustion control. It is also found that a split injection strategy has advantages in soot reduction and thermal efficiency.