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The objective of the work presented here is to evaluate the potential of rape oil methyl ester (RME) to improve the combustion process in a high-speed direct injection (HSDI) Diesel engine equipped with high-pressure common-rail injection system. The study, based on the comparison of three different fuels (standard gas-oil, RME and 30% RME/gas-oil mixture), takes into account the main aspects that control Diesel combustion, from the injection rate characteristics to the spray behaviour characterised using an optical pressurised chamber. This global study of the whole injection-combustion process allows identifying some causes of the decrease in pollutant emissions observed when the engine operates with RME.

Four 1998 Mitsubishi Carismas, two equipped with direct injection and two with port fuel injection engines, were tested in 20,100 km intervals to determine the effect of mileage accumulation cycle, engine type, fuel and lubricant on vehicle deposits and emissions, acceleration and driveability performance. The program showed that engine fuel system deposits, including specifically those on intake valves, combustion chambers and injectors are formed in higher amounts in the GDI engine than the PFI engine. The fuel additive used reduced injector deposits and combustion chamber deposits in the GDI, but had no significant effect on intake valve deposits, which are affected by crankcase oil formulation. In GDI vehicles, deposited engines were found to have increased hydrocarbon and carbon monoxide emissions and poorer fuel economy and acceleration, but lower particulate emissions.

A combination of various different fuel additive qualities and lubricant qualities were evaluated in a Mitsubishi direct injection gasoline engined vehicle over a standardized road test route using a controlled driving regime. The evaluation was conducted using a matrix of a single base fuel combined with two inlet system detergent additives; one prepared using a synthetic fluidiser base and one a mineral oil fluidiser base. In addition a mineral and a synthetic based crank case lubricant were evaluated with clear base fuel only. Engine inlet and exhaust valve deposits and combustion chamber deposits were measured along with regulated emissions, fuel economy and injector fouling. Methods of measuring and evaluating deposit build up in the inlet and exhaust system and combustion chamber were constructed by developing existing Coordinating European Council (CEC) test methods and in house derived test methods and protocols.

Squish flow control is well known as a key technology for improving knock limit in spark ignition engines. However, to acquire a sufficient squish area in a four-valve engine is difficult. In order to achieve a maximum effect of knock suppression with a minimum squish area, we have developed, what we call, a Slant Squish Combustion Chamber for new engines. A slant squish compared with a conventional squish produces an effective reverse squish flow in the early expansion stroke, resulting in higher flow velocity and turbulence. Furthermore, flame propagation to squish area and end gas is accelerated. These improvements are considered to suppress the knock phenomenon. Consequently, with a slant squish, a high compression ratio, to achieve low fuel consumption and high engine performance is realized.

In this study it is tried to reduce NOx and particulate emissions simultaneously in a direct injection diesel engine based on the concept of two-stage combustion. At initial combustion stage, NOx emission is reduced with fuel rich combustion. At diffusion combustion stage, particulate emission is reduced with high turbulence combustion. The high squish combustion chamber with reduced throat diameter is used to realize two-stage combustion. This combustion chamber is designed to produce strong squish that causes high turbulence. When throat diameter of the high squish combustion chamber is reduced to some extent, simultaneous reduction of NOx and particulate emissions is achieved with less deterioration of fuel consumption at retarded injection timing. Further reduction of NOx emission is realized by reducing the cavity volume of the high squish combustion chamber. Analysis by endoscopic high speed photography and CFD calculation describes the experimental results.

Increasing concern about the impact of internal combustion engines on the environment has led to ever more stringent emission legislation, and the introduction of more sophisticated equipment to enable the requirements to be achieved. One way of improving the emissions from direct injection (DI) diesel engines is to use multi-stage fuel injection, and an investigation performed on such a system is reported in this paper. In this case, the multi-stage fuel injector caused an increase in the exhaust smoke at low load, and an in-cylinder photographic technique was used to examine why this occurred. A multi-stage fuel injector with a VCO nozzle was fitted to a small, high-speed, direct injection diesel engine fitted with a transparent piston for optical access. The combustion process was filmed using a high-speed 16 mm cine camera, and the fuel injection process was illuminated by a high power, copper-vapour laser.

A six-stroke DI diesel engine proposed by the authors had second compression and combustion processes which were added on a conventional four-stroke diesel engine. This engine had the first and second power strokes before the exhaust stroke. Numerical predictions and experiments previously carried out had shown that this six-stroke diesel engine could reduce NO exhaust emission. Further, the ignition delay of the second combustion process could be shortened by a high temperature effect in the second compression stroke. This advantage of short ignition delay could be utilized for an ignition improvement of a fuel with low cetane number. In the engine system reported here, a conventional diesel fuel was supplied as the fuel of first combustion process, and in the second combustion process, methanol was supplied.

Four 1998 Mitsubishi Carismas, two equipped with direct injection (GDI) and two with port fuel injection engines (PFI) were tested in a designed experiment to determine the effect of mileage accumulation cycle, engine type, fuel and lubricant type on engine wear and engine oil performance parameters. Fuel types were represented by an unadditised base fuel meeting EEC year 2000 specifications and the same base fuel plus synthetic deposit control additive packages. Crankcase oils were represented by two types (1) a 5W-30 API SJ/ILSAC GF-2 type engine oil and (2) a 10W-40 API SH/CF ACEA A3/ B3-96 engine oil. The program showed that specific selection of oil additive chemistry may reduce formation of intake valve deposits in GDI cars.. In general, G-DI engines produced more soot and more pentane insolubles and were found to be more prone to what appears to be soot induced wear than PFI engines.

A gasoline spark-ignition (SI) engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injection, but the combustion stability at idle is not improved compared to a carburetted engine. The combustion variability in SI engines limits the use of lean mixtures, the amount of recycled exhaust the engine will tolerate, and lower idle speeds because of increased emissions and poor engine stability. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of ignition energy, fuel injection timing, spark timing, and air-fuel ratio on gasoline engine stability at idle.

The formation of Nitric oxide (NO) in a Diesel engine has been studied as a function of crank angle through-out the whole combustion cycle, using the Laser Induced Fluorescence (LIF) technique. Measurements were performed in an optically accessible one-cylinder, two-stroke, direct injection Diesel engine. The engine was operated in steady state at different loads and compression ratios. A tunable ArF excimer laser beam was used to excite the NO molecules in the D2∑+(v′=0) ← X2Π(v″=1) band at 193 nm. Dispersed fluorescence spectra allowed to discriminate between NO and interfering oxygen fluorescence. From the spectra, a relative measure for the NO density present in the probed volume of the cylinder was obtained. This density was transformed into an in-cylinder NO content, taking into account the changes in laser intensity, pressure, temperature and volume during the stroke.

A new concept of misfire detection in spark ignition engines using a wide-range oxygen sensor is introduced. A wide-range oxygen sensor, installed at the confluence point of the exhaust manifold, was adopted to measure the variation in oxygen concentration in case of a misfire. The signals of the wide-range oxygen sensor were characterized over the various engine-operating conditions in order to decide the monitoring parameters for the detection of the misfire and the corresponding faulty cylinder. The effect of the sensor position, the transient response characteristics of the sensor and the cyclic variation in the signal fluctuation were also investigated. Limited response time of a commercially available sensor barely allowed to observe misfire. It was found that a misfiring could be distinguished more clearly from normal combustion through the differentiation of the sensor response signal. The differentiated signal has twin peaks for a single misfiring in a cylinder.

The paper describes how laser light sheet illumination was used to study the onset and development of cavitation in a scaled up plain orifice nozzle. In addition, measurements were taken using laser Doppler velocimetry and the refractive index matching technique, and these establish the velocity profiles within the orifice under non-cavitating conditions. The light sheet makes visible new detail in the cavitating flow field and additional stages in the cavitation process are identified. The mechanism which causes hydraulic flip is demonstrated and confirms the authors' hypothesis from previous studies. An investigation into the form which the cavitation takes is included: flow conditions are demonstrated in which the cavitation produces an opaque mass of small bubbles, and alternative conditions in which large transparent vapour pockets are produced.

An experimental study was made to investigate the effect of combustion chamber configuration, top clearance, nominal swirl ratio, and spark plug position on in-cylinder combustion in a spark-ignited natural gas engine, which is converted from a direct injection diesel engine. Flame propagation in a single-cylinder visualization engine was measured from the cylinder axis direction by the high speed schlieren method, over the wide range of combustion chamber configuration, top clearance, nominal swirl ratio, and spark plug position. The results showed that flame does not propagate concentrically to the spark plug, but is shifted by swirl, which is the main flow in this engine. Smaller piston cavity diameter led to more rapid flame propagation, resulting in larger heat release rate and larger cylinder pressure. Piston cavity diameter does not affect the initial combustion until TDC.

The interaction of fuel sprays and airflow in the intake system of a port fuel-injected spark-ignition engine has been examined experimentally in a pulsating-flow rig which comprised the cylinder head and intake manifold of a production engine connected to a large-capacity plenum chamber, with the camshaft of the intake valves driven by an electrical motor at engine speeds between 1000 and 5000 rpm and with air sucked through the system by a suction fan. Static pressure measurements in the intake port showed periodic pulsations with frequencies of 360 and 200 Hz with open and closed valves, respectively, and these corresponded to quarter- and half-waves in the manifold and were independent of engine speed.

Experiments have been conducted in a firing single-cylinder spark-ignition engine employing a Ford Zetec cylinder head that has been modified to operate with either standard port-fuel-injection, air-forced port-fuel-injection or direct-injection. The engine utilizes a fused silica cylinder and therefore provides extensive optical access to the combustion chamber. Tests were conducted using a constant speed simulated cold start procedure, which is composed of an initial start-up transient and a quasi-steady-state idle period. In this procedure, the engine is briefly motored at 889 rpm and then combustion commences shortly after the start of fuel injection. Measurements which were performed include in-cylinder pressure as well as intake valve, exhaust valve, piston, cylinder, head, and intake air temperature throughout each cycle of the test period. The engine-out total hydrocarbon emissions were also measured.

A thermodynamic methodology of TDC determination in IC engines based on a motoring pressure-time diagram is presented. This method consists in entropy calculation and temperature-entropy diagram analysis. When the TDC position is well calibrated, compression and expansion strokes under motoring conditions are symmetrical with respect to the peak temperature in the (T,S) diagram. Moreover, in case of error on the TDC position, a loop appears, which has no thermodynamic significance. Hence, an easy methodology has been conceived to obtain the actual position of TDC. This methodology is applied to motoring measurements in order to present its performance, which are compared to usual methods.

The effects of the cetane improvers* 2-ethylhexyl nitrate (EHN) and di-tertiary-butyl peroxide (DTBP) on regulated exhaust emissions from a 1993 Detroit Diesel Series 60 heavy-duty diesel engine were studied. EHN and DTBP were added to two commercially available fuels at concentrations ranging from 500 to 12,000 ppm by volume. Both additives reduced CO, NOx, and particulate emissions as measured in the hot start portion of the FTP heavy-duty transient emissions cycle. A comparison of the emissions response of the two additives shows that the nitrogen in EHN does not contribute to NOx emissions at typical treat rates.

During the last 10 years many researchers and technical groups have studied and performed tests in the area of diesel fuel lubricity [1]1. Protection of diesel engine fuel delivery system components from excessive wear has been the major mission of these efforts. Understanding of the issue, developing laboratory test methods, specifying appropriate fuel properties, and creating mechanical modifications to the equipment, as well as adding lubricity additives to the fuels, describes the bulk of the work which has been performed in this area. Technical groups from several organizations such as the Society of Automotive Engineers (SAE), the Coordinating European Council (CEC), and the International Organization for Standardization (ISO) have made substantial progress and some have come up with test methods and fuel specifications [2].

Experiments were performed in an optically-accessible DI Diesel engine to investigate the effects of the addition of oxygenated blending compounds to Diesel fuel. The focus of the study was to determine how the structure and boiling point of the oxygenating compounds affect the emissions of NOx and soot. NOx, CO2 and CO concentrations in the engine exhaust were measured using gas analyzers. Laser light extinction was used to measure time-resolved, in-cylinder soot concentrations. Two different oxygenate families, maleates and glycol ethers, were chosen to study the effects of molecular structure on emissions. For both families, oxygenates of various boiling points were examined within the distillation range of the base Diesel fuel. All oxygenates were blended into the base Diesel fuel to obtain two percent oxygen by mass.

I The effect of Cetane Number (CN) of the fuel and the addition of cetane improvers on the cold starting and white smoke emissions of a diesel engine was investigated. Tests were conducted on a single-cylinder, four-stroke-cycle, air-cooled, direct-injection, stand-alone diesel engine in a cold room at ambient temperatures ranging from 25 °C to - 5 °C. Five fuels were used. The base fuel has a CN of 49.2. The CN of the base fuel was lowered to 38.7 and 30.8 by adding different amounts of aromatic hydrocarbons. Iso-octyl nitrate is added to the high aromatic fuels in order to increase their CN to 48.6 and 38.9 respectively. Comparisons are made between the five fuels to determine the effect of CN and the additive on cylinder peak pressure, heat release rate, cold start-ability, combustion instability, hydrocarbon emissions and solid and liquid particulates.