s: Diesel fuel injection is the most dominant in ignition process of the diesel engines combustion. Diesel engines have been widely used in heavy-duty and light-duty vehicles due to their higher fuel economy, efficient and powerful than spark ignition (SI) engines. The principal objective of this research is to seek the effect of temperature and pressure on the spray characteristics, as well as fuel-air mixing characteristics. Experiments were performed in a constant volume chamber at specified ambient gas temperature and pressure. This research was continued with injecting diesel fuel into the chamber using a Bosch common rail system. Direct photography technique with a digital camera was used to clarify the real images of mixture formation such as spray penetration, fuel evaporation and spray interference. The liquid phase of the spray reaches a maximum penetration distance soon after the start of injection, while the vapour phase of the spray continues to penetrate downstream. The condition to which the fuel is affected was estimated by combining information on the wall chamber temperature, ambient temperature and photographs of the spray. The increases in ambient pressure inside the chamber resulting in gain of spray area and wider spray angle. Thus predominantly promotes for a better fuel-air premixing.
The use of biodiesel as an alternative fuels in the diesel engine is very effective due to less of emissions and high performance. This study investigated the effect of palm oil blending and engine speed on performance and emission in diesel engine. The performance of biodiesel blends were investigated in terms of brake power, fuel consumption rate, flywheel torque, while emissions parameter was tested in terms of smoke opacity, hydrocarbon (HC), nitrogen oxide (NOx), carbon oxide (CO), carbon dioxide (CO2) and oxygen (O2) at various engine speed 1500, 2000, 2500 and 3000 revolution per minute (rpm). Biodiesel was blended with ordinary diesel fuel in various proportions. The engine was tested up to 50% load conditions by using Ordinary Diesel (OD), B5, B10 and B15 fuels. The properties of biodiesel fuel were tested including density, kinematic viscosity, water content and flash points test. Experimental results indicated that biodiesel blend shows the flywheel torque obtained is higher compared to the OD but fuel consumption rate and the brake power are quite similar when tested at ambient temperature. All biodiesel blends released good emissions compared to the OD. The CO2, CO, HC and O2 content released from the biodiesel fuels were clearly lower than the normal fuel except for NOX contents. Biodiesel released higher smoke opacity compared to OD at all range of engine speeds under 50% load condition. In conclusion, biodiesel fuels are found to offer better performances and emissions and are suitable to be used in unmodified diesel engine.
s :This paper reviews of some applications of optical visualization system to compute the fuel-air mixing process during early stage of mixture formation and late injection in Diesel Combustion Engine. This review has shown that the mixture formation is controlled by the characteristics of the injection systems, the nature of the air swirl and turbulence in thecylinder, and spray characteristics. Few experimental works have been investigated and found that the effects of injection pressure and swirl ratio have a great effect on the mixture formation then affects to the flame development and combustion characteristics.This paper presents the significance of spray and combustion study with optical techniques access rapid compression machine that have been reported by previous researchers. Experimental results are presentedin order to provide in depth knowledge as assistance to readers interested in this research area. Analysis of flame motion and flame intensity in the combustion chamber was performed using high speed direct photographs and image analysis technique. The application of these methods to the investigation of diesel sprays highlights mechanisms which provide a better understanding of spray and combustion characteristics.
Precise control of fuel injection is essential in modern diesel engines especially in controlling the precise injection quantity, flexible injection timing, flexible rate of injection with multiple injections and high injection pressures. It was known that the fuel-air mixing is mainly influenced by the fuel injection system and injector nozzle characteristics. Thus, mixture formation during ignition process associated with the exhaust emissions. The purpose of this study is to investigate the influence of spray characteristics on the mixture formation. In this study, common rail injector systems with different model of injector were used to simulate the actual mixture formation inside the engine chamber. The optical visualization system was constructed with a digital video camera in order to investigate the detailed behavior of mixture formation. This method can capture spray penetration length, spray angle, spray evaporation and mixture formation process clearly. The spray characteristic such as the penetration length, spray angle and spray area are increasing when the injection pressure increased. The mixture formation can be improved effectively by increasing the injection pressure.
ABSTRACT. Among the challenges faced by diesel engines combustion nowadays are to reduce emission especially Nitrogen Oxide (NO x ) and Particular Matter (PM) while enhancing fuel efficiency and power. The purpose of this review is to explore the mixture formation of biodiesel combustion using constant volume chamber and optical visualization. This paper will review the development of a single-shot combustion system and constant volume chamber. An overview of the relation of mixture formation and combustion process in diesel combustion is provided first. This review has shown that the application of Rapid compression Machine (RCM) is used to simulate actual condition especially the injection pressure and air motion. The review also found that the mixing between fuel and air is unavoidable and very important during ignition delay period thus predominantly influences the exhaust emission. The detailed behaviour of injection characteristic that strongly effects the mixture formation especially the spray evaporation and spray interference are discussed.
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