급속압축팽창기를 이용한 프로판-디젤 이중연료 엔진의 연소제어 전략에 관한 연구

Abstract

A direct injection strategy on compression ignition is considered to achieve higher performance and produce lower pollutant emissions due to a higher volumetric efficiency compared to intake manifold injection. Applying the DI strategy on compressed gas fuel such as propane gives a better advantage due to the lower boiling temperature of the fuel, as it improves the atomization characteristics and reduces the possibility of pressure-temperature reduction compared to when the fuel is injected at the intake manifold. Propane itself is one of the promising alternative fuels for internal combustion engines as it contains a higher calorific value and produces cleaner combustion compared to diesel and gasoline. This characteristic of fuel makes it possible to apply lean combustion strategies where the excess of air in a lean-burn engine emits far fewer hydrocarbons. The experimental setup has been modified to be sufficient for dual direct injection; Propane and diesel as the ignition assistant. The validated model CFD was applied to study the combustion and emission of propane as well as the spatial distribution of propane in the research engine. The objective of this study was to analyze the combustion characteristics and emissions of Propane and find the optimum parameter to achieve the best emissions and performance. The results show that the reactive combustion state of propane increases the mean temperature in the premix combustion phase significantly. This phenomenon occurs due to the flame produced by propane developing much faster compared to diesel. Consequently, it increases the MPRR and peak pressure during combustion. However, it produces higher HRR at the mixing-controlled combustion phase as the fraction of the propane increases. It causes longer burn duration and reduces combustion efficiency. Compared to diesel, propane produces fewer particulates. The fluctuation of CO/CO2 shows the indication of better combustion performance when propane up to 50% was applied. The lower CO2 emission on the other propane energy fraction indicates the incapability to burn the fuel efficiently during the combustion process. An increase in the propane energy fraction indicates a rise in NOx when the LPG-Di was applied at CR 19. The auto-ignition resistance of propane makes a longer NOx formation compared to diesel. A higher propane energy fraction shows the indication of soot reduction. However, propane shows high auto-ignition resistance when 0o and 40oBTDC were applied. Consequently, significant soot emission was produced.