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Abstract

The purpose of this research is to investigate the effect of low injection pressure and variant ambient temperature towards the ignition delay period and emission. Three types of biodiesel blend which are B5, B10 and B15 were tested in the rapid compression machine (RCM) at low injection pressures of 80 MPa and 90 MPa. The ambient temperature of constant volume chamber (CVC) Ti, cvc, was varied at 70°C and 80°C while the ambient temperature of combustion chamber (CC), Ti,cc, was varied at 70°C and 90°C. The result shows that at specific ambient temperature combination of the CVC and CC, the higher value of ambient temperature combination produces shorter ignition. The initial combustion rate becomes low and the combustion duration became longer. This produces complete combustion process and good fuel conversion efficiency. Too short ignition delay results in decreased premixed combustion, which cannot provide enough energy for subsequent air-fuel mixing. While, with too long ignition delay, ignition occurs late in the expansion stroke that caused incomplete combustion process, reduced power output and poor fuel conversion efficiency. The emission shows that under the condition of higher ambient temperature, the product of CO, O2, and HC becomes lower but results in increasing of NOx level. Increased blends of biodiesel ratio are found to enhance the combustion process, resulting in decreased HC emissions.