Injection Characteristics of Rapeseed Methyl Ester versus Diesel Fuel in Pump-Line-Nozzle Injection System

The transformation of rapeseed oil into methyl ester through the transestrification process normally produce biodiesel fuel with kinematic viscosity almost double that of the commercial diesel fuel. The bulk modulus of biodiesel is also higher than that for the conventional diesel fuel. In this paper, the effects of the two physical properties on the injection characteristics of Rapeseed Methyl Ester (RME) are discussed. The injection characteristics considered here were namely; nozzle chamber pressure, needle lift, and fuel injection rate. The mutual effects of engine speed and delivery pipe length were also analyzed. A previously developed computer model was used to simulate the injection process of the conventional pump-line-nozzle injection system. An explicit finite difference scheme was adopted to solve the unsteady flow equation within the delivery pipe. The maximum injection pressure inside the nozzle chamber, the needle lift, and the rate of fuel injection were found to be consistently increasing with the higher kinematic viscosity and bulk modulus of biodiesel fuel. The effects of these physical properties were found to be much more pronounced as the pipe length increased.