Performance and exhaust emission of a diesel engine using crude palm oil as a fuel extender

Abstract

This paper investigates into the use of Crude Palm Oil (CPO) as a fuel extender for diesel engines. Three mixtures of CPO with ordinary diesel fuel (OD) were used in a direct-injection, stationary Perkins diesel engine. The three CPO-OD mixtures contained 25%, 50% and 75% of CPO by volume. In order to reduce the viscosity of the CPO-OD mixtures they were preheated to about 60oC before injection. The paper compares the performance of these CPO-OD mixture, with that of ordinary diesel fuel, at a fixed throttle opening but variable engine speed of 1000-3000 rpm. The results obtained show two distinct trends when the speed is below or above an intermediate speed of about 2000 rpm. At speeds lower than 1800 rpm, all three CPO-OD mixtures gave higher torque and power output, but their brake specific fuel consumption (BSFC) was also higher compared to that of OD. The exhaust-gas analysis show that CPO-OD mixtures gave higher emission of CO, and lower emissions of NOx, compared to that of diesel fuel. The performance of CPO-OD mixtures became comparable to that of diesel fuel at speeds above 2000 rpm. Although the brake power of CPO-OD mixtures was less than that of OD in the high-speed range, their BSFC improves. These results indicate that when the engine is fuelled by a CPO-OD mixture, the fuel-pump and injection system tend to deliver more fuel than needed at low speeds, but less fuel at high speeds