Experimental Study The Effect of Octane Number on Performance of The Spark Ignition Engine

Abstract

This research aimed to an experimental study the effect of octane number of the fuel on the performance of the spark ignition engine . The study included the preparation of fuel with octane number (70,75,80,85,90) which are attempted in this research using the researches and control laboratories of oil refinery company at Baji, by using a standard engine (CFR). The experiments had been carried out using four stroke, single cylinder type (TD110) , with compression ratio(6:1), coupled to hydraulic dynamometer type (TD115). The study showed that, using fuel with octane number (70 and 75) had problems at the beginning of starting and acceleration. The difficulty are knock and delay in warming up of the engine. The results show that the engine performance are increased step by step according to the increases of the octane number of fuel, and this appeared clearly in the obtained results of samples (70 and 90) as follows: At the speed 2800 r.p.m the torque and the brake thermal efficiency are increased by 9.75% and 12.48% respectively. While at the speed 3400r.p.m the brake power and exhaust temperature are increased by 8.97% and 3.7% respectively. also the brake specific fuel consumption decreased by 15% at 2800 r.p.m .