This paper aims at investigating the performance, emission and combustion characteristics of a diesel engine fuelled with CSPO (coconut shell pyro oil)-diesel blends as fuel. In the first phase of work CSPO was produced from fast pyrolysis of raw coconut shell at a reaction temperature of 700°C. Attempts were made to obtain homogeneous mixtures of different amounts (such as 5%, 10%, 15% and 20% by volume) of CSPO with diesel. Beyond 15% separation of the fuel was observed. Hence it was decided to use the blends of 5%, 10% and 15% of CSPO with diesel as fuels. Experiments were carried out on a single cylinder, water cooled, direct injection diesel engine using different blends of CSPO with diesel as fuel. Performance, emission and combustion parameters were obtained at different power outputs for all the tested fuels and analyzed.
Engine test results indicated reduced thermal efficiency, increased smoke density, unburned hydrocarbon and carbon monoxide emissions with the blends of CSPO as compared to conventional diesel fuel at all power outputs. The maximum thermal efficiency was found as 30.5% with diesel where as it was 29%, 27.5% and 26% for the CSPO blends of 5%, 10% and 15% respectively with diesel at the rated power output of 3.7 kW. Smoke emission was found as higher with all the blends of CSPO as compared to neat diesel at all power outputs. However, NO emission was reduced with all the blends. 15% CSPO showed the minimum NO emission at all power outputs. Combustion studies indicated increased ignition delay and combustion duration with all the blends as compared to neat diesel at all power outputs. The maximum ignition delay was found as 13°CA with the blend of 15% CSPO at peak power where as it was 10°CA with neat diesel. Cylinder pressure and maximum rate of pressure rise were observed as lower with all the blend of CSPO as compared to neat diesel operation. Among the blends tested the blend of 5% CSPO with diesel gave increase in smoke emission within 12.5%, unburned hydrocarbon within 5% and CO within 10% of diesel fuel. The reduction in thermal efficiency was within 5% of neat diesel fuel.