An experimental investigation on the cylinder pressure of a biogas-diesel dual fuel engine

Abstract

By substituting a considerable amount of diesel fuel in diesel engines, combustible biogas is considered to be a renewable and promising alternative gaseous fuel. In this paper, biogas was made from agricultural and forestry residues with a gasifier. Its high quality was ensured by the process of cooling to obtain high density and condensation and by filtering to remove water vapor and tar. The dual fuel engine that was refitted from a diesel engine was fueled with biogas as the main fuel and diesel as the pilot fuel. In order to compare the combustion characteristics of biogas-diesel dual fuel engine and diesel engine, the cylinder pressure of dual fuel engine and diesel engine under load characteristics at different speeds was measured, and the characteristic combustion parameters such as combustion start timing, the maximum combustion pressure and the corresponding phase at different load and speed were analyzed. Meanwhile, the influence of different fuel supply advance angle on engine combustion process was measured and studied. The results show that the start timing of combustion of dual fuel engine is later than that of diesel engine, and that the maximum combustion pressure and the maximum pressure rise rate are higher than those of diesel engine at low speed and high load, but lower in all other conditions. Post combustion is more significant and exhaust temperature is higher under the biogas-diesel dual fuel operation at most operating conditions except for low speed and high load. The peak cylinder pressures of engines increase as fuel injection timing advances.