Performance and emission characteristics of a small diesel engine run in dual-fuel (diesel-biogas) mode

A small compression ignition (CI) engine with a rated power of 4.41 kW has been tested in dual-fuel (diesel-biogas) mode without any significant modification. The objectives are to explore the effects of biogas flow rate and methane concentration on the performance and emissions of the CI engine run in dual-fuel mode. The experiments have been carried out at engine load and speed vary from 1000 rpm to 1500 rpm and 600 W to 1500 W, respectively. The results show that the output power and specific fuel consumption of the CI engine run in dual-fuel mode are higher than the CI engine run in pure diesel mode. Brake thermal efficiency of the CI engine run in dual-fuel mode strongly affected by biogas flow rate and methane concentration. There exists an optimum biogas flow rate for a maximum brake thermal efficiency. The biogas can reduce the diesel fuel consumption significantly. In the present CI engine, diesel replacement ratio varies from 15.3% to 87.5%. At engine load and speed of 1500 W and 1500 rpm, to get maximum efficiency, the present CI engine should be operated at biogas energy ratios of 15% and 18% using biogas with 60% and 70% methane concentrations, respectively.