A computer simulation of the effect of the inert gas volume fraction in low-caloric biogas on the performance of an engine

A computer simulation of a gas engine was performed to investigate the effects of the inert gas volume fraction in biogas on engine performance, specifically the engine torque and the brakespecific fuel consumption (BSFC) using GT-Power®. The engine speeds used in the simulation were 900 and 1800 rpm, while the simulated engine loads were 25, 50, 75 and 100%. The volume fraction of the inert gas N2 in the biogas was varied from 20 to 80% with an interval of 10%. In a simulation of a naturally aspirated gas engine which is operated with an 80% volume fraction of N2 in biogas, the optimal air-fuel ratio in terms of the fuel economy and brake power generation was 3.5. In a simulation of a turbo intercooler gas engine operated with an 80% volume fraction of N2 in biogas, the optimal air-fuel ratios with regard to the fuel economy and brake power generation were 5.0 and 3.5, respectively.