Study of a SI engine using biogas for driving a small generator

Abstract

The increase in conventional fuel prices is bringing fOlWardthe research on alternative fuels. Running of conventional internal combustion engines using alternative fuels is a research area where different types of existing engines, used world wide in different fields of application, are being tried out with different degrees of modifications. Bangladesh is a low income developing country with some reserves of natural gas and no oil. With gradual development Bangladesh is facing difficult economic and technological barriers while trying to meet the increasing power demand of the vast population. Small-scale petrol generators are widely used to cope-up with the frequent power failures and load-shedding. This research work investigates the possibility of using biogas as an alternative fuel for running such small scale power generators. The use ofbiogas as an alternative fuel in a 1.5 kW portable electric generator run by a SI engine was studied, keeping engine modifications to a minimum. The biogas was produced synthetically using a mixture of line supply of natural gas and a regulated flow of carbon-di-oxide from. a cylinder. The engine performance was studied using proportional mixtures of the two gases having 55%, 60%, 65% and 70% methane contents by volume, simulating a range of biogas sources. Maximum output power was reduced by 20% with biogas having about 60% methane content. The brake specific fuel consumption rates were comparatively high due to high CO2 content in biogas but overall peak efficiencies were comparable with petrol. Such performance with reduced maximum load capacity was only possible if the methane content of the biogas used was 60% or more. The findings of this study may have potential significance regarding small-scale power generation in agricultural and poultry firms, using biogas plants in rural Bangladesh.