Experimental investigations on the influence of compression ratio and piston crown geometry on the performance of biogas fuelled small spark ignition engine

The present research work is an attempt to develop a dedicated biogas fuelled SI engine technology from a 100 cc motor cycle. Such a small engine is coupled with alternator especially suitable in remote rural electrification which is still not connected to grid line or has a limited access. The experimental work presents the performance results of a small 98 cc, single-cylinder, four stroke cycle gasoline engine which is optimized to run on scrubbed biogas (CH4 93.8%) and raw biogas (CH4 56.6%) with successive modifications to the engine and its components. The work is carried out in stages to develop a dedicated biogas engine technology. The various aspects like piston crown geometry and compression ratio (CR), is investigated in this research work to evaluate the performances using biogas as fuel and comparing the same with gasoline is also made with the results obtained during experimental tests. The tests were conducted at 3000 rpm using three pistons having different crown geometries and cleavage on its crown. The selected three pistons enable to study the significance of CR (in the range of 6–9) and piston crown geometry to achieve the optimal configuration. The experimental results have revealed that increase in CR in a close range of 8:1 with larger cleavage on piston crown geometry enhances engine performance for Biogas fuelled small S.I. engine 100 cc category. It has been observed during comparative analysis that the maximum power produced by the biogas fuelled engine has improved by 13.4%, BSEC has increased by 23.30% and there is an 18.18% improvement in BSFC.