Ignition timing and compression ratio as effective means for the improvement in the operating characteristics of a biogas fueled spark ignition engine

In the current investigation, a four stroke, variable speed, single cylinder, variable compression ratio (VCR) SI engine is operated with raw biogas at wide open throttle (WOT) condition and at five different CRs ranging from CR 10 to CR 14 over the operating speed range of the engine. The ignition timing (IT) of the engine is also varied from 23○CA to 47○CA before top dead centre (bTDC) at each operating CR. The optimized operating CR and IT of the engine are obtained through series of experiments and its effects on the performance, combustion and emission characteristic are analysed herein. The rise in operating CR from CR 10 to CR 12 enhanced the power output and efficiency of the biogas fueled SI engine by 12.72% and 5.68%, respectively and reduced fuel consumption by 5.42% at 1400 rpm. Enhancing the CR from CR 10 to CR 12, limited the intensification of NOx and unburnt hydrocarbon emission by 10.17% and 15.6%, respectively at 1400 rpm. Hence, CR 12 is recommended as the optimum CR and its combination with 1400 rpm and WOT setting is recommended as the best operating condition of the engine.