Optimal Operating Parameters for Performance Improvement of a Biogas Fueled Spark Ignition Engine

Abstract

The environmental concerns and the uncertainties associated with the future availability of fossil fuel are driving the interest of utilizing renewable biofuels in the internal combustion (IC) engines. Among the renewable gaseous fuels, biogas is an attractive source of energy in rural areas and is mainly composed of CH4 (50-70%), CO2 (25-50%), H2 (1-5%), N2 (0.3-3%) with traces of H2S. Direct use of biogas as a standalone fuel in CI engine is almost impossible due its properties such as higher self-ignition temperature, higher resistance to auto ignition and knock. But, the physical and chemical characteristics of biogas have a great resemblance on the octane fuels in higher compression ratio (CR) SI engines. Although SI engines are best suitable for renewable or non-renewable high-octane fuels, they need special attention to accommodate biogas. The combustion process in a SI engine is greatly influenced by the operating parameters. Various techniques such as alteration in CR and IT, preheating, pre-chamber ignition, etc. were proposed to enhance the performance, combustion and emission characteristics of the biogas fueled SI engine. Thus, one of such techniques, with proper optimization of operational parameters, can be employed to develop an efficient biogas-based SI engine. The current research is mainly focused to determine the optimal operating parameters (optimum compression ratio, maximum brake torque timing, throttle position and optimum air-fuel ratio) of a biogas fueled SI engine through a multi fuel, variable compression ratio (VCR), spark ignited research engine setup for effective implementation in a commercial SI engine.