Investigation of combustion and emission characteristics of an SI engine operated with compressed biomethane gas, and alcohols

Alternative fuels in spark-ignition engines significantly reduce engine exhaust emissions and improve fuel efficiency. This research investigates the performance of a multicylinder SI engine using 10%, 20% (ethanol, methanol, methyl acetate), and 100% compressed biomethane gas (CBG) as alternative fuels. Engine performance parameters (BTE, ITE, ME, BP), BSFC, ISFC, FF, combustion phenomenon (cylinder pressure, crank angle, cylinder volume, mass fraction burned, net heat release, mean gas temperature, cumulative heat release, rate of pressure rise), and emission characteristics (HC, CO, CO(2), NOx) are measured. CBG achieved a maximum BTE of 23.33% compared to all other fuels. Minimum fuel consumption rate of 1.72 kg/h at maximum rpm achieved BSFC value of 0.44 kg/kWh and ISFC value of 0.261 kg/kWh. The highest cylinder pressure of 6.79 bar was achieved in the G90M10 with a cylinder volume of 48.58 cc. NHR of 3.08 j/deg was found in the G80M20 at a crank angle of 376°, and the maximum MGT was 390.20 °C in the G80E20. The highest CHR values of 0.12 kJ at crank angles of 432°, 420°, 422°, and 427° were achieved in the G100, CBG, G80E20, and G90E10. G90M10 reached a maximum value of 0.14 bar/degree of rate of pressure rise at a crank angle of 374°. Average minimum emission gas was found in CBG at a minimum and maximum RPM, indicating that CBG gives the best emission result with engine performance compared to all alternative fuels.