An experimental assessment of combustion and performance characteristics of a spark ignition engine fueled with co-fermentation biogas and gasoline dual fuel

Abstract

Natural gas, biogas and alcohols are alternative fuels for spark ignition engines which can be used for reducing exhaust emissions and improving performance metrics. At the first stage of the study, a pilot scale biogas system was built, and biogas was produced from a mixture of manure and water called slurry, consisting of 40% cattle manure, 35% water, 17% whey and 8% poultry manure by co-fermentation method. Scrubbing and desulfurization were applied to remove the harmful gasses (CO₂, H₂S) from the produced biogas in two stages. In the end of the purification process, biogas with a CH₄ content of 51%, 57% and 87% was produced. In the second stage, these biogas fuels were used in an SI engine, and their impacts on performance and combustion characteristics were investigated experimentally. A 4-cylinder, 4-stroke, water cooled SI engine with an 11:1 compression ratio was used in the experiments. Tests were conducted at various loads and constant speed. Results showed that daily amount of mean biogas production has reached 1.6 m³/day and biogas methane content has reached 72%. In engine tests, as the methane ratio in biogas increases, cylinder pressure and exhaust temperature values increase and brake specific fuel consumption decreases.