Ignition and combustion characteristics of biomass gas in a HCCI Engine

Auto-ignition and combustion characteristics of biomass gas were investigated experimentally. Mock biomass gas consisted of H₂, CH₄, CO, N₂ and CO₂, was used assuming a wood pyrolysis gas. A test engine was a 3-cylinder 1.6 L gas engine modifying compression ratio from 9.5 to 24 and equipping the intake air heating system. Experiments were carried out by varying equivalence ratio and fuel composition. The engine could realize auto-ignition and combustion at higher thermal efficiency with mock biomass gas, IMEP was 0.28 MPa and indicated thermal efficiency was 37% at 600 rpm. The knock did not cause at higher equivalence ratio over 0.4, because the fuel had much dilution components, which made combustion speed slower like as EGR. Higher hydrogen content caused the combustion speed to be high, but it did not influence on the ignition timing. On the contrary, the high carbon monoxide content retarded ignition timing, but it did not influence on the combustion speed. Auto-ignition temperature of biomass gas was from 1 000 K to 1 050 K as same as hydrocarbon fuels.