Influence of H₂ and CO of biomass gas fuel on ignition and combustion in HCCI Engine

Aiming to understand applicable component of biomass gas to HCCI engines, combustion characteristics were investigated experimentally for mock biomass gas with varying fuel components. Mock biomass gases consisted of H₂, CH₄, CO, N₂ and CO₂, were used assuming wood pyrolysis gases. Using modified gas engine with air inlet heaters and high compression ratio pistons, experiments were carried out. Auto-ignition timing is temperature domain regardless of fuel component, ignition temperature is about 1 000 K as same as hydrocarbon fuels. Combustion speed following auto-ignition is influenced largely on H₂ and CO₂ content, it is clarified that combustion speed is proportional to H₂ and CO ₂ ratio of fuel. Meanwhile CO of fuels does not effect on combustion speed. H₂ and CO₂ ratio of fuel is also largely concerned with knock, and it is one of index of minimum IMEP that knock yield. About Exhaust emissions, THC and CO is higher level because of lower cyclic maximum temperature for inert component of fuel, in another hand, NO_x is near zero regardless of fuel components and operation conditions.