Effect of Fuel Components on Engine Abnormal Combustion 2012-01-1276
These days, improving fuel economy is essential from the view point of energy security and global warming. Engine technologies, such as high compression engines and turbocharged engines, have already been introduced into the market. Furthermore new technologies like lean boosted engines are now being developed. However, these engines are susceptible to abnormal combustion like knocking, auto-ignition, and pre-ignition at low or high engine speeds, because these engines are run at higher combustion pressures and temperatures compared to naturally aspirated engines.
It is well known that fuels have some affect on combustion characteristics. This paper examines the effects of fuel characteristics on various types of abnormal combustion. The results show that temperature and pressure have a direct impact on abnormal combustion. The engine results show that fuel Research Octane Number (RON) has an impact on auto-ignition at the engine started with a fully warmed up engine and pre-ignition at low engine speed. Conversely, Fuel Motor Octane Number (MON) has an impact on the pre-ignition characteristics at high engine speed. Calculation results support that pre-ignition at high engine speed is dominated by a degeneracy chain branching reaction, and that auto-ignition at engine start with a fully warmed engine is dominated by a low temperature oxidation reaction. The calculation results also support that pre-ignition at low engine speed is dominated by not only the hot spot temperature at the moment of pre-ignition, but also the chemical reaction of air fuel mixtures under adiabatic compression period.