Effect of Start of Injection on the Particulate Emission from Methanol Fuelled HCCI Engine

New combustion concepts developed in internal combustion engines such as homogeneous charge compression ignition (HCCI) have attracted serious attention due to the possibilities to simultaneously achieve higher efficiency and lower emissions, which will impact the environment positively. The HCCI combustion concept has potential of ultra-low NOX and particulate matter (PM) emission in comparison to a conventional gasoline or a diesel engine. Environmental Legislation Agencies are becoming increasingly concerned with particulate emissions from engines because the health and environmental effects of particulates emitted are now known and can be measured by sophisticated instruments. Particulate emissions from HCCI engines have been usually considered negligible, and the measurement of mass emission of PM from HCCI combustion systems shows their negligible contribution to PM mass. However some recent studies suggest that PM emissions from HCCI engines cannot be neglected. In this paper, effect of start of injection (SOI) of fuel on particulate emission of a HCCI engine fuelled with methanol is experimentally investigated. In this study, port fuel injection technique is used for preparing homogeneous mixture of methanol and air. The experiment is conducted with varying SOI timings for different amount of fuel, and intake air temperature. The engine exhaust particle sizer (EEPS) is used for size, surface area and volume distributions of soot particles emitted under each of these different operating conditions. It was found that total concentration of particles increase with increasing intake air temperature and particles are mainly in the size range from 10 to 150 nm. It was found that number and size distribution of HCCI generated soot particles depends on SOI, amount of fuel injected and the intake air temperature.