Reduction of nitric oxides and soot by premixed fuel in partial HCCI engine

In order to obtain the reduction effect of NOx, and soot emission in a partial homogeneous charge compression ignition engine, premixed fuel was supplied with direct injection diesel fuel. Several additional systems such as a premixed fuel injection system, exhaust gas recirculation (EGR) system, supercharger and air heating system were equipped in the intake manifold of conventional diesel engine. Premixed fuel with air was compressed and ignited by the directly injected diesel fuel in the combustion chamber at the end of compression stroke. The effect of premixed fuel on combustion and emission characteristics of HCCI diesel engine was investigated experimentally under various conditions of intake air temperature, pressure, and EGR rate. The results showed that in case of the use of gasoline as a premixed fuel, single stage ignition is found, but premixing the diesel fuel accompanies the cool flame prior to the combustion of the directly injected diesel fuel. For the gasoline premixed fuel, both NOx and soot can be reduced by the increase of premixed ratio simultaneously. However for the diesel premixed fuel, the increase of premixed ratio does not have a significant effect in reducing the soot emission.