Controlling PCCI Combustion with Mixed Fuel - Application of Flashing Spray to Early Injection

A diesel engine operating in premixed charge compression ignition (PCCI) mode promises the reduction of engine-out emissions of NO_x and particulate matter. A serious issue for PCCI operation with the early injection timing during the compression stroke is the difficulty of controlling the mixture formation process.

In this study, a mixed fuel consisting of high volatility fuel and high ignitability one is applied in order to develop a control technique for the mixture preparation. In particular, we focuses on a flash boiling phenomenon of mixed fuel. For pure substance, the quality of flashing spray is dominated by the degree of superheat. In contrast, that of mixed fuel is affected much by low boiling point fuel. Therefore, the present study defined a new variable making it possible to distinguish the flashing atomization regime of mixed fuel and, then, investigated both the effects of it and ambient condition on the behavior of flashing spray of mixed fuel in a constant volume vessel. In addition, the engine test was performed to validate the effect of flashing spray on the combustion characteristics of PCCI.