Issues that must be addressed to make Homogeneous Charge Compression Ignition (HCCI) engines a practical reality include the difficulty of controlling the ignition timing and suppression of rapid combustion under high load conditions. Overcoming these issues to make HCCI engines viable for practical application is indispensable to the further advancement of internal combustion engines. Previous studies have reported that the operating region of HCCI combustion can be expanded by using DME and Methane blended fuels.(1), (2), (3), (4), (5) The reason is that the reaction characteristics of these two low-carbon fuels, which have different ignition properties, have the effect of inducing heat release in two stages during main combustion, thus avoiding excessively rapid combustion. However, further moderation of rapid combustion in high-load region is needed to expand the operation region. This study focused on supercharging and use of blended fuels.
For the purpose of promoting the practical implementation of HCCI engines, experiments were conducted in the present study with the aim of expanding the HCCI operating range over a wide region of combustion loads by using the reaction characteristics of a fuel blend of DME/methane. The results revealed that the pressure rise rate was substantially reduced while maintaining the indicated mean effective pressure level. It was also observed that HCCI operation over a wide range of engine loads was possible by making use of two-stage heat release during main combustion.