Abstract
Homogeneous Charge Compression Ignition (HCCI) combustion has attracted widespread interest because it achieves high efficiency and can reduce particulate matter (PM) and nitrogen oxide (NOx) emissions simultaneously. However, combustion proceeds extremely rapidly in the HCCI process due to simultaneous ignition at multiple locations in the cylinder. Accordingly, the rapid nature of HCCI combustion must be moderated in order to expand the operating range on the high load side. Methods of accomplishing that include the use of a blended fuel and supercharging. In this study, experiments were conducted to investigate the effects of such methods on moderating the rapidity of HCCI combustion. An air-cooled single-cylinder test engine fitted with an external supercharger was used in the experiments. The effects on combustion of varying the heating value of the injected fuel and the intake air pressure were investigated using dimethyl ether (DME) as the test fuel. In addition, a blended fuel of methane and DME was used to examine the effects on combustion of varying the fuel mixing ratios and the ignition timing. In both sets of experiments, the HCCI combustion process was analyzed by using a spectroscopic measurement method and measure the light absorption characteristics. The results revealed that it was also observed that the rapidity of HCCI combustion can be moderated by suitably controlling the temperature fields in the combustion chamber on the basis of the mixing ratios of methane and DME and the application of supercharging.
