Auto-ignition and combustion analysis of DME air mixture in a HCCI engine by radical luminescence measurement and numerical calculation

The auto-ignition and combustion mechanism in homogeneous-charge compression-ignition (HCCI) engine were elucidated and comparable results in numerical calculations with elementary reactions were acquired. Chemical luminescences from radicals were measured in single cylinder 4-stroke optical access engine with DME fuel. DME showed multistage heat release with low temperature reaction (LTR) and high temperature reaction (HTTR) at compressed rapidly. At fuel concentration heterogeneity condition, cyclic variation of pressure profile was smaller, but distribution of chemical luminescence intensity in combustion chamber was larger. The luminescence spectra of DME/Air mixture at auto-ignition and combustion was sum of chemical luminescence band spectrum of OH, CH, C₂, HCO, HCHO and the continuum spectrum from 300 to 500 nm. Luminescence intensity of the continuum spectrum from 300 to 500 nm at HTR was larger than LTR.