Auto-ignition and combustion analysis of DME air homogeneous charge compression ignition engine by chemiluminescence measurement (The influence of charge inhomogeneity on HCCI combustion)

In HCCI engine, inhomogeneity of fuel distribution and temperature in pre-mixture has possibilities to affect ignition and combustion. An experimental study has been carried out to investigate the influence of inhomogeneity of fuel distribution on auto-ignition and combustion by using 4 stroke optical access engine. DME was used as the test fuel. Pressure profiles and two-dimensional luminescence image from chemical species have been measured and analyzed. Changing the fuel injection point and fuel injection duration in the intake chamber, inhomogenity was changed. Combustion duration in inhomogeneus condition was longer than homogeneous condition. Fluctuation of maximum pressure of cycles in inhomogeneous condition was larger than homogeneous condition. Luminescence started and stopped uniformly whole the combustion chamber in homogeneous condition, but in inhomogenous condition, luminance had variety in space and time.