Study on an HCCI Engine fueled by Biomass Gas (Effect of Inhomogeneity of Premixture)

Abstract

In this study, applicability of the gas fuel generated from wood biomass by thermal chemical processes to an homogenous charge compression ignition engine is investigated in experiment. In particular, the availability of inhomogeneity of both fuel concentration and temperature is evaluated to control the combustion against the variation of fuel composition. Inhomogeneity of premixture is varied by changing the ratio of fuel injected to two points, one far from the intake valve and another near the intake valve. In this system, both local fuel concentration and local temperature of premixture vary; the lower fuel concentration point has higher initial temperature. Two test fuels with difference in H₂ concentration are used. The influence of the inhomogeneity on both ignition timing and combustion duration was found. Higher inhomogeneity retards ignition timing for its lower temperature and prolong combustion duration for its distributed combustion in the cylinder. Furthermore, the effect of inhomogeneity and the acceptable inhomogeneity depended on fuel composition. Higher H₂ content fuel can use higher inhomogeneity and receive much favors for decreasing maximum in-cylinder gas pressure rising rate.