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A zero-dimensional, thermodynamic model with detailed chemical kinetics and cylinder wall heat transfer correlations has been used to study the detailed oxidation mechanism of natural gas in homogeneous charge compression ignition (HCCI) engine. A short mechanism made up of 241 reversible elementary reactions among 47species has been assembled from a previously extended detailed mechanism. The mechanism was numerically investigated at different operating and geometry conditions of HCCI engine during the time period in which both intake and exhaust valves are closed. The study is performed to elucidate the mechanisms of extinction and combustion behaviors of natural gas fuel with the effect of hydrogen addition to overcome the control of autoignition timing over a wide range of speeds and loads, limiting the heat released rate at high load operation, and meeting emission standards.

Homogeneous charge compression ignition (HCCI) is a new combustion concept which achieves high efficiency, low nitrogen oxides (NOx), and particulates matter (PM) emissions. In order to realize the HCCI combustion, a homogenous mixture preparation plays an important role in the HCCI engine. However, it is well known that diesel fuel is very difficult to achieve a uniform mixture distribution within the engine cylinder because of its high viscosity and poor fuel vaporization. In order to eliminate these problems, the low viscosity and high volatility Dimethyl ether (DME) was added into diesel fuel to enhance the spray and atomization. The spray tip penetration and spray cone angle of DME/diesel-blended fuel has been examined by using direct photography technology. Measurements were achieved by using spray images taken with a high-resolution CCD camera synchronized with strobe light.