Advanced combustion operation in a single-cylinder engine

In this paper advanced combustion concepts such as HCCI and PCCI were studied in a single-cylinder engine. PCCI was achieved by the combination of part aspiration and part direct injection of DME in the experiments, which was a compromise to obtain HCCI in that only a portion of the fuel was premixed and the portion of combustion was still controlled by the injection timing. Basic investigations toward the PCCI and HCCI combustion in a DME engine were carried out. DICI operation was also conducted to make a comparison. Results showed that as for the PCCI combustion operation, p_max, (dp/dθ) _max and heat release rate were between the values of HCCI and DICI operation and they increased with a rise of premixed ratio. The combustion duration for the PCCI combustion was longer than those of HCCI combustion, but was shorter than that of DICI combustion. Furthermore, the combustion duration decreased and the brake thermal efficiency increased with an increase in premixed ratio. CO and HC emissions for the PCCI combustion operation were lower than those of the HCCI engine. In comparison to conventional DICI operation, NO_x emissions for the PCCI combustion operation decreased significantly. Experiments also indicated that the fuel injection timing had a great influence on the performance and emissions of a DME engine at a PCCI combustion mode.