Spark discharge energy effect on in-cylinder characteristics performance of rapid compression and expansion machine with spark ignition direct injection strategy

Abstract

A spark ignition strategy in compression ignition has been considered to achieve high performance of gasoline direct injection engines. The spark ignition energy depends on the discharge current and the spark discharge duration. However, the respective roles of both on the rapid compression and expansion machine (RCEM) running with spark ignition and gasoline direct injection in-cylinder pressure have not been fully investigated. Both experiments and simulations were carried out in this study to investigate the spark discharge energy’s effect on in-cylinder characteristics performance. Three spark ignition strategy ranging from 50 mA up to 200 mA is applied to enhance the ignition discharge energy according to six selected cases of ignition timing variation (0.7 ms, 1.0 ms, 2.0 ms, 3.0 ms, 4.0 ms, and 5.0 ms). The results show the total released energy at the simultaneous ignition strategy was the largest (around 190 mJ/s), followed in order by the pair ignition strategy and individual ignition strategy. The highest turbulent kinetic energy of gasoline RCEM with spark ignition strategy is 1.43 m2/s2 (an increase 27.96 % from RCEM fueled with diesel). When the start of injection (SOI) of direct injection gasoline was set the same as the SOI of direct injection diesel at 10 oCA BTDC resulted in the thermal efficiency of gasoline RCEM with spark application slightly increased when spark time duration is prolonged at the average of 15.96 %. Finally, the establishment of a compression ignition engine combined with spark energy discharge might contribute to faster plasma formation, as well as expose the kernel development to a wider range of spark duration.