Combustion Enhancement in a Gas Engine Using Low Temperature Plasma

Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended by low temperature plasma ignition while a voltage drop during discharge, leading to the transition to arc discharge, was found. In this study, the structure of plug and power supply’s performance with steep voltage rising with time, dV/dt, are examined to investigate the effects on combustion performance. As a result, the following conclusions were deduced. (1) The lean combustion limit was extended when a four-pole plug with IES power source was used due to volumetric ignition. (2) A modified one-pole plug to improve the electric insulation, leading to prevent the voltage drop, could not extend the lean limit due to less volumetric ignitability. The specifications of plug must be improved to expand the ignition volume. (3) Using a variable dV/dt power source, the effect of dV/dt was tested. The combustion characteristics were not affected by dV/dt in this test range. (4) Comparing three power sources of CIC, IES and variable dV/dt, steep dV/dt realized small cycle-to-cycle variation and shorter combustion period, leading to higher peak value of the rate of heat release and better indicated thermal efficiency by relatively 6% and 4% compared to CIC and IES, respectively.