Efficiency and Erosion of Plasma Jet Igniters-Variation with Voltage

Abstract

The erosion and thermal efficiency of a plasma jet igniter operating at much higher than the usual discharge voltage has been monitored over a range of voltage. The working voltage range is from 5-30 kV with the stored energy being kept constant at about one Joule. It is found that igniter lifetime is increased by about an order of magnitude over the figure previously reported for the same type of igniter operating at the more conventional voltage level of ∼1 kV.

At the same time, contrary to expectation, the thermal efficiency is found to remain more or less constant with voltage. Since such desirable properties as turbulence and radical formation can be expected to increase with thermal efficiency it now seems that the present, very severe limitation upon igniter lifetime can be reduced to manageable proportions without reduction of igniter performance by operating at high voltages. Measurements of the damping of the oscillatory currents obtained at high voltages allow the time-averaged plasma resistance to be calculated as a function of the cavity length. It is found that resistance is proportional to length, reinforcing the findings of other researchers that longer cavities are to be preferred.