Momentum imparted by plasma igniters to the surrounding gas

Publisher Website
Google Scholar
Abstract
It is expected that the momentum transfer from a plasma igniter to the surrounding gas plays a critical part in determining the subsequent combustion process. The momentum imparted by several types of plasma plug igniter has been measured by mounting each igniter in a simple pendulum and recording the steady state amplitude attained when the igniter is energised in sychronism with the swings of the pendulum. This technique, being far more sensitive than the previous single-shot method, allows relatively fine comparisons to be made between different types of igniter. The individual momentum measurements lie reasonably close to a theoretical limit based on the conversion of the translational energy of the Joule heated gas within the cavity to kinetic energy. On this basis it seems unlikely that substantial increases in imparted momentum can be expected from plug redesign etc. A separate series of measurements with energy storage at capacitor voltages of 5-20 kV instead of the usual range of 0.3-1 kV reveals that the imparted momentum decreases by less than 30%. Since recent measurements have demonstrated that the marginal igniter lifetime can be substantially extended by working at such high voltages, the above small decrease encourages the view that high voltage operation may be a desirable option.