Influence of nanosecond-pulsed high frequency discharges on CH4-Air diffusion flames’ extinction strain rates:A numerical parametric study

There is a growing interest in methane combustion for liquid rocket applications. Due to its low C/H ratio, relatively high boiling point and density, and its availability on other celestial objects, methane is considered as a promising replacement for large chain hydrocarbons or hydrogen. However, Methane’s relatively low heating value, ignitability and flame speed may lead to combustion instabilities. These issues are especially highlighted when non-premixed combustion is considered. Recently, it was shown that Nanosecond-Pulsed High Frequency Discharges (NPHFD) may enhance stability characteristics such as increased air stream lift-off and blow-out velocities of methane-air flames in coaxial burners. In these, each discharge acts on both the air and methane inlet streams.

In the current study, we conduct a parametric numerical investigation where 0D atmospheric pressure (high energy density) discharges simulations are coupled with 1D opposed flow diffusion flames simulations to study the influence of NPHFD on the extinction strain rate. In addition, the individual and combined contributions of the discharge kinetic and thermal effects are studied.

It is found that extinction strain rates are exponentially dependent on discharge energy density. Moreover, in high energy density discharges, extinction strain rates are dependent on the kinetic and thermal effects of the discharges in a synergetic manner.