Investigation on the effects of nanosecond pulsed discharge on combustion characteristics of C3H8/air mixtures using a rapid compression machine

Abstract

The non-equilibrium plasma generated by nanosecond pulsed discharge (NPD) effectively enhances ignition stability and accelerates the combustion process due to its unique physical and chemical properties. This investigation is conducted using a linear motor-driven rapid compression machine to investigate the effects of different nanosecond pulsed discharge parameters (pulse number: PN; pulse interval: PI) on the initial flame kernel shape, development process, and combustion characteristics of C₃H₈/air mixtures. The experiments are carried out under varying excess air coefficients and initial temperatures. The results show that the initial flame kernels mainly appear spherical and elliptical, and due to the presence of turbulence, an ‘8’ -shaped flame kernel is formed. As PN increases, the radius of the initial flame kernel enlarges and the flame propagation speed accelerates; in contrast, an increase in PI initially enlarges the flame kernel radius before causing it to decrease, with the flame propagation speed showing a trend of initially accelerating and then decelerating. Additionally, the increase in initial temperature raises the number of molecules capable of overcoming the activation energy barrier, thereby accelerating the combustion rate, which further enlarges the initial flame kernel radius and enhances flame propagation. The investigation also reveals that with an increase in PN, the peak combustion pressure rises while the ignition delay and combustion duration decrease. Conversely, the increase in PI has a negligible effect on the peak pressure and the pressure rise rate, but the combustion duration exhibits a trend of initially decreasing followed by an increase.