Numerical study of plasma assisted combustion in a sequential combustor

Abstract

The effects of Nanosecond Repetitively Pulsed Discharges (NRPDs) on the second stage flame of a sequential combustor is investigated using numerical tools supported by experiments. In this work, Large Eddy Simulations (LESs) with an accurate description of the combustion chemistry and a simplified model of the plasma kinetics are performed and successfully reproduce experimental observations of the combustion enhancement obtained with NRPDs. Detailed plasma kinetics calculations and experimental data demonstrate that the simplified plasma modelling retrieves the main energetic routes for the dissipation of the electron energy during the discharges. This model initially developed for discharges in pure air, is still valid for the highly air-diluted mixture considered in this study. The results of the LESs are analyzed to explain the underlying physics. Chemical Explosive Mode Analysis (CEMA) is used to identify the combustion modes of the ignition kernels, which result from the fast gas heating and the radical production by the NRPDs. These ignition kernels quickly give rise to propagating flames, advected through the sequential burner. Moreover, it is shown that the oxygen atoms produced by the Non-Equilibrium Plasma (NEP) dramatically accelerate the oxidation of the fuel.