Plasma-combustion coupling in a dielectric-barrier discharge actuated fuel jet

Abstract

A plasma-combustion coupling mechanism is proposed and applied to the laser-induced atmospheric-pressure ignition and combustion of a hydrogen jet as assisted by a dielectric-barrier discharge (DBD). The specific configuration matches corresponding experiments, and the proposed coupling mechanism leads to an improvement of the prediction for ignition probability and explains the observed electrical power increase during burning conditions. To realize this, the model includes the key effects of the fast DBD microflimentary plasma structure on combustion time scales, which would not be included in a simpler quasi-steady approximation. It also explains observed plasma emission patterns and the dependence of the DBD power absorbed on the cross-flow velocity. The main conclusion of the present computational analysis is that the interaction of plasma and combustion supports a two-way coupling rooted in the electron and neutral energy equations. The coupling selectively amplifies the energy and radical contributions by the discharge at the ignition hot spot. These contributions dominate the evolution of hot spots interacting with the local electric field over dielectric surfaces and are a key ingredient of predictive ignition models. Results are discussed in the context of the lower pressure, lower equivalence ratio and lower dimensional (often premixed and quasi-one-dimensional) studies that provide insights for developing this integrated model while illuminating the important differences of the coupling in non-premixed conditions at atmospheric pressure.