Effects of thermal expansion on the stabilization of an edge-flame in a mixing-layer model

This paper examines the influence of thermal expansion on the stabilization of an edge-flame in a mixing layer. We find, similar to the earlier predictions based on a constant-density model, two modes of flame stabilization: a steady mode at low injection velocities and an oscillatory mode at higher velocities. The gas expansion has an effect on the flame standoff distance: as a result of the reduced density in the preheat zone the flow accelerates when crossing the flame which consequently forces its edge to relocate at an upstream position where its propagation speed balances the gas velocity. The onset of oscillations at relatively high flow rates is predicted with or without invoking the constant-density approximation; the critical conditions of the onset, however, are affected by density variations.