Ignition characteristics of a novel mixed-flow trapped vortex combustor for turboshaft engine

Abstract

This paper describes an experimental investigation of the effect of flow conditions on the ignition performance of a conceptual combustor. This novel combustor is the first time designed and evaluated for turboshaft engine, known as the mixed-flow trapped vortex combustor (TVC) that utilizes a single cavity to provide flame stabilization. The single cavity is located obliquely on the right side of the combustor. Liquid RP-3 kerosene is directly injected into the cavity. The basic ignition process and the sound theoretical foundation for relating ignition characteristics to all the relevant operating variables were examined experimentally for the first time of the TVC. Simultaneous imagines of flame structure by high-speed camera were obtained to study the basic ignition process in the combustor. The key factors of the success of each ignition process were analyzed. The ignition process of the TVC consists of three stage: 1) the formation of a flame kernel, 2) the subsequent propagation from this flame kernel to all parts of the primary zone, and 3) the spread of flame from a lighted dome to an adjacent unlighted dome. Ignition was made easier by increasing in pressure, temperature, and was impaired by increasing in velocity. Stable flame was achieved in the mixed-flow TVC for a wide range of flow conditions. As the temperature increased, the range of ignition was broadened and the ignition fuel to air ratio (FAR) was reduced. The successful completion of this testing verified that this novel mixed-flow TVC has reasonable structural design and good ignition performance.