Effect of subsonic microjets on cold flow in dump combustors

Fluidic control of shear layers in air-breathing liquid-fuel combustors is considered as a viable means for improving performance. The increasing demand for compact combustion accompanied by low drag, high turndown ratio, and a reliable flame anchor calls for concurrent application of advanced control strategies such as counter-current shear and microjets. Traditional flame holders, such as the backward-facing step dump combustor, provide a protective environment for the flame to reside. However, these systems also carry a significant drag penalty. The focus of this research is to explore the role of microjets as a shear layer control strategy in dump combustors via numerical simulation. The simulations have been conducted within the Reynolds-averaged Navier-Stokes (RANS) framework. Results for cold flow have shown that increasing the momentum of the microjets leads to greater non-uniformity in the turbulent flow field. Microjets can also affect the recirculation zone, thus influencing flame stabilization. Many parameters such as the location, size, mass flow rate ratio, and momentum ratio of the microjets determine the overall performance. A detailed parametric study is conducted to investigate the effect of various parameters.