Computational Study of the Effect of Dual Air Swirling Injection on Turbulent Combustion of Kerosene–Air at a High Pressure

Abstract

The air compression ratio in a modern aero engine has been significantly increased to enhance the engine’s thermal efficiency, thereby leading to high-pressure combustion, with the combustor pressure exceeding the fuel’s critical pressure (~23 atm for the aviation kerosene). In this work, large eddy simulations are conducted to investigate the effect of two air swirling injections on the flow dynamics and turbulent combustion of kerosene–air in a dual-swirl model combustor at a supercritical pressure of 4 MPa. The flamelet progress variable (FPV) model is applied to handle turbulent/chemistry interaction, and the extended corresponding states (ECS) method is adopted to evaluate thermophysical property variations. The results indicate that the inner air swirler controls flow and chemical reactions inside the injector, while the outer air swirler exerts a strong impact on the flow and flame characteristics in the combustor. A precessing vortex core (PVC) is generated by the inner swirling flow, and its frequency increases significantly as the inner air swirler angle varies from 25° to 40°. A modified Strouhal number is proposed for PVC frequency analyses, which reveal that the PVC frequency is influenced by the inner swirl number and the maximum axial velocity in the inner injector. The results obtained herein should help in developing a fundamental understanding of swirling flow and flame dynamics at high pressures.

Keywords

• gas turbine combustor
• large eddy simulation
• swirl number
• PVC frequency
• Strouhal number