Influence of nonuniform velocity and temperature inlet on the mixing characteristics of a TBCC multibypass combustor with a double-mixer configuration

Abstract

Turbine-based combined cycle (TBCC) engines are characterized by strong nonuniformity flow in the turbine outlet and mode transition involving multiple bypasses, which may lead to failure of mode transition. In this paper, the mixing characteristics and flow losses of a TBCC multibypass combustor with a double-mixer configuration under nonuniform velocity and temperature inlet conditions are investigated through numerical simulation. The results show that the antiphase double-lobed mixer has a higher mixing efficiency than the in-phase double-lobed mixer at x/h < 0.8 (x/h are dimensionless axial coordinates), and the total pressure loss is greater; moreover, the mixing efficiency is reversed, and the total pressure loss is basically the same at x/h > 0.8. For both nonuniform velocity and temperature conditions, the mixing efficiency at peak profiles less than 50% is lower than that at the uniform inlet. With increasing velocity nonuniformity, the total pressure loss cost of increased mixing characteristics increases. The effect of the variation in the airflow velocity in the combustor on the total pressure loss is greater than that of the variation in airflow mixing characteristics when the mass flow rate in the combustor is changed. The change in mixing characteristics caused by the nonuniform temperature inlet profile is due to the temperature distribution and is independent of the type and performance of the mixer.