Numerical study of steady flow characteristics of a rear variable-area bypass injector with alternating area regulator

The mixing effectiveness of the airflow between the inner and outer bypass inlets of a Rear Variable-Area Bypass Injector (RVABI) is the key to the afterburner performance of variable cycle engines. This paper describes an optimized RVABI design based on an alternating area regulator to improve the velocity/temperature uniformity of the incoming flow at the afterburner. Compared with a classical RVABI, numerical simulations show that the proposed alternating RVABI performs better in terms of thermal mixing efficiency and total pressure loss in different variable cycle engine modes. Both the increasing air contact area between the inner and outer bypass of alternating structure RVABI, and a larger streamwise vortex in the inner bypass inlet due to the proposed alternating lobe structure in the RVABI contribute to the significantly increase of mixing effectiveness. Besides, the alternating regulator induces strong streamwise vortex, which helps to improve the airflow mixing with its vortex-induced velocity. The interaction between the streamwise vortex and azimuthal vortex further promises the velocity/temperature uniformity after the RVABI. With the increase of alternating lobe's height ratio, the covering area of the streamwise vortex and the azimuthal vortex is enlarged, which further enhances the thermal mixing efficiency of the RVABI. This design gives an insight into the future design and optimization of RVABI.