Mixing characteristics assessment for a blade-type rear variable area bypass injector in a variable cycle engine

The mixing performance of a rear variable area bypass injector (RVABI) is a crucial issue for a variable cycle engine with afterburner. Herein, the mixing performance and flow field between an improved Blade-type RVABI (BT-RVABI) and a Lobe-type RVABI (LT-RVABI) are compared under different operating modes. Additionally, the influence of the width-to-length ratio (WLR) of the regulating plates on mixing performance is investigated. In the three-bypass mode, reducing the WLR from 1.085 to 0.599 improves the mixing performance. For the LT-RVABI, the thermal mixing efficiency rises by 40.127 %, whereas the total pressure recovery coefficient drops by 0.481 %. The BT-RVABI shows greater improvements, with thermal mixing efficiency increasing by 46.774 % and the total pressure recovery coefficient decreasing by 0.748 %. Notably, under the same aerodynamic losses, the mixing performance of the BT-RVABI is slightly lower than that of the LT-RVABI at longer distances. However, within shorter distances, the mixing performance of the BT-RVABI significantly outperforms that of the LT-RVABI, which is highly beneficial for the efficient combustion of the afterburner. In the two-bypass mode, lowering the WLR slightly enhances the thermal mixing efficiency of the LT-RVABI, yet the performance of the BT-RVABI is not affected. Moreover, compared with the BT-RVABI, both the total pressure losses and thermal mixing efficiency increase for the LT-RVABI.