Experimental investigations of aero-engine pre-swirl system performance improvement with consideration of inner seal flow effect

The pre-swirl system is essential for delivering cooling air to turbine blades within aviation engines. To explore the impact of the inner seal on the pre-swirl system, a high pressure ratio and high rotational speed experimental platform was constructed. The impact of inner seal inflow and outflow on the pre-swirl system's performance was evaluated. In response to the adverse effects of inner seal inflow on the system, a bypass structure was proposed to divert the inner seal flow, and the optimization effects and underlying mechanisms of the bypass structure were analyzed through a combination of experimental and numerical simulation approaches. The results indicate that the impact of inner seal outflow on the system is minimal, with the maximum variation in the temperature drop efficiency remaining below 1.9% under experimental conditions. Inner seal inflow, on the other hand, can have a significant negative impact on the system's performance. At a pressure ratio of 1.6, increasing inner seal inflow ratio leads to a decline in temperature drop efficiency from 0.55 to 0.43, representing a reduction of 21.8%. The bypass structure for inner seal can effectively prevent the mixing of inner seal flow with the mainstream within the pre-swirl cavity, reducing the pressure and temperature within the pre-swirl cavity. At a pressure ratio of 1.6 and inner seal inflow ratio of 15%, the specific work done by the airflow increased from 9.23 to 12.72 kW/(kg/s), increased by 37.8%, and the system temperature drop efficiency increased from 0.426 to 0.546, representing a 28.0% increase.