Numerical analysis of air supply parameters and non‐uniform characteristics in a cover‐plate pre‐swirl system with the adjustable flow path

Summary The pre‐swirl system can transfer the cooling air from the compressor to the turbine rotor blades with a lower relative total temperature to avoid extreme thermal shock. This work proposes a novel test rig to investigate the flow and aero‐thermal characteristics in a cover‐plate type pre‐swirl system. The performed experimental and numerical studies focus on the effects of the partial pre‐swirl nozzle closing modes on the mass flow rate of air supply, temperature, and uniformities in a pre‐swirl system by application of the pre‐swirl nozzle adjustable flow path. Especially, the transient problem of the pre‐swirl system with the time‐space variation characteristics is approximately explored by changing the rotor‐stator phases, within the framework of a frozen‐rotor formulation. Results show that the opening of the pre‐swirl nozzle is of great importance for flow uniformity. A pre‐swirl nozzle closing of 14.3% will result in a 10.9% decrease in the mass flow rate of the pre‐swirl nozzle and a 9.9% decrease in the mass flow rate of air supply at the system pressure ratio of 1.32 and the rotating Mach number of 0.678. The maximum amplitude of the non‐uniformity coefficient of mass flow rate increases from 1.1% to 5.4% for a single supply hole. Moreover, the relative total temperature of air supply decreases by about 1 K with the increase of the fluctuation from 0.5 to 1.5 K. Thus, the performance of the aero‐engine can be improved due to a reduction in the amount of cooling air into the rotating turbine blades. This work proposes a novel test rig to investigate the flow and aero‐thermal characteristics in a cover‐plate type pre‐swirl system. The performed experimental and numerical studies focus on the effects of the partial pre‐swirl nozzle closing modes on the mass flow rate of air supply, temperature, and uniformities in a pre‐swirl system by application of the pre‐swirl nozzle adjustable flow path. Especially, the transient problem of the pre‐swirl system with the time‐space variation characteristics is approximately explored by changing the rotor‐stator phases, within the framework of a frozen‐rotor formulation.