An adjustable vane-shaped nozzle-based modulated pre-swirl system for gas turbine aero-engine: Structure parameters and aerodynamic performance analysis

The pre-swirl system of an aero engine provides cooling air with suitable temperature and pressure for turbine blades, rarely contributing to thrust. However, the traditional pre-swirl system with a fixed geometry leads to significant wastage of cooling air during part-load conditions, such as subsonic cruising, resulting in a decrease in engine performance. Unlike the existing approach, which uses valves to close a part of the pipeline, a novel modulated pre-swirl system based on the adjustment of the vane-shaped nozzle is proposed to overcome the flow nonuniformity in the circumferential air supply. The effects of the number of pre-swirl nozzles and receiver hole parameters (number, length, and structure) on the system performance are discussed in design and subsonic cruising conditions. The results demonstrate that increasing the number of pre-swirl nozzles significantly improved the flow adjustment efficiency and performance of the modulated pre-swirl system. A larger number and shorter length of receiver holes resulted in a higher system temperature drop in both design and subsonic cruising conditions. With regard to the configurations of the receiver holes, the vane-shaped receiver hole exhibited optimal aerodynamic performance. Compared to the baseline case, the system with N_p = 60, N_Rec = 60, l_Rec = 3 mm, and vane-shaped receiver hole showed a 27.6 % and 26.7 % improvement in the temperature drop efficiency in the design and subsonic cruising conditions, respectively.