Designers and researchers have traditionally sought to minimize aerodynamic losses in turbomachinery without considering the influence of fillets, seals and cavities. The validity of this assumption is investigated in the present paper. Three different cavity geometries have been implemented in the third stage of a four-stage high-speed axial compressor. To better understand the interaction between the main flow path and the secondary flow caused by leakage through labyrinth seals, three different cavity outlet angles have been investigated: 90°, 45°, and 135° with respect to the main flow path direction. Moreover, three different clearances between the seal tips and the stator have been used in order to investigate the leakage mass flow inside the cavity. Three-dimensional steady RANS simulations with two different turbulence models using the TRACE solver by DLR have been performed in all cases. The SST turbulence model showed higher fidelity when compared to experimental data and proved more sensitive to variations of parameters studied. A comparison of aero-thermodynamic results in the main flow path for the different configurations at the inlet and outlet of the cavities shows that the radial profiles are strongly influenced by clearance height H and cavity outlet angle a in the third stator as well as rotor. A cavity outlet directed against the main flow direction gives the best results in terms of compressor overall efficiency. The results also reveal some modeling limitations in that neither of the two turbulence models can precisely predict the progressive temperature rise noticed in the experimental data above of 55% blade height in the third stator and rotor, pointing at deficiencies in modeling the tip clearance vortex.
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