Mechanism of stability enhancement of vane diffuser with different combined treatment methods

To solve the problem of a narrow flow range of a vane diffuser at high speed while maintaining adequate centrifugal compressor performance, the wing diffuser of a turbocharged transonic compressor is taken as the object; the numerical simulation method is adopted, the effects of low-solidity treatment, combined treatment of low solidity and slotting, combined treatment of low solidity, and casing on compressor stability and aerodynamic performance are studied, respectively. The results of low-solidity treatment show that a low-solidity diffuser can broaden the flow range, even 1.8 times that of the vaneless diffuser. The performance decrease is smaller than the vaneless diffuser (the maximum reduction of pressure ratio is 6.4% less, and the maximum reduction of efficiency is 4.1% less), but the stall boundary is shifted to the right. Then, the low-solidity diffuser is slotted in different axial and radial locations. They are slotting treatment of vane root, slotting treatment of vane tip, and casing treatment of circumferential slot at wheel cover. The results show that the location of the slot is the critical parameter; the location of the shockwave core area can determine it. Slotting treatment of the vane root, casing treatment of the circumferential slot, and slotting treatment of the vane tip can enhance stability from strong to weak and performance loss from large to small. Among them, slotting treatment at the front half-chord root of the low-solidity diffuser vane can maximise the stable working flow range while the problem of stall boundary shifts to the right can be solved. The stall margin is widened to 1.8 times, the flow range is enlarged to 1.7 times, and the flow range is even 2.3 times that of the vaneless diffuser. Although it also causes the greatest loss of aerodynamic performance, the performance is still better than the vaneless diffuser.