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Numerical Investigation of Fuid Injection Effects on Improving the Stability of Centrifugal Compressors

Hajaghaee, Ali | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55750 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Ghorbanian, Kaveh
  7. Abstract:
  8. Increasing the surge margin of compressors and preventing surge and stall phenomena have always been one of the main concerns of gas turbine engines. This research aims to numerically investigate the fluid injection effects on the surge margin in centrifugal compressors. In this regard, the NASA CC3 compressor is selected for validation purposes. Considering the available geometrical data, a simulation is performed by using Ansys software, and results are compared with those available from public literature.After the performance and accuracy of the fluid injection simulation results are validated, fluid injection is implemented in the newly selected location and its impact on the compressor surge margin is examined. Here, the new injection location is set in the middle of the diffuser channel. The results indicate that by injecting a flow rate of 1% of the inlet flow, the outlet pressure may increase by 2%. It has also been shown that injection at a negative angle to the channel axis and a lower position which is close to the down wall have a better effect on the surge margin. Here, the value of the surge margin increases from 2.9% in the non-injection mode to 4.225% in the mid-channel injection mode. Further, the secondary fluid, which was initially selected as air, is replaced with nitrogen gas, and the molecular mass of the injected fluid and its kinetic energy effect on controlling the stability is also investigated.
  9. Keywords:
  10. Centrifugal Compressor ; Stability Margin ; Fluid Injection ; Gas Turbine Engines ; Surge Phenomenon

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