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Probabilistic CFD Computations of the NASA Low-Speed Centrifugal Compressor (LSCC) under Uncertain Operational Conditions

Mazloumi, Amir Hossein | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57875 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Karimi, Mohammad Sadeq
  7. Abstract:
  8. Centrifugal compressors are widely utilized in various industrial systems; however, their performance under uncertain operating conditions is influenced by random variations parameters. This research presents a comprehensive investigation and analysis of uncertainties in the performance of the NASA low-speed centrifugal compressor (LSCC). The primary focus of this study is to analyze the impact of uncertain operating conditions such as total inlet pressure, total inlet temperature, mass flow rate, inlet flow angle, and rotational speed, all of which are modeled using the beta probability distribution. To conduct this analysis, the non-intrusive polynomial chaos expansion method has been employed. This approach effectively quantifies uncertainties and evaluates their effects on the flow characteristics and performance of the compressor. Furthermore, to achieve a more detailed sensitivity analysis of the model with respect to random inputs, Sobol indices are used. These indices enable the identification of the relative influence of each random input on the model’s output results. The results of the uncertainty simulations revealed significant impacts of uncertainties on the isentropic effciency and flow fields of the centrifugal compressor. In particular, the findings demonstrated that random variations in rotational speed and inlet flow angle play a critical role in influencing changes in the Mach number around the blades and the static pressure coeffcient of the compressor. Furthermore, minor fluctuations in input parameters, such as a 0.3% variation in mass flow rate, 0.067% in total inlet pressure, and 1% in rotational speed, result in notable changes of 10.48% and 1.52% in normalized input power and isentropic efficiency, respectively. In conclusion, it is evident that under uncertain operating conditions, the performance of the LSCC is significantly influenced by variations in input characteristics. This can lead to a reduction in system effciency and deviations from the expected outcomes predicted by the designer. Overall, the impacts of uncertainties highlighted in this study underscore the importance of precision in the design and analysis of centrifugal compressors operating under stochastic conditions. Ultimately, these findings can assist engineers and designers in identifying critical variables and developing centrifugal compressors with more stable and resilient performance in uncertain operating environments. Overall, the impacts of uncertainties highlighted in this study emphasize the importance of precision in the design and analysis of centrifugal compressors operating under stochastic conditions. Ultimately, these findings can assist engineers and designers in identifying influential variables and developing more robust centrifugal compressor designs.
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Uncertainty Quantification ; Low-Speed Centrifugal Compressor ; Non-Intrusive Polynomial Chaos ; Uncertain Operational

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