A New Model for Predicting Two-Zone Parameters Based on Geometric Modifications in Computational Fluid Dynamics Simulations

Author

Jason B. Metten, Brigham Young UniversityFollow

Abstract

This study uses Computational Fluid Dynamics (CFD) to create a new and improved model for key Two-Zone modeling parameters, 𝜒 and 𝛿2𝑝. It explores how geometric changes to centrifugal compressors impact these modeling parameters. While centrifugal impellers are an important part of many systems, the flow through such impellers is inherently complex, making performance often difficult to predict. There are many approaches for modeling this complex flow environment, one method being the Two-Zone model developed by Dave Japikse. Values for 𝜒 and 𝛿2𝑝 are often determined from data obtained from test rigs or correlations. In this study high-fidelity CFD simulations were used to create an expansive dataset of unique impellers from which information about theoutlet flowfieldcanbeextracted. Meridionalvelocity wasused to define the primary and secondary flow zones. The CFD simulations werevalidatedwithmeasuredtestdatatoensuretheiraccuracyandmesh independence. Changes were made to the geometries of the original nine compressors to vary the nondimensional tip clearance from 1-20% andblade loading ±25%fromnominal. This provided 158 simulations at the benign incidence point which were then used to develop predictive models for 𝜒 and 𝛿2𝑝. 𝜒 was most influenced by specific speed and the exit absolute flow angle. 𝛿2𝑝 was most influenced by the blade turning angle. The combined model of 𝜒 and 𝛿2𝑝 has an average error of 1.21%. Two validation cases were used to evaluate the accuracy of the model. Thepowerwaspredictedwithin3.67%and2.05%comparedtothepower calculated directly from the CFD simulations. Such low errors in the predicted power demonstrate that these new models are accurate and capable of predicting 𝜒 and 𝛿2𝑝 for centrifugal compressor design and performance prediction.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

BYU ScholarsArchive Citation

Metten, Jason B., "A New Model for Predicting Two-Zone Parameters Based on Geometric Modifications in Computational Fluid Dynamics Simulations" (2025). Theses and Dissertations. 11111.
https://scholarsarchive.byu.edu/etd/11111

Date Submitted

2025-12-12

Document Type

Thesis

Keywords

Centrifugal compressors, Two-Zone model, CFD

Language

english