Investigation on the Aerodynamic Performance of the Centrifugal Compressor Stage with Ideal Gas

摘要

China is a large country and has constructed a natural-gas pipeline to transmit the gas produced in the western provinces to the eastern cities. The centrifugal compressor stage is used for this work because it can produce a high pressure. The centrifugal compressor stage has three main components including impeller, diffuser, and return channel.In this work, the flow feature in impeller, diffuser and return channel are investigated. The grids of the 3-D model are produced by the grid commercial program. Five different LE diffuser are developed and investigated by the numerical method, the CFD commercial program is used for simulation with theturbulence model.Flow behavior and losses in the impeller, diffuser passage, and return passage are investigated. The loss in flow passage due to the flow dissipation, the return passage has address four main locations the first is the impeller outlet section, the second is the diffuser outlet section, the third is the 180o return bend section, and the fourth is 90o the return bend section. The flow loss is reduced by developing the diffuser.The numerical simulation is validated with experimental test, the limit of stability centrifugal compressor stage has two behavior, and they are surge and choke respectively. The surge occurs at low mass flow rate due to back-flow while the choke occurs at high mass flow rate because of the sonic flow which is generated somewhere in centrifugal compressor stage .Based on an assessment of the original diffuser, the leading edge of the diffuser is developed for eliminating separation in the centrifugal compressor stage and studied comparatively. The magnitude of the efficiency, pressure ratio, and losses dissipation in the compressor are changed by the development of leading edge. The loss coefficient of the new diffuser is lower than the original diffuser and the performance is higher than the original model.

目录

声明

Nomenclature

Chapter 1 Introduction

1.1 Development of Centrifugal Compressor and Computational Fluid Dynamics (CFD)

1.2 Centrifugal Compressor Stage

1.3 Instability of Centrifugal Compressor

1.4 Centrifugal compressor diffusers research

1.5 Research Objectives and Scope

Chapter 2 Internal Flow Equations of Centrifugal Compressor Stage

2.1 The Basic Component of Centrifugal Compressor Stage

2.2 The Basic Flow Equation

2.3 Summary

Chapter 3 Numerical Method of Centrifugal Compressor Stage

3.1 Reynolds Time Averaging and Averaged Transport Equations

3.2 Reynolds Averaged and N-S Equation

3.3 Mesh Generation

3.4 Performance Metrics

3.5 Characteristics of Losses on the Return Passage Flow

3.6 Axisymmetric Parameterization

3.7 Summary

Chapter 4 Experimental Validation and Numerical Method Investigations

4.1 Grid independence Check

4.2 Validations of Experiment and Numerical Methods

4.3 Flow Passage Assessment

4.4 Surge Region, Operational Region, and Choke Region Flow Features.

4.5 Summary

Chapter 5 Optimization of Diffuser

5.1 Flow Feature in Diffuser

5.2 Flow Feature Comparison

5.3 Performance Comparison

5.4 Summary

Chapter 6 Conclusion

6.1 Summary

6.2 Future Work

参考文献

致谢