A hybrid performance prediction method for centrifugal compressors based on single-zone and two-zone models

Significance 

Centrifugal compressors are widely applied in aircraft engines and their efficiency is of paramount importance. This is why developing a high-accuracy one-dimensional performance prediction method is highly desired. Precise performance prediction or analysis enables designers to make quick assessments and necessary refinements of the geometry during the early design stages of centrifugal compressors.

The current one-dimensional performance prediction methods are divided into three categories: zero-zone, single-zone, and two-zone. The zero-zone technique is a non-dimensional map analysis method for which efficiency is predicted from empirical correlations according to non-dimensional parameters such as tip-speed, Mach Number and flow coefficient. These techniques are used in the early design stage, and for the limited inputs requirements, they only give fairly rough estimations.

The single-zone technique, which is more-geometry-based, divides the loss in the centrifugal compressors into numerous individual components and a loss model formulated for each component. Researchers have proposed several collections of loss models, but purely empirical and semi-empirical models in these collections significantly limit their application.

The two-zone technique, which is a more advanced method, has been proposed to model jet-wake flow pattern in flow analyses. However, effectiveness parameters may vary significantly with flow parameters such as Rynolds number, blockage, blade-loading, incidence, Mach number, etc. Even when the effectiveness parameters are set as constants, the lack of a detailed guideline for parameter selection forces designers to rely on their own experience. The fact that there is still no specific definition of the two zones to differentiate between the primary and secondary zone is another shortfall of the two-zone method.

In all, the two-zone method falls short of a basic guideline for parameter selection despite its upside of trying to model real flow structure with introduced parameters. The single zone method predicts the loss from basic physics, but some loss mechanisms aren’t sufficiently understood yet. This is why PhD candidates Pengcheng Xu, Liming Xuan and led by Professor Zhengping Zou from Beihang University in China developed a new hybrid performance prediction method combining the loss models of the single-zone technique and the division idea of the two-zone technique. The researchers introduced two additional parameters for wake zone analysis to specifically analyze the loss mechanisms not clearly understood in the single-zone method. Their research work is currently published in journal, Aerospace Science and Technology.

Going by the two-zone definition, the proposed hybrid system splits the flow into a jet zone and a wake zone. The authors adopted the well-understood models in the jet zone analysis as an alternative to the empirical parameters of the two-zone method. In the wake zone analysis, the researchers introduced two parameters as an alternative to the endwall loss model in the single-zone model. For the first time, the authors were able to completely define the wake zone and proposed a sensitivity analysis. They then presented the loss models for the jet zone and parameter selection guideline for the wake zone. The authors finally validated their proposed hybrid method on four centrifugal compressors and compared the results with the single and two-zone methods.

The novel hybrid method implicitly took into account the endwall loss with the two introduced wake zone parameters on the assumption that all the endwall loss was contained in the wake zone. Models for the wake zone parameter predictions were proposed by evaluating the dominant factors from one-dimensional level. The authors then extracted the coefficients from sufficient datasets using statistical methods. They found it to be convenient to update them from corresponding database when a new design feature needs to be introduced. The researchers then validated the hybrid method on four centrifugal compressors, and they were able to accurately predict both the shape and performance curves values. They reported an efficiency error of less than 1% at design points and no more than 4% at off-design points.

The findings of Pengcheng Xu and colleagues show that compared with the single-zone and two-zone methods, the proposed hybrid method gives more reliable and accurate predictions in the whole operating range.

A hybrid performance prediction method for centrifugal compressors based on single-zone and two-zone models - Advances in Engineering

About the author

Zhengping Zou is a tenured full professor as well as a doctoral supervisor in Research Institute of Aero-Engine and National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics, School of Energy & Power Engineering, Beihang University, Beijing, China.

Professor Zou has over twenty years of teaching and research experience in the fields of aero-engines, hypersonic precooled engines as well as supercritical medium Bryton cycles. The main research interests include: refined flow mechanism and organization methods in gas turbines, advanced design technique for high performance gas turbines, uncertainty analysis of turbomachinery aerodynamic performance and robust design, full range hypersonic precooled engines and supercritical medium Bryton cycles

Professor Zou has published more than 150 papers in academic journals and conferences (more than 30 papers in SCI journals), as well as a textbook and a monograph. He has obtained 24 national invention patents and 3 software copyrights. He has been awarded 2nd prize of AVIC Industry Science and Technology Progress Award, 3rd prize of National Defense Science and Technology Progress Award and 2nd prize of National Technological Invention Award, etc. Professor Zou is also a senior member in the Hypersonic Air-breathing Precooling Propulsion Team of Beihang University. The team has won the National Innovation Competition Award in 2020.

Mail: [email protected]

About the author

Pengcheng Xu is a Ph.D. candidate supervised by Prof. Zhengping Zou in National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics, School of Energy & Power Engineering, Beihang University, Beijing, China.

His main research interests include: turbomachinery aerodynamics, design and analysis of turbines and compressors especially those working with special medias such as helium and CO2, deep learning technology used in turbomachinery, etc.

Mail: [email protected]

About the author

Liming Xuan is a PhD student of Beihang University, following Prof. Zhengping Zou, Beijing, China. He obtained bechelor degree in thermal energy & power engineering from Harbin Institute of Technology in 2014, and master degree in power engineering from University of Shanghai for Science and Technology in 2017.

His main research interests include: aerothermodynamics of turbomachinery, tip leakage flow control method of high-pressure turbine, influence of non-uniform clearance of turbine rotor, etc.

Mail:[email protected]

Reference

Pengcheng Xu, Zhengping Zou, and Liming Xuan. A hybrid performance prediction method for centrifugal compressors based on single-zone and two-zone models. Aerospace Science and Technology, issue 108 (2021), 106358.

Go To Aerospace Science and Technology

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