Casing treatment is an effective passive technology for improving the compressor stability. However, the current design methods for the casing treatment rely excessively on trial and error experiences, presenting significant challenges to actual engineering applications. In this paper, we propose a multi-objective optimization design method based on stall margin evaluation and data mining to enhance the stability of axial compressor rotors. We have developed a multi-objective optimization platform that combines geometric parameterization, mesh generation, numerical calculations, optimization algorithms, and other relevant components. To optimize six design variables and two objective functions, we have implemented two optimization strategies based on direct stall margin calculation and stall margin evaluation. The optimization results revealed that optimal casing treatment structures can be obtained by considering both compressor stability and efficiency. Furthermore, we employed data mining of self-organizing maps to explain the tradeoffs from the optimal solutions. The aerodynamic analysis demonstrated that the casing treatment enhances stability by restricting negative axial momentum of tip leakage flow and reducing passage blockage. Four categories of stall margin evaluation parameters were quantified, and their effectiveness was assessed through a correlation analysis. Finally, we used the axial momentum of the tip leakage flow-related evaluation parameter for the optimization of stall margin evaluation. Compared with direct stall margin calculation-based optimization, the evaluation of the parameter-based optimization method effectively predicted the stability enhancement of casing treatment while revealing the optimal geometric features. It suggests that the stall margin evaluation-based optimization method should be utilized in the initial optimization process of casing treatment due to its advantages in the optimization speed.

Compressed air energy storage systems must promptly adapt to power network demand fluctuations, necessitating a high surge margin in the compression system to ensure safety. It is challenging to completely eliminate blade geometric variations caused by limited machining precision, the important effects of which should be considered during aerodynamic shape design and production inspection. The present paper explores the uncertainty impact of geometric deviations on the stability margin of a multi-stage axial compressor at a low rotational speed. Initially, an adaptive polynomial chaos expansion-based universal Kriging model is introduced, and its superior response performance in addressing high-dimensional uncertainty quantification problems is validated through rigorous analytical and engineering tests. Then, this model is used to statistically evaluate the stability margin improvement (SMI) of the compressor due to the Gaussian and realistic geometric variabilities separately. The results show that the mean and standard deviation of SMI are −0.11% and 0.5% under the Gaussian geometric variability, while those are 0.33% and 0.39% under the realistic variability. For both the geometric variabilities, the stagger angle and maximum thickness deviations of the first-stage rotor are the most influential parameters controlling the uncertainty variations in the stability margin. Finally, the underlying impact mechanism of the influential geometric deviations is investigated. The variation in the stability margin caused by the geometric deviations primarily results from the alteration of inlet incidences, affecting the size of the tip leakage vortex blockage and boundary-layer separation regions near the blade tip of the first-stage rotor.

In the present study, various groove casing treatments were evaluated under a high-speed subsonic axial flow compressor using experimental and numerical simulation methods. The aim of this study was to explore the effect of inclination of grooves on compressor stability and performance. The potential flow mechanisms were also evaluated. Three different inclination grooves were designed in this study: grooves with no inclination, grooves with 30 degrees upstream inclination and grooves with 30 degrees downstream inclination. Similar effect of the grooves on the compressor stability and efficiency was observed under experimental and numerical analyses. The grooves with no inclination, 30 degrees upstream inclination and 30 degrees downstream inclination enhanced stall margin by 6.08%, 8.74% and 3.03%, respectively. The peak efficiency losses of the three types of grooves were 1.62%, 0.94% and 2.33%, respectively. Tip flow field analyses demonstrated that the radial transport effect caused by grooves effectively reduced tip loads and alleviated tip blockage. This explains why the grooves enhanced the compressor stability. The radial transport effect was enhanced, and a larger stall margin improvement was obtained when grooves inclined upstream were applied. The tip flow loss was the dominant loss observed after grooves were applied on the compressor. The grooves with upstream inclination markedly reduced the tip flow loss, indicating that they exhibited the lowest effect on reducing compressor efficiency compared with the other types of grooves.