One of the important ways of improving axial compressor performance is to control the tip leakage flow near the endwall region. Numerical computations were conducted to investigate the impact of blade tip suction on the axial compressor cascade performance in current paper. Three suction schemes located on the blade tip with different chordwise coverage were investigated in total. The results show that the cascade overall performance can be effectively enhanced by the proper suction scheme on the blade tip and the best scheme should be arranged at slightly downstream of the onset point of the tip leakage vortex (TLV). The control effectiveness and mechanisms are different for the different suction schemes. For the suction scheme covering the starting point of TLV, the onset point of TLV is shifted downstream, while an additional induced leakage flow near the blade leading edge is generated resulting in the increase of mixing loss. It is more effective when the structure of the main TLV is destroyed and divided into different parts by applying the blade tip suction arranged slightly behind the onset point of TLV. In addition, the blade loading is redistributed near the blade tip after the blade tip suction and the total pressure loss caused by the suction slots should also be considered in the design process.
In this paper, compressor aerodynamic performance has been predicted based on throughflow theory, combined with a surrogate model, which is a combination of the Genetic Algorithm (GA) and generalized Radial Basis function (RBF) neural network. And the predicting results have been compared with those from the traditional models and spanwise mixing model, which still widely be used to predict the aerodynamic performance. We first predicted the deviation angle and total-pressure loss coefficient (TPLC) by the surrogate model, and then using these two intermediate variables connected the model with throughflow theory. The pressure ratio and efficiency, representing the compressors’ total performance parameters, are predicted and compared with experimental data. In order to increase the accuracy of prediction, a data augmentation method based on the piecewise cubic Hermite interpolation (PCHIP) algorithm is introduced to enlarge the training database. At the same time, considering the vast differences of deviation angle and loss in different working conditions as well as aerodynamic and geometric differences of rotor and stator, the database and the network should be split into six components based on the choke, the normal and the stall conditions as well as rotor and stator. Then, the performance curves of pressure ratio and efficiency can be determined by an iteration process. The predicting results are compared with experimental data, which shows that the surrogate model matches experiments much better than those from the traditional models and spanwise mixing model.
Tip leakage flow is usually responsible for the deterioration of compressor performance and stability. The current paper conducts numerical simulations on the impact of casing aspiration on the axial compressor cascade performance. Three aspiration schemes with different chordwise coverage are studied and analyzed. It is found that the cascade performance can be effectively improved by the appropriate casing aspiration, and the optimum aspiration scheme should cover the area including the onset point of tip leakage vortex and its vicinity. The control mechanisms are different for the aspiration schemes located at different blade chord ranges. For the aspiration scheme covering the onset point of tip leakage vortex, the improvement of the cascade performance is mainly due to that the starting point of the tip leakage vortex is shifted downstream. The original tip leakage vortex structure is divided into two parts if the aspiration scheme is located behind the onset point of tip leakage vortex and the final control effect is the combination of the influence from the two different parts of tip leakage vortex. Additionally, the casing aspiration redistributes the blade loading along the chord near blade tip. The results of these investigations may offer guidance for the appropriate design of aspiration scheme in the future updated compressors and the overall total pressure loss coefficient caused by aspiration slot should be considered in the design process.
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