Control and Entropy Analysis of Tip Leakage Flow for Compressor Cascade under Different Clearance Sizes with Endwall Suction

Abstract

To investigate the influence of the change of tip clearance size on the control effect of the endwall suction, the effects of endwall suction on the aerodynamic performance of the axial compressor cascade were studied numerically. Three tip clearance sizes of 0.5% h, 1.0% h, and 2.0% h (h is the blade height) were mainly considered. The results show that the endwall suction scheme whose coverage range was 8–33% axial chord can reduce the leakage flow and improve the aerodynamic performance by directly influencing the structure of tip leakage vortex. The overall total pressure loss coefficients of the three clearance size schemes at 0° angle of incidence with 0.4 inlet Mach number are reduced by about 10.3%, 10.8%, and 6.0%, respectively, at the suction flow rate of 0.7%. Under the same suction flow rate, the onset position of the tip leakage vortex of the cascade with small clearance is shifted from the 15% of the axial chord length of original to the 48% of the axial chord length, which with large clearance is nearly no changed. The leakage flow rate and the distance from the leakage vortex to the suction slot are the main reasons for the different control effect of the endwall suction under different tip clearance sizes. The difference of the spanwise distribution of flow field parameters may also cause the difference of flow control effect.

Improved Aerodynamics of a Hollow-Blade Axial Flow Fan by Controlling the Leakage Flow Rate by Air Injection at the Rotating Shroud

“…To study the losses production generated by the leakage flow, it is recommended to use the entropy analysis [ 2 , 6 , 27 ]. It is shown that for turbulent flow with severe complex structure separation, the entropy analysis can be the better method to estimate these losses and to perform the possibilities of selective flow control conditions.…”

“…Throughout a investigation, You et al [ 5 ] emphasized and confirmed that the effect of this dimensions on noise generation and vibration. In addition, in the compressor cascade, Zhang et al [ 6 ] studied numerically the influence of the endwall suction under different tip clearance size. The obtained results showed that the tip leakage vortex is influenced by a particular endwall suction with performance improvement.…”

Effect of endwall suction on aerodynamic performance of compressor cascade with tip clearance at a large incidence angle

“…According to the influence of the number of grid nodes in the inner gap in spanwise on the prediction effect of the flow field in reference, 22 there were 21 grid nodes along the radial direction in the blade tip gap to ensure the leakage flow field could be captured reliably. Considering the calculation cost and accuracy, referring to the verification results of the grid independence carried out by previous research, 26 the total number of cascade grids was set to about 1.3 million. The minimum grid spacing of the first layer near the solid wall was set to 1 Â 10 À6 m, so that the normalized wall distance y þ < 2:5.…”

“…In combination with references, 24,26 considering the onset position of the tip leakage vortex and its coherent effect on the flow field, the endwall suction scheme for tip leakage flow control as showed in Figure 6 was designed. The suction slot is located on the upper endwall of the cascade, which contains the onset position of the tip leakage vortex and some regions nearby, within the range of 5%-35% of the axial chord length of the blade.…”

“…25 In addition, the change of tip clearance size also affects the suction control effect on clearance leakage flow. 26 The above research on suction control of the tip leakage flow is basically carried out for a single working condition similar to the design condition, but the real compressors often work under off-design conditions. Especially, when the compressor works at the large incidence angle, the internal flow field deteriorates seriously, so it is more necessary to adopt flow control techniques to maintain good aerodynamic performance.…”