# The Investigation of a New End Wall Contouring Method for Axial Compressors
###### Abstract  
To further control corner separation in high-load axial compressors, this study proposes a new end wall contouring method. It defines multiple standard \"surface units\" with particular flow control effects and then applies a linear combination, finally forming the geometry of the end wall surface. Based on design experiences, three different end wall contouring cases are generated and calculated on a high-load compressor cascade in the first step. The results show that the new method achieves a clear and intuitive influence on the end wall geometry, with a proper number of design variables, and can effectively combine variables with the development of secondary flow. In the second step, the new method was applied to an axial compressor, with an improvement in the design variables. Although the end wall contouring only improved the efficiency of the compressor stage on the right part of its operating map, the experimental results of the flow field show that the corner separation and end wall loss are suppressed at multiple inflow conditions. The results thus verified the practical effect of the newly developed end wall contouring method. corner separation; end wall contouring; flow control; compressor Article  
The Investigation of a New End Wall Contouring Method for Axial Compressors [PERSON] et al. (2022), [PERSON], [PERSON], [PERSON], and [PERSON] (2022), [PERSON]  
finally reducing the corner separation and increasing the peak efficiency by 0.45%. The DPS is also found in a much more recent study of a compressor cascade by [PERSON] [8], where the end wall contouring similarly reduced 18% of the total pressure loss. An afterward study by [PERSON] et al. [2] combined the end wall contouring with the SS corner profiling, proving that even using a straight-shaped DPS would suppress the end wall second flow and benefit the separation control. Note that the DPS is not the only contouring rule for loss control. The exception is in [PERSON]'s research [9], where the end wall contouring is manually constructed with an upslope from PS to the SS (called UPS for short), thus accelerating the end wall secondary flow to pre-mix with the accumulated low-energy fluid. Finally, the spanwise distribution of the loss coefficient was reduced by up to 7% relative to the original case. Therefore, it is hard to say whether decelerating or accelerating the end wall secondary flow would be more effective in separation control. The other end wall contouring method, i.e., the optimization method, shows more diversity than the empirical method. The parametric end wall surface is traditionally constructed using a lofted surface over dozens of uniformly distributed free control points, thus enabling highly flexible variation to work out the best end wall contouring in the design space. According to the optimization results, some research found weakening of the end wall secondary flow to be most effective in controlling corner separation [10; 11; 12; 13; 14; 15]. However, the results are different from the DPS in the empirical method. The end wall might have a downslope, but it is more likely a localized surface near the SS [10] or from the center of the blade channel [11] rather than a full-range structure. Some even find that the optimum end wall generates a streamwise groove, thus inducing a contour vortex to the passage vortex and deflecting the end wall secondary flow before it reaches the SS corner [12; 13; 14; 15]. The most frequently reported effective flow control is the acceleration of cross and climbing flow in the SS corner [3; 16; 17; 18; 19]. The optimization results show their diversity even with a common feature. In [PERSON]'s study [16], the acceleration of the end wall secondary flow is caused by a localized fillet-like upslope surface to the SS corner. [PERSON]'s research [17] shows a similar feature but a different position and area.