Advanced Non-Axisymmetric Endwall Contouring for Axial Compressors by Generating an Aerodynamic Separator—Part I: Principal Cascade Design and Compressor Application

Abstract

Modern methods for axial compressor design are capable of shaping the blade surfaces in a three dimensional way. Linking these methods with automated optimization techniques provides a major benefit to the design process. The application of non-axisymmetric contoured endwalls is considered to be very successful in turbine rotors and vanes. Concerning axial compressors non-axisymmetric endwalls are still a field of research. This two-part paper presents the recent development of a novel endwall design. An aerodynamic separator, generated by a non-axisymmetric endwall groove, interacts with the passage vortex. This major impact on the secondary flow results in a significant loss reduction because of load redistribution, reduction of recirculation areas and suppressed corner separation. The first paper deals with the development of the initial endwall design using a linear compressor cascade application. A brief introduction of the design methods is provided, including the automated optimization, the 3D process chain with a focus on the endwall contouring tool. Hereafter the resulting flow phenomena and physics due to the modified endwall surface are described and analyzed in detail. Additionally, the endwall design principal is transferred to an axial compressor stage. The endwall groove is applied to the hub and casing endwalls of the stator and the initial numerical investigation is presented. For highly loaded operating points the flow behaviour at the hub region can be improved in accord with the cascade results. Obviously, the casing region is dominated by the incoming tip vortex generated by the rotor and still remains an area for further investigations concerning non-axisymmetric endwall contouring.

Advanced Endwall Contouring for Loss Reduction and Outflow Homogenization for an Optimized Compressor Cascade

“…Figure 11 shows the optimized endwall member 555 as a contour plot and as a 3D view. There is a groove along the suction side, as already observed by Dorfner [9,10], and a hill and valley structure behind the blade, as already observed by Reutter et al [13]. The valley near the suction side reduced the Mach number level, whereas the hill near the pressure side increased it.…”

“…Early designs were axisymmetric, like in the patents of Spear and Biedermann [2] or of Hoeger and Schmidt-Eisenlohr [3]. Later works used non-axisymmetric attempts, like in the works of Harvey [4], Harvey and Offord [5], Iliopoulou et al [6], Reising and Schiffer [7,8], Dorfner [9], Dorfner et al [10], or Heinichen et al [11]. Overviews of EWC are given in Gier et al [12] and Harvey [4].…”

Numerical investigation of the influence of non-axisymmetric hub contouring on the performance of a shrouded axial compressor stator

“…Attempts to apply 3D hub contouring to axial compressor rotors on the other hand did not yield significant improvements [15,24]. More recently, Dorfner et al [3] as well as Hergt et al [12] and Lu et al [18] improved stator near hub flow fields for linear cascade as well as low speed compressor cases.…”

Enhancing the Performance of an Axial Compressor Cascade using Vortex Generators

“…Endwall boundary layer separation, horseshoe vortex, corner vortex, tip vortex, endwall crossflow, and passage vortex are secondary flow components in the cascade. Many researchers investigated the impact of three-dimensional blades and endwall boundary layer separation as well as flow separation in corners of blade passages on the development of secondary flows [1][2][3][4][5]. To control the secondary flows, both passive and active methods have been applied to reduce or overcome the effects of secondary flows in axial compressors.…”