Application of Casing Circumferential Grooves for Improved Stall Margin in a Transonic Axial Compressor

Abstract

Experimental and numerical investigations were conducted to study the fundamental flow mechanisms of circumferential grooves in the casing of a transonic compressor and their influence on compressor stall margin. Three different groove configurations were tested in a highly loaded transonic compressor. Experimental results show that circumferential grooves increase the stall margin of the compressor at the tested operating condition. Grooves with a much smaller depth than conventional designs are shown to be similarly effective in increasing the stall margin. Steady-state Navier-Stokes analyses were performed to study flow structures associated with each casing treatment. The numerical procedure calculates the overall effects of the circumferential grooves correctly. Detailed investigation of calculated flow fields indicates that losses are generated by interaction between the main passage flow and flow exiting the grooves. The grooves increase the stall margin by reducing the flow incidence angle on the pressure side of the leading edge, despite an overall increase in the endwall boundary layer thickness. This is due to complex interaction of the main passage flow with the additional radial and tangential flows created by the grooves.

State-of-Art of Transonic Axial Compressors

“…So it is a goal to maintain the positive effects (increased surge pressure ratio in combination with high efficiency) while at the same time reducing the geometric volume of the device. On this regard, an experimental and numerical investigation on the first rotor of a two-stage compressor showed that grooves with a much smaller depth than conventional designs are similarly effective in increasing the stall margin (Rabe & Hah, 2002). The same work also showed that two shallow grooves placed near the leading edge are better than five deep or shallow grooves all over the blade tip.…”

Toward Optimum Configuration of Circumferential Groove Casing Treatment in Transonic Compressor Rotors

“…In the following section, three recent studies that combine both experimental and numerical methods are reviewed. Rabe and Hah [2002] studied effects of circumferential grooves on a two-stage transonic axial compressor. Detailed numerical study was conducted to investigate flow mechanism of circumferential grooves.…”

“…Paulon and Dehoudt [1982] conducted a theoretical investigation of the effects of circumferential grooves. Rabe and Hah [2002] investigated circumferential grooves applied to the first stage rotor in a modern highly loaded two-stage transonic axial compressor. They found that the local flow incidence near the pressure side of the leading edge is reduced due to the circumferential grooves.…”

“…With the advance of CFD technology, several attempts have been made to investigate the effects of casing treatments on compressor performance (Crook et al [1993], Hall et al [1996], Rabe and Hah [2002]). Paulon and Dehoudt [1982] conducted a theoretical investigation of the effects of circumferential grooves.…”

Numerical and Experimental Investigations of Steady Micro‐Tip Injection on a Subsonic Axial‐Flow Compressor Rotor

“…Perhaps one of the most successful techniques alleviating the stall/surge phenomena is the different configuration of casing treatment means such as slots or grooves over a rotor blade tip [1][2][3][4]. Unfortunately, most of the suggested and investigated casing treatment configurations cause a significant drop in efficiency.…”