Mechanism of affecting the axial rotor stability and performance with center offset degrees of axial skewed slots

Abstract

A subsonic axial rotor with axial skewed slot casing treatment (ASSCT) was investigated with experimental and numerical methods to explore the effects of the center offset degree (Cod) on the rotor stability and performance. Cod is defined as the ratio of the central difference between the rotor tip section and ASSCT to the rotor tip axial chord length. The Cod values are selected as 1.16, 0.608, 0, and −0.36, respectively. When the ASSCT is located upstream, the value of the Cod is positive. The experimental and unsteady calculated results show that the stall margin improvement (SMI) and peak efficiency loss (PEL) are reduced when the slots move to the rotor upstream or downstream. The slots with 0 Cod (ASSCT1) achieve 50% SMI with 8.67% PEL. The slots with 0.608 Cod (ASSCT2) gain 48.5% SMI with 2.12% PEL. The slots with 1.16 Cod (ASSCT3) and −0.36 Cod (ASSCT4) gain −3.41%, 20.1% SMI, respectively. Considering the compromise between the SMI and PEL for the rotor, ASSCT5 was designed by changing the slot number of ASSCT2 from 180 to 90. The unsteady calculated result shows that ASSCT5 can gain 22.28% SMI and 0.485% PEL. The detailed analysis of the flow field in the compressor tip passage indicates that there are adverse effects made by the slots on the flow field near the rotor blade tip leading edge for ASSCT3. Moreover, the ability of reducing the range of low-velocity zones for ASSCT4 is much lower than that for ASSCT1 or ASSCT2, and ASSCT1 generates bigger flow losses in the rotor tip passage than ASSCT2. The positive effects and flow losses made by the slots with 0.608 Cod both become smaller with the slot number decreasing from 180 to 90.

Keywords

Axial flow compressor center offset degree slot casing treatment stability subsonic

Get full access to this article

View all access options for this article.

References

Bailey EE. Effects of grooved casing treatment on the flow range capability of a single stage axial flow compressor. Report No. NASA TM X-2459, 1 January 1972. Cleveland, OH: NASA Lewis Research Center.

Müller MW, Biela C, Schiffer H and Hah C. Interaction of Rotor and Casing Treatment flow in an axial single-stage transonic compressor with circumferential groove. In: ASME turbo expo, Berlin, Germany, 9–13 June 2008, paper no. GT2008-50135.

Matthias R, Martin L and Konrad V. Experimental investigation of circumferential groove casing treatments for large tip clearances in a low speed axial research compressor. In: ASME turbo expo, Montreal, Canada, 15–19 June 2015, paper no. GT2015-42646.

Bozak R, Hughes C and Buckley J. The aerodynamic performance of an over-the-rotor line with circumferential grooves on a high bypass ratio turbofan rotor. Report No. GT2013-95114, 1 August 2013. Washington, DC: ASME.

Zhang HG, Tan F, An K, et al. Experimental and numerical investigation of effect of center offset degree on compressor stability with circumferential grooved casing treatment. In: ASME turbo expo, Seoul, South Korea, 13–17 June 2016, paper no. GT2016-56757. New York, NY: ASME.

Zhang

, et al. Flow mechanism of affecting an axial flow compressor performance and stability with cross-blade slot casing treatments. Proc IMechE, Part A: J Power and Energy 2018; 233: 17–36.

Osborn WM, Lewis GE and Heidelberg LJ. Effect of several porous casing treatments on stall limit and on overall performance of an axial flow compressor rotor. Report No. NASA TN D-6537, 1 November 1971. Cleveland, OH: NASA Lewis Research Center.

Moore RD, Kovich G and Blade RJ. Effect of casing treatment on overall and blade element performance of a compressor rotor. Report No. NASA TN D-6538, 1 November 1971. Cleveland, OH: NASA Lewis Research Center.

Prince DC, Wisler DC and Hilvers DE. Study of casing treatment stall margin improvement phenomena. Report No. NASA CR-134552, 1 March 1974. Cleveland, OH: NASA Lewis Research Center.

10.

Liu

Zhang

Shi

. Several observations and mechanism explored of slots casing treatment. Sci Tech Inform Northwest Polytech Univ 1985; 21: 1–35.

11.

Liu

Zhang

Shi

. Study on the effect of axial position on the performance of compressor by skewed slot casing treatment. J Eng Thermophys 1987; 8: 52–54.

12.

Ma N, Nan X and Lin F. Numerical study on effects of axial-slot casing treatment on peak efficiency of axial compressor. In: ASME turbo expo, Seoul, South Korea, 13–17 June 2016, paper no. GT2016-56554.

13.

Zhang

Chu

. Mechanism of influences of axial positions of axial skewed slot casing treatment on a compressor performance. J Aerosp Power 2011; 26: 92–98.

14.

Zhu

Chu

. Exploring mechanism of flow instability and stall margin enhancement of a subsonic axial-flow compressor due to casing treatment. J Eng Thermophys 2008. 10: 1657–1662. .

15.

Chu

Zhu

. Analysis of the coupled flow through axial skewed slots casing treatment and rotor passage. J Eng Thermophys 2006; 27(02): 226–228.

16.

Emmrich RR, Hönen HH and Niehuis RR. Time resolved investigations of an axial compressor with casing treatment: part 1 – experiment. In: ASME turbo expo: power for land, sea, and air, vol. 6, paper no. GT2007-27581, pp.189–198. New York, NY: ASME.

17.

Emmrich RR, Kunte RR, Hönen HH, et al. Time resolved investigations of an axial compressor with casing treatment: part 2 – simulation. In: ASME turbo expo: power for land, sea, and air, vol. 6, paper no. GT2007-27582, pp.199–208. New York, NY: ASME.

18.

Wilke I and Kau H-P. A numerical investigation of the flow mechanisms in a HPC front stage with axial slots. In: ASME turbo expo, Atlanta, GA, 16–19 June 2003, paper no. GT2003-38481.

19.

Wilke I. Numerically aided design of a high-efficient casing treatment for a transonic compressor. In: Proceedings of ASME turbo expo, Reno, NV, 6–9 June 2005, paper no. GT2005-68993.

20.

Florian CT. Experimental and numerical analysis of axial skewed slot casing treatments for a transonic compressor stage. In: Proceedings of ASME turbo expo, Orlando, FL, 8–12 June 2009, paper no. GT2009-59647.

21.

Chu

Liu

Zhu

. Experimental research and analysis of sloped slotted casing treatment. J Aerosp Power 1999; 14: 270–274.

22.

Lu XG, Chu WL and Zhu JQ. Experimental and numerical investigation of a subsonic compressor with bend skewed slot casing treatment. In: ASME turbo expo: power for land, sea, and air, Barcelona, Spain, 8–11 May 2006, vol. 6, paper no. GT2006-90026, pp.49–59. New York, NY: ASME.