Effects of cutback squealer tips on the vortices and local loss in the tip region of axial turbine rotor

Abstract

Tip leakage loss is a significant source of aerodynamic loss in the turbine rotor and can be controlled by using a cavity tip. In this paper, three configurations with cutback rims are numerically investigated to control the formation and development of vortices in the tip region. The results indicate that the suction side cutback squealer tips effectively suppress the development of the upper passage vortex (UPV) and its associated losses. The suction side cutback rim increases the leakage rate and strengthens the leading-edge tip leakage vortex (LTLV), which in turn intensifies the interaction between the LTLV and the UPV, thereby inhibiting the development of the UPV. The pressure side cutback rim has a lesser impact on the LTLV but significantly enhances both the tip leakage vortex (TLV) and the UPV, which is unfavorable for controlling local losses in the tip region. When the suction side rim cutback is slightly downstream, it can generate a stronger LTLV for suppressing the development of the UPV. This configuration could effectively reduce the total pressure loss coefficient in the range of 50%–80% span by up to 28%, although it also leads to an increase above 80% span. Overall, the suction side cutback squealer tip could still reduce the average total pressure loss coefficient in the region above 50% span by approximately 5%.

Keywords

Tip leakage flow / Cutback squealer tip / Vortex / Local loss / Turbine

References

[1] Denton JD. Loss mechanisms in turbomachines. J Turbomach, 1993, 115(4): 621-656.

[2] Bunker RS. Axial turbine blade tips: function, design, and durability. J Propul Power, 2006, 22(2): 271-285.

[3] Zhou C, Zhong F. A novel suction-side winglet design philosophy for high-pressure turbine rotor tips. J Turbomach, 2017, 139111002

[4] Kavurmacioglu L, Senel C, Maral H, et al. . Casing grooves to improve aerodynamic performance of a HP turbine blade. Aerosp Sci Technol, 2018, 76: 194-203.

[5] Wang Y, Yu J, Song Y, et al. . Parameter optimization of the composite honeycomb tip in a turbine cascade. Energy, 2020, 197117236

[6] Zhou C, Hodson H. The tip leakage flow of an unshrouded high pressure turbine blade with tip cooling. J Turbomach, 2011, 133(4041028

[7] Yu J, Yu J, Chen F, et al. . Numerical study of tip leakage flow control in turbine cascades using the DBD plasma model improved by the parameter identification method. Aerosp Sci Technol, 2019, 84: 856-864.

[8] Zou Z, Shao F, Li Y, et al. . Dominant flow structure in the squealer tip gap and its impact on turbine aerodynamic performance. Energy, 2017, 138: 167-184.

[9] Wang Y, Zhang W, Huang D, et al. . Control strategies for tip leakage vortex using inclined squealer rim in axial turbines. Phys Fluids, 2022, 34036101

[10] Prakash C, Lee CP, Cherry DG, et al. . Analysis of some improved blade tip concepts. J Turbomach, 2006, 1284): 639-642.

[11] Zeng F, Zhang W, Wang Y, et al. . Effects of squealer geometry of turbine blade tip on the tip-leakage flow and loss. J Therm Sci, 2021, 30(4): 1376-1387.

[12] Wang Y, Zhang W, Mu Y, et al. . Effects of inclined squealer rims on tip leakage vortex and loss in a transonic axial turbine. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2023, 237(2): 236-250

[13] Gao J, Zheng Q. Effect of squealer tip geometry on rotor blade aerodynamic performance. Acta aeronautica et astronautica sinica, 2013, 34(2): 218-226(in Chinese)

[14] Wang Y, Zhang W, Huang D, et al. . Numerical study on vortex structures and loss characteristics in a transonic turbine with various squealer tips. Energies, 2022, 15: 1018.

[15] Lomakin N, Granovskiy A, Shchaulov V et al (2015) Effect of various tip clearance squealer design on turbine stage efficiency. Paper presented at the ASME Turbo Expo: Turbine Technical Conference and Exposition. Montreal, CANADA, 15–19 June 2015.

[16] Lu S, Ma H, Zhang Q, et al. . Cutback squealer tip trailing edge cooling performance. Int J Heat Mass Transf, 2020, 154119632

[17] Zhang W, Wang Y, Chen K, et al. . Vortex interactions and loss mechanisms in the tip region of axial turbine rotors with cutback squealer tip. Energy, 2025, 314134214

[18] Qi L, Zou Z, Liu H, et al. . Upstream wake–secondary flow interactions in the endwall region of high-loaded turbines. Comput Fluids, 2010, 39(9): 1575-1584.

[19] Liu C, Gao Y, Dong X, et al. . Third generation of vortex identification methods: Omega and Liutex/Rortex based systems. J Hydrodyn, 2019, 31(2): 205-223.

[20] Kock K, Herwig H. Local entropy production in turbulent shear flows: a high-Reynolds number model with wall functions. Int J Heat Mass Transf, 2004, 47(10–11): 2205-2215.

[21] Li Z, Du J, Jemcov A et al (2017) A study of loss mechanism in a linear compressor cascade at the corner stall condition. Paper presented at the ASME Turbo Expo: Turbine Technical Conference and Exposition. Charlotte, NC, 26–30 June 2017

[22] Petukhov BS. Heat transfer and friction in turbulent pipe flow with variable physical properties. Advances in Heat Transfer, 1970, 6: 503-564.

Funding

National Natural Science Foundation of China(No. 52176033)

RIGHTS & PERMISSIONS

The Author(s)