Unsteady flow mechanism of the integrated aggressive inter-turbine duct in low Reynolds number condition

Abstract

Aggressive inter-turbine duct, which has ultra-high bypass ratio and ultra-short axial length, is widely applied in the modern turbofan engine because it can reduce engine weight and improve low-pressure rotor dynamic characteristics. However, the aggressive inter-turbine duct that has swirling flow, wake, shock, and tip clearance leakage flow of upstream high-pressure turbine, and even has structs in its flow channel, is liable to separate, especially in high-altitude low Reynolds number (Re) condition. In addition, its downstream low-pressure turbine is on the edge of separation too. In this paper, an integrated aggressive inter-turbine duct embedded with wide-chord low-pressure turbine nozzle is adopted to eliminate the aggressive inter-turbine duct's end-wall separation. Since there are many studies on suppressing the blade suction surface's separation by upstream wake, in this study inherent wake is utilized to suppress the boundary layer separation on low-pressure turbine nozzle's suction surface in the integrated aggressive inter-turbine duct. The paper studies the unsteady flow mechanisms of the integrated aggressive inter-turbine duct (especially the separation and transition mechanisms of low-pressure turbine nozzle's suction surface boundary layer) by the computatioinal simulation method.

Keywords

Integrated aggressive inter-turbine duct low Reynolds number unsteady flow mechanism

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References

Dominy

Kirkham

. The influence of blade wakes on the performance of inter-turbine diffusers. J Turbomach 1996; 118: 347–352.

Dominy

Kirkham

Smith

. Flow development through inter-turbine diffusers. J Turbomach 1998; 120: 298–304.

Axelsson LU, Osso CA, Cadrecha D, et al. Design, performance evaluation and endwall flow structure investigation of an S-shaped intermediate turbine duct. In: ASME turbo expo 2007: power for land, sea, and air. New York: American Society of Mechanical Engineers, 2007, pp.693–701.

Axelsson LU and Johansson TG. Experimental investigation of the time-averaged flow in an intermediate turbine duct. In: ASME turbo expo 2008: power for land, sea, and air. New York: American Society of Mechanical Engineers, 2008, pp.1313–1322.

Miller RJ, Moss RW, Ainsworth RW, et al. The development of turbine exit flow in a swan-necked inter-stage diffuser. In: ASME turbo expo 2003: power for land, sea, and air. New York: American Society of Mechanical Engineers, 2003, pp.863–875.

Dominy

Kirkham

. The influence of swirl on the performance of inter-turbine diffusers. VDI Berichte 1995; 1186: 107–122.

Bailey DW and Carrotte JF. The influence of inlet swirl on the flow within an annular S-shaped duct. In: ASME 1996 international gas turbine and aeroengine congress and exhibition. New York: American Society of Mechanical Engineers, 1996.

Hu SZ, Zhang YF, Zhang XF, et al. Influences of inlet swirl distributions on an inter-turbine duct: part I—casing swirl variation. In: ASME 2011 turbo expo: turbine technical conference and exposition. New York: American Society of Mechanical Engineers, 2011, pp.619–630.

Zhang YF, Hu SZ, Zhang XF, et al. Influences of inlet swirl distributions on an inter-turbine duct: part II—hub swirl variation. In: ASME 2011 turbo expo: turbine technical conference and exposition. New York: American Society of Mechanical Engineers, 2011, pp.631–641.

10.

Norris G, Dominy RG and Smith AD. Strut influences within a diffusing annular S-shaped duct. ASME-98-GT-425, 1998.

11.

Marn A, Göttlich E, Cadrecha D, et al. Shorten the intermediate turbine duct length by applying an integrated concept. In: ASME turbo expo 2008: power for land, sea, and air. New York: American Society of Mechanical Engineers, 2008, pp.1041–1051.

12.

Meyer

. The effect of wakes on the transient pressure and velocity distributions in turbomachines. ASME J Basic Eng 1958; 80: 1544–1552.

13.

Hodson

Howell

. The role of transition in high-lift low-pressure turbines for aero-engines. Prog Aerosp Sci 2005; 41: 419–454.

14.

Stieger RD. The effects of wakes on separating boundary layers in low pressure turbines. Dissertation, Cambridge University, UK, 2002.

15.

Zhang XF. Separation and transition control on ultral-high-lift low pressure turbine blades in unsteady flow. Dissertation, Cambridge University, UK, 2005.

16.

Ali M. Aerodynamics of a low pressure turbine airfoil under steady and periodically unsteady conditions. Dissertation, Carleton University, Canada, 2004.

17.

Norris G, Dominy RG and Smith AD. Flow instability within a diffusing, annular S-shaped duct. ASME-99-GT-70, 1999.

18.

Göttlich E, Marn A, Pecnik R, et al. The influence of blade tip gap variation on the flow through an aggressive S-shaped intermediate turbine duct downstream a transonic turbine stage: part II—time-resolved results and surface flow. In: ASME turbo expo 2007: power for land, sea, and air. New York: American Society of Mechanical Engineers, 2007, pp.843–853.

19.

Pfeil H and Herbst R. Transition procedure of instationary boundary layers. ASME-79-GT-128, 1979.

20.

Liu

, et al. Influence of Reynolds number on the unsteady aerodynamics of integrated aggressive intermediate turbine duct. J Therm Sci 2018; 27: 294–303.

21.

Wang

. Structural characteristics of the supersonic turbulent boundary layer subjected to concave curvature. Appl Phys Lett 2016; 108: 114102.

22.

Wang

Zhao

. On the impact of adverse pressure gradient on the supersonic turbulent boundary layer. Phys Fluids 2016; 28: 116101.

23.

Schulte VS and Hodson HP. Prediction of the becalmed region for LP turbine profile design. ASME-97-GT-398, 1997.