Parametric studying of low-profile vortex generators flow control in an aggressive inter-turbine duct

Abstract

This paper presents a study of low-profile vortex generators flow control on the effect of casing boundary layer separation in an aggressive inter-turbine duct. Counter-rotating and co-rotating vortex generators configurations were tested parametrically to obtain the optimum low-profile vortex generators’ setup within the aggressive inter-turbine duct, in terms of the axial location, height, angle of attack and streamwise vortices per swirl vane pitch. Surface oil flow visualization was used to qualitatively examine the low-profile vortex generators eliminating the casing separation and subsequently the detailed seven-hole probe measurements were carried out to evaluate the loss reduction quantitatively. The inter-turbine duct examined for this study was more aggressive compared with the geometries found in the most current modern engine designs. Measurements were made inside the aggressive inter-turbine duct annulus at Reynolds number of 150,000. The flow structures within the aggressive inter-turbine duct were found to be dominated by counter-rotating vortices evolved by the swirl vanes and boundary layer separation in both casing and hub regions. A massive casing boundary layer separation extending from the duct first bend to the second bend was found within the aggressive inter-turbine duct. The primary source of pressure loss in the aggressive inter-turbine ducts was the result of the extensive casing boundary layer separation. Flow control by utilizing the low-profile vortex generators installed on the casing was conducted to eliminate the casing separation. Regardless of the vortex generator mitigating the casing separation associated with consequential loss reduction, a pair of casing counter-rotating vortices was always evident at the duct second bend in all cases. Among the tested low-profile vortex generator configurations, two of the most effective low-profile vortex generator configurations, one counter-rotating and one co-rotating low-profile vortex generator configurations, were acquired as a result of successfully eliminating the casing separation. Despite that the inter-turbine duct is aggressively designed, it is concluded that this duct associated with proper flow control techniques is considered as a potential candidate for weight saving in a high bypass ratio engine.

Keywords

Aggressive inter-turbine duct low-profile vortex generator boundary layer separation counter-rotating vortex pair loss

Get full access to this article

View all access options for this article.

References

Dominy

Kirkham

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

Dominy

Kirkham

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

Dominy

Kirkham

Smith

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

Hu SZ, Zhang YF, Zhang XF, et al. Influence of inlet swirl distributions on an inter-turbine duct – part I: casing swirl variation. ASME paper GT2011-45554, 2011.

Zhang YF, Hu SZ, Zhang XF, et al. Influence of inlet swirl distributions on an inter-turbine duct – Part I: hub swirl variation. ASME paper GT2011-45555, 2011.

Miller RJ, Moss RW, Ainsworth RW, et al. The development of turbine exit flow in a swan-necked inter-stage diffuser. ASME paper GT2003-38174, 2003.

Marn A, Göttlich E, Pecnik R. et al. The influence of blade tip gap variation on the flow through an aggressive S-shaped intermediate turbine duct downstream of a transonic turbine stage – part I: time-averaged results. ASME paper GT2007-27405, 2007.

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 of a transonic turbine stage – part II: time-resolved results and surface flow. ASME paper GT2007-28069, 2007.

Marn A, Göttlich E, Malzacher F, et al. The effect of rotor tip clearance size onto the separation flow though a super-aggressive S-shaped intermediate turbine duct downstream of a transonic turbine stage. ASME paper GT2009-59934, 2009.

10.

Göttlich

. Research on the Aerodynamics of Intermediate Turbine Diffusers. Prog Aerosp Sci 2011; 47: 249–279.

11.

Lin

Howard

Selby

. Small submerged vortex generators for turbulent flow separation control. J Spacer Rockets 1990; 27: 503–507.

12.

Kerho

Hutcherson

Blackwelder

. Vortex generators used to control laminar separation bubbles. J Aircr 1993; 30: 315–319.

13.

Velte

Hansen

MOL

Cavar

. Flow analysis of vortex generators on wing sections by stereoscopic particle image velocimetry measurements. Environ Res Lett 2008; 3: 015006–015017.

14.

Hergt A, Meyer R, Müller M, et al. Loss reduction in compressor cascades by means of passive flow control. ASME paper GT2008-50357, 2008.

15.

Holmes AE, Hickey PK, Murphy WR, et al. The application of sub-boundary layer vortex generators to reduce canopy mach rumble interior noise on the gulfstream. AIAA paper 87-0084, 1987.

16.

Satta

Simoni

Ubaldi

. Velocity and turbulence measurements in a separating boundary layer with and without passive flow control. Proc IMechE, Part A: J Power Energy 2007; 221: 815–823.

17.

Wallin F and Eriksson L-E. A tuning-free body-force vortex generator model. AIAA paper AIAA-2006-0873, 2006.

18.

Santner C, Göttlich E, Marn A, et al. The application of low-profile vortex generators in an intermediate turbine diffuser. ASME paper GT2010-22892, 2010.

19.

Marn A. On the aerodynamics of intermediate turbine ducts for competitive and environmentally friendly jet engines. PhD Thesis, Graz University of Technology, Graz, 2008.

20.

Lin

. Review of research on low-profile vortex generators to control boundary-layer separation. Prog Aerosp Sci 2002; 38: 389–420.

21.

Gregory-Smith

Graves

Walsh

. Growth of secondary loss and vorticity in an axial turbine cascade. ASME J Turbomach 1988; 110: 1–8.

22.

Zhang

. Flow control in an aggressive inter-turbine transition duct using low profile vortex generators. J Eng Gas Turbines Power 2014; 136: 112604–1–112604-8.