0
Research Papers

The Effect of Rotor Tip Clearance Size onto the Separated Flow Through a Super-Aggressive S-Shaped Intermediate Turbine Duct Downstream of a Transonic Turbine Stage

[+] Author and Article Information
A. Marn

Institute for Thermal Turbomachinery and Machine Dynamics,  Graz University of Technology, Graz, 8010 Austriaandreas.marn@tugraz.at

E. Göttlich, H. P. Pirker

Institute for Thermal Turbomachinery and Machine Dynamics,  Graz University of Technology, Graz, 8010 Austria

F. Malzacher1

Institute for Thermal Turbomachinery and Machine Dynamics,  Graz University of Technology, Graz, 8010 Austria

1

Corresponding author.

J. Turbomach 134(5), 051019 (May 11, 2012) (12 pages) doi:10.1115/1.4004446 History: Received March 08, 2011; Revised May 30, 2011; Published May 11, 2012; Online May 11, 2012

The demand for a further increased bypass ratio of aero engines will lead to low pressure turbines with larger diameters, which rotate at a lower speed. Therefore, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any loss generating separation or flow disturbances. Due to costs and weight, this intermediate turbine duct (ITD) has to be as short as possible. This leads to an aggressive (high diffusion) and, furthermore, to a super-aggressive s-shaped duct geometry. In order to investigate the influence of the blade tip gap size on such a high diffusion duct flow a detailed test arrangement under engine representative conditions is necessary. Therefore, the continuously operating Transonic Test Turbine Facility (TTTF) at Graz University of Technology has been adapted: An super-aggressive intermediate duct is arranged downstream of a transonic high pressure (HP)-turbine stage providing an exit Mach number of about 0.6 and a swirl angle of –15 deg. A second low pressure (LP)-vane row is located at the end of the duct and represents the counter-rotating low pressure turbine at a larger diameter. A following deswirler and a diffuser are the connection to the exhaust casing of the facility. In order to determine the influence of the blade tip gap size on the flow through such a super-aggressive s-shaped turbine, duct measurements were conducted with two different tip gap sizes, a 1.5% span (0.8 mm) and a 2.4% span (1.3 mm). The aerodynamic design of the HP-turbine stage, ITD, LP-vane, and the de-swirler was done by MTU Aero engines. In 2007 at the ASME Turbo Expo, the influence of the rotor clearance size onto the flow through an aggressive ITD was presented. For the present investigation, this aggressive duct has been further shortened by 20% (super-aggressive ITD) so that the flow at the outer duct wall is fully separated. This paper shows the influence of the rotor tip clearance size on to this separation. The flow through this intermediate turbine duct was investigated by means of five-hole-probes, static pressure taps, boundary layer rakes, and oil flow visualization. The oil flow visualization showed the existence of vortical structures within the separation where they seem to be imposed by the upstream HP-vanes.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

(a) Meridional section with probe measurement planes, (b) blade counts and profiles, and (c) definition of non- dimensional duct length l/hexit,blade  = 1.6

Grahic Jump Location
Figure 2

Performance chart of Sovran and Klomp

Grahic Jump Location
Figure 3

Loading coefficient distribution in plane C

Grahic Jump Location
Figure 4

(a) Mach number distribution, (b) total pressure distribution, (c) static pressure distribution for 1.5% span gap, and (d) Mach number distribution, (e) total pressure distribution, and (f) static pressure distribution for 2.4% span gap

Grahic Jump Location
Figure 5

(a) Yaw angle distribution, and (b) pitch angle distribution for 1.5% span gap and (c) yaw angle distribution, and (d) pitch angle distribution for 2.4% span gap

Grahic Jump Location
Figure 6

Boundary layer profiles at the hub in planes C1, C5, C7, and D (left) and boundary layer profiles at the casing in planes C1, C3, C5, and C7 (right)

Grahic Jump Location
Figure 7

Total pressure distribution in plane E for (a) 1.5% span, and (b) for 2.4% span

Grahic Jump Location
Figure 8

(a) Mach number distribution, (b) total pressure distribution, (c) static pressure distribution for 1.5% span gap, and (d) Mach number distribution, (e) total pressure distribution, and (f) static pressure distribution for 2.4% span gap

Grahic Jump Location
Figure 9

(a) Yaw angle distribution, (b) pitch angle distribution for 1.5% span gap and (c) yaw angle distribution, and (d) pitch angle distribution for 2.4% span gap

Grahic Jump Location
Figure 10

Oil flow visualization; outer duct wall

Grahic Jump Location
Figure 11

Oil flow visualization; inner duct wall

Grahic Jump Location
Figure 12

Simulated surface streamlines and wall shear stress at the outer (left) and inner duct (right)

Grahic Jump Location
Figure 13

Static temperature distribution at the casing

Grahic Jump Location
Figure 14

Explanation of the formation of these vortices at the casing for high pressure ratios; outflow of the rotor without swirl of the absolute velocity component

Grahic Jump Location
Figure 15

Dependence of the flow structure at the outer duct wall on the pressure ratio

Grahic Jump Location
Figure 16

Pressure rise coefficient

Grahic Jump Location
Figure 17

Loss production

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In