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Research Papers

# Axial Loss Development in Low Pressure Turbine Cascades

[+] Author and Article Information
Bastian Muth

Research Assistant
Mem. ASME
e-mail: bastian.muth@unibw.de

Reinhard Niehuis

Professor
Mem. ASME
e-mail: reinhard.niehuis@unibw.de
Institute of Jet Propulsion,
Department of Aeronautics and Aerospace,
University of the German Federal Armed Forces,
Munich D-85577, Neubiberg, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute of ASME for publication in the Journal of Turbomachinery. Manuscript received July 3, 2012; final manuscript received August 16, 2012; published online June 6, 2013. Assoc. Editor: David Wisler.

J. Turbomach 135(4), 041024 (Jun 06, 2013) (8 pages) Paper No: TURBO-12-1118; doi: 10.1115/1.4007580 History: Received July 03, 2012; Revised August 16, 2012; Accepted August 17, 2012

## Abstract

The objective of this work presented in this paper is to study the performance of low-pressure turbines in detail by extensive numerical simulations. The numerical flow simulations were conducted using the general purpose code ANSYS CFX. Particular attention is focused on the loss development in the axial direction within the flow passage of the cascade. It is shown that modern computational fluid dynamics (CFD) tools are able to break down the integral loss of the turbine profile into its components, depending on attached and separated flow areas. In addition, the numerical results allow one to show the composition of the loss depending on the Reynolds number. The method of the analysis of axial loss development presented here allows for a much more comprehensive investigation and evaluation of the quality of the numerical results. For this reason, the paper also demonstrates the capability of this method to quantify the influence of the axial velocity density ratio, the inflow turbulence level, the inflow angle, and the Reynolds number on the loss configuration and the flow angle of the cascade as well as a comparison of steady state and transient results. The validation data of this low pressure turbine (LPT) cascade have been obtained at the High Speed Cascade Wind Tunnel of the Institute of Jet Propulsion. For this purpose, experiments were conducted within the range of $Re2th$ = 40,000 to 400,000. To gather data at realistic engine operation conditions, the wind tunnel allows for an independent variation of Reynolds and Mach number. The experimental results presented herein contain detailed pressure measurements as well as measurements with 3D hot-wire anemometry. However, this paper shows only integral values of the experimental as well as the numerical results to protect the proprietary nature of the LPT design.

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## Figures

Fig. 1

Computational grid and boundary conditions [12]

Fig. 2

Design point (Re = 60,000)

Fig. 3

Study of mesh independence

Fig. 4

Influence of the axial velocity density ratio

Fig. 5

Reynolds number lapse rate

Fig. 6

Flow angle and loss development (Re = 400,000)

Fig. 7

Loss breakdown approach

Fig. 8

Loss breakdown, absolute values

Fig. 9

Loss breakdown, percental values

Fig. 10

Flow angle and loss development (Re = 60,000) for both turbulence cases

Fig. 11

Axial development of the integral turbulence intensity level

Fig. 12

Influence of the inflow angle

Fig. 13

CFD domain with the moving bar

Fig. 14

Design point unsteady (Re = 60,000)

Fig. 15

Periodically unsteady inflow angle and velocity (CFD)

Fig. 16

Space-time plot pressure surface (Re = 60,000)

Fig. 17

Space-time plot suction surface (Re = 60,000)

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