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TECHNICAL PAPERS: Gas Turbines: Controls, Diagnostics, and Instrumentation

# Application of Hot-Wire Anemometry in a Blow-Down Turbine Facility

[+] Author and Article Information
T. Yasa, G. Paniagua, R. Dénos

Turbomachinery and Propulsion Department, von Karman Institute for Fluid Dynamics, Chaussée de Waterloo 72, B1640-Rhode Saint Genèse, Belgium

J. Eng. Gas Turbines Power 129(2), 420-427 (Feb 01, 2006) (8 pages) doi:10.1115/1.2364191 History: Received October 01, 2005; Revised February 01, 2006

## Abstract

In order to test HP turbine stages under engine representative conditions on a heat transfer point of view, blow-down test rigs are often used. In these rigs the evolution of gas temperature, pressure, and density is similar to a step function. Hence, the use of hot-wires, which are sensitive to flow velocity, density, and temperature, is more difficult than in an incompressible flow at constant temperature. This investigation describes how the data reduction can be performed in such an environment in order to extract the velocity. The gas temperature is measured with a thermocouple and the gas density is derived from the measurement of the total pressure thanks to an iterative procedure. Once the velocity is derived, the turbulence can be computed. The effectiveness of the method is first demonstrated in a heated jet where both pressure and temperature are varied. Tests in the turbine facility are performed at turbine inlet temperatures of $480K$. Thus, overheat ratios up to 1.9 had to be used, leading to a very high temperature of the tungsten platinum coated wire. The aging of the probe was very fast, causing a drift in the voltage output between the successive tests. A technique is proposed to minimize the aging effect. It consists in adapting the calibration based on the resistance of the wire measured before each test. Measurements were carried out at the turbine inlet and rotor outlet. At the turbine inlet, velocity radial profiles are obtained together with measurements of the turbulence intensity. The time-averaged data is compared with pneumatic probe measurements. At the rotor exit, the time-resolved periodic velocity fluctuations are analyzed using a phase-locked average technique.

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## Figures

Figure 1

Pressure and temperature evolution during a test

Figure 2

Hot-wire probe manufactured at VKI

Figure 3

Scheme of the VKI free jet calibration facility

Figure 4

Calibration results based on King’s law

Figure 5

Calibration results based on Collis and William’s correlation

Figure 6

Change of sensor wire resistance in consecutive tests

Figure 7

Aging effect on hot-wire measurements without correction (a) and with correction (b)

Figure 8

Data processing methodology

Figure 9

Free jet velocity while the flow temperature and pressure are varying

Figure 10

Figure 11

Turbulence intensity profile at the turbine inlet

Figure 12

Signal to noise ratio of the inlet measurements

Figure 13

Inlet pressure, temperature (a) and velocity distribution (b) along the span

Figure 14

Mach number distribution at the stage exit along the span-wise direction

Figure 15

FFT of the hot-wire signal downstream of the rotor

Figure 16

Periodic component (left) and random unsteadiness (right) downstream of the rotor along the height (% span is indicated above each curve)

## Errata

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