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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

# Unsteady Pressure Measurements With a Fast Response Cooled Probe in High Temperature Gas Turbine Environments

[+] Author and Article Information
Mehmet Mersinligil

Department of Turbomachinery and Propulsion, von Kármán Institute for Fluid Dynamics, 72, Chaussée de Waterloo, B-1640 Rhode-Saint-Genèse, Belgiummersinli@vki.ac.be

Jean-François Brouckaert

Department of Turbomachinery and Propulsion, von Kármán Institute for Fluid Dynamics, 72, Chaussée de Waterloo, B-1640 Rhode-Saint-Genèse, Belgiumbrouckaert@vki.ac.be

Julien Desset

Department of Turbomachinery and Propulsion, von Kármán Institute for Fluid Dynamics, 72, Chaussée de Waterloo, B-1640 Rhode-Saint-Genèse, Belgiumdesset@vki.ac.be

J. Eng. Gas Turbines Power 133(8), 081603 (Apr 07, 2011) (9 pages) doi:10.1115/1.4002276 History: Received June 02, 2010; Revised July 11, 2010; Published April 07, 2011; Online April 07, 2011

## Abstract

This paper presents the first experimental engine and test rig results obtained from a fast response cooled total pressure probe. The first objective of the probe design was to favor continuous immersion of the probe into the engine to obtain a time series of pressure with a high bandwidth and, therefore, statistically representative average fluctuations at the blade passing frequency. The probe is water cooled by a high pressure cooling system and uses a conventional piezoresistive pressure sensor, which yields, therefore, both time-averaged and time-resolved pressures. The initial design target was to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit $(800–1100°C)$ with a bandwidth of at least 40 kHz and in the long term at combustor exit (2000 K or higher). The probe was first traversed at the turbine exit of a Rolls-Royce Viper turbojet engine at exhaust temperatures around $750°C$ and absolute pressure of 2.1 bars. The probe was able to resolve the high blade passing frequency (≈23 kHz) and several harmonics of up to 100 kHz. Besides the average total pressure distributions rom the radial traverses, phase-locked averages and random unsteadiness are presented. The probe was also used in a virtual three-hole mode yielding unsteady yaw angle, static pressure, and Mach number. The same probe was used for measurements in a Rolls-Royce intermediate pressure burner rig. Traverses were performed inside the flame tube of a kerosene burner at temperatures above $1600°C$. The probe successfully measured the total pressure distribution in the flame tube and typical frequencies of combustion instabilities were identified during rumble conditions. The cooling performance of the probe is compared with estimations at the design stage and found to be in good agreement. The frequency response of the probe is compared with cold shock-tube results and a significant increase in the natural frequency of the line-cavity system formed by the conduction cooled screen in front of the miniature pressure sensor were observed.

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## Figures

Figure 1

(a) Fast response cooled total pressure probe concept and (b) tip region of the finished probe after sealing and welding

Figure 2

Yaw calibration in VKI-C4 calibration facility, pressure recovery ratio plot, M=0.3

Figure 3

Experimental frequency spectrum from the shock-tube test for the frequency response of the probe tested

Figure 4

Average total pressure (a) and sensor temperature (b) distributions behind the rotor at 8000 RPM and 10,000 RPM

Figure 5

Probe angular response in engine at 8000 RPM and 10,000 RPM

Figure 6

Power spectrum at 10,000 RPM, immersion depth=43 mm, Tgas=503°C

Figure 7

Comparison of screen-cavity resonance frequencies calculated using PREMESYS and Helmholtz formulation in Eq. 1

Figure 8

Example of raw pressure signal at 10,000 RPM, immersion depth=5 mm, Tgas=503°C

Figure 9

Pressure fluctuations at 8000 RPM and 10,000 RPM, Tgas=503°C

Figure 10

Phase-locked average of the pressure signal at 10,000 RPM for different number of blade passages, immersion=23 mm from hub, Tgas=503°C

Figure 11

Phase-locked average of the pressure signal at 10,000 RPM, immersion=23 mm from hub, Tgas=503°C

Figure 12

Phase-locked average map of the turbine exit total pressure at 10,000 RPM, Tgas=503°C

Figure 13

Yaw coefficient with respect to yaw angle

Figure 14

Unsteady yaw angle calculated-raw and phase shifted

Figure 15

Total pressure distribution-raw, corrected for yaw angle, corrected for phase shift and yaw angle

Figure 16

Pseudostatic pressure distribution at 10,000 RPM, immersion=23 mm from hub, Tgas=503°C

Figure 17

Mach number distribution at 10,000 RPM, immersion=23 mm from hub, Tgas=503°C

Figure 18

Rolls-Royce IP combustion rig, total pressure along a continuous probe traverse down to the center of the flame tube. Tbulk=1521°C, Pcan=1.82 bar relative

Figure 19

Rolls-Royce IP combustion rig, time series of fluctuating pressure at rumble conditions. Tbulk=1556°C, Pcan=2.28 bar relative

Figure 20

Rolls-Royce IP combustion rig, full power spectrum, and low frequency content at rumble conditions, Tbulk=1556°C, Pcan=2.28 bar relative

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