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Research Papers

A New Intermittent Aspirated Probe for the Measurement of Stagnation Quantities in High Temperature Gases

[+] Author and Article Information
Michela Massini

Whittle Laboratory, University of Cambridge, Madingly Road, Cambridge CB3 0DY, UKmm436@cam.ac.uk

Robert J. Miller

Whittle Laboratory, University of Cambridge, Madingly Road, Cambridge CB3 0DY, UKrjm76@cam.ac.uk

Howard P. Hodson

Whittle Laboratory, University of Cambridge, Madingly Road, Cambridge CB3 0DY, UKhph1000@cam.ac.uk

J. Turbomach 133(4), 041022 (Apr 26, 2011) (6 pages) doi:10.1115/1.4002414 History: Received October 07, 2009; Revised October 29, 2009; Published April 26, 2011; Online April 26, 2011

This paper presents the design, manufacture, and testing of a new probe for the measurement of temperature and pressure in engine environments. The probe consists of a choked nozzle located in the flow and a system downstream including a cooler, a flow measuring device, and a valve. It operates in two modes: In the first mode the valve is open, the probe is aspirated, and the nozzle is choked. The mass flow through the probe is measured using instrumentation placed downstream of the cooler, so that it does not have contact with the hot flow. In the second mode, the valve is closed, and the stagnation pressure is measured using the same instrumentation downstream the cooler. The total temperature is computed as a derived variable from the measurements of stagnation pressure and mass flow rate. There are a number of advantages of the probe over existing methods of temperature measurement. The measurement inaccuracy due to conduction and radiation errors and calibration drift found in thermocouples is significantly reduced; it can measure both stagnation temperature and pressure, halving the instrumentation costs; it has no wiring or transducer in the sensor head; the system can self-calibrate while located within an engine. This paper describes the design of a probe for use in engine environments. The probe prototype is tested up to 900 K and is shown to have an accuracy of ±6 K.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the probe system: (1) probe head, (2) cooling system, (3) mass flow meter, (4) downstream valve, and (5) gas analyzer

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Figure 2

Prototype of the ceramic probe

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Figure 3

Prototype of the metallic probe: (a) picture and (b) sketch

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Figure 4

Sketch of the orifice plate

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Figure 5

Picture of the probe system for temperature calibrations in the Lenton oven

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Figure 6

Calibration curve

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Figure 7

Calibration curves for different probe geometries

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Figure 8

Deviation from the linear fit of four series of experiments

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Figure 9

Effects on the calibration curve of variability of γ with temperature

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Figure 10

Absolute errors for a nonlinear calibration function

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