Development of a TDLS-based ambient water vapour sensor for aeroengine intake temperature determination

Bain, James Roderic Peter and Lengden, Michael and Stewart, George and Black, John and Johnstone, Walter (2011) Development of a TDLS-based ambient water vapour sensor for aeroengine intake temperature determination. In: 8th International Conference on Tunable Diode Laser Spectroscopy, 2011-07-11 - 2011-07-15. (Unpublished)

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Abstract

The development of a TDLS-based sensor for determining the temperature of ambient water vapour is described. For the purposes of ground testing, aeroengine intake temperature is typically measured using platinum resistance temperature detectors but under certain conditions these devices become unreliable and an alternative is needed. The sensor requirements are to measure gas temperature over the range of 0-40°C with an absorption path determined by the intake cross section, whilst recording continuously in a harsh environment. Wavelength modulation spectroscopy (WMS) with balanced detection is used to interrogate two water vapour absorption features near 1430nm. The lines can both be accessed by a single DFB laser current scan, yet have good spectral isolation and temperature sensitivity[1-3]. The use of autobalanced noise cancellers[4-6] for stand alone two-line ratio thermometry sensors is investigated. When used in conjunction with second harmonic detection in WMS, the detector bandwidth and dynamic range need to be optimised to ensure any temperature calibration is not susceptible to long-term drift and changing optical conditions. Initial calibration and testing is performed in an environmental chamber with temperature and humidity control.

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