Abstract
In this paper, the 2f/1f tunable diode laser wavelength modulation spectroscopy is used for the simultaneous measurement of concentration and temperature of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in the exhaust plume of an aero engine. The suitability of the R48 spectral feature of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> at 1997.2 nm is discussed for this project and for further application of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> tomographic imaging on large-scale aero-engines. To ensure accurate recovery of gas parameters at the high exhaust temperatures, a full spectral characterization of the absorption feature is presented using a direct spectroscopy. The 2f/1f method is validated in the laboratory for controlled gas mixtures and temperatures to recover concentration and temperature. Good agreement with the actual temperature and concentration values is demonstrated. Finally, single path measurements are presented for an aero engine exhaust showing good correlation with the measured engine conditions.
Highlights
T HE fiber Laser Imaging of Turbine Exhaust Species (FLITES) project is a collaborative project between university partners Edinburgh, Manchester, Southampton and Strathclyde and several companies including Rolls-Royce, Shell and the Instituto Nacional Técnica Aeroespacial (INTA)
This paper only presents path integrated CO2 concentration data for a single beam path and on a smaller engine type to the one proposed for the tomographic imaging system, consideration must be given to the scheme proposed for the FLITES project [1]
An Eblana Photonics Multi Quantum Well Distributed Feedback (DFB) laser (EP1997-DMB01-frequency modulation (FM)) was chosen to access this wavelength, which is within the amplification range of a thulium doped fiber amplifier designed and manufactured by Feng et al at the University of Southampton as part of the FLITES project [10]
Summary
T HE fiber Laser Imaging of Turbine Exhaust Species (FLITES) project is a collaborative project between university partners Edinburgh, Manchester, Southampton and Strathclyde and several companies including Rolls-Royce, Shell and the Instituto Nacional Técnica Aeroespacial (INTA). One of the main deliverables in this project is the production of a cross-sectional, 2-dimensional tomographic image of CO2 concentration using 126 individual beams paths directed through the engine exhaust plume. The current methodology for ascertaining the CO2 emission of a particular engine type, and ensuring it fulfils the necessary regulatory requirements, requires intrusive, extractive sampling of the exhaust at multiple locations This implies that engines under test are operational over significantly longer periods than would be necessary with real time imaging methodologies. We present the validation of the CO2 concentration measurement system designed for the FLITES project This has been achieved by measuring the path-integrated absorbance from the exhaust of a commercial aero engine for a single beam path using the 2f/1f technique developed by Rieker et al [7]. A high degree of correlation with the measured engine core temperature is demonstrated
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