Optical Spectroscopic Measurement of Unburnt Hydrocarbons in Emission from Aero-Engine Combustion Systems

摘要

The aim of this work is to develop non-intrusive methods to determine the presence of unburnt hydrocarbons (UHC) in the emissions from aero-engine combustion systems. In addition to the detection of UHCs for legal certification of aero-engine performance, the consequences of their release into the upper atmosphere has environmental considerations. The usual detection technique is centred upon extraction of samples of the exhaust using a probe placed at the back of the engine. The usual detection technique is centred upon extraction of samples of the exhaust using a probe placed at the back of the engine. The sample of gas extracted is then brought, through a heated piping systems, to the analysing apparatus that can be, for example, a gas chromatograph, or a Flame Ionisation Detector (FID) system. The approach presented here is non-intrusive and is based on optical techniques to obtain the inforamtion abotu the emission content. These techniques allow the detection, without sampling, of unburnt hydrocarbon compounds using Fourier Transform Infrared (FTIR) spectroscopy. Measurements were made of UHCs produced under different combustion conditions, some by gas turbine engines and combustor rigs while others were obtained by burning kerosene in the laboraotry. The observatiosn were performed using Bruker Equionox 55 FTIR and Mattson Research Series spectrometers. The Spectrometers were equipped with liquid nitrogen cooled Mercury-Cadmium-Telluride (MCT) and Indium-Antimonide (InSb) detectors. The use of the MCT detector allowed the detection of spectral features int he Fingerprint Region (approx400-1500 cm~(-1) allowing the identification of the hydrocarbons present in the exhaust gases by comparison with reference spectra. The results of using the previously reported~1 White Cell in conjunction with an MCT detector were compared with those obtained using an InSb detector. The spectral features observed in teh C-H stretch region in spectra obtained from laboratory experiments were compared with those obtained from engine exhaust. The spectral features of 1-hexene were found to be in very good agreement with those recorded from the burning of kerosene in a laboratory burner and with those from jet engine exhaust.