In Situ Optical Techniques for Jet Engine Exhaust Hydrocarbon Detection.

摘要

An investigation was conducted to determine the feasibility of developing an in situ optical technique suitable for jet engine exhaust diagnostics of gaseous hydrocarbon concentrations. Two absorption spectroscopy techniques were investigated: (1) high-resolution interferometric spectroscopy in the 1/2800-3250 cm region of the IR and (2) the absorption of the radiation of a modified He-Ne laser emitting in the IR. A candidate for use as a radiation source in a correlation spectrometer, a microwave-excited methane infrared source, was also evaluated. Another spectroscopic technique, the detection of CH visible emission, was also investigated. As a means of investigating the possible effects of mechanical probing on the chemical identify and hence the spectroscopic properties of the hydrocarbon constituents of exhaust gases, a simulation of the effects of probing on methane containing exhaust constituents was performed. A preliminary investigation of the gaseous hydrocarbon content of a combustor using in situ optical probing and online conventional gas analyzers as well as optical probing and laboratory gas analysis of samples drawn with an orifice-type emissions probe is also reported. It was concluded that the best approach to in situ gaseous hydrocarbon detection may be a multiple-pass, tuneable diode laser system.