Raman and fluorescence lidar measurements of aircraft engine emissions

Laser induced Raman and fluorescent measurements were made in the exhaust of a gas turbine engine with a new field portable instrument devised specifically for gas turbine exhaust measurements. The gas turbine exhaust was analyzed by conventional instruments for CO, CO₂, NO, NO_x, total hydrocarbons, smoke and temperature, and these data were used as a ‘calibration’ standard for the evaluation of the laser Raman instrument. Results thus far indicate good correlations for CO₂, O₂, smoke, hydrocarbons and temperature. The instrument was not sensitive enough for NO detection but the data analysis indicates that 100 ppm may be detectable with instrument improvements. CO analysis was not attempted, but it is expected that CO could be detected with further research. NO₂ (or NO_x) was not attempted because theoretical and experimental laboratory analysis indicated severe interference with CO₂. The conclusion was that laser Raman shows a good potential for aircraft gas turbine emission analysis.