Nonintrusive optical measurements of aircraft engine exhaust emissions and comparison with standard intrusive techniques

Nonintrusive systems for the measurement on test rigs of aeroengine exhaust emissions required for engine certification (CO, NO sub x, total unburned hydrocarbon, and smoke), together with CO sub 2 and temperature have been developed. These results have been compared with current certified intrusive measurements on an engine test. A spectroscopic database and data-analysis software has been developed to enable Fourier-transform Infrared measurement of concentrations of molecular species. CO sub 2, CO, and NO data showed agreement with intrusive techniques of approximately plus/minus 30 %. A narrow, band spectroscopic device was used to measure CO sub 2 (with deviations of less than plus/minus 10 % from the intrusive measurement), whereas laser-induced incandescence was used to measure particles. Future improvements to allow for the commercial use of the nonintrusive systems have been identified and the methods are applicable to any measurement of combustion emissions.