Evaluation of FTIR emission spectrometry for the determination of turbine exhaust composition in test beds

The capability of taking non-intrusive species measurements in a jet plume of a modified mid-size low by-pass aero-engine running on a sea level test bed at several thrust levels was demonstrated. Also conventional intrusive measurements were performed with a spatially resolved method using a traversing single-point sampling probe which fulfills ICAO standards. The FTIR spectrometry measurements included both emission and absorption mode with a multi-path reflection compartment as well as the single emission mode. Due to the lack of a common/unique definition for the exhaust plume diameter it was found that the column density was the best measure to compare the different techniques. The FTIR engine measurement results for CO 2 , CO, and NO have been proven to be in agreement with the intrusive data within plus or minus 30%. Several error sources during the radiometric radiance calibration were identified which lead to uncertainties in the FTIR retrievals, namely (1) incomplete knowledge of the optical surface emissivities, (2) incomplete knowledge and inhomogeneities of the optical surface temperature, and (3) undefined instrumental drifts and non-linearities during the calibration.