SDLA/DLAS measurements on the APZ combustor at DLR

Abstract

This presentation describes measurements performed using an infrared diode laser absorption spectrometer (DLAS) in an Atmospheric Primary Combustor (APZ) at DLR Cologne. This work was performed in the frame of the European Project MENELAS “Minority effluent measurements of aircraft Engine emissions by infrared Laser Spectroscopy” (5th Framework). A description of the burner and the optical accessible combustor are given. The combustor was operated at atmospheric pressure and air preheat temperature and equivalence ratio were set to provide a temperature, velocity and species distribution typical for future low emission combustors. Spatially resolved measurements of the gas velocity, temperature and composition (O2, CO, CO2, NOx and unburned hydrocarbons) in the reacting burner flow field and at the combustor exit are presented. The measurements were conducted with generally accepted standard techniques using Laser Doppler Anemometry (non-intrusive), thermocouple probes and conventional exhaust gas analysis respectively. The measured results act as a benchmark and reference for the SDLA/DLAS measuring campaign. The DLAS instrument was used primarily on the CO molecule to acquire series of measurements on inside and outside combustor(5 mm scanning horizontal and vertical). Measurements were performed with a repetition rate of 20kHz to cope with the temporal fluctuations of the combustor. Data reduction allowed deriving pressure, temperature and CO concentration on the absorption path. The given values are hence averaged values but there were some attempts to compare with the results of the classical probing. Spatial deconvolution is yet to be performed for a more thorough exploitation and comparison. The CO2 molecule was also probed but wavelength and envelope calibration are more difficult because of inadequate spectral filtering and ambient CO2 presence giving intense background absorption lines. Some H2O lines were also found present in the spectra which are still being data reduced. There was also trials to probe the NO molecule but the allowed NO lines with the present laser diodes did not have sufficient sensitivity to probe the weak NO concentration present in/outside the combustor. This first attempt of DLAS in an APZ combustor proved that infrared absorption spectroscopy is possible in such a media. Improvements in data acquisition, spectral filtering and data reduction are now necessary for a better exploitation of this technique to perform measurements of pressure, temperature and concentrations of CO, CO2, NO and H2O in such combustion devices.