ИСТИНА

Tunable Diode Laser Absorption Spectrometry (TDLAS) is now widely used for diagnostics of combustion processes in different engines and propulsion facilities. The design of a TDLAS sensor depends on real conditions in a hot zone. For low total pressures (below 1 atm) the absorption lines of a test molecule are relatively narrow, which makes possible to use a single TDL for detection of several lines within the spectral range of fast TDL tuning (1-2 cm-1). At higher pressures (above 1-1.5 atm) the lines are widened and the scheme of a sensor with a single TDL is no more possible. The alternative approach for high pressure sensing of the hot zones is the use of two DFB lasers radiating in different spectral ranges. The different combinations of the absorption lines of H2O molecule from different spectral ranges are discussed in the presentation with the emphasis on the attainable uncertainties in the temperature evaluation. The construction of the developed sensor is described. The combination of two TDLs generating in the 1.39 and 1.34 µm wavelength ranges was tested. In the laboratory experiments the cell with stable and adjustable temperature and pressure was used. The performance of the sensor was checked for two temperatures (600 and 900 K) and 3 pressures (1, 2, 3 atm). Reasonable agreement between the temperatures measured by a thermocouple and TDLAS for all three pressures was obtained.