CARS application in measurement of flame temperature

Abstract

Flame temperature distribution is very important for combustion diagnosis, but it is very hard to measure it because of the instability of flame and possible transient variability. Classical method used for measurement of flame temperature is always a contact method utilizing a thermocouple. Limitations on the use of thermocouples include long response time, disturbance on target temperature field, inelasiticity in rigorous measurement circumstance. Only coarse qualitative results can be acquired. A potential laser spectrum diagnostic technology was therefore introduced. The method of coherent anti-stokes Raman spectroscopy (CARS) in the measurement of temperature distribution was discussed using CARS theory. The design of measurement system was put forward and preliminary experiment results are shown. Theoretical CARS spectrums at 2000K were calculated utilizing the model of molecule transition in CARS process. Experimental results were compared to those of thermocouple measurement, and since results of two methods are close, feasibility of CARS application in the measurement of flame temperature was verified. Although the resolution of this method is not applicable for real-time measurement, a single measurement can be accomplished in a few nanoseconds. The resolution of temperature measurement is 5% better than results of measurement by thermocouple. Furthermore, future research is suggested to overcome the insufficiency of this method was pointed out with direction suggested.