Basic Research On Simultaneous Measurement Of Flame Temperature Field And Species Concentration Field

The flame temperature field and species concentration field are the most basic and important parameters to describe the flame in the process of flame detection.Their measurement is of important practical significance.On the basis of Multispectral Radiation Thermometry(MRT),multispectral radiation measurement technique is proposed by improving Differential Optical Absorption Spectroscopy(DOAS)in this paper.This technique is utilized to realize the simultaneous measurement of flame temperature field and species concentration field.This paper aims at conducting an in-depth theoretical study of the method along with the corresponding experimental verification.MRT is developed based on blackbody radiation law.The spectral emissivity ?(?,T)is a bridge connecting the blackbody and the actual object,which is also the assurance of measurement accuracy.In the measurement of flame temperature,MRT is considered as the most accurate temperature measurement method because the measured object is not seen as a gray body.The index order linear equation is used as an emissivity solving model in this paper.At the same time,the improved least-square method is used to calculate the flame temperature field.DOAS,based on the absorptivity of molecular to different wavelength spectral radiance,is used to calculate the concentration of gas.In this paper,spectral emissivity is obtained by MRT.Therefore,a modified DOAS method cancelling the light source is proposed according to Kirchhoffs law,which combines MRT and DO AS,and makes a theoretical development of MRT to measure the temperature and component concentration at the same time.The gas radiation characteristic parameter,absorbance k(?),is the basis data of the concentration measurement.This paper adopts the latest HITRAN2012 database and uses the line-by-line method to calculate the absorbance k(?).A multispectral detection system based on the principle of MRT is designed,which is calibrated in this paper.In the calibration,the least square method based on relative error is used to fit H-E curve based on the CCD brightness values and spectral emissivity,which lays a foundation for measuring the concentration and temperature.Finally,experimental verification is made for the measurement principle of multispectral imaging method which combines DOAS principle,which takes alcohol lamp and alcohol blow lamp as measuring objects and Infrared Thermal Imager as temperature detection object.The results show that,different part of flame temperatures of alcohol lamp are as follows:inner flame 657.55?>outer flame 538.47?>center flame 407.17?;as for alcohol blast burner,the flame temperature decreases gradually from inside to outside,and the maximum temperature is 984.45?,which agrees with actual situation.And the center flame temperature,detected by Infrared Thermal Imager,is higher than the actual one,which indicates that Infrared Thermal Imager should be calibrated firstly by the object emissivity when measuring the temperature.It causes the restriction for non gray media,and is less accurate than multispectral radiation measurement technique proposed in this paper.