Concentration Measurement Of CO And NO Pollutant In Combustion Field Base On Mid-infrared Absorption Spectroscopy

The measurements of temperature and species concentration in combustion are significance for combustion process analysis.CO and NO,as the main pollutants in combustion and the limiting pollutant emitted from combustors and engines,causes serious environment problem.Therefore,fast and real-time detection of combustion gases,such as CO and NO,is of great value for safety production,environmental protection and combustion diagnosis.The mid-infrared band corresponds to the strong fundamental absorption lines of many molecular,which is suitable for combustion species measurements.Tunable diode laser absorption spectroscopy(TDLAS)is widely used in the diagnosis of combustion flow field because of its advantages of non-contact measurement,strong anti-interference ability,fast response and simple structure,and can simultaneously measure the gas parameters such as temperature,component concentration and flow velocity.In this paper,aiming at measurements of CO and NO pollutants in the combustion field,the study on temperature and concentration measurements in combustion field based on TDLAS technology has been carried out.According to the simulation and analysis of the combustion environment by HITEMP database,the intensity ratio of two absorption spectra lines of H2O 7154.35cm-1 and 7467.77cm-1 are selected to calculate temperature,and two mid-infrared strong fundamental absorption lines of CO 2060 cm-1 and NO 1900cm-1 are used to measure the concentration.The system uses multi-beam time-dividing scanning technology to make several lasers work cooperatively,which achieves simultaneous measurements of temperature and concentration in combustion field.Firstly,the combustion temperature and concentration measurements system based on TDLAS technology is built,and its structure and data processing are analyzed in detail.Secondly,the test of temperature measurement on a high temperature tube furnace is carried out.The fluctuation of test temperature is less than 45K at each set temperature step,which indicates the system is reliable.At the same time,the calibration experiments of CO and NO concentration are carried out respectively.The measurement error is within 3.0%and 3.5%respectively,and the linearity is over 0.999.Finally,the system is placed on an elevating optical platform,which can realize the concentration measurement of CO and NO at the different equivalent ratio and height on a McKenna CH4/AIR premixed flame furnace with a diameter of 60 mm.The measurement error is 5.1%and 5.6%,respectively,and then,the results are discussed.The feasibility and reliability of TDLAS technology with non-intrusive and rapid measurement of combustion temperature and concentration are verified.In this paper,spectral line selection,temperature and concentration measurement are carried out,and a measurement technology of combustion temperature and concentration of CO and NO based on mid-infrared TDLAS technology has been developed.The non-intrusive,rapid and accurate measurement of the concentration of the combustion field is realized,which is beneficial to the study of the combustion process analysis has a certain value of engineering application.