Study On The Relationship Between Sound Velocity And Temperature And Reconstruction Of Temperature Field In Flame

Temperature field monitoring plays an important role in the safe operation and economic benefit improvement of industrial boilers.Acoustic temperature measurement method has been used more and more because of its advantages of non-contact and quick response.However,there is no systematic study on the relationship between sound velocity and temperature in the flame environment,and the applicability of the existing temperature field reconstruction method needs to be improved.Therefore,this paper first studies the relationship between sound velocity and temperature in the flame through experiments,and improv es the existing reconstruction method of temperature field by simulation.On this basis,the flame temperature is measured by acoustic method,hoping to improve the ac curacy of temperature field monitoring of industrial boilers.The acoustic temperature measurement experiment shows that the error of the relation between sound velocity and temperature of ideal gas is small in non-flame environment,but large in flame environment.The actual measured value of sound velocity in flame is smaller than that calculated according to ideal gas relation,and for the same fuel flame,the sound velocity decreases with the increase of flame temperature,which may be due to the violent chemical reaction in flame,so that it can not be regarded as ideal gas.After the data of flame sound velocity and temperature are obtained,the correction formula of sound velocity and temperature is given for the reconstruction of temperature field.In order to enhance the applicability of temperature field reconstruction algorithm,the existing typical temperature field reconstruction method was improved by simulation.The existing reconstruction methods are effective for low gradient temperature field reconstruction,but have the disadvantages of large error at the region vertex and weak applicability for high gradient temperature field reconstruction.The DEL4 reconstruction algorithm proposed in this paper reduces the area with large vertex errors.The improvement of acoustic path and the new radial basis function greatly improve the reconstruction accuracy of high gradient temperature field.Compared with the former,the improved temperature field reconstruction algorithm improves the reconstruction accuracy of middle and high gradient temperature field,and the average relative errors are reduced to 0.06%,1.12% and 1.10%,respectively,which greatly improves the reconstruction result of temperature field.After obtaining the relation of flame sound velocity and temperature and the improved reconstruction algorithm,the real temperature field is reconstructed and measured.For non-flame high temperature environment,the reconstructed temperature field error is very large,and the relative erro r in the central high temperature area can reach 25.8%.The improved reconstruction method can well reflect the variation trend of environmental temperature gradient and reduce the relative error of high temperature region to 4.8%.For flame environment,b ecause the sound velocity and temperature relationship is different from that of non-flame environment,the flame temperature error obtained by directly using the ideal gas sound velocity and temperature relationship is 62.4%.The experimental formula of sound velocity and temperature and the improved algorithm of temperature field reconstruction are used to measure the temperature field in typical combustion flame environment.The error of the temperature field obtained is 2.64% compared with the measured value of thermocouple,which shows good accuracy.