A Research Of Biomass Flame Temperature Measurement Technology Based On Multi-spectral Thermometry

Biomass is a renewable energy-saving and environmentally friendly fuel.Biomass reserves are abundant and can meet the needs of global renewable energy.The new combustion equipment based on high-temperature combustion method can improve the fuel utilization rate and thermal energy conversion efficiency,and provides a new solution for improving the utilization of biomass energy.Flame is the central reaction zone of the combustion process.Flame temperature is an important indicator of fuel performance,and it also affects the emissions of combustion pollutants such as NOx and CO.Accurate measurement of flame temperature is an important basis for the optimization design of new combustion equipment parameters,and is essential for the safe and stable operation of combustion equipment.Traditional thermocouple and CCD image temperature measurement methods are difficult to meet the real-time and accurate temperature measurement requirements for high-temperature flame in the development of new biomass combustion equipment.The research of accurate on-line measurement technology of high temperature combustion flame temperature can provide technical support for the development of new biomass combustion equipment and other high temperature measurement fields,which has important significance and practical application value.This topic focuses on the topic of on-line temperature detection of high temperature combustion flame.In order to improve the real-time and accuracy of high temperature combustion flame,the temperature and emissivity inversion algorithm of multi-spectral radiation temperature measurement technology is studied.A multi-spectral radiation temperature inversion algorithm that does not need to assume the emissivity model first is proposed,which provides a solution for online measurement of biomass flame temperature based on multi-spectral radiation temperature measurement technology.The main research work of this paper is as follows:(1)On the basis of in-depth analysis of the research status of biomass combustion temperature detection at home and abroad,aiming at the shortcomings of current visual and non-visual temperature detection technology in this field,according to the characteristics of multi-spectral radiation temperature measurement technology,a biomass flame temperature detection scheme based on multi-spectral radiation temperature measurement technology is proposed.The problems that need to be solved urgently in the application of multi-spectral radiation thermometry technology to on-line measurement of biomass flame temperature are elaborated.(2)In order to solve the problem that various types of biofuels and the second measurement method in the multi-spectral radiation temperature inversion algorithm takes a long time,a multi-spectral radiation temperature inversion algorithm based on bias constraints is proposed.The iteration cut-off condition and emissivity search method of the second measurement method of multispectral radiation temperature inversion algorithm are improved.Compared with the second measurement method,the new algorithm improves the inversion speed significantly on the basis of ensuring the measurement accuracy to meet the requirements,and provides the possibility for on-line measurement of biomass flame temperature.However,this method still requires the assumption that the emissivity at the selected wavelength is approximately linear with the adjacent temperature.(3)Because inversion process for biomass flame temperature must be removed from the impact of emissivity model assumptions,the constrained optimization algorithm is combined with the inversion algorithm of multi-spectral radiation temperature measurement.The inversion algorithms of multi-spectral radiation temperature measurement based on gradient projection method and interior penalty function method are proposed respectively.The simulation experiment results show that both algorithms achieve adaptive inversion of true temperature and spectral emissivity for multi-spectral radiation temperature measurement for continuous spectral radiation target oriented.By comparing the simulation results of the two algorithms,it is found that compared with the gradient projection method,the internal point penalty function method has higher inversion precision,stronger anti-noise ability and shorter inversion time.However,the internal penalty function method is greatly influenced by the initial point selection,and the inversion time can not meet the requirements of online measurement of biomass flame temperature.(4)Due to inversion speed of multispectral radiation temperature measurement algorithm based on constrained optimization can not meet the real-time measurement requirements of biomass flame temperature,combining generalized inverse matrix theory and constrained optimization method,a multi-spectral radiation temperature inversion algorithm based on generalized inverse-external point method is proposed.The generalized inverse matrix theory is combined with the reference temperature mathematical model of multi-spectral radiation temperature measurement.The underdetermined equations of multispectral radiation temperature measurement are solved by generalized inverse theory.The simulation experiment results show that the inversion value obtained by this method is close to the target value,but some of the emissivity inversion results are greater than 1 and not consistent with the actual situation due to the lack of constraints.To solve this problem,a multispectral radiation temperature measurement inversion algorithm(generalized inverse-exterior penalty)is proposed,which combines the generalized inverse algorithm with the exterior penalty function method in the constrained optimization algorithm.The results show that the generalized inverse-exterior penalty method has obvious advantages in the inversion accuracy and computation speed,and can meet the requirements of on-line measurement of biomass flame temperature.(5)Based on the theoretical analysis,a multi-spectral radiation temperature measuring device based on optical fiber spectrometer is built.The flame temperature of husk powder biomass boiler is measured.The experimental scheme and equipment parameters are introduced.Reference temperature radiation information is obtained through the blackbody furnace,and the accuracy of measurement is verified by thermocouple.The temperature measurement process and measurement results are described in detail.Finally,the uncertainty of the device measurement is analyzed.The experimental results show that the device can be used for on-line measurement of biomass flame temperature.