多光谱辐射外点罚函数反演算法的生物质锅炉火焰温度测量

Multi Spectral Radiation External Penalty Function Inversion Algorithm for Flame Temperature Measurement of Biomass Boiler

近年来,为了减少对石化燃料的依赖和节能环保的强烈需求,以稻壳、秸秆等可再生资源为燃料的生物质锅炉越来越受到业界的广泛重视。为了进一步提高生物质锅炉的燃烧效率,优化炉膛结构,需要实时监测火焰温度。传统的热电偶测温法不利于长时间高温测量, CCD测温法又难以测量真实温度,而多光谱辐射测温法具有响应速度快、无测量上限以及可以获得真实温度等优点,是生物质锅炉火焰温度测量的最有力工具之一。多光谱辐射测温是通过测量待测物某点的多个光谱辐射强度信息,通过普朗克公式反演获得真实温度。但是,未知的光谱发射率是多光谱辐射测温反演过程的最大障碍。目前,多采用事先假设一组发射率模型(发射率-波长或发射率-温度模型),假设模型如果与实际情况相符,则反演结果能够满足要求,假设模型如果与实际情况不符,则反演结果误差很大。能否在无需任何光谱发射率假设模型的情况下,实现真温和光谱发射率的直接反演一直是多光谱辐射测温理论研究的热点和难点。为此,提出外点罚函数约束优化算法,将多光谱辐射测温反演问题转化为约束优化问题,给出了罚函数的表达式和相关参数。与其他约束优化算法相比,外点法的优势在于不受发射率初值的影响,进一步提高了算法对不同材料发射率的适应度。基于微型光纤光谱仪,搭建了稻壳粉生物质锅炉炉膛火焰温度测量装置,通过实验室黑体炉标定后,对稻壳粉生物质锅炉炉膛火焰从初燃到稳燃过程的温度进行了测量,并与热电偶测量结果进行了对比。结果表明,与热电偶测量结果相比,多光谱辐射测温的最大绝对误差为35.7 K,最大相对误差为3.2%。表明该测量装置及反演算法可实现生物质锅炉炉膛火焰燃烧温度的测量,为后续生物质锅炉燃烧诊断及锅炉设计优化提供了基础。

In recent years,in order to reduce the dependence on fossil fuels and the strong demand for energy conservation and environmental protection,biomass boilers with rice husk,straw and other renewable resources as fuel have attracted more and more attention in the industry.In order to further improve the combustion efficiency of the biomass boiler and optimize the furnace structure,it is necessary to monitor the flame temperature real-time.The traditional thermocouple temperature measurement method is not conducive to long-term high temperature measurement,and the CCD temperature measurement method is difficult to measure the real temperature,while the multispectral radiation temperature measurement method has the advantages of fast response,no upper limit of measurement and can obtain the real temperature,which is one of the most powerful tools for measuring the flame temperature of a biomass boiler.Multispectral radiation thermometry is to obtain the real temperature by measuring the spectral radiation intensity information of a certain point of the object to be measured and inversing it with Planck formula.However,the unknown spectral emissivity is the biggest obstacle in the inversion process of multi-spectral radiation thermometry.At present,a group of emissivity models(emissivity wavelength or emissivity temperature models)are usually assumed in advance.If the assumed models are consistent with the actual situation,the inversion results can meet the requirements.If the assumed models are inconsistent with the actual situation,the inversion results have a large error.Whether the direct inversion of true and moderate spectral emissivity can be realized without any spectral emissivity hypothesis model is always a hot and difficult topic in the theoretical research of multispectral radiation thermometry.For this reason,a constrained optimization algorithm of penalty function is proposed,which transforms the inversion problem of multi spectral radiation temperature measurement into a constrained optimization problem.Because the outer point method is adopted,it is not affected by the initial value of emissivity,which further improves the adaptability of the algorithm to the emissivity of different materials.Based on the flame-s model optical fiber spectrometer produced by American ocean optics,a flame temperature measuring device of rice husk biomass boiler furnace was built.After the calibration of blackbody furnace in the laboratory,the temperature of the furnace flame of rice husk biomass boiler from initial combustion to stable combustion was measured,and the results were compared with those of thermocouple.The results show that the maximum absolute error is 35.7 K,and the maximum relative error is 3.2%compared with the thermocouple.The results show that the measurement device and the inversion algorithm can realize the measurement of the combustion temperature in the furnace of the biomass boiler,which provides the preliminary research basis for the subsequent combustion diagnosis and boiler design optimization of the biomass boiler.