【作者】 陈波；

【导师】 王玉涛；

【作者基本信息】 东北大学 ， 检测技术与自动化装置， 2018， 硕士

【摘要】 工业锅炉炉膛温度场的测量具有重要的现实意义,锅炉燃烧的基本要求在于建立和保持稳定的燃烧火焰,确定炉膛内部各点的温度分布就显得尤为重要。然而传统的温度检测方法因其测温区域、实时性、使用寿命等限制,很难应用于炉膛温度场的测量,基于声学法的温度场重建技术具有非接触、测量空间大、测温范围广、可连续实时测量、维护方便等优点,可以有效弥补传统测温方法的不足。考虑到声学测温方法应用于炉膛温度检测时,由于声学传感器需要安装在炉膛的开口处,所以声学传感器数目比较少,因此本文重点研究了传感器较少的条件下,二维和三维温度场重建算法的重建误差,并分析了影响温度场重建精度的因素,利用有限元方法分析了忽略弯曲效应对温度场重建结果的影响。本文的主要工作可以概括为:(1)针对目前大部分声学温度场重建算法所存在的共同问题,即必须满足有效声波路径条数大于网格数,重建结果温度点数少,温度场成像分辨率低,本文采用Tikhonov正则化方法,根据温度场连续的特性选择正则化矩阵,对温度场重建问题进行求解。该方法计算得到的温度点数远多于路径条数,可以避免对结果插值引入的误差;(2)网格划分数目小于有效路径条数时,温度场重建方程为超定方程,通过二维温度场仿真实验发现在这种条件下,LSM、SVD和Tikhonov正则化算法均能够得到误差比较小的结果,但是由于温度点数少,重建结果需要进行插值处理,插值之后,温度场重建误差显著增大;(3)网格划分数目大于有效路径条数时,温度场重建方程为欠定方程,常规方法无法求解,本文采用改进的Tikhonov正则化方法,对典型二维温度场模型进行了重建,单峰、单峰偏斜和双峰对称温度场的重建结果均方根误差均在2.7%以内,针对二维温度场重建问题,分析了正则化参数、网格数目、传感器数目和区域内温差对重建结果的影响,给出了二维温度场重建改进方案;(4)本文采用Tikhonov正则化方法重建三维温度场,利用三种典型温度场模型进行仿真实验,各温度场的重建结果均方根误差均在8%以内,并分析了传感器数目、分布方式和网格划分对三维温度场重建结果的影响;(5)考虑到声波在非等温场内传播会发生弯曲效应,本文利用有限元工具COMSOL建立二维声波传播瞬态模型,分析了声波在等温场和非等温场内的传播时间,并且研究了忽略弯曲效应对温度场重建结果的影响。更多还原

【Abstract】 The measurement of temperature field in boiler furnace is of great practical significance.The basic requirement of boiler is to establish and maintain a stable combustion flame.It is particularly important to determine the temperature distribution inside the furnace.However,the traditional temperature detection method is difficult to apply to the measurement of temperature field in furnace because of its limitation.The temperature field reconstruction based on acoustic method has many advantages,such as non-contact,large measuring space,wide measuring range,continuous real-time measurement,maintenance etc.These advantages can effectively compensate for the lack of traditional temperature measurement methods.When the acoustic thermometry method is applied to the furnace temperature detection,the acoustic sensors need to be installed at the opening of the furnace,so the number of acoustic sensors is relatively small,this thesis focuses on the reconstruction error of 2D and 3D temperature field reconstruction with fewer sensors and analyzes the factors that affect the reconstruction accuracy.The finite element method analyzes the effect of neglecting the acoustic wave bending on the reconstruction.The main work of this thesis can be summarized as follows:(1)Aiming at the common problems existing in most acoustic temperature reconstruction algorithms at present,it must satisfy that the number of effective acoustic wave paths is larger than the number of grids,the reconstruction temperature points are few.Tikhonov regularization method is used to solve the temperature field reconstruction problem.The temperature points calculated by Tikhonov regularization method are far more than the number of paths,which can avoid the error introduced by the result interpolation.(2)When the number of grids is less than the number of effective paths,the reconstruction equation of the temperature field is overdetermined equation.It is found through simulation experiments that the LSM,SVD and Tikhonov regularization algorithms can get relatively small error results under these conditions.However,due to the small number of temperature points,the reconstruction result needs to be interpolated.After interpolation,the temperature field reconstruction error increases significantly.(3)When the number of meshes is larger than the number of effective paths,the reconstruction of the temperature field is underdetermined,which can not be solved by the conventional method.In this thesis,an improved Tikhonov regularization method is used to reconstruct the 2D temperature field model,the root mean square error of the reconstruction results of all the temperature fields is less than 2.7%.The results show that the regularization parameters,the number of grids,the number of sensors and the temperature difference in the region have an important influence on the reconstruction results.(4)In this thesis,the Tikhonov regularization method is used to reconstruct the 3D temperature field.Three typical temperature field models are used in the experiments.The root mean square errors of the reconstruction results are all within 8%.The influence of sensor number,distribution mode and meshing on the reconstructed 3D temperature field is analyzed.(5)Considering the bending effect of sound waves propagating in non-isothermal field,a 2D transient model of acoustic wave propagation is established by finite element tool COMSOL.The acoustic propagation time in isothermal and non-isothermal fields is analyzed.The effect of neglecting the bending effect on the temperature field reconstruction is also studied.更多还原