燃煤火电机组煤粉浓度超声检测机理与方法研究

In coal-fired power plant, the mixture of air and coal powder in the primary air pipe is a typical gas-solid two-phase flow with spare solid phase. How to measure the concentration of the solid pahse (coal powder) is difficut in the thermal process. Therefore, this project aim to investigate the principle and method on measuring concentration of coal powder based on the principle of ultrasonic acoustic. Firstly, an experiment station is established, with which, the principle of measuring concentration of coal powder by using ultrasonic can be investigated by conducting series of experiments. Secondly, by combination of orthogonal experiments and ultrasonic theory analysis, the propagation characteristics of ultrasonic waves including ultrasonic attenuation and velocity are investigated under diferent conditions where a wide various of concentrations of coal powder, distribution of coal powder, physic parameters of coal and air,and ultrasonic frequency are considered.The mechanism model is then established just for the air-coal two-phase. Thirdly, an inverse inference algorithm is proposed based on theory of belief fnction, which is used to obtain an inverse model. By combination of established mechanism model and inverse model, the real (or optimal) concetration of coal powder can be inversely inferred for the sample to be measured. Note that, the proposed inverse inference algorithm based on theory of belief function can be used online due to its low computational complexity and robustness. Hence, a ultrasonic method is finally proposed to measure the concentration of coal powder online. The researches in this project can make significant contributions on realizing the optimization of boiler combustion, enhancing the efficiency of boiler combustion, and reducing the amount of pollutant discharge.

火电机组燃煤锅炉一次风管道中空气与煤粉的混合流动是具有稀疏固相特征的复杂气固两相流动，实现固相（煤粉）浓度检测是锅炉燃烧优化面临的技术难题之一。本项目开展燃煤锅炉煤粉浓度的超声检测机理与方法研究。首先，构建实验平台用于机理和实验研究；其次，采用机理分析与实验测试相结合的方法，设计与煤粉浓度、煤粉颗粒粒径、物性参数及超声频率相关的多因素多水平正交实验，研究风粉两相流中超声波的衰减机理和声速传播特性，建立适用于燃煤锅炉风粉两相流的超声衰减和声速传播特性模型（简称超声响应机理模型）及其样本矩阵；第三，开展证据理论研究，提出一种证据反演推理算法，用于实现由超声响应机理模型（或样本矩阵）反演测算获得煤粉浓度，该方法具有较高的算法适用性、计算复杂度小等特点，可用于在线实时反演，确保提出的煤粉浓度超声检测方法可用于实时检测。本项目研究成果对实现锅炉燃烧优化、提高燃烧效率、降低燃烧污染物排放具有重要意义。

燃煤火电机组煤粉浓度的检测，对于电厂的安全、经济、高效运行具有重要意义。但其过程的复杂性和随机性致使参数的检测比较困难。本项目对用超声法检测煤粉浓度进行了研究。.第一，基于ECAH模型建立了稀疏气固两相流的反演模型，通过数值模拟，研究了稀疏气固两相流固相粒径、浓度以及物性参数与超声频率和衰减系数之间的关联规律，为搭建稀疏气固两相流自由落体实验台和正交试验方案奠定基础。.第二，建立了验证稀疏气固两相流固相粒径、浓度和物性规律的自由落体实验台。基于LabVIEW开发了用于实验的控制和数据的采集与处理的超声测量系统。在稀疏气固两相流自由落体实验台上，对固相粒径、固相浓度、超声频率和衰减系数进行了正交试验；获得不同固相粒径和超声频率下，超声衰减系数与固相浓度的关联关系，研究了超声在稀疏气固两相流中的传播机理。.第三，建立了模拟电厂一次风管道环境的风粉系统实验台。在风粉（空气与煤粉两相流）系统实验台上，测试了温度、湿度、气相流速等因素对风粉系统煤粉浓度的影响，建立了相关因素的修正模型；验证了超声在稀疏气固两相流中的传播机理；构建包含颗粒粒径、浓度、超声频率和超声衰减系数的风粉系统煤粉浓度样本集，并对样本集的有效性进行了验证。.第四，基于处理不精确和不确定信息的证据理论，提出了基于广义T范数融合的证据回归算法；基于风粉系统煤粉浓度样本集构建了证据样本集，建立了包含风粉系统煤粉浓度置信区间的证据回归反演模型。