基于静电传感器的燃烧器火焰检测机理与方法研究

On-line measurement and characterization of burner flames play an important part in the fundamental research, condition monitoring and operation optimization of industrial combustion processes. Existing flame detectors are primarily based on the thermal, acoustic and optical properties of flames, and seldom rely on their electrical properties. It is due to the lack of an effective measurement technique for the flame electrical field, little is known about the electrical properties of flames. The proposed project aims to develop an on-line flame monitoring technique based on electrostatic sensors. Single wire, wire mesh and strip-shaped sensor array will be designed and optimized through finite element simulations. The local concentration, velocity and other dynamics of charged particles will be measured and their three dimensional distribution will be reconstructed using tomographic techniques. Based on the dynamics and distribution of charged particles, the flame characteristic parameters will be derived. New methods for the characterization of flame electrical properties will also be proposed. The electrostatic-based flame monitoring technique will be assessed through extensive experimentation under laboratory and industrial conditions. The flame electrical properties will be comprehensively investigated and compared to its thermal, acoustic and optical properties. It is expected that a deeper understanding of the flame mechanism will be achieved. The theoretical, numerical and experimental studies to be carried out, which are of great value for both scientific research and industrial applications, are expected to result in a brand new technique for the on-line monitoring and diagnosis of industrial combustion processes.

火焰特征参数的在线测量对促进燃烧过程的科学研究、状态监测和节能减排具有重要的现实意义。现有的火焰检测装置主要依靠火焰的热学、声学和光学特性，而极少利用其电学特性进行测量。也正是由于缺少对火焰电场进行测量的有效手段，人们对火焰的电学特性知之甚少。本项目旨在研究基于静电传感器的火焰特征参数在线测量方法：提出单丝、丝网与条形电极阵列设计方案，通过有限元分析实现结构的优化设计；提出火焰中带电粒子和微细颗粒的局部浓度、速度等动态特性的测量方法及其三维分布的层析重构算法；提出基于带电粒子和微细颗粒分布特性的火焰特征参数测量方法，提出新的火焰电学特性的表征方法；在实验室与实际工业环境下完成火焰静电检测技术的测试验证，全方位观测火焰电学特性并与火焰的热、声、光学特性相比较，获得对火焰机理的深入认识。拟开展的理论、仿真与实验研究将为工业燃烧过程的在线监测提供全新的技术手段，具有重要的科学研究和应用价值。

燃烧器火焰内部及附近存在着正负离子、电子和带电的碳烟颗粒，静电传感器能够通过静电感应和电荷转移实现对火焰的检测。基于上述原理，本项目提出了基于静电传感器的新型燃烧器火焰监测方法，通过机理分析、系统设计、实验研究等途径深入揭示了静电传感器的工作机理及火焰的电学特性，实现了火焰边缘、脉动频率和电荷密度等特征参数的测量。主要研究内容包括：1）设计研制了静电传感器阵列和静电探针样机、集成式信号调理电路以及离子电流传感器。2）提出了多路静电信号的数据融合、指数回归分析、频谱分析等方法实现火焰边缘和脉动频率的测量，采用了静电信号均方根值表征火焰内部带电粒子电荷密度。3）搭建了火焰边缘、脉动频率和电荷密度测量实验装置，通过绝缘电极与裸露电极的对比实验，确定了火焰静电信号的主要来源；以火焰成像测量系统为参考，对比实验验证了静电火焰测量系统的有效性；结合离子电流传感器的实验测试验证了静电探针的有效性。4）通过实验研究了不同火焰轴向高度和燃料流量下火焰边缘、脉动频率及电荷密度测量结果的准确性及可重复性，系统地评估了静电传感器及静电探针的测量性能。通过开展上述研究，本项目对基于火焰电学特性的火焰监测有了深入认识，形成了较为系统的新型火焰状态监测理论和方法，为工业燃烧过程的在线监测提供了一种全新的技术手段。