用于火焰成像的ECT系统导纳测量精度分析  

Analysis of Admittance Measurement Accuracy for ECT System Used in Flame Imaging

作　　者：王超 王健宇 金硕 Wang Chao;Wang Jianyu;Jin Shuo(School of Electrical and Information Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学电气自动化与信息工程学院,天津300072

出　　处：《天津大学学报(自然科学与工程技术版)》2025年第4期387-394,共8页Journal of Tianjin University:Science and Technology

基　　金：国家自然科学基金资助项目(62271343);天津市研究生科研创新资助项目(2022BKY080).

摘　　要：火焰的导纳包括介电和导电特性,可从不同角度反映燃烧状态,火焰导纳的精确测量对于获取燃烧状态具有重要意义.电容层析成像(ECT)在火焰检测中获得了成功的应用,也正从测量介电常数单一参数向测量导纳虚部和实部参数发展,但同时也对导纳的测量精度提出了更高的要求.本文使用电探针测量了火焰不同位置的相对介电常数和电导率,以此为基础,建立ECT测量火焰导纳的仿真模型,发现火焰导纳虚部和实部的差距随着频率的升高而增大.在经典ECT系统中使用的500 kHz激励频率条件下,火焰导纳的虚部约比实部大5个数量级,使火焰导纳信息难以精确测量.对不同频率下火焰和空气导纳的差值进行分析,结果表明,为了保障系统测量精度,应使得导纳实部采集分辨率不超过0.207.导纳实部采集分辨率与模拟数字转换器(ADC)采样位数和激励频率都有关.在ADC采样位数一定的情况下,降低激励频率能够获得更小的导纳实部信号采集分辨率,从而提高系统的测量精度.对于14位ADC,应采用26.4 kHz以下的激励频率.激励频率为500 kHz的经典ECT系统,其电流转电压(C/V)电路简化为以电容反馈为主导.针对降低激励频率使得经典ECT系统的C/V电路简化的输入输出关系不再适用的问题,在电路中考虑反馈电容和反馈电阻的综合作用,给出了测量火焰导纳的前端电路方案.Flame admittance reflects dielectric and conductive properties and can represent the combustion state from various perspectives.Accurate measurement of flame admittance is crucial for achieving the combustion state.Electrical capacitance tomography(ECT)has been successfully applied in flame detection,and it evolves from measuring a single parameter of permittivity to measuring the imaginary and real parts of admittance.However,this evolution also requires high admittance measurement accuracy.This study uses an electric probe to measure the relative permittivity and conductivity of a flame at various spatial locations,based on which a simulation model for the ECT-based measurement of flame admittance is established.Notably,the difference between the imaginary and real parts of flame admittance increases with increasing frequency.At an excitation frequency of 500 kHz,which is used in classical ECT systems,the imaginary part of flame admittance is approximately five orders of magnitude larger than the real part,thereby making it difficult to accurately measure the flame admittance information.The analysis results of the difference between flame and air admittances at various frequencies show that the acquisition resolution of the real part of the admittance should not exceed 0.207 to ensure the measurement accuracy of the system.The resolution of the real part of the admittance acquired is related to the sampling bit number and excitation frequency of the analog-todigital converter(ADC).With a fixed number of ADC sampling bits,a reduction in the excitation frequency can result in a small acquisition resolution of the real part of the admittance,thereby increasing the measurement accuracy of the system.An excitation frequency less than 26.4 kHz should be used for a 14-bit ADC.For classical ECT systems with an excitation frequency of 500 kHz,the current-to-voltage(C/V)circuit can be simplified to a model where the capacitor feedback is the primary factor.To address the issue,wherein the simplified input-output relatio

关 键 词：火焰 电容层析成像 导纳 测量精度 

分 类 号：TP271.4[自动化与计算机技术—检测技术与自动化装置]