基于多光谱成像技术的火焰温度及辐射率分布测量方法研究

Flame Temperature and Emissivity Distribution Measurement Me thod Based on Multispectral Imaging Technology

火焰燃烧参数能直接反映火焰燃烧状态,并对燃烧过程进行诊断、预测和优化。火焰温度及辐射率是燃烧状态的重要表征参数,火焰温度及辐射率的准确测量对于建立燃烧模型、优化燃烧过程和控制污染物排放有着非常重要的意义。随着数字图像技术与光谱学的发展,多光谱成像技术逐步应用于火焰燃烧温度及辐射率测量。针对光谱仪空间分辨率低和RGB彩色相机光谱分辨率低的问题,多光谱成像技术能获得兼顾空间分辨率及光谱分辨率的火焰光谱图像,实现火焰温度及辐射率分布测量,具有高时空分辨率、响应快速及测温范围宽等优点。因此,提出了基于多光谱成像技术的火焰温度及辐射率测量方法,搭建标准高温黑体辐射实验测量系统,对多光谱相机665~960 nm波段开展高温黑体辐射响应系数标定实验,获得多光谱相机25波段光谱响应标定系数,通过四阶多项式拟合建立多光谱相机各波段下仪器响应值与理论辐射强度之间的关系,并开展多光谱成像技术测量验证实验,结果显示温度与辐射率测量的相对偏差分别小于1%与4%。在此基础上,以蜡烛火焰为研究对象,建立了火焰多光谱成像测量系统,获得了蜡烛火焰多光谱辐射图像,基于普朗克辐射定律参数拟合方法,实现了蜡烛火焰温度与辐射率分布测量。测量结果表明:火焰竖直平面上火焰中心区温度及辐射率均高于火焰上部和底部;蜡烛火焰温度测量结果范围约为1350~2050 K,火焰中心区最高温度约为2050 K;蜡烛火焰辐射率测量结果范围约为0.04~0.36,火焰中心区最高辐射率为0.36。测量结果与蜡烛火焰燃烧过程及辐射特性分布规律一致。

Flame combustion parameters can directly reflect the flame combustion state and diagnose,predict and optimize the combustion process.The accurate measurement of flame combustion temperature and emissivity is of great importance for building combustion models,optimizing combustion processes and controlling pollutant emissions.With the development of digital image technology and spectroscopy,multispectral imaging technology has been gradually applied to flame combustion temperature and emissivity measurement.For the problems of low spatial resolution of the spectrometer and low spectral resolution of RGB color camera,multispectral imaging technology can obtain flame spectral images with both spatial and spectral resolution and realize temperature and emissivity distribution measurement of flame,which has the advantages of high spatial and spectral resolution,fast response and wide temperature range.Here,the temperature and emissivity measurement method of flame based on multispectral imaging technology was proposed.The standard high-temperature blackbody radiation experimental measurement system was built to carry out the high-temperature blackbody radiation response coefficient calibration experiments for the 665~960 nm band of multispectral imaging camera.The 25 band spectral response calibration coefficient of multispectral imaging camera was obtained,and the relationship between the instrument response value and theoretical radiation intensity at each band of multispectral imaging camera was established by fourth-order polynomial fitting.The measurement-validated experiment of multispectral imaging technology was carried out.The relative deviation of temperature and emissivity measurement is less than 1%and 4%,respectively.The flame multispectral imaging measurement system was established with a candle flame as the research object.The multispectral radiation images of the candle flame were obtained,and the temperature and emissivity distribution measurement was realized based on Planck s radiation law parameter fitting method.The measurement results show that the temperature and emissivity in the vertical plane of the central area of flame are higher than those in the upper and bottom in the vertical plane of flame;the range of flame temperature measurement results is about 1350~2050 K and the highest temperature in the central area is approximately 2050 K;the range of flame emissivity measurement results is about 0.04~0.36,and the highest emissivity in the central area is 0.36.The measurement results are consistent with the candle flame-burning process and the distribution pattern of radiation characteristics.