Transient two-dimensional temperature measurement of open flames by dual-spectral image analysis

Abstract

A novel optical instrumentation system has been developed for on-line continuous measurement of two-dimensional temperature distribution of a combustion flame. The system comprises a special optical assembly, a charged coupled device camera, a frame-grabber and associated software. Based on the two-colour principle, the transient two-dimensional temperature of a flame is determined from the ratio of grey levels of corresponding pixels within two images, which are simultaneously captured at two different wavelengths. Accordingly, the instantaneous two-dimensional temperature distribution of the flame is presented by pseudo-colour. Discreet considerations in the design of the instrumentation system are also described, including the choice of wavelengths, correction of location and intensity of pixels, elimination of noise, and calibration of the instrument factor. A series of experiments was conducted for butane-fired open flames on a combustion test rig. The results show that the temperature of a fuel-rich premixed flame is higher than a diffusion flame and decreases linearly with the equivalence ratio. For a diffusion flame, however, the temperature increases with the fuel flow rate.

3-D Reconstruction of Flame Temperature Distribution Using Tomographic and Two-Color Pyrometric Techniques

“…Given a voxel's monochromatic emissive power at R and G wavelengths, its temperature can be obtained based on the two-color pyrometric method [4] …”

“…Gong et al [3] further combine the optical sectioning tomography with two-color method to reconstruct the 3-D temperature distribution of the gasifier. Huang and Yan [4] introduce a beam-spilt optical system to concurrently capture the images of a flame at two different wavelengths using a single monochromatic charge-coupled device (CCD) camera and two narrow bandpass filters. Then, the transient 2-D temperature is determined from the ratio of gray levels of corresponding pixels within the two images based on the two-color principle.…”

“…However, getting synchronous two monochromatic images for two-color pyrometric formula is not easy. The methods using beam splitter [4]- [8], [12], [13] provide two or more optical paths for capturing two or more monochromatic images synchronously, but the complex optical paths will bring spatiotemporal matching errors. The methods using color camera [9]- [11], [13] are flexible to capture multichannel flame images, but substituting the Dirac delta function for spectral response function results in the inaccuracy of the measurement results.…”

Three-dimensional reconstruction of flame temperature and emissivity distribution using optical tomographic and two-colour pyrometric techniques

“…Some efforts have also been made to measure the gas-particle spectral emissivity and temperature in both laboratory and industrial scale flames based on infrared sensor techniques [9,10]. Camera-based passive imaging techniques have been developed for measuring the temperature and soot concentration of coal-fired flames on industrial-scale combustion test facilities [11,12]. However, they are mainly 2D based and the flame information from the third dimension is lost.…”

“…Optical tomography has clear advantages over other techniques in the 3D grey-level reconstruction of a flame [2]. In addition, optical radiation pyrometry is regarded as a practical and non-intrusive method of measuring the radiative temperature of solid particles in a flame [11]. The combination of optical tomography and radiation pyrometry has led to the possibility of developing a new methodology for the 3D reconstruction of flame temperature and emissivity distributions [26].…”