Research On Incineration Flame Image Based Temperature Reconstruction Technology

So far, the main measurement device of temperature in a rotary kiln incinerator processing hazardous waste is still conventional such as thermocouples, so the temperature field of incinerator can't be achieved. With the rapid development of the computer and the optical sensor technology, temperature field reconstructing from the incineration flame image has been proved available and are getting the attentions of scholars home and abroad. In this paper, the progress of study on flame temperature field reconstruction is discussed. The common idea of these methods is that using optical sensors such as CCD to acquire the radiation projection along the viewing direction, and then, based on the research of radiative transfer in the incineration medium and reconstruction techniques, the temperature distribution inside the flame can be revealed. In general, a 2D flame image is the projection of the radiation energy in the 3D incineration space. Given the parameters, radiative transfer properties and reconstruction model, to reconstruct temperature field distribution according to flame image is the inverse problem of this projection process.The radiative transfer process in the diffusion media of the incineration system and the radiation heat transfer equation are discussed. It's the most important equation that almost the whole reconstruction problem in this paper is based on it. In order to establish the function of the relationship between image grey level and the actual radiation, the CCD optical imaging characteristics is analyzed and a kind of calibration method is proposed to determine that function. After calibration, the gray level images of different channels can be transferred into radiation and then temperature can be calculated through the two-color method.Hydrocarbon diffusion flame is selected as the research object. Some assumptions and simplifications of the radiation characteristics of flame cross-section are made. Then heat transfer equation is simplified into a line integral equation. With discretization of the flame cross-section and CCD view angle, the reconstruction problem turns into solving a large matrix equation. The LSQR method is introduced to solve this problem. Simulating reconstructions are carried out both in axisymmetric and non-symmetrical cross-section flame. The reconstruction results show good accuracy and stability.Base on the numerical simulations, reconstructions of real hydrocarbon flame are carried out in the laboratory. Cameras acquire sets of flame images and temperature fields of the flame cross-sections are determined through the reconstruction method. In the end of this paper, the method is applied to a hazardous waste incineration chamber to measure the temperature field.