Radiation Thermometry And Its Application In Temperature Measurement In Drop Tube

Drop tube is a ground-based facility that has been simulated to be space condition. It offers special conditions of microgravity and containerless. A temperature measurement system to monitor samples in the whole progress of experiments plays an important role for the studies. Since the samples are small and move rapidly, the detection system is severely limited. Radiation thermometry can carry out noncontact measurement involving objects that move rapidly, so radiation thermometry becomes the only choice. The principle, significance and methods of radiation thermometry are studied detailedly in this thesis, and its application in temperature measurement in drop tube is discussed. The main work concerned is as follows:This thesis presents the theory of the radiation temperature measurement in detail, including the radiometry and the blackbody radiance law. Based on the theory, various radiation thermometries have been introduced, such as the total radiation pyrometer, brightness pyrometer, two-wavelength pyrometer and multi-wavelength pyrometer. The theory of multi-spectral radiation thermometry is particularly discussed. Different mathematical models of multi-spectral radiation thermometry are presented, and the data processing methods based on interpolation and least squares techniques are analyzed and their features are discussed.The whole temperature measurement system consists of the light-triggering circuit, the infrared pyrometer and the kinetic temperature measurement system. An infrared pyrometer used for temperature measurement of fixed points was designed, which shows a measurement range of 900-1800K, a response time of less than 1 ms. and an accuracy of about 1%. Coupling the Newtonian heat transfer law with the classical nucleation theory, the calculation formula of cooling rate and undercooling of droplets is acquired. According to the formula, the relationship between the cooling rate and undercooling and the droplet size can be analyzed. Finally, a scheme of kinetic temperature measurement system is designed. A method of optimal parameter selection for determining two operating wavelengths and their bandwidths of the pyrometer is proposed, and two working wavelengths were selected to be 0.8μm and 0.95μm, whose bandwidths both being 0.03μm. Based on the operating wavelengths, Si-PIN photodiode is chosen to be the detector. The corresponding measurement circuit and program are designed according to character of dynamic temperature measurement, which realizes the requirement of environment of drop tube. According to the testing results, the two-color temperature measurement is testified to be a practicable way for experiments in drop tube.