Design And Study On System Of Radiation Temperature Measurement In Drop Tube

Drop tube is an experiment facility which simulates the microgravity environment on the ground. It is used to research the undercooling and solidification process of metals and alloys in the containless, microgravity environment. Its temperature measurement system is an important part. This thesis has discussed the actuality and development, radiation thermometry theory, the detector and its operating wavelengths and bandwidths, measurement circuit of the temperature measurement system in drop tube. The principle, significance and methods of radiation temperature measurement are studied in this thesis, and a system of radiation temperature measurement is designed in drop tube. The main work concerned is as follows:This thesis presents the theory of radiometry and transmission character of radiant energy. Based on Planck's law, the theories of radiation temperature measurement are introduced, which are the basic of radiation thermometry. The theories and characters of various radiation thermometries are also introduced, including total radiation pyrometer, brightness pyrometer, colorimetry pyrometer and multi-wavelength pyrometer. Colorimetry pyrometer and colorimetric thermometry are studied detailedly. The configurations and characters of various colorimetry pyrometers are analyzed respectively. And then different mathematical models and the data processing methods of multi-spectral thermometry have been simply introduced.This thesis also discusses the structure, the work theory, the infrared pyrometer and the dynamic temperature measurement system of the temperature measurement system in drop tube. In order to measure the beginning temperature of the samples, the infrared system is designed according to the radiation thermometry theory, such as the pyrometer, the data collecting system, the data processing and displaying system. It is demarcated and its error is analyzed as ±0.57%.Next, a scheme of the dynamic temperature measurement system is designed. The PIN photoelectricity diode has been chosen with a type of BPV10NF, which shows a spectral range of 790～1050nm, a peak wavelength of 940nm, and a response time of 2.5ns. A method of optimal parameter selection for determining character of the detector, two operating wavelengths and their bandwidths of the pyrometer is proposed. Two working wavelength were selected to be 0.81μm and 1.02μm, whose bandwidths being 0.03μm and 0.02μm.The transformation rule of diameter of droplets between cooling rate and undercooling can be analyzed in drop tube. The signal measurement circuit and the data collecting and displaying system are designed according to the character of the dynamic temperature measurement system. Finally, the error of the dynamic temperature measurement system is discussed. The influence of environment radiation on radiation temperature measurement by the method of mono-color and two-color is analyzed, as well as the relationships of object temperature,environment temperature,object emissivity and work wavelength. The lowest value of the object's temperature is analyzed when the error of environment radiation is within 0.5%, and the relationships of them are studied.