Study Of Optical Fiber High Temperature Measurement System Based On Blackbody Cavity

In the fields of spaceflight, material, energy sources, metallurgy and chemical industry, it is very important to measure the high temperature of strong immersed-erode medium. At present, Pt-Rh thermocouple and optical fiber pyrometer are in common use. In condition of high temperature, thermocouple has disadvantages such as short life, rapid consumed, be lack of anti-erode and EMI.Fiber pyrometer can measure high temperature effectively, however, it still has some limitation. For example, radiation pyrometer bring great error attributed to its incapable of embed into temperature source, intensity pyrometer has a bad precision, the structure of dual-wavelength pyrometer is complicated and difficult to interchange, so its reliability is not good. Sapphire optical fiber pyrometer possesses a pretty high price and difficult to make into practice as a result.In this paper, a blackbody cavity sensor is issued instead of noble metal thermocouple and sapphire optical fiber pyrometer that can be contact to the measured temperature directly. At the same time, optical fiber radiation temperature measurement system is designed to incept the radiation sent by blackbody cavity through an airtight space in non-contact way. In this way, advantages belong to contact and non-contact temperature measurement are combined and the disadvantages belong to them are avoided. The primary content in this paper includes:The basic law of blackbody radiate, radiation exchange principle between blackbody surfaces and cavity radiation theory are introduced, which provide theory foundation for realizing temperature measurement and supply method for computing emissivity of the blackbody cavity.Blackbody cavity sensor is designed. Model of integral emissivity of cylindrical blackbody cavity is established based on integral equation theory. Optimize structure parameters are obtained through analyzing the impact caused by geometry dimension, material emissivity, the size and location of detector, so the precision is improved.Entire optical fiber high temperature measurement system is present by combining blackbody cavity sensor to fiber radiation pyrometer, and every component is introduced in particular. Lens group and optical fiber collimator are adopted to gather radiation signal issued by blackbody cavity sensor and couple the light into common fiber. Two narrowband interferential filter are applied to get two different wavelength lights.Si and InGaAs integrated-encapsulation photoelectric detector are chose here to change the light signal to electrical signal. After magnify and signal process, the temperature is displayed in Labview interface in real time.ANSYS finite element software is applied to simulate the dynamic characteristics of blackbody cavity sensor. The temperature distribution and dynamic changing of every point in blackbody sensor is present, and the factors that influence temperature measurement accuracy and dynamic characteristics, such as preheating temperature, thermo-physical properties and boundary conditions are analyzed. Optical fiber high temperature measurement system is tested by stationary and dynamic experiments, which get a good effect.