Research And Design Of Primary Spectrum Pyrometer

Since the Planck's Law was presented in 1900,the temperature measurement based on thermal radiation has always been emphasized.The key problem in radiation thermometry is that the emissivity is unknown.Although some solutions have been found,various problems present in practical application,such as special requirement, needing calibration,etc.A temperature field measurement method which is general, simple,and efficient,and have high performance-cost ratio is needed.A radiation thermometry which is named "Primary Spectrum Pyrometry"(PSP) has been established in previous theoretical study.By introducing the linear model for emissivity and measuring the radiation in three different wavelength bands at the same time,the PSP can make the measurement equations closed,solve the problems caused by unknown emissivity and calibration,and measure the temperature field efficiently.The theory of the method has almost been mature,but the application,which is indeed needed,is still preliminary.Therefore,the main work is to develop a PSP system based on the theory of PSP and CCD color digital camera for hardware,solve technical problems,and improve the theory if necessary.First,a development process of PSP system composed of hardware work and software work is researched and developed.The hardware work includes the device selection and calibration.The device selection means determining the required functions of the system,and selecting the device which meets the requirements.The calibration mainly consists of the calibration of the effect of control parameters and the calibration of the relative spectral response curve of camera.The main purpose of calibration is to check the device and obtain the information of camera which is needed in calculation.The software work means the programming of application software of PSP system.The software is the kernel of PSP system.It realizes the functions such as controlling of hardware,obtaining,processing and storing of data,designing of the database used in temperature calculation,statistics and display of results.Among them, the key point is the controlling of hardware and designing of database.The former realizes various functions of camera based on the interface functions provided by producer.The later achieves the real-time calculation of temperature field. Second,as the noise exists in PSP system and affects the temperature result,a set of de-noising methods based on digital image process is proposed.According to the difference between different working modes and statistical features of noise,pertinent measures are taken.In single-frame analysis mode,the fourier transform filtering is used to decrease the stripping noise,the neighborhood average filtering and the median filtering is used to decrease the random noise.In continuous acquisition mode, the multi-frame weighted average method,which is improved from the multi-image average method,is proposed to process various noises.Third,as the normalization and graphic method make it meaningless to analyze the error propagation in traditional way,the error propagation analysis model of normalized multichannel measurement is proposed.The model based on geometric concepts is direct and efficient.Analysis shows that not only the absolute value,but also the relative value of different channels can affect the error propagation.So it is possible to decrease error propagation with branch gains.Therefore,the affect of changing the branch gains on the solving coordinates on the normalized plane is analyzed further,and both the affects on normalization and coordinates are comprehensively considered.The result shows that the error propagation in a certain area on the normalized plane can be decreased by changing the branch gains,and the cost is increasing the error propagation in other area.Some detail results in typical conditions are given.Finally,verification experiment is carried out to check the accuracy,and application experiments are carried out to check the reliability of the PSP system.The verification experiment is a contrast experiment of heated thermocouple,in which a heat source with weak visible radiation is used to heat a thermocouple which emits visible thermal radiation.Taking the thermocouple as measurement target avoids the error brought by thermal non-equilibrium and heat source.The average temperature obtained by PSP system meets the thermocouple result,while the temperature of single pixel fluctuates.The application experiments include temperature field measurement of converter, primary air heater and pool fire of aviation kerosene.In these experiments,the reliability and feasibility in practical application have been proved,some problems are revealed,and a lot of firsthand data is obtained for future improvement.