Study On The Fast Determination Of Temperature Fields By A Tri-band Pyrometer

Radiation thermometry technology is suitable for rapid measurement of temperature under non-contact condition,and has important applications in many fields,such as aviation,aerospace,metallurgy,forging and so on.The temperature measurement methods based on 3CCD camera can easily realize temperature fields measurement,however,still face the problems of unknown emissivity and the fast calculation demand of temperature fields.Based on 3CCD camera radiation temperature field measurement,a tri-band radiation thermometry method by coefficient-storaged dichotomy,a dual-band colorimetric method by coefficient-storaged dichotomy and a tri-band colorimetric method by coefficient-storaged dichotomy have been developed in this work to determine the temperature field rapidly and more accurately.Using the simulated light source algorithm,the solution characteristics of the three methods mentioned above have been investigated,which can provide an important reference to temperature field measurement by a tri-band pyrometry.The main work of this thesis is as below:(1)Based on the radiation signal measurement equation of 3CCD camera,the isothermal surface equation of tri-band radiation thermometry has been derived with a linear emissivity model,and an improved solution strategy for coefficient-storaged dichotomy has developed to consider the dual solution problem of the equation;(2)A dual-band colorimetric method by coefficient-storaged dichotomy has been proposed based on the assumption of gray body for the average emissivity of the two wavebands,and a tri-band colorimetric method by coefficient-storaged dichotomy has been developed based on the assumption of the average emissivity of the three wavebands being equal ratio relation.Based on the simulated light source algorithm,the solution characteristics of the above three algorithms were studied.The results show that the tri-band colorimetric method is better in accuracy and stability,and the dual-band colorimetric method has a better tolerance to signal error;(3)The above three algorithms were applied to the calculating temperature fields of a kiln.The results showed that under this condition,the tri-band colorimetric method has a better result;(4)A welding seam extraction algorithm based on virtual spectral response—changing the coefficients of three bands spectral response functions has been proposed in this work,since the contrast between different temperature regions in the grayscale map may be more obvious by changing the coefficients of three bands spectral response functions,which may provide a reference for welding defect recognition algorithm.