The Fast Measurement Research Of Blackbody Cavity Liquid Steel Continuous Temperature Sensor

The accurate and rapid temperature measurement of molten steel has always been a very important issue in the progress of tundish.As the traditional rapid-response type expendable thermocouple sensor,with the high measurement accuracy,can't achieve temperature tracking,this research approach of the continuous temperature measurement sensor is proposed.At present,the blackbody cavity sensor gets certain application due to the high precision and great continuity,however it always has the longer measurement time and the serious hysteresis caused by the structure and other factors.In order to reduce the lag time,the finite element model of the sensor is established,the heat transfer mechanism of sensor and the influence factors of temperature hysteresis are analyzed.Then the compensation system is established to achieve the rapid measurement of molten steel temperature,through solving the analytical mathematical model of sensor.Firstly,the heat transfer process of the sensor is analyzed,and the initial thermophysical properties of the measuring tube are calculated and verified.The symmetric analytical heat transfer model of the sensor plane is established,and the temperature equation of the measuring tube is deduced by superposition principle and separation variables.The results show that the maximal deviation between the analytical solution and the finite element solution is 7 ? and 5 ?,when the temperature of molten steel is 1450 ? and 1550 ?.So the two solutions are in good agreement with each other,and the analytic model is correct,which can provide theoretical basis for subsequent analysis.Then the 3-D finite element model of the temperature sensor is established.Based on the analysis,the maximum error of the finite element solution and the measured datas is less than 10 ?,and the error accuracy is less than 1%,which accords with the design requirement of the sensor.Based on the heat transfer model,the influence of the sensor insertion depth,the initial preheating temperature,the wall thickness of the measuring tube and the thermophysical properties on the lag time of the temperature measurement are analyzed.By optimizing the sensor,the state response time can be decreased to 400s,and steady-state error is less than 1.2 ?.At last,the temperature prediction model of the molten steel is obtained by deriving the deformation of the analytical heat transfer model,and the temperature prediction compensation system is established.The results show that the error between the predicted temperature and the actual temperature is less than 3 ? when the temperature is from 1400 ? to 1600 ? and the measurement time is 120s,which indicates that the system can realize the rapid and accurate measurement of molten steel temperature.