| Industrial high-temperature furnace is one of the most energy consumption in large industry.Uneven heating in the furnace is one of the main reasons for fuel waste.The temperature distribution in the furnace is an important parameter for judging the operating status of the equipment.Therefore,precise control of combustion temperature plays an important role in improving combustion quality,prolonging furnace life and saving energy.At present,the more commonly used temperature measurement methods in the industry mainly include thermocouples,expansion thermometers and infrared thermometers.It is aimed at high-temperature and harsh environments such as coal-fired boilers in power stations,chemical smelting heating furnaces,and heat treatment furnaces that require multi-point and segmental temperature measurement.The above temperature measurement methods have certain limitations.For example,although the thermocouple has high measurement accuracy,it is difficult to measure the temperature at multiple points in the furnace;the expansion thermometer is simple in structure,but it is extremely easy to damage,the internal liquid is toxic and volatile,and the response speed is slow;the infrared thermometer is easily affected by the furnace.The influence of internal smoke and fog will reduce the accuracy of temperature measurement.Ultrasonic temperature measurement is a research hotspot in the field of science today.Compared with conventional temperature measurement methods,it has the advantages of fast response,high flexibility,and strong environmental adaptability,and can meet the needs of online control and distributed temperature measurement.Based on the principle of ultrasonic guided wave temperature measurement,this paper constructs a plurality of 90 ° elbows at the ends of Chromel wires as temperature measurement sections,uses a 250 k Hz piezoelectric transducer to excite the L(0,1)mode in the curved waveguide to realize ultrasonic temperature measurement,and uses the finite element simulation method to analyze the acoustic propagation characteristics of the L-shape waveguide at different temperatures.In addition,the system design is completed through hardware design and software development.The hardware system includes ultrasonic signal transmitting circuit,echo receiving circuit,digital acquisition circuit and USB communication circuit.The software system is developed based on Lab VIEW and can realize parameter control,echo signal display,distributed temperature value display,data storage and other functions.Finally,the signal processing algorithm is designed for the collected experimental data,and the time difference information is decoupled through the cross-correlation algorithm to complete the experimental calibration of the sensor,and then the time-temperature characteristic curve is obtained.Finally,based on the temperature measurement theory and design scheme,the system platform was built,and the system was calibrated for three temperature measurement sections in the range of normal temperature to 1100 ℃ for many times.The performance indicators were analyzed from the aspects of system real-time,sensor sensitivity and repeatability.The results showed that the system response time was within 100 ms,and the sensitivity of the three sensor sections was 79.45 ℃/ μs、81.90℃/ μs、80.86℃/ μs.The repeatability was 3.82%,4.043% and 4.363% respectively.The research results in this paper can provide application guidance for the thermal efficiency utilization and safety control of electric coal-fired boilers,chemical reaction kettles,metallurgical heating furnaces and heat treatment furnaces,and have broad application prospects. |
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