Research On Temperature Monitoring System Of Power Station Boiler Based On Acoustic Temperature Measurement Principle

In the process of thermal power generation,the temperature distribution in the furnace is an important indicator to judge the combustion safety of the boiler and to guide the combustion conditions.Therefore,it is of great significance to accurately measure the temperature inside the furnace.Acoustic temperature measurement is a non-contact measurement method,which has the advantages of high precision,large measuring range,real-time continuous,convenient installation and maintenance,and makes acoustic temperature measurement stand out among many temperature measurement methods.According to the principle of acoustic temperature measurement,this paper designs a set of temperature monitoring system for power station boilers with high measurement accuracy and continuous and stable operation.In the design process of temperature monitoring system,the accuracy of acoustic wave transit time measurement is the precondition for determining the accuracy of system temperature measurement.Therefore,the method of cross-correlation algorithm combined with pseudo-random code ultrasonic spread spectrum technology is used to measure the time of sound wave flight.It is verified that the flight time measured by this method and the theoretical flight time error value are about 10 us,which meets the requirements of design accuracy.The pseudo-random code generated by the FPGA and the signal modulated by the 40 KHz square wave signal are used as the signal source,which greatly enhances the anti-interference of the signal during transmission.The industrial grade ultrasonic transducer can withstand the complicated working conditions on site,and the self-developed transducer drive circuit and signal receiving circuit can make the measurement distance reach about 20 meters.The high-speed AD acquisition card is used to collect the received signals,and the collected data is sent to the self-developed LabVIEW host computer for cross-correlation calculation to obtain accurate temperature values.Finally,the two-dimensional temperature field of the furnace is reconstructed by the least squares method.The experimental results show that the measurement results of the temperature monitoring system have high precision and reliability.In order to make the system usable in the furnace environment,a large number of experiments were carried out,and a series of temperature values under the condition of varying coal powder concentration were measured and obtained.By analyzing the experimental data,a mathematical model of gas medium concentration and gas medium coefficient was constructed.It laid the foundation for further improving the temperature measurement system.The main content of this paper is:(1)A large number of literatures were reviewed to understand the current research status of acoustic temperature measurement at home and abroad.Through the research on the traditional furnace temperature measurement method and other non-contact temperature measurement methods,the advantages of acoustic temperature measurement in temperature field measurement are clarified.(2)By studying the principle of acoustic temperature measurement,it is clear that the accurate measurement of the flight time is the key to the success of the temperature monitoring system design.Therefore,the cross-correlation algorithm is used to calculate the flight time of the acoustic wave.The concept and related characteristics of pseudo-random code and m pseudo-random sequence are introduced.The relevant parameters of ultrasonic transducer are also introduced.(3)Hardware design of temperature monitoring system: design of power supply circuit,introduction of FPGA main control system,design of signal modulation/enhancement circuit,design of ultrasonic transducer drive circuit,design of signal amplification circuit,design of band pass filter circuit,AD Introduction of the capture card and PCB drawing.(4)The software design of the temperature monitoring system: the design of the parameters of the signal source,the pseudo-random signal and the carrier signal generated by the FPGA,the upper computer calculation software design based on LabVIEW to realize the cross-correlation algorithm,and the accuracy of the design of the upper computer is verified by MATLAB.(5)Through a large number of experiments and analysis of experimental data,the accuracy and reliability of the temperature monitoring system were verified,and a mathematical model of gas medium concentration and gas medium coefficient was constructed.(6)Design of power station boiler temperature monitoring upper computer based on least squares method.