Study Of Measurement Of The Temperature Using Ultrasonic

In large coal-fired power plant, Accurate measurement of the furnace temperature is important in practical value and scientific meaning for furnace to operate safely and efficiently, to lower pollution, and to realize the essence of the combustion.However, the processing of combustion in power plant furnace is huge size of the devices and in hard environment, instantaneous, random on flow. it is difficult to measure the temperature in furnace on-line, so more accurate and credible measuring technique for the furnace temperature is needed. The main technical challenges that limit acoustic Pyrometer widely used in large power station boilers is how to generate strong and reliable acoustic signal can be detected from serious background noise. At the same time, this research carried out was late.For these reasons, acoustic temperature measurement technology research of our country is still in the research stage.With excellent character of direction and beam emission when transmitting and low-cost, easy to produce, the technology to detect it is easy, ultrasonic wave is widely used in many fields.Based on acoustic Pyrometer theory, The complexity considered in the environment of furnace, a new kind of acoustic temperature measurement system by ultrasonic method is designed in this thesis.Based on pulse compression thechniques commonly used in radar and the analysis techniques of cross-correlation function used in Signal processing, the paper is written by the statement how the acoustic pyrometer measure the times-of-flight(TOF) of acoustic waves. The method that Using the high-frequency carrier signal modulated by low-frequency pseudo binary sequence(PRBS) to stimulate ultrasonic transducer and the cross correlation function to measure the time of flight of the sound wave is given.The system structure of the acoustic pyrometer is introduced in detail and the circuit is given in the paper. In addition, the paper provide a detailed explanation on the principle of the design of transmitting and receiving circuits. The design of m sequence parameters and the modulation mode between PN codes and ultrasonic carrier were analyzed.Relative algorithm of the time delay estimation based on FFT is studied. The sampling frequency and algorithm integral points are analyzed.According to acoustic propagation in the flow characteristics, the impact of flow on the acoustic disturbance was analysed and a method to correct this impact is proposed.The method is that the time of flight of the sound is replaced by the results calculated form the time of flight of the positive and negative direction measured on the same path. Experimental results indicate that the system under normal temperature condition can measure the time of flight of the acoustic wave in noisy environment accurately, the peak of the cross correlation function is remarkable, the ability to resist interference is so strong. Experiments in outdoor were done on the equipment we developed, the correction of the impact of flow on the acoustic disturbance were studed. Results showed that, with the help of the method proposed in this thesis, the impact of air flow on Temperature measurement accuracy was overcomed.