Research On The Characteristics Of Fiber Optic Microphone In Furnace Temperature Measurement System

The temperature field of the power plant boiler is of great significance to the boiler control and combustion diagnosis,which will directly affect the stability of the combustion stability and the pollutants emissions.As one of the non-contact temperature measurement technique based on acoustic wave theory,acoustic temperature measurement has numerous advantages of continuous measurement and real-time monitoring,which make it widely applicated in the field of temperature field measurement.The temperature field measurement results are usually affected by the accuracy of the acoustic signal,which call for a better performance of the microphones.However,The electromagnetic microphones are difficult to have long-term application in boiler furnace due to their poor performance of high-temperature resistance and anti-electromagnetic interference.As a result,a more advanced microphone is desiderated which can significantly improve the measurement accuracy and durability in complex furnace environments.In this paper,the fiber optic microphone is selected as the object of study after comparing several acoustic measurement method In this paper,the performance of optical fiber microphones is studied by mechanism modeling and Finite element analysis at first.and experimental platform testing are conducted to validate the theoretical results at the same time.The main contents of this paper can be summarized as follows:1.The mathematical model and performance evaluation index of the acoustic measurement are established on the basis of the mathematical modeling and characteristic analysis of the optical fiber microphone diaphragm vibration and the optical fiber intensity modulation function.The influence of fiber optic microphone structure parameters on the sensitivity,frequency response and linearity is studied,which provides the theoretical basis for the development of fiber optic microphone.2.Based on the theoretical analysis and finite element analysis,the influence of thermal environment on optical fiber microphones is studied.The finite element modeling and simulation by ANSYS is carried out to analyze the vibration characteristics of the optical fiber microphone under the thermal environment.At the same time,the performance of the optical fiber microphones with different materials and structures is analyzed and compared to provide the theoretical support of optimal structure design of the fiber optic microphone in thermal environment.3.The acoustic test platform of optical fiber microphone is built based on the theoretical analysis.Appropriate type and structure of the experimental facilities are also considered to conform the reality.Firstly the light intensity instability was compensated by the method of spectral intensity ratio.The performance of the optical fiber microphones with different diaphragm materials and structural parameters is tested as well.At the same time,the performance of the optical fiber microphone and the electromagnetic microphone is compared considering the signal reduction degree,sensitivity and frequency response.The experimental results show that the optical fiber microphone can achieved the equivalent performance with the electromagnetic microphone,which verify the feasibility of the acoustic measurement method in acoustic temperature measurement...