Research On Key Technologies Of Coal Mine Gas Pressure Measurement Based On Fiber Bragg Grating

Gas is the biggest threat to the safety of coal mines in China.It is an important reason for coal gas outburst and gas explosion.It is an important measure to ensure the safety of production.This article intends to adopt Fiber Bragg grating pressure sensors which have characters of safety,explosion-proof,anti-electromagnetic interference,corrosion-resistant,distributed measurement and so on.In this paper,a series of in-depth studies with the relevant theory and key implementation of the technology have been carried in order to realize high-sensitivity distributed pressure measurement and gas pressure prediction in coal mine.The main research works are as follows:Firstly,a method of FBG pressure sensor encapsulation based on metal elastic diaphragm for gas pressure distribution measurement is proposed for solving the problems of low accuracy and poor safety of traditional coal wall.The pressure measurement range is 0~10MPa to meet the requirements of linearity,sensitivity,stability.Secondly,according to the application requirements and designed objectives of coal gas pressure,the theoretical analysis and ANSYS simulation analysis of coal mine working environment are carried out.The optimal design of pressure sensor is completed by experiment calibration.And through the program by overall processing of diaphragm and cavity can effectively avoid the installation error and hysteresis error.Furthermore,the development of FBG pressure sensor is completed.Thirdly,Aiming at the temperature-stress cross-sensitivity problem of FBG pressure sensor,the solution of temperature compensation is researched,and the sensor is calibrated by pressure experiment and temperature experiment.The experimental results show that the temperature sensitivity coefficient of FBG pressure sensor is 27pm/MPa,the pressure sensitivity after warming is 251.88pm/MPa.And the error of the pressure sensor is analyzed by according to the pressure sensor identification procedure”.Fourthly,according to the requirements of distributed dynamic measurement of coal gas pressure distribution and real-time prediction of coal seam stability in the production process,a distributed array measurement system based on optical fiber sensing technology is constructed,which can monitor and forecast the operation area in real time.The results show that the measurement system has good linearity and stability,it can meet the requirement of 0.01 MPa pressure measurement accuracy.