Flow Sensing Technology Based On Fiber Braggg Rating

Nowadays, flow measurement is critical in national life and production. Because the traditional mechanical and electronic flow meters have problems such as low automation and susceptible to electromagnetic interference, it is difficult for them to be used in some harsh environments. For flow measurement in practical environment, because the fluid medium is complex and changeable, new methods and new ideas are needed to be explored for the development of new flow measurement systems with expanded application scopes. As a new type of sensor, fiber Bragg grating (FBG) is intrinsically safe and corrosion-resistant. Fiber Bragg grating sensing technology brings a new life to the flow metering field.In this thesis, a flow measurement system that combines fiber Bragg grating sensing technology and the traditional vortex flow measurement method is proposed and studied. The sensing principle is expounded after a certain theoretical research. In vortex flow sensor, the simulation and analysis is carried out by using the simulation software Fluent. The transmission information and pressure changing with time curve of the vortex in the internal flow field is obtained. The vortex street frequency information is then obtained by Matlab data processing. The key components of the fiber Bragg grating vortex flow sensor system including vortex street, cantilever beam and fiber Bragg grating are designed and fabricated. The gas flow in wind tunnel laboratory is used for testing and calibration of the fiber Bragg grating vortex flow sensor system. The response of wavelength of FBG along with time can be detected by using a fiber Bragg grating demodulation instrument. The corresponding relation curve of wind speed and vortex frequency is obtained by data processing. Compared with the applied frequency, the measured frequency is in a good agreement. It also presents good linear relationship to the wind speed. These experimental results show that the fiber grating vortex flow sensor we developed can be used for measuring wind speed of0～20m/s with high sensitivity.The fiber Bragg grating vortex flow measurement system not only has the advantages of the traditional vortex flowmeter, but also has the advantages of fiber grating sensors such as simple structure, high sensitivity, strong anti-jamming capability and wide application range. It is therefore of high research value and application prospect in the flow measurement field.