Vortex Flowmeter Based On Fiber Bragg Grating Sensing

Measurement is the eye of industrial production.The flow of fluid in the pipeline exists in almost all industrial production and equipment.The transmission of flow is inseparable from the hydraulic pipeline.The monitoring of the hydraulic pipeline is very key and affects the operation of the whole system.In the production of petroleum industry,the flow measurement is indispensable for the exploitation,transportation,refining and processing of petroleum,otherwise the normal production of petroleum industry cannot be guaranteed.In chemical production,the proportion of chemical reagents must be strictly measured,otherwise there will be potential safety hazards.In the production of aerospace industry,the monitoring of aviation fuel plays a key role in the control of engine.Rocket engine consumes a large amount of liquid fuel at one time.If the measurement is inaccurate,it will not only cause serious economic losses,but also cause remote range.Among them,vortex flowmeter belongs to fluid oscillation flowmeter,which has the advantages of small pressure loss,large range and high precision.It is almost unaffected by fluid density,pressure,temperature,viscosity and other parameters when measuring volumetric flow under working conditions.In recent years,it has been found that fiber Bragg grating has the advantages of anti electromagnetic interference,good electrical insulation,small volume,light weight,anti-corrosion and high sensitivity.In this paper,a fiber Bragg grating flowmeter based on frequency measurement is designed through the research of hydraulic small pipe.The flowmeter design is based on Carmen vortex street principle,and the flow is measured by measuring the fluid vibration frequency.It is more suitable for special occasions such as flammable and explosive,strong electromagnetic interference and so on.The main research contents are as follows:(1)According to the basic knowledge of fluid mechanics,the stress analysis,stability analysis,position fixed analysis and fluid flow field parameter analysis of the sensing cantilever beam probe in the optical fiber vortex flowmeter are completed by using the relevant finite element software.Ensure that the optical fiber cantilever can be placed in a stable vortex field,and will not cause the fracture of the optical fiber when the vortex field makes a mechanical impact on the optical fiber.(2)The overall structure of fiber Bragg grating vortex flowmeter is designed.It mainly includes the design of shell,the size of triangular column generator,the design of sealing device,the design of fiber Bragg grating cantilever,the selection of optical fiber and the fixation of optical fiber position.The experimental platform of fiber Bragg grating vortex flowmeter is built.The structure and performance of fiber Bragg grating vortex flowmeter are tested and analyzed.(3)The data processing method based on Hilbert Huang transform and the data processing method based on ensemble empirical mode are applied to the signal processing of vortex flowmeter.Comparing the two methods with the relative error in frequency domain,it is found that the data processing method based on ensemble empirical mode is better than the data processing method based on Hilbert Huang transform.