Fiber Bragg Grating Body Vortex Shedding Flowmeter Based

The flow is one of the important thermal instrumentation parameters which are used in the field of petrochemical, industrial, agricultural production, environmental protection, metallurgy industry, energy management and scientific research. Currently, according to the manufacturing crafts, the measurement principle and method, flow meters can be divided into the volumetric flowmeter, float-type flowmeter,differential pressure flowmeters, vortex flowmeter,and so on,a total of11classes. Vortex flowmeters develop rapidly and has become one of the universal flowmeters, because of high precision, small pressure loss, simple structure and wide range.From the angle of signal processing, the vast majority of these flowmeters collect measurement datas with electrical or magnetic signals, the datas is transformed to non-electricity.So in many industrial applications, it must have explosion-proof or Anti-spark measures to its supply line, output signal and installation site.In recent years, fiber optic sensing technique is used in the detection field widely, because of its anti insulation, anti-electromagnetic interference, resistance to corrosion and small volume.The article combines fiber grating sensing technique with vortex separation principle to develop a fiber bragg grating flowmeter which is based on vortex shedder. The flowmeter has characteristics such as anti-electromagnetic,anti-insulation and anti-corrosion, and is suitable for the petrochemical, metallurgy, nuclear industry and other special industrial site. The main research contents are as follow:1The cantilever strain mechanism is analyzed, and the sensing model of fiber Bragg grating combined with cantilever is introduced. The lowest natural frequency of the cantilever is calculated.2The vortex shedder which is the core component of the fiber bragg grating flowmeter is designed. The triangular prism is selected as vortex shedder to guarantee the stability and strong degree of vortex separation, and its specific structure and size are determined. A pressure transmission cavity is set in the middle of the vortex shedder, and the location, shape and size of pressure transmission cavity are determined. So the vortex signal generated by both sides of shedder can be reflected to the disturbance situation of cantilever.3According to the related testing requirements, The flow test platform is built for experiment and the actual performance of fiber grating flowmeter is tested. The experimental results show that has a wide range and high sensitivity.