| Flux measure is applied widely on many fields such as production of industry and agriculture , constructing of national defence , scientific research,commercial transport of products,people daily life and so on. It is helpful to save the energy sources and protect the environment. China is a developing country whose average sources is very few. The importance of environmental protection and sources saving is emphasized by the strategy of sustainable development. Thus flux measure is very important. Then there is far-reaching significance to the application and research of flowmeters.There are many methods and instruments to measure flux. However,any flowmeter has own application field,because the environment of industry is different and any kind of flowmeter has its character. To make suitable to flux measure of different environment and matter, there are various flowmeters to come into existence. For example,cubage flowmeter,pressure differential flowmeter,floater flowmeter,turbine flowmeter,electromagnetism flowmeter and so on. Vortex flowmeter is a new type flowmeter. It has only developed from 1970's. Nowadays,the Fiber Optics Vortex Flowmeter combines the speciality of liquid oscillation which Karman vortex has in a class by itself with inimitable advantages of fiber optics sensing. It attracts people's attention more and more. Although most of researches on the Fiber Optics Vortex Flowmeter are carried out on the primary stage in the lab,its advantages will appear in measuring velocity of flow and flux of gas and liquid when the researches go on.The thesis rooted in the preview subject of Da Qing Oil Field. It was aim of this subject to make use of multiphase optical-fiber sensor tomeasure temperature,pressure,flux and scale of matter of oil well. In the producing of industry,it is absolutely necessary to measure and control temperature,pressure,flux and liquid position. Flux measure is the most difficult among them,if we want to achieve the precision and reliability that we want to get. Except the quality problem of instrument,it has connections with craftwork data which we provide and rationality which type ,installation,use and maintenance of instrument are or not.Combining the aim of subject that Da Qing Oil Field previewed,this thesis has achieved the jobs about the Fiber Optics Vortex Flowmeter as follow:(1) The paper has summarized the developing status of familiar flowmeters which we make use of to measure flux. Have found methods to measure flux of oil well. Compared the advantages and disadvantages of these methods. Discovered that the fiber optics flowmeters were paid attention to widely in flux measure of oil well,because they have unique advantages with others. The Fiber Optics Vortex Flowmeter is the most especial among them. It combines the vortex theory with fiber sensing technic. It is a new member of flowmeters. It has some advantages as follow:high exactness and sensitivity;enduring high temperature and pressure,resisting electromagnetic molestation;be on the safe side in inflammable and explosive environment;wide frequency bandwidth,extensive dynamic bound;be convenient for measure and control at long distance;small cubage and light mass.(2) In theory,combining wave theory of light,Karman Vortex theory with hydrodynamics,this thesis analysed sensing theory of the Fiber Optics Vortex Flowmeter. The light that the light source emits is coupled to the fibre by the focus lens. The optical fibre is stretched across the pipediameter perpendicular to the flow at 10～15cm in the back of bluff body. Above a threshold flow corresponding to a bluff body Reynolds number R e~40,the vortices are shed alternately from each side of the bluff body. According to Karman vortex theory,the vortex-shedding frequency is known to follow the simple relation where u is the flow speed, S t is the dimensionless Strouhal number and d is a characteristic length of the bluff body. S t is a function of R e but is approximately constant and equal to 0.16 for a triangle cylinder in the range 3×102 |
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