Experimental And Simulation Research On Fluid Oscillation Characteristics Of Vortex Type Fluid Oscillatory Flowmeter

The dissertation "Experimental And Simulation Research On Fluid Oscillation Characteristics Of Vortex Type Fluid Oscillatory Flowmeter'' is supported by The National High Technology Research and Development Program (863 Program) "The key technology of Oscillatory Type Flowmeter" (No.2002AA423180) and The National Science Foundation Project "The control theory and method of representative exciting flow field in hydraulic component"(NO.59835160).The vortex type fluid oscillatory flowmeter based on measurement of vortex hydrodynamic vibration generated by specific flow passage, and the frequency of fluid oscillations is in direct proportion to flow rate. There are two kinds of vortex type oscillatory flowmeter: vortex flowmeter and vortex precession flowmeter. Since it has the advantage of no moving components, impulse signal output, strong medium adaptability, high measurement accuracy, wide measurement range, low-pressure drop, no zero drift and easy to maintenance, it is wide accepted that the vortex type fluid oscillatory flowmeter is ideal flowmeter in the measurement of gas, liquid, steam and mix/corrosive fluid. However, it has unsolved disadvantages up to present time, such as poor noise immunity in low flux, low interference immunity and adhesion of the sensor surface that affects the meter sensitivity.In order to overcome those defects, we chose the fluid oscillation characteristics of vortex type fluid oscillatory flowmeter as research subject on the basis of the former achievement. The technique of fluid mechanics simulation and the technique of modern fluid mechanics experiment were applied to research on the fluid oscillation characteristics of vortex flowmeter and vortex precession flowmeter. In this work, a new dual triangulate bluff body vortex flowmeter was developed, the flux lower limit value of which lower by 50% that of the old single bluff body vortex flowmeter. The linear correlation of the correlation between the velocity pressures of fluid disturbs wave and that of vortex precession in vortex precession flowmeter was brought to light, and a spectrum phase discrimination method based on FFT to remove the effect of fluid pulsating interference on vortex precession flowmeter was advanced. The main content of each chapter is as following.The first chapter at first generally introduced the history and the actuality of flowmeter on the basis of relevant publications search. One of most promising flowmeter-the vortex type fluid oscillatory flowmeter-was selected as research subject. The literature about primary instrument and secondary instrument of vortex type fluid oscillatory flowmeter was summarized. And then, the recently new development of vortex type fluid oscillatory flowmeter and its limits were discussed. At last, the project significance, background, main research contents were provided.In the second chapter, the fluid mechanics principle of vortex flowmeter at first was introduced. The classical theory about vortex flowmeter and the method ofcomputational fluid dynamics about flow around body were expanded on, and the model of the single bluff body and the dual bluff body vortex flowmeter were constructed. And then, FVM-finite volume method-analysis software FLUENT was applied to analyze the flow phenomenon of flow over single bluff body or dual bluff body. By analyzing result of simulation, the intensity amplification effect of velocity pressure, which is induced by flow over dual bluff body, and the measurement accuracy of the dual bluff body flowmeter were projected. The assemble criterion of sensor for design was advanced. At last, a method of increasing signal-to-noise ratio and reducing flux lower limit value of vortex flowmeter was advanced. The experiment program was advanced.In the third chapter, the method and choosing principle of the test system component at first were brought out. The component of test device was introduced. And then, the characteristics, such as Strouhal number, vortex street strength, vortex street stability and pressure drop coeffi...