Characteristic Analysis On Compact Electromagnetic Vortex Flowmeter With Non-circular Cross Section

Vortex flowmeter has been widely studied after it was arised because it does not have any moving parts and can not be affected by the changes of the physical property of the fluid to be measured.Currently,the pizeo-type vortex flowmeter is most commonly used,but it can not resist the external vibration signal and easy to cause noise.Electromagnetic vortex flowmeter is a novel kind of vortex flowmeter emerged in recent years,which can resist the vibration disturbances like electromagnetic flowmeter,also can not be influenced by the physical properties of the measured fluid like vortex flowmeter.For the urgent demand of flow measurement in ringlike cross section of 80~150mm pipes in diameter in petroleum and chemical industry,the following aspects are presented in this paper.Firstly,the elementary overall scheme of the electromagnetic vortex flowmeter based on installation space requirements is proposed.In this paper,in order to fit the small and ringlike installation space,the cross section of the pipe is non-circular.Also,a new kind of bluffbody with slit between front semicircle and rear concave is designed.Secondly,the dimension of the bluffbody is optimized using the computer aided optimization platform Isight.According to the theory of computational fluid dynamics,modeling,meshing and definition of boundary conditions are deployed in pretreatment software Gambit.Thereafter the grid division way of the computatuinal domain is detemined,also,the suitable simulation model and the parameters needed for calculation are detemined in the CFD software Fluent.All of these found the theoretical basis for the next optimization.Then,Gambit,Fluent and Excel are integrated to optimize the dimension of the bluffbody by applying Isight which is one of computer aided optimization software.Subsequently,the dimension of the bluffbody is defined as the design parameter,also,the linearity of the Strouhal number and the velocity of cutting the magnetic induction line are defined as the object function.In order to determine the need of the existence of variables,DOE is utilized to define the Pareto contribution ratio of the design paremeters to the object functions.Then,NSGA-II optimization algorithm is selected to optimize the dimension of the bluffbody.Thirdly,the best position for probe is determined to detect the induced electromotive force.Fluent and Excel are integrated into Isight to define the position of monitor point asdesign variable and the amplitude of speed as object function,also,to search the better position for probe to detect the signals through monitoring functions in Fluent.Thereafter,the fluid field behind the bluffbody is simulated in three-dimensional environment.Subsequently,postprocessing software Tecplot is used to creat the iso-surface of the vorticity in the pipe.Finally,trough the iso-surface,the flow field situation of the vortex shedding behind the bluffbody is observed in the three dimensions.