Research On Wide Range Ratio Vortex Flowmeter Based On Numerical Simulation

Vortex flowmeter has the advantages of simple structure,no moving parts,low maintenance cost and high measurement accuracy,and is widely used in the field of liquid and gas flow measurement.To some extent,the study of vortex flowmeter with wide range ratio can solve the problem of difficult measurement under small flow rate of vortex flowmeter,and the method of reduced diameter structure is the most effective.The vortex flowmeter with reduced diameter structure is called the reduced diameter vortex flowmeter.At present,most enterprises still use the traditional empirical design method to design the reduced diameter vortex flowmeter.After the fluid passes through the reduced diameter structure,the turbulence degree of the fluid changes,which leads to more noise in the vortex street signal and affects the measurement accuracy.In order to solve this problem,this paper uses numerical simulation method to optimize the design of the reduced diameter structure of the reduced diameter vortex flowmeter.This paper mainly completes the following work:(1)the structure and theoretical basis of the wide range ratio realized by the reducing diameter vortex flowmeter were analyzed,and a new contraction curve equation was designed by summarizing the variation law of fluid velocity in the commonly used contraction section.(2)the numerical simulation software FLUENT was used to determine the optimal location of the detection points in the model,and the cross-section velocity uniformity was selected as the index to evaluate the degree of fluid turbulence,and the corresponding relationship between the size of the cross-section velocity uniformity and the number of noise signals in the vortex street signal was demonstrated.(3)an experimental scheme with flow rate(1.6m/s,3.2m/s,6.0m/s),contraction ratio(4,9,16)and contraction curve(straight line,vickers curve,bicubic curve,quintic and new curve)as variables was designed.FLUENT software was used to establish models of different reducing diameter structures and carry out simulation experiments.The simulation results show that the section velocity uniformity of the curvilinear reducing diameter structure is smaller than that of the linear reducing diameter structure.The influence of the change of fluid velocity on the uniformity of section velocity is small.Compared with several curvilinear reduced diameter structures,the section velocity uniformity of the reduced diameter structure with a contraction ratio of 9 is the minimum.At the same flow rate,when the contraction ratio is 4 and 9,the section velocity uniformity of the bicubic structure is the minimum.When the contraction ratio is 16,the section velocity uniformity of the quintic reducing diameter structure is the minimum.The cross-section velocity uniformity of the new structure is close to that of the quintic reducing diameter structure,which indicates that the new curve can be used as the contraction curve of the reducing diameter structure,which verifies the correctness of the design method of the contraction curve equation.(4)in order to verify the simulation results,a linear reducing diameter vortex flowmeter,a bicubic reducing diameter vortex flowmeter and a new curvilinear reducing diameter vortex flowmeter were made according to the reducing diameter structure model in the simulation experiment and calibration experiments were carried out.The results of calibration experiments show that the measurement error and repeatability of the linear reducing diameter vortex flowmeter are large,and the error and repeatability of the double cubic reducing diameter vortex flowmeter are minimal,and the error and repeatability of the new curvilinear reducing diameter vortex flowmeter are in the middle.It is shown that the curvilinear reducing diameter structure is conducive to improving the measurement accuracy of the reducing diameter vortex flowmeter,which also confirms the conclusion of the simulation experiment.The results of simulation and calibration show that the cross-section velocity uniformity is reasonable and feasible as a parameter to judge the degree of fluid turbulence,and the curve-reducing structure is beneficial to improve the measuring accuracy of the reducing diameter vortex flowmeter.The new curve meets the requirement as a contraction curve,which verifies the correctness of the new contraction curve equation.