Research On Measurement Accuracy And Flow Measurement Method Of Helical Gear Flowmeter

Gear flowmeter is widely used in many fields such as metallu rgy,pharmacy,industry and so on because of its simple structure,high linearity and wide measuring range.However,the flow pulsation of spur gear flowmeter is large,and the periodic pressure impact,vibration and noise caused by oil trapping will have a certain impact on the measurement accuracy of the instrument,which limits its application in servo and proportional systems with high accuracy,high response and high stability.The helical gear flowmeter not only improves the meshing coefficient,but a lso improves the meshing stability because of the helical angle.Therefore,helical gear flowmeter not only has the most advantages of spur gear flowmeter,but also has the advantages that spur gear flowmeter does not have,such as stable operation,high c oincidence,high allowable circumferential velocity,low flow fluctuation and low energy loss when liquid passes through.In order to improve the measurement accuracy of helical gear flowmeter,on the one hand,the influence of mechanical structure paramet ers of helical gear flowmeter on its measurement accuracy is studied;on the other hand,the by-pass flow measurement method is studied and analyzed to indirectly improve its measurement accuracy.To this end,the following work has been carried out:1.This thesis briefly introduces the gear flowmeter,elaborates the research background and significance of the subject,introduces the development trend of the flowmeter and the research status at home and abroad,and on this basis,emphatically describes the main work content and innovation points of the subject.2.Study the internal leakage problem affecting the measurement accuracy of helical gear flowmeter,the radial gap leakage model,the end gap leakage model and the total leakage model considering the meshi ng gap leakage of helical gear flowmeter are established by referring to the basic theory of hydrodynamics and combining with the working conditions of helical gear flowmeter.The optimum theoretical reference gap range is obtained by means of theoretical calculation and numerical simulation which can provide reference for the design of gap of helical gear flowmeter in the future.3.Study the flow fluctuation of helical gear flowmeter,the formulas for calculating the critical helical angle and critical tooth width of helical gear,which can eliminate oil trapping and reduce the flow fluctuation,are deduced through formulas,which provide theoretical basis for the design of the three-dimensional geometric model of this subject.4.Referring to the main measuring parameters of VC series gear flowmeters,four kinds of helical gear flowmeters with equal single tooth geometric volume,but with different helical angles are established.The relationship between helical angle,modulus and measuring accuracy of helical gear flowmeters is studied by theoretical calculation,CFD flow field simulation and numerical simulation,which can provide reference for the selection of structural parameters of helical gear flowmeters in the future.The energy loss of spur gear flowmeter and helical gear flowmeter in instantaneous flow measurement is studied and analyzed.5.Beginning with the research and optimization of the measurement method of helical gear flowmeter,and studies a method of indirect measurement of flow by by-pass,which makes full use of the advantages of helical gear flowmeter and improves its measurement accuracy indirectly.