Research On Influencing Factors Of The Cylindrical Gear Flowmeter Measuring Accuracy

Cylindrical gear flowmeter belongs to the positive displacement flowmeter(PDF)is one of the flow measuring devices that are most widely-used.It is widely used in departments of the defense industry such as aerospace,aviation,weapon system and various industries of civil field such as chemical industry,food service industry and pharmacy.With the progress of society and metrology,the application of flow measurement is more and more widely,at the same time flow measurement which is convenient,fast with higher accuracy become people's yearning today.Measuring accuracy,as one of the main performance parameters in flowmeter,is affected by various factors and there is also a very complicated interaction between these various factors,is one of the key and difficult points in flowmeter metering characteristics research.Previous research method of cylindrical gear flowmeter error characteristics is unitary,usually through theoretical calculation and experimental testing method,but there are always some disadvantages and limitations with two research methods.On the one hand,method of the theoretical calculation needs to simplify the model of real problem,therefore the result would have deviation with the actual situation,on the other hand,though experiment and testing are extremely close with the actual working condition,but once the test conditions such as the measured medium changed,it would requires a lot of manpower and material resources.So this dissertation chose to use CFD numerical simulation method to research the effects of factors such as mechanical structure,fluid properties and flow pulsation on the measuring accuracy.In the field of hydraulic,cylinder gear flowmeter is mainly used in the measure-ment of hydraulic oil in aircraft and weapons equipment hydraulic system,lubricating oil measurement of the lubrication system and hydraulic servo system which requires for obtaining flow signal with high precision and so on.In view of the importance of its usage,this dissertation mainly did the following related work:1.This paper concluded the development of flow metering discipline and research situation of flow measuring elements domestic and abroad,introduced the research status and development trend of the field,on the basis of these the research purpose and significance of this article are put forward and research content of the master's thesis is also determined.2.Through the related theory of fluid mechanics,the effects of internal axial gap and radial gap size on the internal leakage and measuring accuracy of flowmeter was analyzed.Optimum clearance and module of gear that can satisfy the requirements of high precision and low abrasion is also obtained by theoretical calculation.3.Reference the concept of simulation imitate experiment,the effects of the oil viscosity changes on the meter measuring accuracy was researched.Mainly analyzed the effects of leakage in axial and radial clearance on the measuring accuracy under different oil viscosity,measurement precision and the small differences between them of VC0.2 type cylindrical gear flowmeter under different working conditions was obtained.Provided reference for determination of actual instrument coefficient.4.Flow pulsation situation and effects of flow pulsation on the measuring accuracy was analyzed through the method that combined theoretical calculation and flow field simulation eventually.Concluded that flow pulsation of the cylindrical gear is almost has no effect on measuring accuracy.Flow pulsation can be considered as a secondary cause of measuring accuracy in subsequent research.