| As a common part in hydraulic systems,gear pumps have the advantages of simple structure,low price,low work requirement and wide application,etc.However,for so long,gear pumps have been faced with some problems induced by the cumbersome design of gear pumps,for example,the working accuracy of gear pumps is not high and the design efficiency is low.With the continuous development and progress of modern technology,this situation has also been greatly improved.Because the gear pump is a common power element used in hydraulic transmission systems,so it has attracted a large number of scholars at home and abroad to study.At present,domestic and foreign scholars mainly focus on the following aspects for the research of gear pumps:(1)Optimization of gear parameters and pump structure design;(2)Research on the flow quality of gear pumps;and(3)Research on variable methods of gear pumps.On the basis of the existing studies of gear pumps,this paper simulates and analyzes the internal flow field of a non-circular gear pump from the perspective of simulation.The non-circular gear pump is also a volumetric pump like a common gear pump.The change of radial dimension of non-circular gear is continuous.Depending on the change of radial dimension and the continuous transmission of gears,the change of cubage between pump body and gears can be realized.The main works accomplished in this paper are divided into the following aspects:1.In the first chapter,the introduction part focused on the research status of gear pumps at home and abroad,thus leading to the issues of non-circular gear pump to be studied.2.On the basis of the meshing transmission theories of non-circular gear,the type of pitch line of non-circular gear was studied.The transmission ratio function and the conditions of achieving continuous one-way rotation for non-circular gears were analyzed.The pitch line parameters of the driving and driven wheels and the oval gears were determined,which provides the basis for the subsequent modeling of tooth profile used by the numerical modeling software SolidWorks.3.The expression and transmission ratio of pitch line of driving wheel in oval gear pair were introduced,and the analysis process of structural parameters was given.At the same time,several solving techniques applied in the corresponding numerical simulation analysis were introduced,including dynamic grid technology,RNG κ-ε model,SIMPLE algorithm and so on.The reasonable selection of this part helped to obtain more accurate numerical simulation results,which is helpful for the analysis and discussion of follow-up results.4.By establishing three-dimensional fluid models of a single pair of oval gear pump and a parallel oval gear pump,the numerical simulation method of flow field based on dynamic meshes is used to simulate the instantaneous variation of fluid pressure and flow for the single pair of oval gear pump.The overall flow line and outlet flow rate of the parallel oval gear pump were also analyzed.The main conclusions in the present study were as follows:(1)The fluid velocity and pressure distribution in cavity are obtained,and the dynamic variation of differential pressure at the meshed position of gears can be extracted.(2)The velocity curve of the outlet flow is in accordance with the theoretical value.The pressure difference at the gear mesh has similar periodic fluctuations.The peak value appears at the time when the long shaft tooth of the driving wheel meshes with the short shaft tooth of the driven wheel.The period is half of a turn of the drive wheel.(3)The use of parallel ovoid gear pump can reduce the flow pulsation.Compared with the single oval gear pump,the new non-circular gear pump can improve the working efficiency and reduce the flow pulsation of 56%.The optimization effect is significant. |
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