轴向柱塞泵英文文献及翻译.docx

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1、精品文档，仅供学习与交流，如有侵权请联系网站删除Modeling and Simulation on Axial Piston Pump Based on Virtual Prototype TechnologyAbstract: A particular emphasis is placed on the virtual prototype technology (VPT) of axial piston pump. With this technology it is convenient and flexible to build a complicated 3D virtual bas

2、ed on real physical model. The actual kinematics pairs of the parts were added on the model. The fluid characters were calculated by hydraulic software. The shape of the parts, the flexible body of parts, etc. were improved in this prototype. So the virtual prototype of piston pump can work in compu

3、ter like a real piston pump, and the flow ripple, pressure pulsation, motion principle, stress of parts, etc. can be investigated. The development of the VPT is introduced at the beginning, and the modeling process of the virtual prototype is explained. Then a special emphasis is laid on the relatio

4、nship between the dynamics model and the hydraulic model, and the simulations on the flow ripple, pressure pulsation, motion principle, the stress and strain distribution of the middle shaft and piston are operated. Finally, the advantages and disadvantages of the VPT are discussed. The improved vir

5、tual prototype of piston pump more tally with the real situation and the VPT has a great potential in simulation on hydraulic components.Key words: virtual prototype, axial piston pump, dynamics【精品文档】第 12 页1 IntroductionAxial piston hydrostatic pump is an important hydraulic component, which is wide

6、ly applied both in industry and mobile machine. As the piston pump has complicated structure and composite high-speed motion, so it is difficult to do exactly research on the pump. The pump model is always simplified to a great degree. And the simplifications bring considerable deviation. With the d

7、evelopment of computer and multi-body dynamics, the virtual prototype technology (VPT) is used for studying hydraulic system and components. Virtual prototype technology is a new engineering technology. With the VPT complex mechanism system model can be made and its dynamics characteristic can be si

8、mulated at a very real condition by integrating modeling tools from several different fields and simulation methods. The core of VPT is the dynamics model, which have several interfaces to connect other models, such as hydraulic model and fitness element method (FEM) model. So the virtual prototype

9、built based on VPT can simulate most of the pump performances, and the simulation results of the virtual prototype are very close to the test results of the physics prototype. Sometimes the simulation can even replace physics test and save the development cost1. Hydraulic virtual prototype technolog

10、y integrate the advanced 3D CAD modeling method and hydraulic simulation technology to predict performance and study characteristics of a machine1. Because of the complicated structure and nonlinear characteristics of the hydraulic-solid coupling, it is time-consuming and expensive with traditional

11、try-and-error design way, and the analysis results of traditional way are not accurate enough2. The virtual prototype of hydraulic machine, such as the axial piston pump, is a better way to predict the performance of hydraulic component3. With the commercial hydraulic and dynamic softwares, a virtua

12、l prototype of piston pump was made by Aachen Technique University, Germany, in 20024. The hydraulic characteristics and frictions between the key tribo-pairs were analyzed56. In order to optimize the incline angle of the swash plate, a virtual prototype of a bent axis piston pump was made in 20037.

13、 The concept of virtual prototype of piston pump was proposed in 2004, the output pressure and flow ripple, the strain and stress of the key parts were all analyzed8. It is very useful for the optimization of pump. The flow ripple of a swash plate piston pump was studied using VPT in 20069. All thes

14、e researches proved the effectivity of this technology, but these models are still simple and need further improving.In this research, a virtual prototype of axial piston pump is developed, which combines 3D model, flexible FEM model and hydraulic modeling together. The performance of the pump is an

15、alyzed, and the optimization of the index angle of swash plate by VPT shows the potential of improving products.2 Modeling of the Piston PumpThe validity of the simulation results lay on the rationality of its model, so the modeling of piston pump is crucial. The virtual prototype of piston pump con

16、nects several different models, including hydraulic system, 3D structural model and FEM parts model, which are built respectively and connected each other in simulation.2.1 Analysis of dynamic relationshipsBefore building the dynamic model and making the interfaces to connect other models, the real

17、kinetic relationships and motion parameters of the necessary parts should be analyzed. There are several hypotheses as follows.(1) In order to simply the simulation, only necessary parts are considered. Some accessories models, such as mechanism of variable displacement and slipper hold-down, are ig

18、nored.(2) The rotation of middle shaft is stable and the speed is defined as constant.(3) The angle of swash plate changes in a defined work range by rotation drive.(4) The oil film between piston and cylinder, swash plate and slipper, cylinder and valve plate is stable, and its friction coefficient

19、 is constant.As shown in Fig. 1, the middle shaft of swash plate type piston pump rotates around its axis and drives the cylinder, pistons and correspond slippers rotating at a same speed1011.The coordinates of point B of intersection between the center line of piston and the surface of swash plate

20、is described as follows: (1)From Eq. (1), it is shown that piston moves along z-axis and rotates around the middle shaft. The track of point B can describe the motion of the piston. Based on Eq. (1), the speed and accelerate of point B are as follows: (2)The slipper is connected with piston by spher

21、ical joint. The track of point B in the spherical joint can describe the motion of slipper. The coordinates of the point B are (3)The motion track of the slipper is ellipse, the vector diameter is (4)The angle between and the Lang-axis of ellipse is (5)The rotation speed of the point B around the po

22、int O is (6)The velocity of the point B is (7)Based on the equations above, the motion of basic parts can be defined.2.2 Structural and dynamic modelAs for swash plate type piston pump, showed in Fig. 2(a), the 3D structural model (Fig. 2(b) was made in a comerical CAD software. To simplify the anal

23、ysis, only necessary parts model were made. The joints and constraints between connecting parts were added. According to the real dynamic relationship between different parts, the proper joints and motion parameters are shown in Table 1 and Table 2. In the dynamic software, all these joints and moti

24、ons were added to corresponding parts. Then the basic dynamic model was finishied with a 3D structural model adding dynamic relationships.Besides, the ration speed of the middle shaft should be added, then the basic model of piston pump can be drove and all parts can move just like a real pump witho

25、ut oil.2.3 Hydraulic model of piston pumpAs there is no fluid force and motion in the basic dynamic model, so the dynamic model can only simulate the motion of piston pump and dont have the function of sucking oil and charging oil to drive load. In order to build the hydraulic model, there are some

26、hypotheses as follows, (1) The piston pump works stably and the rotation speed of middle shaft is defined constant.(2) The oil film in the gap between piston and cylinder, slipper and swash plate, cylinder and valve plate is stable. And there is only leakage of laminar flow.(3) There is hydrostatic

27、balance in the gap between cylinder and valve plate, slipper and swash plate, and the pressure ratio is constant (=0.9).(4) The viscidity of the fluid oil is invariable.Based on the motion relationship between the pump parts and the flow influence on the pump, the hydraulic model of the piston pump

28、starts with the basic flow model.As shown in Fig. 3, the low pressure oil is sucked to the cylinder bore when the piston moves to the right. While the piston moves to the left, the piston charges the oil out to drive loads.The model shown in Fig. 3 is the basic unit of one piston. And this unit incl

29、uding three important leakages, qv1 between piston and cylinder, qv2 between slipper and swash plate and qv3 between cylinder and valve plate, which are described in Eqs. (8)(10)11:, (8), (9), (10)where dr Diameter of piston,hr1Gap height between piston and cylinder,lr Contact length between cylinde

30、r and piston, Dynamic viscidity of the fluid, Eccentricity ratio of piston,p1 Pressure inside piston chamber,p0 Environment pressure inside pump, Pressure ratio,hr2Gap height between the swash plate and slipper,r1, r2 Structural parameters of slipper,hr3Gap height between valve plate and cylinder,1,

31、 2, R1,R2, R3, R4 Structural parameters of valve plate.The input oil and output oil in the cylinder bore are supplied through the valve plate, so the open area of the kidney bore in valve plate is used for controlling oil sucking and charging. Fig. 4(a) shows the open area coefficient curves with ch

32、anging of rotation angle. Because the angle difference of the two different bore is 180 (Fig. 4(b), so it can be modeled with a throttle valve controlled by the open area size. The distributed flow is controlled by the cylinder bore open area size, which is shown in Fig.4(b).Fig. 4. Model of valve p

33、lateTo simplify the modeling, the flow model and the valve plate model were combined to an integrated unit (Fig. 5). As one pump has nine pistons, so the whole pump model includes nine integrated piston models, which is shown in Fig. 6.Fig. 5. Encapsulation of the flow model and valve plate modelFig

34、. 6. The whole hydraulic model of the pump2.4 Finite element method of the key partsThe stress and deformation of some key parts in pump working process should be researched by flexible body analysis8. The middle shaft and the piston are two typical parts needed to consider the flexibility character

35、. It is necessary to analyze the model with FEM and to convert the rigid body to flexible one. In an FEM software environment, the flexible body of piston can be read to the dynamic model and be assembled to the whole pump model. Fig. 7 shows the finite element model of the piston with flexible char

36、acteristics. The middle shaft model was also made in the same way. Fig. 8 shows the two flexible parts in the assemble pump. Then the solver can simulate the pump and get the stress results and deformation results of the piston and the shaft. The intensity of corresponding parts is analyzed in this

37、way. Fig. 7. Flexible body model of the pistonFig. 8. Assemble pump with flexible bodyof piston and middle shaftAccording to the above analysis, the virtual prototype of piston pump includes several different models. So interfaces are needed to connect these models into one unit. Thereby, the hydrau

38、lic interface, the dynamic interface and flexible body interface are built according to the working environment. Fig. 9 shows the relationship of these models. The virtual prototype of piston pump are built by assembling all these models together.Fig. 9. Models relationship of pump virtual prototype

39、3 Results and DiscussionMany aspects of the piston pump can be investigated based on the pump virtual prototype, such as the output characters, the force of pistons, the stress and deformation of the pistons and the middle shaft, etc.3.1 Output characters of pumpThe output flow and pressure of pump

40、are used directly for driving loads in the hydraulic system. So the output character is one of the most important performances of the pump. With the virtual prototype of piston pump, it is easily to get the output characters. Fig. 10 shows the output flow changing with angle of the swash plate. The

41、flow ripple is clearly shown in the result curves. The cycle time of flow ripple is the same based on the rotation speed. The flow ripple amplitude is getting higher with the swash plate angle increasing. Besides, the flow condition in each piston chamber can also be presented with the simulation.Fi

42、g. 10. Output flow with angle of swash plateAs there are gaps between the two kidney bores in the valve plate, the output flow is discontinues. So the pressure ripple and corresponding noise are produced during fluid distribution process. One new structured valve plate with no-symmetrical kidney bor

43、es is developed 12. This valve plate has a difference angle (index angel) between the two kidney bores. With this structure, the pressure ripple of the pump can be reduced obviously, shown in Fig. 11. Fig. 11 presents the comparison of pressure condition inside piston chamber between valve plates wi

44、th difference angle and without difference angel.Fig. 11. Output pressure of the pump3.2 Force on the pistonsIn the piston pump, the pistons are used for sucking and charging oil. So the fluid force on the pistons is variable and complex. With the virtual prototype of piston pump, the force on the b

45、ackside of the pistons can be investigated. With different angle of swash plate (including 0, 2.5, 5, 7.5, 10, 12.5, 15) at the same load condition, the force on each of the nine pistons is different and the force presents a periodic change with time, shown in Fig. 12. The vibration amplitude of for

46、ce is getting higher with the swash plate angle increasing.In order to analyze the influence of the swash plate angle, the fluid force was simulated with the angle changing continuously. The curve in Fig. 13 shows the trend of the force. It starts with a very small value, and the value of the force

47、rises quickly while the angle of swash plate reaches 5. Fig. 12. Fluid force on the pistons Fig. 13. Pressure with the angle of swashplate changing3.3 Stress and deformation of the pistons and middle shaftWith the FEM technology, the middle shaft and pistons model are improved from rigid body to fle

48、xible body, which is more tally with the actual situation. In dynamic environment, the stress and strain of the flexible body can be simulated when the virtual prototype is running. And the intensity of the flexible body parts can be investigated.The stress and strain can describe the intensity and

49、deformation to a degree. Fig. 14 shows the stress and strain when the simulation time is at 0.135 s. The maximum stress at this state is about 196 MPa and the maximum strain is about 0.002 mm. The most serious deformation region appears nearby the spline.(a) Stress of the middle shaft at 0.135 s (MPa)(b) Stra