amesim教程培訓(xùn)2013年8月2123用part2

1、Design of Hydraulic Systems and Components - Part 2LMS Imagine.Lab AMESim training HYD21 copyright LMS International - 2011Resistance to flow in hydraulic networks2 copyright LMS International - 2012Hydraulic ResistanceHR library proposes components for hydraulic networks modeling.It helps evaluatin

2、g pressure losses and flow distribution thanks to elements such as bends, expansion -contraction, T- junctions, bearing, 3 copyright LMS International - 2012Hydraulic Resistance Application examples Lubrication circuit Water supply Oil piping The HR resistance is used for liquid networks where the f

3、low velocity in the pipes and bends is quite high.This is the case when you have a system with a quite homogeneous cross sectional area. A water piping with a constant diameter of 1” for piping and accessories is keen to enable high flow velocities and well distributed pressure losses. In this case,

4、 the HR library is of great help. If you add a small restriction in the 1” piping, the flow velocity will be lowered in the rest of the piping. The pressure loss will be dominant at the restriction and can be disregarded in the pipes, bends and T-junctions.4 copyright LMS International - 2012Hydraul

5、ic Resistance Application examplesHow to design a liquid network?What is the function of your fluid network? e.g. fluid transport (oil and gas industry, water industry), fluid dosing (injection), fluid actuation (mobile hydraulics), fluid conditioning (pressure, temperature)Do you have ramifications

6、 and branches in parallel?Are the components mounted in series?Were do you rich the highest velocities.5 copyright LMS International - 2012Hydraulic Resistance Application examplesIf you have a T-junction with a given split of the flow rates, you can reduce the diameter of the piping after the T-jun

7、ction accordingly.The internal diameter of the branches are adjusted as a function of the nominal flow rate in the consumers connected to it (e.g. bath, shower, kitchen sink).6 copyright LMS International - 2012Hydraulic ResistancePipePressure dropelementsCentrifugalelementsCentrifugal PumpVolumetri

8、c PumpAnnular pipeGrooved bushingStatic PressuresensorElements of the library7 copyright LMS International - 2012Hydraulic ResistanceMain Use of the HR library To evaluate pressure drops and flow rates in a network consisting of a succession of pipes, restrictions, changes of direction (bends), sect

9、ion (sudden and progressive expansion-contraction), etc Steady-State analysis = pressure and flow rate maps of the circuit for an operating point Transient analysis to see the evolution of pressures and flow rates with an increase pump speed, for example8 copyright LMS International - 2012Hydraulic

10、ResistanceIn all the hydraulic libraries, the pressure information at ports are relative total pressure Hydraulic Resistance library: distinction made between static pressures and total pressures but most of the time pressures are expressed as total pressuresMain Assumptions of the HR library)U,Umax

11、(2zgU2pzgU2p222122pTot22211pTot211 9 copyright LMS International - 20122min22AQU Hydraulic ResistanceMain features of the HR library Full compatibility with the HYD library HR Library is mainly used for networks with:Low pressures (0 10 bar)High speeds ( 3-4 m/s)5 m/s 0.11 bar dynamic pressure Press

12、ure drops across various restriction geometries result from experimental studies conducted by I.E. Idelchik* *Handbook of Hydraulic Resistance 3rd edition I.E. Idelchik (Begell House)10 copyright LMS International - 2012Hydraulic ResistanceMain elements family of the HR library CausalityCPressure ba

13、rFlow rate l/minRCapacitive elementResistive elementPressure barFlow rate l/minPressure barFlow rate l/min11 copyright LMS International - 2012Hydraulic ResistanceMain elements family of the HR library CausalityHRL00 elements are often considered as Connecting elements They represent only a volume w

14、ithout any friction. Direct connectionConnection componentsHRL0012 copyright LMS International - 2012Hydraulic ResistanceRegular losses of the HR library Frictional drag categoryLaminar:Turbulent: 2min2hAQ2.Dp(Re)rr(Re,Harp of Nikuradse13 copyright LMS International - 2012Hydraulic ResistanceR eleme

15、nts of the HR library Local resistance categoryAMESim elementsReferences frictions factors tables in HR library manual 14 copyright LMS International - 20122locU2.pHydraulic ResistanceExample Venturi tubeCreate the following model thanks to the HR library :Use also static pressure sensors to compute

16、 the static pressure difference between neck and diffuser.15 copyright LMS International - 2012Venturi.ameHydraulic ResistanceExample Venturi tubeFrom 0 to 100 L/min in 10 sec 30mm 10 mm 10mm 40 mm3 barsTube length: 0.1 m16 copyright LMS International - 2012Venturi.ameHydraulic ResistanceExample Ven

17、turi tube17 copyright LMS International - 2012Static pressure recovery in the diffuserVenturi.ameReminder Orifices in AMESim18 copyright LMS International - 2012In HYD library, the flow rate is computed using the maximum flow coefficient Cq and the critical flow number.In HR library, the pressure dr

18、op is computed using the friction factor and the critical Reynolds number.P2ACQrestq2rest2AQ2PP2DhHYD libraryHR libraryBernoulli equationDarcy-WeibachequationFlow numberReynolds numberAQDRheFlow coefficientFriction factor Cqmax Cq crit Turbulent Laminar min Recrit Re Laminar Turbulent Reminder Orifi

19、ces in AMESim19 copyright LMS International - 20122qqC1 OR 1CReor CReqEquivalence between Cq and Equivalence between crit and RecritmincritcritcritmaxqcritReor CReAHydraulic cross-sectional area CqFlow coefficient DhHydraulic diameter QVolumetric flow rate ReReynolds number Flow number pPressure dro

20、p Friction factor Density of the fluid Kinematic viscosity of the fluid NotationIntroduction to the HCD libraryHydraulic Component Design library presentationWhy HCD library?21 copyright LMS International - 2012Consider this question : How many different types of hydraulic jack can you think of ? We

21、 have assumed here that the jack body is fixed. If we allow the body to move, we double the number of possibilities ! Why HCD library?Even if the standard hydraulic library includes a lot of classical components, some problems remain:Diversity of components:no matter how many componentsyou have, it

22、is never enough !Diversity of models usage:static, quasi-static or dynamic simulationDiversity of users skills:novice, advanced or expert user Diversity of data available:measured characteristics or technical drawing22 copyright LMS International - 2012Why HCD library?Consider the simple check valve

23、 of the AMESim hydraulic standard library:otherwisePcoefQPPifQcrack 0 This is a mathematical representation of the check valve function. This simple model does not allow to take into account the real geometry of the seat valve, the valve inertia, the fluid compressibilityA graphical programming lang

24、uage has been invented, dedicated to physical modeling: the HCD library.23 copyright LMS International - 2012The basic element philosophy24 copyright LMS International - 2012check valvepiston type 1piston type 2The basic element philosophy25 copyright LMS International - 2012Technical drawingHYD lib

25、rary for system modelingHCD library for component designThe basic element philosophy26 copyright LMS International - 2012The HCD concept enables the user to build the greatest number of hydraulic components from a very small number of submodels !Absolute motion and relative motion27 copyright LMS In

26、ternational - 2012Fixed sleeve (absolute motion)Moving sleeve (relative motion)Moving sleeveMoving pistonRelativemotionEquations: F2 = F3 P Apiston v3 = v2Q1 = - A v2Vol = - A x2A displaced flow rate and a displaced volume are computed, but no volume is taken into account inside the pistonThe HCD li

27、brary piston component28 copyright LMS International - 2012Mechanical portHydraulic portExternal variables:A piston does a power conversion : Hydraulic MechanicalThe HCD library volume component29 copyright LMS International - 2012A volume component has to be connected to the piston in order to take

28、 into account the displaced flow rate and displaced volumeof the pistonEquations: The volume component from the HYD library has no volume variable at its port. As a rule, always connect the HCD volume to a pistonportsVVQBdtdP0portsVVVol0Volume variableHydraulic variablesExternal variables:A valve do

29、es a power conversion : Hydraulic MechanicalIt includes also a flow through a specific geometryEquations: F3 = F4 P2 Apiston v4 = v3Vol2 = - A x3The flow area is computed with geometrical equations, in function of the spool displacement xThe HCD library valve components30 copyright LMS International

30、 - 2012Mechanical portHydraulic portExternal variables :32. 2).(.vAPxSCQqThe HCD library valve components31 copyright LMS International - 2012The Bold area with the arrows indicates :-Where the pressure is applied-The port(s) where the displaced volume and displaced flow rate are computedPressure at

31、 port 2 is taken into account for the force computationPiston motion genders displaced volume and displaced flow rate at port 2 Pressure at port1 and port2 are taken into account for the force computationPiston motion genders displaced volume and displaced flow rate at port1 and port2 MMoving mass:X

32、” = f(mass, damping, end stops)Conical poppet with flat seat:A = f(valve lift)F = f(P)Piston & spring:Q = f(velocity)F = f(P, K, lift)Line: ideal or dynamical model?Volume:P = f(Bulk, Vol, Q, fluid props) 0Underlap 0In order to make the valve work, the underlap parameters of the 2 hole section v

33、alves need to be set properlyThe underlap is the opening of the spool valve compared to the sleeve :The underlap parameter has to be set at a reference position85 copyright LMS International - 2012The displacement x of the spool valve is imposed by a connected mass or any displacement source The und

34、erlap parameter of the valve is defined at the reference zero position (x = 0 m)Designing a 3 way spool valve with HCDUnderlap(x=0) = mmxx0 = -0.2 mmx0 = +0.2 mmx0 = mmxxxUnderlap(x=0) = mmUnderlap(x=0)= mmExample 1Example 2Example 386 copyright LMS International - 2012Designing a 3 way spool valve

35、with HCDThe stroke of the valve is 1.5 mm One solution to make the valve working properly is to configure the underlaps of the 2 holes as follows :Underlap(x=0) = -0.75 mmUnderlap(x=0) = 0.75 mm The spool valve works properly :87 copyright LMS International - 2012Designing a 3 way spool valve with H

36、CDTry to tune the underlaps of the 2 holes to get this result:88 copyright LMS International - 2012Flow forces for HCD valves Geometrical data Restriction characteristic Opening (underlap) definition Flow leakage when fully closed and flow restriction when fully open Flow forces Dead volumesParamete

37、rs of an HCD valve :89 copyright LMS International - 2012 Physical interpretationThe static pressure field on the left is uniform whereas the one on the right is affected by the conversion of the potential energy (static pressure) into kinetic energy. A net force is produced in a direction that alwa

38、ys closes the valve. For 1D simulation, this phenomenon is modeled using a virtual force called the jet force or flow force.Flow forces for HCD valvesCFD resultsinputsleeveoutputspoolipressure field90 copyright LMS International - 2012Flow forces for HCD valvesWhen the valve is opened, a fluid flow is established. This flow generates a force called jet force. This force is an aspect of the momentum conservation.The jet fo