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MapleSim Hydraulics Library from Modelon

DCV_3_2_PAT  Directional Control Valve with first-order spool dynamics, a spool with 3 ports, and 2 stable positions; when in the not activated position, ports P and A are connected and port T is closed

The DCV_3_2_PAT component describes a directional control valve with first-order spool dynamics, a spool with 3 ports, and 2 stable positions. When in the not activated position, ports P and A are connected and port T is closed.

The laminar/turbulent flow through the valve is modeled as flow through orifices without cavitation. The commanded opening of the valve is input at commandB.

The parameter qnom gives the nominal flow rate of the fully opened flow path at the pressure drop Δpnom.

Amax=qnom12ρk2Δpnom

dmax=2Amaxπ

For example, the maximum diameter for the flow path from P to T is given by dmaxPB:

AmaxPT=qnomPT12ρk2Δpnom

dmaxPT=2AmaxPBπ

There is leakage flow modeled when the respective flow path is nominally closed. The position of the spool is modeled as a first-order system.

Input signal: commandB.

Command signals

Flow paths and diameter of metering orifice

commandB=false

Flow from P  A. T is closed. Flow diameter from P  T: dleak. Flow diameter from P  A: dmax_P_A+dleak.

commandB=true

Flow from P  T. A is closed. Flow diameter from P  T: dmax_P_T+dleak. Flow diameter from P  A: dleak.

When the pump pressure and the flow rate are high, the unbalanced forces and flow forces acting on the spool are higher than the force generated by the solenoid and the valve is partially closed. The effect can be modeled by the parameters P_max and coeff_P. Specify the maximum hydraulic power in W (where the valve is still completely open) and use coeff_P to adjust the model to the manufacturer's data. When the specified hydraulic power is exceeded, a warning is printed in the log window (Mode Simulation / Simulation / Show Log).

The movement of the spool is described by a first-order system. This is appropriate for valves that are directly actuated by a spool. The time to shift from the neutral position to an end position (τopening) may be different than the time to shift to the neutral position (τclosing).

Use the modifier(s)

VolumeA(port_A(p(start=1e5,fixed=true)))

and/or

VolumeB(port_A(p(start=1e5,fixed=true)))

and/or

VolumeP(port_A(p(start=1e5,fixed=true)))

to set the initial condition(s) for the pressure of the lumped volume(s) Pa.

Note: There are also valves that close all three ports in the intermediate position.

Events

There is a new boolean reduceEvents (selected by default) in the Advanced section under the Inspector tab. Selecting reduceEvents lets the model use noEvents(expr) to generate fewer events for boolean expressions that should not generate events. In some cases the solver might reduce the stepsize too much and generate a lot of steps. If this happens, try clearing reduceEvents.

Connections

Name

Description

Modelica ID

portA

Port A, one of valve connections to actuator or motor

port_A

portP

Port P, where oil enters the component from the pump

port_P

portT

Port T, where oil flows to the tank

port_T

commandB

Command signal for valve

commandB

oil

 

oil

Parameters

General Parameters

Name

Default

Units

Description

Modelica ID

use volume A

true

 

If true, a volume is present at port_A

useVolumeA

use volume B

true

 

If true, a volume is present at port_B

useVolumeB

use volume P

true

 

If true, a volume is present at port_P

useVolumeP

use volume T

true

 

If true, a volume is present at port_T

useVolumeT

VA

10-6

m3

Geometric volume at port A

volumeA

VB

10-6

m3

Geometric volume at port B

volumeB

VP

10-6

m3

Geometric volume at port P

volumeP

VT

10-6

m3

Geometric volume at port T

volumeT

ΔTsystem

0

K

Temperature offset from system temperature

dT_system

Advanced Parameters

Name

Default

Units

Description

Modelica ID

reduce events

true

 

If true, reduce event generation

reduceEvents

Dynamic Parameters

Name

Default

Units

Description

Modelica ID

τopening

0.03

s

Switching time to open valve 95 %

tau_opening

τclosing

0.02

s

Switching time to close valve 95 %

tau_closing

Flow Parameters

Name

Default

Units

Description

Modelica ID

Δpnom

7.·105

Pa

Pressure drop at nominal flow rate qnom

dpnom

qnomPA

0.00158

m3s

Nominal flow rate from P -> A

qnom_P_A

qnomAT

qnomPA

m3s

Nominal flow rate from A -> T

qnom_A_T

Pmax

1.26·105

W

Max. hydraulic power

P_max

coeffP

10

 

Influence of hydraulic power on flow rate

coeff_P

k1

10

 

Laminar part of orifice model

k1

k2

2

 

Turbulent part of orifice model, k2=1Cd2

k2

Spool Geometry Parameters

Name

Default

Units

Description

Modelica ID

dleak

1.67·10-5

m

Diameter of equivalent orifice to model leakage of closed valve

dleak

See Also

DirectionalControl, MapleSim Hydraulics Library from Modelon Overview


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