Reducing Valve with Pressure-Dependent Area - MapleSim Help
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Reducing Valve with Pressure-Dependent Area

Reducing valve with opening area computed from table of pressure vs. area

 

Description

Equations

Variables

Connections

Parameters

Description

The Reducing Valve with Pressure-Dependent Area (or Reducing Valve Pressure Dependent Area) component models the flow through an orifice where the relationship between the area of the orifice and the pressure difference between port A and port B is supplied in the form of a table. Based on the orifice area, the pressure vs flow rate relationships are derived by the formulation used in the Orifice component.

Pressure vs Area

For this component, the orifice area must be specified as a function of the pressure difference in the form of a table. The following parameters allows users to specify the necessary data for this calculation.

Data Source: This parameter allows users to specify the nature of the source file for the Pressure vs. Area table. The available options are file, attachment, and inline.

file: Use this option to specify a source file (an Excel or a CSV file) located on the hard drive. Use the AdP parameter to browse to and/or select the data file. The data file will not be attached to the MapleSim model.

attachment: Use this option to specify a data file (an Excel or a CSV file) that is attached to the MapleSim model. To be used as an attachment, data files must be attached to the MapleSim model and be categorized under Data Sets. The attached files in a MapleSim model can be viewed in the Attachments pane under the Data Sets section. For more information, see Attaching a File to a Model. If the required file is not already attached to the MapleSim model, use the AdP parameter to attach a new file.

Note:

If the file option is used, subsequent changes to the source file will be incorporated into MapleSim simulations

If the attachment option is used, subsequent changes to the source file will not affect the version attached to the MapleSim model. To ensure updates to the source files are incorporated in the simulation, the file must be reattached.

The Data Generation App can be used to generate table data from mathematical functions using Maple code. For more information about MapleSim apps, see Opening MapleSim Apps and Templates.

inline: Use this option to directly specify the pressure vs. area relationship in the form of a table. In the AdP parameter, enter an m×2  matrix. The first column must contain values of pressure difference and the second column must contain corresponding values of the area.

Note: To change the dimensions of table, right-click (Control-click for Mac®) the parameter field and select Edit Matrix Dimensions. In the Matrix Dimensions dialog, enter values for the number or rows and columns and then click OK.

Skip rows: This option allows users to specify the number of top rows to be ignored during the calculations. This option can be useful when the Excel file contains header information.

Smooth: The smooth option specifies how the data table is interpolated.

Pressure difference unit: This option specifies the unit of pressure used in the supplied data.

Area unit: This option specifies the unit of area used in the supplied data.

Formulation Approaches

One of two approaches can be selected for modeling the flow in the device. When the boolean parameter Use constant Cd is true, a constant coefficient of discharge (Cd) is used, otherwise a variable coefficient of discharge with maximum value (Cdmax) and a critical flow number (Critno) are used.

Optional Volumes

The boolean parameters Use volume A and Use volume B, when true, add optional volumes VA  and VB to ports A and B, respectively. See Port Volumes for details.

If two orifices or valves are connected, enabling a volume at the common port reduces the stiffness of the system and improves the solvability.

Equations

p=pApB

Orifice Fluid Equations

{p=π4ρνqCd2AcsπAcs16q4π2Acs2ν4+ReCr414Use constant Cd=trueq=Cdmaxtanh4Acsπ2pρνCritnoAcs2pρsignpotherwise

Ai=MapleSim.Interpolate1Dtable,ppunit,2,smoothness,skipRows

Acs=maxAiAunit,Amin

Optional Volume Equations

VfA={Va1+pAElUse volume A=true0otherwiseVfB={Vb1+pBElUse volume B=true0otherwise

q=qAqVA=qBqVB

qVA={dVfAdtUse volume A=true0otherwiseqVB={dVfBdtUse volume B=true0otherwise

Variables

Name

Units

Description

Modelica ID

p

Pa

Pressure drop from A to B

p

pX

Pa

Pressure at port X

pX

q

m3s

Flow rate from A to B

q

qX

m3s

Flow into port X

qX

Ai

m2

Interpolated area

Ai

qVX

m3s

Flow rate into port X's optional volume

qVX

VfX

m3

Effective volume at port X

VfX

Connections

Name

Description

Modelica ID

portA

Upstream hydraulic port

portA

portB

Downstream hydraulic port

portB

Parameters

Area vs. Pressure

Name

Default

Units

Description

Modelica ID

Data source

inline

 

Data source

datasourcemode

AdP

100.,0.001

 

Data set

table

Skip rows

0

 

Number of rows to skip

skipRows

Smooth

linear

 

Smoothness of table interpolation

smoothness

Pressure difference unit (punit)

kPa

 

Unit of pressure used in the data

pressUnit

Area unit (Aunit)

cm2

 

Unit of area used in the data

areaUnit

Orifice

Name

Default

Units

Description

Modelica ID

Use constant Cd

true

 

True (checked) means a constant coefficient of discharge is implemented, otherwise a variable Cd is used in flow calculations

UseConstantCd

Cd

0.7

 

Flow-discharge coefficient; used when Use constant Cd is true

Cd

ReCr

12

 

Reynolds number at critical flow; used when Use constant Cd is true

ReCr

Cdmax

0.7

 

Maximum flow-discharge coefficient; used when Use constant Cd is false

Cd_max

Critno

1000

 

Critical flow number; used when Use constant Cd is false

Crit_no

Optional Volumes

Name

Default

Units

Description

Modelica ID

Use volume A

false

 

True (checked) means a hydraulic volume chamber is added to portA

useVolumeA

VA

1·10−6

m3

Volume of chamber A

Va

Use volume B

false

 

True (checked) means a hydraulic volume chamber is added to portB

useVolumeB

VB

1·10−6

m3

Volume of chamber B

Vb

For more information see Port Volumes.

Fluid Parameters

The following parameters, used in the equations, are properties of the Hydraulic Fluid component used in the model.

Name

Units

Description

Modelica ID

ν

m2s

Kinematic viscosity of fluid

nu

ρ

kgm3

Density of fluid

rho

El

Pa

Bulk modulus of fluid

El

See Also

Hydraulics Library

Valves