Reducing Valve with Pressure-Dependent Flow

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Reducing Valve with Pressure-Dependent Flow

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

Description

The Reducing Valve with Pressure-Dependent Flow (or Reducing Valve Pressure Dependent Flow) component models the flow through an orifice where the relationship between the flow-rate and the pressure difference between port A and port B is supplied in the form of a table.

Pressure vs Flow Rate

For this component, the flow rate 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. flow rate 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 $q (dP)$ 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 $q (dP)$ 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 Using MapleSim Apps.

inline: Use this option to directly specify the pressure vs. area relationship in the form of a table. In the $q (dP)$ parameter, enter an $m \times 2$ 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.

Flow unit: This option specifies the unit of flow rate 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 ( $C_{d}$ ) is used, otherwise a variable coefficient of discharge with maximum value ( $C_{d (\max)}$ ) and a critical flow number ( ${Crit}_{no}$ ) are used.

	Optional Volumes
	The boolean parameters Use volume A and Use volume B, when true, add optional volumes $V_{A}$ and $V_{B}$ 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

$p = p_{A} - p_{B}$

$Orifice Fluid Equations$

${\begin{array}{c} p = \frac{π}{4} \frac{ρ ν q}{C_{d}^{2} A_{cs} \sqrt{π A_{cs}}} {(\frac{16 q^{4}}{π^{2} A_{cs}^{2} ν^{4}} + {Re}_{Cr}^{4})}^{\frac{1}{4}} & Use constant Cd = true \\ q = C_{d (\max)} \tanh (4 \frac{\sqrt{\frac{A_{cs}}{π} \frac{2 |p|}{ρ}}}{ν {Crit}_{no}}) A_{cs} \sqrt{\frac{2 |p|}{ρ}} sign (p) & otherwise \end{array}$

$q = \frac{1}{{flow}_{unit}} MapleSim.Interpolate1D (table, p \cdot p_{unit}, 2, smoothness, skipRows)$

$Optional Volume Equations$

$V_{f_{A}} = {\begin{array}{c} Va (1 + \frac{p_{A}}{El}) & Use volume A = true \\ 0 & otherwise \end{array} V_{f_{B}} = {\begin{array}{c} Vb (1 + \frac{p_{B}}{El}) & Use volume B = true \\ 0 & otherwise \end{array}$

$q = q_{A} - q_{V_{A}} = - (q_{B} - q_{V_{B}})$

$q_{V_{A}} = {\begin{array}{c} \frac{d V_{f_{A}}}{d t} & Use volume A = true \\ 0 & otherwise \end{array} q_{V_{B}} = {\begin{array}{c} \frac{d V_{f_{B}}}{d t} & Use volume B = true \\ 0 & otherwise \end{array}$

Variables

Name	Units	Description	Modelica ID
$p$	$Pa$	Pressure drop from A to B	p
$p_{X}$	$Pa$	Pressure at port X	pX
$q$	$\frac{m^{3}}{s}$	Flow rate from A to B	q
$q_{X}$	$\frac{m^{3}}{s}$	Flow into port X	qX
$A_{i}$	$m^{2}$	Interpolated area	Ai
$q_{V_{X}}$	$\frac{m^{3}}{s}$	Flow rate into port X's optional volume	qVX
$V_{f_{X}}$	$m^{3}$	Effective volume at port X	VfX

Connections

Name	Description	Modelica ID
$portA$	Upstream hydraulic port	portA
$portB$	Downstream hydraulic port	portB

Parameters

Flow Rate vs. Pressure

Name	Default	Units	Description	Modelica ID
Data source	inline		Data source	datasourcemode
$q (dP)$	[0,0.001;100,0.001;100,0;200,0]		Data set	table
Skip rows	$0$		Number of rows to skip	skipRows
Smooth	linear		Smoothness of table interpolation	smoothness
Pressure difference unit ( $p_{unit}$ )	$kPa$		Unit of pressure used in the data	pressUnit
flow unit ( ${flow}_{unit}$ )	$\frac{liter}{s}$		Unit of flow-rate used in the data	flowUnit

Optional Volumes

Name	Default	Units	Description	Modelica ID
$Use volume A$	$false$		True (checked) means a hydraulic volume chamber is added to portA	useVolumeA
$V_{A}$	$1 \cdot 10^{−6}$	$m^{3}$	Volume of chamber A	Va
$Use volume B$	$false$		True (checked) means a hydraulic volume chamber is added to portB	useVolumeB
$V_{B}$	$1 \cdot 10^{−6}$	$m^{3}$	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 System Properties component used in the model.

Name	Units	Description	Modelica ID
$ν$	$\frac{m^{2}}{s}$	Kinematic viscosity of fluid	nu
$ρ$	$\frac{kg}{m^{3}}$	Density of fluid	rho
$El$	$Pa$	Bulk modulus of fluid	El

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