Pressure Compensator Valve (IL)
isothermal liquid network pressure compensation valve.
Description
The Pressure Compensator Valve (IL) unit is a pressure compensation valve in an isothermal liquid network, such as a pressure relief valve or pressure reducing valve. Use this valve to maintain pressure at the valve based on signals from another part of the system.
The differential pressure between ports X and Y is the control pressure . When the control pressure value reaches or exceeds the set pressure, the valve opens or closes depending on the value of the Valve specification parameter. The pressure control range starts from the set pressure . The setpoint pressure control mode can be selected:
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If the Controlled set pressure check box is not selected, the set pressure is constant.
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If the Controlled set pressure checkbox is selected, the set pressure is controlled and its value is set and adjusted via the Ps port.
Pressure control
The unit regulates the pressure when exceeds . The unit continues to regulate pressure up to the value , defined as , where is the pressure control range.
The unit supports two control modes:
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If the Controlled set pressure checkbox is selected and a pressure value is received at the Ps port, the unit keeps the pressure control range constant. The valve regulates pressure when is greater than the signal value on the Ps port and less than .
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If the Controlled set pressure checkbox is not selected, the Set pressure differential parameter defines a constant set pressure.
Mass Conservation
The mass conservation equation for the flow through the valve:
The mass flow rate through the valve is calculated as follows:
where
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- flow coefficient, the value of the Discharge coefficient parameter;
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- is the instantaneous opening area of the valve;
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- Cross-sectional area at ports A and B;
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- is the average density of the fluid;
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- pressure difference in the valve .
Critical pressure drop, - the pressure drop associated with the value of the critical Reynolds number , given by the Critical Reynolds number parameter, the transition point between laminar and turbulent flow. The block calculates the critical pressure drop as:
Pressure loss describes the pressure drop in the valve due to the reduced valve area and is calculated as:
Pressure recovery describes a positive change in valve pressure due to an increase in valve area. To disregard pressure recovery, uncheck the Pressure recovery box. In this case the pressure loss .
The unit calculates , using the opening parameterization and the valve opening dynamics.
Valve opening parameterization
If the Opening parameterization is set to `Linear', the valve area for normally open valves is as follows
This figure shows how the block controls the opening area of a normally open valve using linear parameterization.
The valve area for normally closed valves is as follows
This figure shows how the block controls the opening area of a normally closed valve using linear parameterization.
The normalised pressure is
When the valve is in the nearly open or nearly closed position in the linear parameterization, it is possible to maintain numerical stability in the simulation by adjusting the Smoothing factor parameter. If the Smoothing factor is non-zero, the unit smoothly maintains the control pressure between and .
If the Opening parameterization parameter is set to Tabulated, then and are the first and last values of the Opening area parameter vector respectively. The block calculates the opening area as
where
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- control pressure, pressure drop between ports X and Y;
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;
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- is the value of the parameter Pressure differential vector;
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- is the change in internal pressure that causes the valve to start closing when ;
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- parameter value Opening area vector.
This figure shows how the block controls the opening area of a normally open valve using tabular parameterization.
This figure shows how the block controls the opening area of a normally closed valve using a table parameterization.
Opening dynamics
If the Opening dynamics checkbox is selected, a delay is introduced in the flow response to the modelled control pressure. The pressure becomes the dynamic control pressure . The instantaneous change in the dynamic control pressure is calculated from the Opening time constant :
By default, the Opening dynamics checkbox is unchecked. For linear parameterization, a non-zero value for the Smoothing factor parameter provides additional numerical stability when the hole is in the nearly closed or nearly open position.
The block calculates the steady-state dynamics according to the Opening parameterization based on the control pressure value .
Ports
Non-directional
A - isothermal liquid port
isothermal liquid
Isothermal liquid port, corresponds to the A side of the valve.
B is the isothermal liquid port
isothermal liquid
Isothermal liquid port, corresponds to the B side of the valve.
X - isothermal liquid pressure
isothermal liquid
The isothermal liquid port associated with determining the pressure at the X point, .
Y is the pressure of the isothermal liquid
isothermal liquid
The isothermal liquid port associated with determining the pressure at the Y point, .
Parameters
Valve specification - valve offset
Normally open (by default) | `Normally closed `
Normal operating condition of the pressure compensator valve. Select Normally open for the pressure reducing valve. Select Normally closed for the pressure relief valve.
Controlled set pressure - enable the port for setting the control pressure
Off (By default) | On
If unchecked, the Set pressure differential parameter defines a constant set pressure.
If the checkbox is selected, the pressure signal is fed to the Ps port. The unit maintains a constant pressure control range. The valve regulates pressure when is greater than the signal value at port Ps and less than .
Opening parameterization - opening parameterization
Linear (By default) | Tabulated data.
Method for parameterization of the valve opening process.
Set pressure differential - range beyond which the constant valve operation is triggered
0.0 MPa (by default) | scalar
The amount of differential pressure at which pressure compensation is triggered.
Dependencies
To use this parameter, clear the Controlled set pressure checkbox.
Pressure regulation range - valve operating pressure range
0.1 MPa (by default) | `positive scalar'.
The operating pressure range of the valve. The pressure regulation range defines the difference between the Set pressure differential parameter and the maximum operating pressure of the valve.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Linear'.
The Maximum opening area is the area of the valve fully open
1e-4 m² (by default) | positive scalar
Cross-sectional area of the valve opening in the fully open position.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Linear'.
Leakage area is the clearance area of the valve in the fully closed position
1e-10 m² (by default) | `positive scalar'.
The sum of all clearances when the valve is in the fully closed position. Any area less than this value is maintained at the specified leakage area. This parameter contributes to the stability of the numerical solution by maintaining flow continuity.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Linear'.
Pressure differential vector - differential pressure values for tabular parameterization
[0.2, 0.4, 0.6, 0.8, 1.0, 1.2] MPa (by default) | `vector'.
Vector of differential pressure values for the tabular parameterization of the valve opening area. The elements of the vector must correspond one-to-one to the elements of the vector from parameter Opening area vector. The elements are listed in ascending order.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Tabulated'.
Opening area vector - vector of valve opening area values for tabulated parameterization
[1e-05, 8e-06, 6e-06, 4e-06, 2e-06, 1e-10] m² (by default) | `vector'.
Vector of valve opening area values for tabular parameterization. The values in this vector correspond one-to-one to the vector elements from the Pressure differential vector parameter. For normally open valves, the elements are listed in descending order. For normally closed valves, the elements are listed in ascending order.
The Opening area vector must have the same number of elements as the Pressure differential vector. The block uses linear interpolation of points from the data table.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Tabulated'.
Cross-sectional area at ports A and B - area at the inlet or outlet of the valve
Inf (By default) | positive scalar
The cross-sectional area at the inlet and outlet ports A and B. This area is used in the pressure-flow equation that determines the mass flow rate through the orifice.
Discharge coefficient - flow coefficient
0.64 (by default) | positive scalar in the range [0,1].
Correction factor that takes into account discharge losses in theoretical flows.
Critical Reynolds number - upper limit of Reynolds number for laminar flow
150 (By default) | positive scalar
Upper Reynolds number limit for laminar flow through the valve.
Smoothing factor - numerical smoothing factor
0.01 (by default) | `positive scalar'.
A continuous smoothing factor that introduces a level of gradual change based on the flow characteristic when the valve is in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation in these modes.
Dependencies
To use this parameter, set the Opening parameterization parameter to `Linear'.
Pressure recovery - whether to take into account the pressure rise when the area expands
disabled (by default) | `enabled
Whether to take into account the pressure rise when fluid flows from a smaller cross-sectional area to a larger cross-sectional area.
Opening dynamics - whether to take into account the flow response to valve opening
off (by default) | on
Whether the transient effects in the fluid system caused by valve opening should be taken into account. Checking Opening dynamics approximates the opening conditions by introducing a first order lag in the flow response. The Opening time constant parameter also affects the modelled opening dynamics.
Opening time constant - valve opening time constant
0.1 s (by default) | on.
A constant that defines the time required for the fluid to reach steady state when opening or closing the valve from one position to another. This parameter affects the modelling of the opening dynamics.
Dependencies
To use this parameter, select the Opening dynamics checkbox.