Pressure Compensator Valve (TL)
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Fluids /
Thermal Liquid /
Valves & Orifices /
Pressure Control Valves
Description
The Pressure Compensator Valve (TL) block represents a pressure compensator in a thermal liquid network, such as a pressure relief valve or pressure reducing valve. Use this block to maintain the pressure at the valve based on signals from another part of the system.
The pressure differential between ports X and Y is the control pressure, Pcontrol. When this value meets or exceeds the set pressure, the valve area opens or closes depending on the Valve specification parameter. The pressure regulation range begins at the set pressure, Pset.
Pressure Control
The block regulates pressure when Pcontrol exceeds Pset and continues to regulate the pressure until Pmax, the sum of Pset and the pressure regulation range. The Set pressure differential parameter defines the constant regulation range.
Conservation of Mass
The block conserves mass such that
The block calculates the mass flow rate through the valve as
where:
Cd is the value of the Discharge coefficient parameter.
Avalve is the instantaneous valve open area.
Aport is the value of the Cross-sectional area at ports A and B parameter.
is the average fluid density.
Δp is the valve pressure difference pA – pB.
The critical pressure difference, Δpcrit, is the pressure differential specified by the Critical Reynolds number parameter, Recrit. This parameter represents the flow regime transition point between laminar and turbulent flow. The block finds the critical pressure difference as
where μ is the dynamic viscosity of the thermal liquid.
The pressure loss, PRloss, describes the reduction of pressure in the valve due to a decrease in area. The block calculates the pressure loss as:
The pressure recovery describes the positive pressure change in the valve due to an increase in area. When you clear the Pressure recovery check box, the block sets PRloss to 1.
The block calculates Avalve using the opening parameterization and the valve opening dynamics.
Valve Opening Parameterization
When you set Opening parameterization to
Linear
, the valve area for normally open valves is
where Aleak is the value of the Leakage Area parameter and Amax is the value of the Maximum opening area parameter. This figure shows how the block controls the opening area for a normally open valve using the linear parameterization.
For normally closed valves, the block uses
This figure show how the block controls the opening area for a normally closed valve using the linear parameterization.
The normalized pressure, , is
When the valve is in a near-open or near-closed position in the linear parameterization, you can maintain numerical robustness in your simulation by adjusting the Smoothing factor parameter. If the Smoothing factor parameter is nonzero, the block smoothly saturates the control pressure between pset and pmax. For more information, see Numerical Smoothing.
When you set Opening parameterization to Tabulated
data
, Aleak and
Amax are the first and last parameters of the
Opening area vector parameter, respectively. The block calculates the
opening area as
where:
pcontrol,TLU,ref = pTLU + poffset.
pTLU is the Pressure differential vector parameter.
poffset is an internal pressure offset that causes the valve to start closing when pcontrol,TLU,ref = pset.
ATLU is the Opening area vector parameter.
This figure demonstrates how the block controls the opening area for a normally open valve using the tabulated data parameterization.
This figure demonstrates how the block controls the opening area for a normally closed valve using the tabulated data parameterization.
Opening Dynamics
When you select Opening dynamics, the block introduces a control pressure lag where pcontrol becomes the dynamic control pressure, pdyn. The block calculates the instantaneous change in dynamic control pressure based on the Opening time constant parameter, τ:
By default, the block clears the Opening dynamics
check box. When Opening parameterization is
Linear
, a nonzero value for the Smoothing
factor parameter provides additional numerical stability when the orifice is in
near-closed or near-open position.
The block calculates the steady-state dynamics according to the Opening parameterization parameter based on the control pressure, pcontrol.
Energy Balance
The energy conservation equation in the valve is
where:
ϕA is the energy flow rate into the valve through port A.
ϕB is the energy flow rate into the valve through port B.
Ports
Conserving
Parameters
Extended Capabilities
Version History
Introduced in R2023a