Pilot-Operated Check Valve (IL)

Check valve with control pressure in isothermal liquid network.

blockType: EngeeFluids.IsothermalLiquid.Valves.DirectionalControl.PilotOperatedCheck

Path in the library:

/Physical Modeling/Fluids/Isothermal Liquid/Valves & Orifices/Directional Control Valves/Pilot-Operated Check Valve (IL)

Description

The unit Pilot-Operated Check Valve (IL) models a flow control valve with variable flow direction depending on the control pressure in the line. The flow is normally restricted to move from port A to port B in a connected or disconnected spool-diaphragm configuration, according to the parameters Pilot configuration.

The figure shows a schematic diagram of a pilot operated check valve.

pilot operated check valve 1 en

The control pressure is defined as:

where

- control differential pressure;
- value of parameters Pilot ratio, the ratio of port area X to port area A: ;
- pressure drop across the valve.

When the control pressure exceeds the value Cracking pressure differential, the platen moves to allow flow from port B to port A.

There is no mass flow between port X and ports A and B.

Controlling the valve pressure by means of the pilot pressure

The control differential pressure to control the valve can be determined in two ways:

If the parameters Opening pilot pressure specification is set to Pressure difference of port X relative to port A, the control pressure is the pressure difference between ports X and A.
If the parameter Opening pilot pressure specification is set to Gauge pressure at port X, the control pressure is the pressure difference between port X and atmospheric pressure.

If the parameter Pilot configuration is set to Gauge pressure at port X, the control pressure is the pressure difference between port X and atmospheric pressure. Disconnected pilot spool and poppet, then the relative pressure at port X must be positive. If the measured control pressure is negative, the control pressure is based only on the pressure difference between ports A and B. If the parameter Pilot configuration is set to . Rigidly connected pilot spool and poppet, the control pressure is the measured differential pressure according to the opening specification.

Mass flow equation

Mass conservation equation for the mass flow through the valve:

The mass flow rate through the valve is calculated as follows:

where

- flow coefficient, the value of parameters Discharge coefficient;
- is the instantaneous opening area of the valve;
- parameter value Cross-sectional area at ports A and B;
- average density of the liquid;
- pressure difference in the valve .

Critical pressure drop, - pressure drop related to the value of the critical Reynolds number , given by the parameter Critical Reynolds number, the point of transition between laminar and turbulent flow:

Pressure loss describes the pressure drop in the valve due to the reduction in valve area and is calculated as:

Pressure recovery describes an increase in valve pressure due to an increase in area. To disregard pressure recovery, uncheck the box Pressure recovery. In this case, the pressure loss .

The block calculates , using the opening parameterization and the valve opening dynamics.

Opening parameterization

With linear parameterization, the valve opening area is defined as:

The normalised pressure represents

When the valve is in the nearly open or nearly closed position, you can maintain numerical stability in the simulation by adjusting the parameters Smoothing factor. If the parameter Smoothing factor is non-zero, the unit smoothly maintains the control pressure between and .

Opening dynamics

If the check box Opening dynamics 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 time constant Opening time constant :

By default, the check box Opening dynamics is unchecked.

Ports

Conserving

# A — isothermal liquid port
isothermal liquid

Details

Isothermal liquid port, corresponds to the valve inlet. When the control pressure exceeds the actuation pressure , the liquid can escape from this port.

Program usage name

inlet

# X — isothermal liquid pressure
isothermal liquid

Details

Pressure to assist in controlling the flow through the valve.

Program usage name

port_x

# B — isothermal liquid port
isothermal liquid

Details

Isothermal liquid port, corresponds to the valve outlet. When the control pressure exceeds the actuation pressure , liquid can enter this port.

Program usage name

outlet

Parameters

# Pilot configuration — valve geometry
Rigidly connected pilot spool and poppet | Disconnected pilot spool and poppet

Details

Valve geometry:

Rigidly connected pilot spool and poppet - the valve opening mechanism is connected to the valve plate.
Disconnected pilot spool and poppet - the valve opening mechanism is aligned with the valve plate but moves freely from it.

The choice of configuration determines the control pressure calculation.

Values	`Rigidly connected pilot spool and poppet` \| `Disconnected pilot spool and poppet`
Default value	`Rigidly connected pilot spool and poppet`
Program usage name	`pilot_configuration`
Evaluatable	No

# Opening pilot pressure specification — differential pressure for valve control
Pressure at port X relative to port A | Pressure at port X relative to atmospheric pressure

Details

The differential pressure used to control the valve. This differential defines the control pressure that is added to the differential pressure between ports A and B and compared to the threshold value Cracking pressure differential.

Values	`Pressure at port X relative to port A` \| `Pressure at port X relative to atmospheric pressure`
Default value	`Pressure at port X relative to port A`
Program usage name	`p_control_type`
Evaluatable	No

# Cracking pressure differential — threshold pressure
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

Setpoint pressure for valve operation.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.01 MPa`
Program usage name	`delta_p_cracking`
Evaluatable	Yes

# Maximum opening pressure differential — maximum pressure drop when the valve is open
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

The maximum pressure drop when the valve is fully open. This value provides an upper pressure limit for the simulation so that the results remain physical.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.02 MPa`
Program usage name	`max_delta_p`
Evaluatable	Yes

# Pilot ratio — control port area ratio

Details

Ratio of port area X to port area A.

Default value	`1.0`
Program usage name	`pilot_ratio`
Evaluatable	Yes

# Maximum opening area — maximum valve area
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Maximum cross-sectional area of the valve. This value is used to determine the normalised valve pressure and the valve opening area during operation.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.0001 m^2`
Program usage name	`max_area`
Evaluatable	Yes

# Leakage area — valve clearance area in fully closed position
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

The sum of all clearances when the valve is in the fully closed position. Any area less than this value equates to the specified leakage area. This parameter contributes to the stability of the numerical solution by maintaining flow continuity.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`1e-10 m^2`
Program usage name	`leakage_area`
Evaluatable	Yes

# Cross-sectional area at ports A and B — area at the inlet or outlet of the valve
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

The cross-sectional area at ports A and B. This area is used when calculating the mass flow rate through the valve.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`Inf m^2`
Program usage name	`port_area`
Evaluatable	Yes

# Discharge coefficient — flow coefficient

Details

Correction factor that takes into account the rarefaction losses in theoretical flows.

Default value	`0.64`
Program usage name	`C_d`
Evaluatable	Yes

# Critical Reynolds number — upper limit of Reynolds number for laminar flow

Details

Upper Reynolds number limit for laminar flow through the valve.

Default value	`150.0`
Program usage name	`Re_critical`
Evaluatable	Yes

# Smoothing factor — numerical smoothing factor

Details

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.

Default value	`0.01`
Program usage name	`smoothing_factor`
Evaluatable	Yes

# Pressure recovery — whether to take into account the increase in pressure when expanding the area

Details

Whether to take into account the pressure increase when the fluid flows from a region with a smaller cross-sectional area to a region with a larger cross-sectional area.

Default value	`false (switched off)`
Program usage name	`pressure_recovery`
Evaluatable	No

# Opening dynamics — whether to take into account the flow response to valve opening

Details

Whether to account for transient effects in the fluid system caused by valve opening. Checking Opening dynamics approximates the opening conditions by introducing a first order lag in the flow response. Parameters Opening time constant also affects the modelled opening dynamics.

Default value	`false (switched off)`
Program usage name	`opening_dynamics`
Evaluatable	No

# Opening time constant — valve opening time constant
d | s | hr | ms | ns | us | min

Details

A constant that determines the time required for the fluid to reach steady state when opening or closing the valve from one position to another. This parameters affects the modelling of the opening dynamics.

Dependencies

To use this parameter, select the checkbox Opening dynamics.

Units	`d` \| `s` \| `hr` \| `ms` \| `ns` \| `us` \| `min`
Default value	`0.1 s`
Program usage name	`tau`
Evaluatable	Yes