Cartridge Valve Actuator (IL)

An actuator that maintains equilibrium between the valve pressure and the control pressure in the isothermal liquid network.

cartridge valve actuator il

Description

The Cartridge Valve Actuator (IL) unit models an actuator that maintains a balance between valve pressure and control pressure. The valve between ports A and B remains closed until the Spring preload force guide spring pressure is exceeded, at which point the piston starts to move. The piston position is output as a scalar signal to port S. The 4 port cartridge valve actuator diagram is shown below.

cartridge valve actuator il 1

Actuator force balance

The actuator piston moves to regulate the pressure in the actuator chamber, which maintains a balance between the actuator port pressure and the linear control pressure:

where:

and are the pressures at ports A and B;
- port area A;
- port area B, which is calculated as:
- , if the parameter Number of pressure ports is set to 3;
- if the Number of pressure ports is set to 4;
- port area X, calculated from Port A poppet to port X pilot area ratio;
- port area Y;
- initial spring force in the system;
- is calculated from the Number of pressure ports:
- , if Number of pressure ports is set to 3;
- If the Number of pressure ports is set to 4.

Piston position

The stable piston displacement is calculated as:

where

- is the value of the Connected valve opening orientation parameter, which specifies movement in the positive (extension) or negative (retraction) direction;
- spring stiffness constant, the value of the Spring stiffness parameter.

The dynamic change in piston position is:

where is the value of the Actuator time constant parameter.

If is less than the value of the Spring preload force parameter, then .

If is greater than the sum of the preload force and , then .

Opening dynamics

If opening dynamics are modelled, a delay is introduced in the flow response to the modelled control pressure. The pressure becomes the dynamic control pressure , otherwise is the steady-state pressure. The instantaneous change in dynamic control pressure is calculated from the Actuator time constant :

By default, the Actuator dynamics checkbox is unchecked.

Numerical smoothing of area and pressure values

When the actuator is almost fully extended or retracted, it is possible to maintain numerical stability in the simulation by adjusting the Smoothing factor parameter. The smoothing function is applied to all calculated forces, but primarily affects the modelling at the extremes of piston movement.

The normalised force is

where

- is the force at port A;
- port force B;
- is the value of Spring preload force;
- port force X.

If the Smoothing factor parameter is non-zero, the block smoothly changes the value of the normalised force between 0 and 1.

Assumptions and limitations

Internal fluid volumes are not modelled in this block. There is no mass flow through ports A, B, X and Y.

Ports

Conserving

# A — pressure port
isothermal liquid

Details

The pressure port associated with the valve inlet.

Program usage name

port_a

# B — pressure port
isothermal liquid

Details

Pressure port associated with the valve outlet.

Program usage name

port_b

# X — pressure port
isothermal liquid

Details

Pressure port at the end of a tubular valve.

Program usage name

port_x

# Y — pressure port
isothermal liquid

Details

Pressure port associated with the valve outlet.

Dependencies

To use this port, set Number of pressure ports to 4.

Program usage name

port_y

Output

# S — position of the pipe valve, m
scalar

Details

The position of a tubular valve, expressed in m.

Data types	`Float64`.
Complex numbers support	No

Parameters

# Number of pressure ports — number of control pressure ports
3 | 4

Details

Number of control pressure ports. Port X measures the pressure at the end of the tubular valve. If this parameter is set to 4, an additional control port Y is used.

Values	`3` \| `4`
Default value	`3`
Program usage name	`port_count`
Evaluatable	No

# Port A poppet area — cross-sectional area of the port A
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Port cross-sectional area A.

Values	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`1e-4 m^2`
Program usage name	`port_a_area`
Evaluatable	Yes

# Port A poppet to port X pilot area ratio — ratio of input port area to control port area

Details

The ratio of the input port area A, to the control port area X. This value is used to calculate the force on port X.

Default value	`0.5`
Program usage name	`port_area_ratio_a_x`
Evaluatable	Yes

# Port Y pilot area — cross-sectional area of the port Y
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Port cross-sectional area Y.

Dependencies

To use this parameter, set the Number of pressure ports to 4.

Values	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`5e-05 m^2`
Program usage name	`port_y_area`
Evaluatable	Yes

# Spring preload force — initial spring force
N | kN | lb | mN | dyn | lbf

Details

Spring force in the valve due to spring preload. This parameter is a threshold value which, when added to the control pressures at ports X and Y, balances the valve opening due to the pressures at ports A and B.

Values	`N` \| `kN` \| `lb` \| `mN` \| `dyn` \| `lbf`
Default value	`25.0 N`
Program usage name	`F_preload`
Evaluatable	Yes

# Spring stiffness — stiffness constant
N/m | lbf/ft | lbf/in

Details

The stiffness constant of a spring.

Values	`N/m` \| `lbf/ft` \| `lbf/in`
Default value	`15e3 N/m`
Program usage name	`k`
Evaluatable	Yes

# Poppet stroke — butterfly valve stroke
m | cm | ft | in | km | mi | mm | um | yd

Details

Maximum possible movement of the pipe valve.

Values	`m` \| `cm` \| `ft` \| `in` \| `km` \| `mi` \| `mm` \| `um` \| `yd`
Default value	`5e-3 m`
Program usage name	`stroke`
Evaluatable	Yes

# Smoothing factor — numerical smoothing factor

Details

A continuous smoothing factor that provides a smooth change in piston position in the nearly extended and nearly retracted positions. Set a non-zero value less than one to increase the stability of the simulation.

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

# Connected valve opening orientation — piston displacement direction
Positive displacement opens valve | Negative displacement opens valve

Details

The direction of displacement of the tubular valve that opens the connected valve. If the parameter is set to `Positive displacement opens valve', the valve extends. If the parameter is set to `Negative displacement opens valve', the valve retracts.

Values	`Positive displacement opens valve` \| `Negative displacement opens valve`
Default value	`Positive displacement opens valve`
Program usage name	`orientation`
Evaluatable	No

# Actuator dynamics — whether to take into account transients during tripping

Details

Option to account for transient effects in the spool position during actuator operation. Checking the Actuator dynamics box approximates the actuator motion by introducing a first order delay in the spool position. The Actuator time constant value also affects the modelled dynamics.

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

# Actuator time constant — piston displacement time constant
d | s | hr | ms | ns | us | min

Details

A constant that determines the time required for the piston to reach steady state when moving from one position to another. This parameter affects the modelled actuator dynamics.

Dependencies

To enable this parameter, select the Actuator dynamics checkbox.

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