3-Way Directional Valve (MA)

3-way directional valve in a moist air network

Since R2025a

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Libraries:
Simscape / Fluids / Moist Air / Valves & Orifices / Directional Control Valves

Description

The 3-Way Directional Valve (MA) block models a valve with three openings in a moist air network, typically between an actuator, pump, and tank. The valve operation is controlled by a single spool displaced according to the signal at port S. You can set the baseline configuration of your valve by specifying the orifices that are open when the spool moves in the positive direction and negative directions in the Positive spool position open connections and Negative spool position open connections parameters, respectively. For more details about how the block calculates flow rate through a variable orifice, see Orifice (MA).

In this configuration, Positive spool position open connections is set to A-T. When the signal at port S moves the spool to a positive position, the path between ports A and T is open to flow. The paths between ports P and A and between ports P and T are closed:

In this configuration, Negative spool position open connections is set to P-A. When the signal at port S moves the spool to a negative position, the path between ports P and A is open to flow and the paths between ports T and A and between ports P and T are closed:

You can open the path between ports P and T by setting either Positive spool position open connections or Negative spool position open connections to P-T or P-A, A-T, P-T.

A flow path can be open in either the positive or negative spool positions, but not both.

Valve Parameterizations

The block behavior depends on the Valve parametrization parameter:

• Cv flow coefficient — The flow coefficient C_v determines the block parameterization. The flow coefficient measures the ease with which the moist air can flow when driven by a certain pressure differential.

• Kv flow coefficient — The flow coefficient K_v, where $$K_v=0.865C_v$$, determines the block parameterization. The flow coefficient measures the ease with which the moist air can flow when driven by a certain pressure differential.

• Sonic conductance — The sonic conductance of the resistive element at steady state determines the block parameterization. The sonic conductance measures the ease with which the moist air can flow when choked, which is a condition in which the flow velocity is at the local speed of sound. Choking occurs when the ratio between downstream and upstream pressures reaches a critical value known as the critical pressure ratio.

• Orifice area — The size of the flow restriction determines the block parametrization.

Visualize Orifice Openings

To visualize the spool offsets and displacement, right-click the block and select Fluids > Plot Valve Characteristics. The plot shows the sonic conductance, K_v flow coefficient, C_v flow coefficient, or orifice area as a function of spool position.

To update the data after changing the block parameters, click Reload Data in the figure window.

This figure shows the valve configuration with default values.

Assumptions and Limitations

• The Sonic conductance setting of the Valve parameterization parameter is for pneumatic applications. If you use this setting for moist air with high levels of trace gases or are modeling a fluid other than air, you may need to scale the sonic conductance by the square root of the mixture specific gravity.

• This block does not model supersonic flow.

• There is no heat exchange between the valve and the environment.

Ports

Conserving

A — Moist air port

moist air

Entry or exit point to the valve.

P — Moist air port

moist air

Entry or exit point to the valve.

T — Moist air port

moist air

Entry or exit point to the valve.

Input

S — Control member displacement, m

physical signal

Spool position displacement in m, received as a physical signal. For flow paths that open in the positive spool position, a positive signal opens the orifice. For flow paths that open in the negative spool position, a negative signal opens the orifice.

Parameters

Valve Configuration

Positive spool position open connections — Flow paths open when the spool is in positive position

All closed (default) | P-A, A-T, P-T | P-A | A-T | P-T

Flow paths open when the spool is in a positive position. This parameter sets the valve configuration and defines the direction of spool movement according to the signal received at port S.

Negative spool position open connections — Flow paths open when spool moves in negative direction

All closed (default) | P-A, A-T, P-T | P-A | A-T | P-T

Flow paths open when the spool moves in the negative direction. This parameter sets the valve configuration and defines the direction of spool movement according to the signal received at port S.

Model Parameterization

Area characteristics — Flow equations for orifices

Identical for all flow paths (default) | Different for each flow path

Whether to apply uniform or individual flow equations for the valve orifice area. When you set this parameter to Identical for all flow paths, the block uses the same orifice and spool geometries, flow rates, pressure, and area vectors for all valve orifices. When you set this parameter to Different for each flow path, you can specify these parameters individually for each orifice. For both settings, orifices A, B, P, and T have the same cross-sectional areas, discharge coefficients, and Reynolds numbers when you set Valve parameterization to Linear - Area vs. spool travel or Tabulated data - Area vs. spool travel.

Valve parameterization — Variable or constant orifice parameterization

Cv flow coefficient (default) | Kv flow coefficient | Sonic conductance | Orifice area

Method the block uses to calculate the mass flow rate from the pressure difference across the orifice or the pressure difference from the mass flow rate.

Spool travel between closed and open orifice — Maximum spool stroke

0.005 m (default) | positive scalar

Maximum distance of spool travel.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths and Opening characteristic to Linear.

Opening characteristic — Method to convert control signal to measure of flow capacity

Linear (default) | Tabulated

Method by which to convert the control signal specified at port S to the chosen measure of flow capacity.

Spool travel vector — Vector of spool opening distances relative to fully closed position

[0, .00125, .0025, .00375, .005] m (default) | 1-by-n vector

Vector of spool travel distances when parameterizing the orifice according to the tabulated valve area data. The vector elements must correspond one-to-one with the elements in the Orifice area vector parameter. List the values in ascending order. The first element must be 0. The block uses linear interpolation between table data points.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths and Opening characteristic to Tabulated.

Maximum Cv flow coefficient — C_v coefficient that corresponds to maximally open component

4 (default) | positive scalar

Value of the C_v flow coefficient when the orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Cv flow coefficient, and Opening characteristic to Linear.

Cv flow coefficient vector — C_v coefficients for values in member position vector

[1e-06, .8, 1.6, 2.4, 3.2, 4] (default) | 1-by-n vector

Vector of C_v flow coefficients. Each coefficient corresponds to a value in the Control member position vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the Control member position vector parameter.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Cv flow coefficient, and Opening characteristic to Tabulated.

Maximum Kv flow coefficient — K_v coefficient that corresponds to maximally open component

3.6 (default) | positive scalar

Value of the K_v flow coefficient when the orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Kv flow coefficient, and Opening characteristic to Linear.

Kv flow coefficient vector — K_v coefficients for values in member position vector

[1e-06, .72, 1.44, 2.16, 2.88, 3.6] (default) | 1-by-n vector

Vector of K_v flow coefficients. Each coefficient corresponds to a value in the Control member position vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the Control member position vector parameter.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Kv flow coefficient, and Opening characteristic to Tabulated.

Maximum orifice area — Maximum orifice opening area

1e-4 m^2 (default) | positive scalar

Largest open area of each orifice during the operation of the valve.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Orifice area, and Opening characteristic to Linear.

Orifice area vector — Vector of valve opening areas

[1e-10, 1e-05, 4e-05, 6e-05, .0001] m^2 (default) | 1-by-n vector

Vector of opening areas when parameterizing the orifice according to the tabulated valve area data. The vector elements must correspond one-to-one with the elements in the Spool travel vector parameter. List the values in ascending order. The elements must be greater than 0.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Orifice area, and Opening characteristic to Tabulated.

xT pressure differential ratio factor at choked flow — Ratio of pressure differentials

0.7 (default) | positive scalar

Ratio between the inlet pressure, p_in, and the outlet pressure, p_out, defined as $$(p_{in}-p_{out})/p_{in}$$ where choking first occurs.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, and Valve parameterization to Cv flow coefficient or Kv flow coefficient.

Discharge coefficient — Discharge coefficient

0.64 (default) | positive scalar

Correction factor that accounts for discharge losses in theoretical flows.

Dependencies

To enable this parameter, set Valve parameterization to Orifice area.

Maximum sonic conductance — Sonic conductance corresponding to maximally open component

12 l/(bar*s) (default) | positive scalar

Value of the sonic conductance when the control signal specified at port S is 1 and cross-sectional area available for flow is at a maximum.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Sonic conductance, and Opening characteristic to Linear.

Critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes

0.3 (default) | positive scalar

Pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Sonic conductance, and Opening characteristic to Linear.

Subsonic index — Exponent used to characterize mass flow in subsonic flow regime

0.5 (default) | positive scalar

Empirical value used to more accurately calculate the mass flow rate in the subsonic flow regime.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths and Valve parameterization to Sonic conductance.

ISO reference temperature — ISO 8778 reference temperature

293.15 K (default) | scalar

Temperature at standard reference atmosphere, defined as 293.15 K in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths and Valve parameterization to Sonic conductance.

ISO reference density — ISO 8778 reference density

1.185 kg/m^3 (default) | positive scalar

Density at standard reference atmosphere, defined as 1.185 kg/m3 in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths and Valve parameterization to Sonic conductance.

Sonic conductance vector — Sonic conductances corresponding to values in spool travel vector

[1e-05, 2.4, 4.8, 7.2, 9.6, 12] l/(bar*s) (default) | vector of positive values

Vector of sonic conductances inside the resistive element. Each conductance corresponds to a value in the Spool travel vector parameter. The size of the vector must be the same as the Spool travel vector parameter.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Sonic conductance, and Opening characteristic to Tabulated.

Critical pressure ratio vector — Critical pressure ratios corresponding to values in spool travel vector

0.3 * ones(1,6) (default) | vector of positive numbers

Vector of critical pressure ratios at which the flow first chokes, with each critical pressure ratio corresponding to a value in the Spool travel vector parameter. The critical pressure ratio is the fraction of downstream-to-upstream pressures at which the flow velocity reaches the local speed of sound. The size of the vector must be the same as the Spool travel vector parameter.

Dependencies

To enable this parameter, set Area characteristics to Identical for all flow paths, Valve parameterization to Sonic conductance, and Opening characteristic to Tabulated.

Leakage flow fraction — Ratio of flow rates

1e-6 (default) | positive scalar

Ratio of the flow rate of the orifice when it is closed to when it is open.

Dependencies

To enable this parameter, set Opening characteristic to Linear.

Smoothing factor — Numerical smoothing factor

0.01 (default) | positive scalar in the range of [0,1]

Continuous smoothing factor that introduces a layer of gradual change based on the flow response when the valve is in the near-open and near-closed positions. To increase the stability of your simulation in these regimes, set this parameter to a nonzero value less than one.

Dependencies

To enable this parameter, set Opening characteristic to Linear.

Laminar flow pressure ratio — Laminar-turbulent transition pressure ratio

0.999 (default) | positive scalar

Ratio of the orifice outlet pressure to orifice inlet pressure at which the fluid transitions between the laminar and turbulent regimes. The pressure loss corresponds to the mass flow rate linearly in laminar flows and quadratically in turbulent flows.

Cross-sectional area at ports A, P, and T — Area at conserving ports

0.01 m^2 (default) | positive scalar

Maximum cross-sectional areas at the entry and exit ports P, T, A, and B, which the block uses in the pressure-flow rate equation that determines the mass flow rate through the valve.

P-A Orifice

Spool position at maximum P-A orifice area — Spool offset for fully open P-A orifice

5e-3 m (default) | positive scalar

Spool offset from the neutral position for a fully open P-A orifice.

Dependencies

To enable this parameter, set one of these parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings do not appear in both the Positive spool position open connections and Negative spool position open connections parameters.

P-A spool travel between closed and open orifice — Maximum spool stroke

0.005 m (default) | positive scalar

Maximum distance of spool travel. This value provides an upper limit to calculations so that simulations do not return unphysical values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Linear, and one of the following parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A constant orifice Cv flow coefficient — Flow coefficient

4 (default) | positive scalar

Value of the constant C_v flow coefficient for the P-A orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-A orifice maximum Cv flow coefficient — C_v coefficient that corresponds to maximally open component

4 (default) | positive scalar

Value of the C_v flow coefficient when the P-A orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice Cv flow coefficient vector — C_v coefficients for values in member position vector

[1e-06, .8, 1.6, 2.4, 3.2, 4] (default) | 1-by-n vector

Vector of C_v flow coefficients. Each coefficient corresponds to a value in the P-A orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the P-A orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A constant orifice Kv flow coefficient — Flow coefficient

3.6 (default) | positive scalar

Value of the constant K_v flow coefficient for the P-A orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-A orifice maximum Kv flow coefficient — K_v coefficient that corresponds to maximally open component

3.6 (default) | positive scalar

Value of the K_v flow coefficient when the P-A orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice Kv flow coefficient vector — K_v coefficients for values in member position vector

[1e-06, .72, 1.44, 2.16, 2.88, 3.6] (default) | 1-by-n vector

Vector of K_v flow coefficients. Each coefficient corresponds to a value in the P-A orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the P-A orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice spool travel vector — Vector of spool opening distances relative to fully closed position

[0, .00125, .0025, .00375, .005] m (default) | 1-by-n vector

Vector of spool travel distances for the tabular parameterization of the valve area. List the values in ascending order. The first element must be 0. The block uses linear interpolation between table data points.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Tabulated, and one of the following parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A maximum orifice area — Maximum orifice opening area

1e-4 m^2 (default) | positive scalar

Largest open area of the P-A orifice during the operation of the valve.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice area vector — Vector of valve opening areas

[1e-10, 1e-05, 4e-05, 6e-05, .0001] m^2 (default) | 1-by-n vector

Vector of opening areas for the tabular parameterization of the valve area. The vector elements must correspond one-to-one with the elements in the P-A orifice spool travel vector parameter. The elements must be greater than 0 and listed in ascending order.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A constant orifice area — Cross-sectional area for constant orifice

1e-4 m^2 (default) | positive scalar

Orifice area when the positive and negative spool positions include the same orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-A orifice xT pressure differential ratio factor at choked flow — Ratio of pressure differentials

0.7 (default) | positive scalar

Ratio between the inlet pressure, p_in, and the outlet pressure, p_out, defined as $$(p_{in}-p_{out})/p_{in}$$ where choking first occurs for the P-A orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient or Cv flow coefficient

3. At least one of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A constant orifice sonic conductance — Sonic conductance for constant orifice

12 l/(bar*s) (default) | positive scalar

Sonic conductance when the positive and negative spool positions include the same orifice. This value is the ratio, measured at the onset of choking, of the mass flow rate through the resistive element to the product of the upstream pressure and mass density at standard conditions as defined in ISO 8778. This parameter determines the maximum flow rate allowed at a given upstream pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-A constant orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes for constant orifice

0.3 (default) | positive scalar

Critical pressure ratio when the positive and negative spool positions include the same orifice. This value is the pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-A orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-A orifice maximum sonic conductance — Sonic conductance corresponding to maximally open orifice

12 l/(bar*s) (default) | positive scalar

Value of the sonic conductance when the P-A orifice is fully open and the area available for flow is at a maximum.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes

0.3 (default) | positive scalar

Pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice sonic conductance vector — Sonic conductances corresponding to values in spool travel vector

[1e-05, 2.4, 4.8, 7.2, 9.6, 12] l/(bar*s) (default) | 1-by-n vector

Vector of sonic conductances inside the resistive element. Each conductance corresponds to a value in the P-A orifice spool travel vector parameter. The size of the vector must be the same as the P-A orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice critical pressure ratio vector — Critical pressure ratios corresponding to values in spool travel vector

0.3 * ones(1, 6) (default) | 1-by-n vector

Vector of critical pressure ratios at which the flow first chokes, with each critical pressure ratio corresponding to a value in the P-A orifice spool travel vector parameter. The critical pressure ratio is the fraction of downstream-to-upstream pressures at which the flow velocity reaches the local speed of sound. The size of the vector must be the same as the P-A orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-A or P-A, A-T, P-T.

   • Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice subsonic index — Exponent used to characterize mass flow in subsonic flow regime

0.5 (default) | positive scalar

Empirical value used to more accurately calculate the mass flow rate in the subsonic flow regime.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice ISO reference temperature — ISO 8778 reference temperature

293.15 K (default) | scalar

Temperature at standard reference atmosphere, defined as 293.15 K in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

P-A orifice ISO reference density — ISO 8778 reference density

1.185 kg/m^3 (default) | positive scalar

Density at standard reference atmosphere, defined as 1.185 kg/m3 in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-A or P-A, A-T, P-T.

• Negative spool position open connections to P-A or P-A, A-T, P-T.

A-T Orifice

Spool position at maximum A-T orifice area — Spool offset for fully open A-T orifice

5e-3 m (default) | positive scalar

Spool offset from the neutral position for a fully open A-T orifice.

Dependencies

To enable this parameter, set one of these parameters.

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings do not appear in both the Positive spool position open connections and Negative spool position open connections parameters.

A-T spool travel between closed and open orifice — Maximum spool stroke

0.005 m (default) | positive scalar

Maximum distance of spool travel. This value provides an upper limit to calculations so that simulations do not return unphysical values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Linear, and one of the following parameters:

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T constant orifice Cv flow coefficient — Flow coefficient

4 (default) | positive scalar

Value of the constant C_v flow coefficient for the A-T orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. One of the following settings in each parameter:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

A-T orifice maximum Cv flow coefficient — C_v coefficient that corresponds to maximally open component

4 (default) | positive scalar

Value of the C_v flow coefficient when the A-T orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice Cv flow coefficient vector — C_v coefficients for values in member position vector

[1e-06, .8, 1.6, 2.4, 3.2, 4] (default) | 1-by-n vector

Vector of C_v flow coefficients. Each coefficient corresponds to a value in the A-T orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the A-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T constant orifice Kv flow coefficient — Flow coefficient

3.6 (default) | positive scalar

Value of the constant K_v flow coefficient for the A-T orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. One of the following settings in each parameter:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

A-T orifice maximum Kv flow coefficient — K_v coefficient that corresponds to maximally open component

3.6 (default) | positive scalar

Value of the K_v flow coefficient when the A-T orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice Kv flow coefficient vector — K_v coefficients for values in member position vector

[1e-06, .72, 1.44, 2.16, 2.88, 3.6] (default) | 1-by-n vector

Vector of K_v flow coefficients. Each coefficient corresponds to a value in the A-T orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the A-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice spool travel vector — Vector of spool opening distances relative to fully closed position

[0, .00125, .0025, .00375, .005] m (default) | 1-by-n vector

Vector of spool travel distances for the tabular parameterization of the valve area. List the values in ascending order. The first element must be 0. The block uses linear interpolation between table data points.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Tabulated, and one of the following parameters:

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T maximum orifice area — Maximum orifice opening area

1e-4 m^2 (default) | positive scalar

Largest open area of the A-T orifice during the operation of the valve.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice area vector — Vector of valve opening areas

[1e-10, 1e-05, 4e-05, 6e-05, .0001] m^2 (default) | 1-by-n vector

Vector of opening areas for the tabular parameterization of the valve area. The vector elements must correspond one-to-one with the elements in the A-T orifice spool travel vector parameter. The elements must be greater than 0 and listed in ascending order.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T constant orifice area — Cross-sectional area for constant orifice

1e-4 m^2 (default) | positive scalar

Orifice area when the positive and negative spool positions include the same orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. One of the following settings in each parameter:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

A-T orifice xT pressure differential ratio factor at choked flow — Ratio of pressure differentials

0.7 (default) | positive scalar

Ratio between the inlet pressure, p_in, and the outlet pressure, p_out, defined as $$(p_{in}-p_{out})/p_{in}$$ where choking first occurs for the A-T orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient or Cv flow coefficient

3. At least one of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T constant orifice sonic conductance — Sonic conductance for constant orifice

12 l/(bar*s) (default) | positive scalar

Sonic conductance when the positive and negative spool positions include the same orifice. This value is the ratio, measured at the onset of choking, of the mass flow rate through the resistive element to the product of the upstream pressure and mass density at standard conditions as defined in ISO 8778. This parameter determines the maximum flow rate allowed at a given upstream pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

A-T constant orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes for constant orifice

0.3 (default) | positive scalar

Critical pressure ratio when the positive and negative spool positions include the same orifice. This value is the pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the A-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

A-T orifice maximum sonic conductance — Sonic conductance corresponding to maximally open orifice

12 l/(bar*s) (default) | positive scalar

Value of the sonic conductance when the A-T orifice is fully open and the area available for flow is at a maximum.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes

0.3 (default) | positive scalar

Pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice sonic conductance vector — Sonic conductances corresponding to values in spool travel vector

[1e-05, 2.4, 4.8, 7.2, 9.6, 12] l/(bar*s) (default) | 1-by-n vector

Vector of sonic conductances inside the resistive element. Each conductance corresponds to a value in the A-T orifice spool travel vector parameter. The size of the vector must be the same as the A-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice critical pressure ratio vector — Critical pressure ratios corresponding to values in spool travel vector

0.3 * ones(1, 6) (default) | 1-by-n vector

Vector of critical pressure ratios at which the flow first chokes, with each critical pressure ratio corresponding to a value in the A-T orifice spool travel vector parameter. The critical pressure ratio is the fraction of downstream-to-upstream pressures at which the flow velocity reaches the local speed of sound. The size of the vector must be the same as the A-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to A-T or P-A, A-T, P-T.

   • Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice subsonic index — Exponent used to characterize mass flow in subsonic flow regime

0.5 (default) | positive scalar

Empirical value used to more accurately calculate the mass flow rate in the subsonic flow regime.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice ISO reference temperature — ISO 8778 reference temperature

293.15 K (default) | scalar

Temperature at standard reference atmosphere, defined as 293.15 K in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

A-T orifice ISO reference density — ISO 8778 reference density

1.185 kg/m^3 (default) | positive scalar

Density at standard reference atmosphere, defined as 1.185 kg/m3 in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to A-T or P-A, A-T, P-T.

• Negative spool position open connections to A-T or P-A, A-T, P-T.

P-T Orifice

Spool position at maximum P-T orifice area — Spool offset for fully open P-T orifice

5e-3 m (default) | positive scalar

Spool offset from the neutral position for a fully open P-T orifice.

Dependencies

To enable this parameter, set one of these parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings do not appear in both the Positive spool position open connections and Negative spool position open connections parameters.

P-T spool travel between closed and open orifice — Maximum spool stroke

0.005 m (default) | positive scalar

Maximum distance of spool travel. This value provides an upper limit to calculations so that simulations do not return unphysical values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Linear, and one of the following parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T constant orifice Cv flow coefficient — Flow coefficient

4 (default) | positive scalar

Value of the constant C_v flow coefficient for the P-T orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-T orifice maximum Cv flow coefficient — C_v coefficient that corresponds to maximally open component

4 (default) | positive scalar

Value of the C_v flow coefficient when the P-T orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice Cv flow coefficient vector — C_v coefficients for values in member position vector

[1e-06, .8, 1.6, 2.4, 3.2, 4] (default) | 1-by-n vector

Vector of C_v flow coefficients. Each coefficient corresponds to a value in the P-T orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the P-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Cv flow coefficient

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T constant orifice Kv flow coefficient — Flow coefficient

3.6 (default) | positive scalar

Value of the constant K_v flow coefficient for the P-T orifice. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Modeling option to Vapor operating condition

2. Area characteristics to Different for each flow path

3. Valve parameterization to Kv flow coefficient

4. One of the following settings in each parameter:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-T orifice maximum Kv flow coefficient — K_v coefficient that corresponds to maximally open component

3.6 (default) | positive scalar

Value of the K_v flow coefficient when the P-T orifice is fully open and the area available for flow is at a maximum. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice Kv flow coefficient vector — K_v coefficients for values in member position vector

[1e-06, .72, 1.44, 2.16, 2.88, 3.6] (default) | 1-by-n vector

Vector of K_v flow coefficients. Each coefficient corresponds to a value in the P-T orifice spool travel vector parameter. This parameter measures the ease with which the vapor traverses the resistive element when driven by a pressure differential. The size of the vector must be the same as the P-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Modeling option to Vapor operating condition

2. Area characteristics to Different for each flow path

3. Valve parameterization to Kv flow coefficient

4. Opening characteristic to Tabulated

5. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice spool travel vector — Vector of spool opening distances relative to fully closed position

[0, .00125, .0025, .00375, .005] m (default) | 1-by-n vector

Vector of spool travel distances for the tabular parameterization of the valve area. List the values in ascending order. The first element must be 0. The block uses linear interpolation between table data points.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Opening characteristic to Tabulated, and one of the following parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T maximum orifice area — Maximum orifice opening area

1e-4 m^2 (default) | positive scalar

Largest open area of the P-T orifice during the operation of the valve.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice area vector — Vector of valve opening areas

[1e-10, 1e-05, 4e-05, 6e-05, .0001] m^2 (default) | 1-by-n vector

Vector of opening areas for the tabular parameterization of the valve area. The vector elements must correspond one-to-one with the elements in the P-T orifice spool travel vector parameter. The elements must be greater than 0 and listed in ascending order.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T constant orifice area — Cross-sectional area for constant orifice

1e-4 m^2 (default) | positive scalar

Orifice area when the positive and negative spool positions include the same orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Orifice area

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-T orifice xT pressure differential ratio factor at choked flow — Ratio of pressure differentials

0.7 (default) | positive scalar

Ratio between the inlet pressure, p_in, and the outlet pressure, p_out, defined as $$(p_{in}-p_{out})/p_{in}$$ where choking first occurs for the P-T orifice.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Kv flow coefficient or Cv flow coefficient

3. At least one of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T constant orifice sonic conductance — Sonic conductance for constant orifice

12 l/(bar*s) (default) | positive scalar

Sonic conductance when the positive and negative spool positions include the same orifice. This value is the ratio, measured at the onset of choking, of the mass flow rate through the resistive element to the product of the upstream pressure and mass density at standard conditions as defined in ISO 8778. This parameter determines the maximum flow rate allowed at a given upstream pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-T constant orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes for constant orifice

0.3 (default) | positive scalar

Critical pressure ratio when the positive and negative spool positions include the same orifice. This value is the pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. One of the following settings in each parameter:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

Note:

This parameter is enabled only when the P-T orifice settings appear in both spool position parameters: Positive spool position open connections and Negative spool position open connections.

P-T orifice maximum sonic conductance — Sonic conductance corresponding to maximally open orifice

12 l/(bar*s) (default) | positive scalar

Value of the sonic conductance when the P-T orifice is fully open and the area available for flow is at a maximum.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice critical pressure ratio — Ratio of downstream and upstream pressures at which the flow first chokes

0.3 (default) | positive scalar

Pressure ratio at which flow first begins to choke and the flow velocity reaches its maximum, given by the local speed of sound. The pressure ratio is the outlet pressure divided by inlet pressure.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Linear

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice sonic conductance vector — Sonic conductances corresponding to values in spool travel vector

[1e-05, 2.4, 4.8, 7.2, 9.6, 12] l/(bar*s) (default) | 1-by-n vector

Vector of sonic conductances inside the resistive element. Each conductance corresponds to a value in the P-T orifice spool travel vector parameter. The size of the vector must be the same as the P-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice critical pressure ratio vector — Critical pressure ratios corresponding to values in spool travel vector

0.3 * ones(1, 6) (default) | 1-by-n vector

Vector of critical pressure ratios at which the flow first chokes, with each critical pressure ratio corresponding to a value in the P-T orifice spool travel vector parameter. The critical pressure ratio is the fraction of downstream-to-upstream pressures at which the flow velocity reaches the local speed of sound. The size of the vector must be the same as the P-T orifice spool travel vector parameter.

Dependencies

To enable this parameter, set:

1. Area characteristics to Different for each flow path

2. Valve parameterization to Sonic conductance

3. Opening characteristic to Tabulated

4. One of the following parameters:

   • Positive spool position open connections to P-T or P-A, A-T, P-T.

   • Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice subsonic index — Exponent used to characterize mass flow in subsonic flow regime

0.5 (default) | positive scalar

Empirical value used to more accurately calculate the mass flow rate in the subsonic flow regime.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice ISO reference temperature — ISO 8778 reference temperature

293.15 K (default) | scalar

Temperature at standard reference atmosphere, defined as 293.15 K in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

P-T orifice ISO reference density — ISO 8778 reference density

1.185 kg/m^3 (default) | positive scalar

Density at standard reference atmosphere, defined as 1.185 kg/m3 in ISO 8778.

You only need to adjust the ISO reference parameter values if you are using sonic conductance values that are obtained at difference reference values.

Dependencies

To enable this parameter, set Area characteristics to Different for each flow path, Valve parameterization to Sonic conductance, and at least one of the following parameters:

• Positive spool position open connections to P-T or P-A, A-T, P-T.

• Negative spool position open connections to P-T or P-A, A-T, P-T.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2025a