# 2-Way Directional Valve (IL)

2-way flow control valve in an isothermal system

• Library:
• Simscape / Fluids / Isothermal Liquid / Valves & Orifices / Directional Control Valves

• ## Description

The 2-Way Directional Valve (IL) block models a two-way valve, such as a shut-off valve. Use this block when you need a flow-reducing control element that responds to pressures in another part of the system.

Within an isothermal fluid system, the two-way directional valve provides flow control by a variable orifice. The block controls the flow between ports A and B via a physical signal at port S, which triggers spool motion to open or close the valve. For more details on the calculation of the flow rate through a variable orifice, see Orifice (IL).

### Valve Parameterization

The valve opening is parameterized in three ways:

• `Linear - area vs. spool travel`

The opening area is a linear function of the spool travel distance, the signal received at port S:

`${A}_{orifice}=\frac{\left({A}_{\mathrm{max}}-{A}_{leak}\right)}{\Delta S}\left(S-{S}_{\mathrm{min}}\right)+{A}_{leak},$`

where:

• Aorifice is the opening area.

• ΔS is the spool travel distance.

• ΔSmax is the Spool travel between closed and open orifice.

• ALeak is the Leakage area.

• Amax is the Maximum orifice area. • `Tabulated data - Area vs. spool travel`

Provide spool travel vectors for your system or for individual flow paths between ports A and B. This data will be used to calculate the relationship between the orifice opening area and spool travel distance. Interpolation is used to determine the opening area between given data points. Aleak and Amax are the first and last parameters of the Opening area vector, respectively. • ```Tabulated data - Volumetric flow rate vs. spool travel and pressure drop```

Provide spool travel and pressure drop vectors. The volumetric flow rate is calculated based on the relationship between pressure change and the spool travel distance. Interpolation is used to determine flow rate between given data points. The mass flow rate is the product of the volumetric flow rate and the local density. ### Numerically-Smoothed Valve Area in the Linear Parameterization

When Orifice parameterization is set to ```Linear - area vs. spool travel``` and the valve is in near-open or near-closed position, you can maintain numerical robustness in your simulation by adjusting the block . A smoothing function is applied to all calculated areas, but primarily influences the simulation at the extremes of the valve area.

The normalized valve area is calculated as:

`$\stackrel{^}{A}=\frac{\left({A}_{orifice}-{A}_{leak}\right)}{\left({A}_{\mathrm{max}}-{A}_{leak}\right)}.$`

The Smoothing factor, s, is applied to the normalized area:

`${\stackrel{^}{A}}_{smoothed}=\frac{1}{2}+\frac{1}{2}\sqrt{{\stackrel{^}{A}}_{}^{2}+{\left(\frac{s}{4}\right)}^{2}}-\frac{1}{2}\sqrt{{\left(\stackrel{^}{A}-1\right)}^{2}+{\left(\frac{s}{4}\right)}^{2}}.$`

The smoothed valve area is:

`${A}_{smoothed}={\stackrel{^}{A}}_{smoothed}\left({A}_{\mathrm{max}}-{A}_{leak}\right)+{A}_{leak}.$`

## Ports

### Conserving

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Entry or exit point to the valve.

Entry or exit point to the valve.

### Input

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Spool displacement in m, received as a physical signal. A positive displacement opens the valve.

## Parameters

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Method of calculating the valve flow area. A linear relationship between the opening area and the control member spool is the default parametrization. Additionally, you can provide your own data if the opening relationship is nonlinear, either in terms of opening area and spool travel or in terms of volumetric flow rate, spool travel, and pressure drop over the flow path.

Position of the spool travel member when the valve is fully open. The default value represents a zero-lapped system. A positive, nonzero value represents an underlapped, or partially closed, system. A negative, nonzero value represents an overlapped system where the valve remains open over a range of displacements.

Spool offset at the maximum valve opened area.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Linear - area vs. spool travel```.

Maximum valve area experienced during simulation. When using `Tabulated data - Area vs. spool travel`, the maximum valve area is the last element of the Orifice area vector.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Linear - area vs. spool travel```.

Sum of all gaps when the valve is in the fully closed position. Any area smaller than this value is maintained at the specified leakage area. This parameter contributes to numerical stability by maintaining continuity in the flow.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Linear - area vs. spool travel```.

Cross-sectional area at the entry and exit ports A and B. This area is used in the pressure-flow rate equation that determines the volumetric flow rate through the valve.

#### Dependencies

To enable this parameter, set Orifice parametrization to:

• ```Tabulated data - Area vs. spool travel```

• ```Linear - area vs. spool travel```

Vector of control member travel distances for the tabular parametrization of the valve opening area. A positive displacement opens the valve. The values in this vector correspond one-to-one to values in the Orifice area vector parameter. The values are listed in ascending order and the first element must be 0. Linear interpolation is employed between table data points.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Tabulated data - Area vs. spool travel```.

Vector of valve area values for the tabular parametrization of opening area. The values in this vector correspond one-to-one with the elements in the Spool travel vector parameter. The first element of this vector is the leakage area, and the last element is the maximum valve area. Linear interpolation is employed between table data points.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Tabulated data - Area vs. spool travel```.

Vector of control member travel distances for tabular parametrization of volumetric flow rate. The spool travel vector forms an independent axis with the Pressure drop vector, dp parameter for the 3-D dependent Volumetric flow rate table, q(s,dp) parameter. A positive displacement corresponds to valve opening. The values are listed in ascending order and the first element must be 0. Linear interpolation is employed between table data points.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Tabulated data - Volumetric flow rate vs. spool travel and pressure drop```.

Vector of pressure drop values for tabular parametrization of volumetric flow rate. The pressure drop vector forms an independent axis with the Spool travel vector, s parameter for the 3-D dependent Volumetric flow rate table, q(s,dp) parameter. The values are listed in ascending order and must be greater than 0. Linear interpolation is employed between table data points.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Tabulated data -Volumetric flow rate vs. spool travel and pressure drop```.

M-by-N matrix of volumetric flow rates based on independent values of pressure drop and spool travel distance. M and N are the sizes of the correlated vectors:

• M is the number of vector elements in the Pressure drop vector, dp parameter.

• N is the number of vector elements in the parameter.

#### Dependencies

To enable this parameter, set Orifice parametrization to ```Tabulated data - Volumetric flow rate vs. spool travel and pressure drop```.

Discharge loss for a hydraulic structure. The default discharge coefficient for an valve in Simscape™ Fluids™ is 0.64.

#### Dependencies

To enable this parameter, set Orifice parametrization to:

• ```Tabulated data - Area vs. spool travel```

• ```Linear - area vs. spool travel```

Upper Reynolds number limit for laminar flow through the valve.

#### Dependencies

To enable this parameter, set Orifice parametrization to:

• ```Tabulated data - Area vs. spool travel```

• ```Linear - area vs. spool travel```

Continuous smoothing factor that introduces a layer of gradual change based to the flow response when the valve is in 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 Orifice parametrization to `Linear - area vs. spool travel`.

Whether to account for pressure increase when the fluid flows from a region of smaller cross-sectional area to a region of larger cross-sectional area. 