2-Way Directional Valve (TL)

2-way directional valve in a thermal liquid network

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• Simscape / Fluids / Thermal Liquid / Valves & Orifices / Directional Control Valves

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Description

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

The block uses a variable orifice to control the flow between ports A and B. The physical signal at port S triggers the spool motion to open or shut the valve. For more details about how the block calculates flow rate through a variable orifice, see Orifice (TL).

Orifice Parameterizations

You can parameterize the valve opening linearly or by using tabulated data.

Linear

When you set Orifice parameterization to Linear - Area vs. spool travel, the opening area is a linear function of the spool travel distance.

$$A_{orifice}=\frac{\left(A_{\max }-A_{leak}\right)}{\Delta S_{\max }}\Delta S+A_{leak},$$

where

• A_orifice is the opening area.

• ΔS is the spool travel distance input at port S. $$\Delta S=S-S_{\max }+\Delta S_{\max }.$$

• ΔS_max is the value of the Spool travel between closed and open orifice parameter.

• A_Leak is the value of the Leakage area parameter.

• A_max is the value of the Maximum orifice area parameter.

Note the linear scaling from A_Leak to A_max in the figure.

When the valve is in near-open or near-closed position, you can maintain numerical robustness in your simulation by adjusting the block Smoothing factor. The block computes the normalized valve area as

$$\widehat{A}=\frac{\left(A_{orifice}-A_{leak}\right)}{\left(A_{\max }-A_{leak}\right)}.$$

The block applies the Smoothing factor parameter, s, to smooth the normalized valve area as

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

Lastly, the block scales the smoothed, normalized valve area as

$$A_{smoothed}={\widehat{A}}_{smoothed}\left(A_{\max }-A_{leak}\right)+A_{leak}.$$

Tabulated

When you set Orifice parameterization to Tabulated data - Area vs. spool travel, the block uses the Spool travel vector and Orifice area vector parameters to define the relationship between A_orifice and ΔS by interpolation. A_leak and A_max are the first and last parameters of the Orifice area vector parameter, respectively.

When you set Orifice parameterization to Tabulated data - Volumetric flow rate vs. spool travel and pressure drop, the block uses the Volumetric flow rate table, q(ds,dp), Pressure drop vector, dp, and Spool travel vector, ds parameters to define the volumetric flow rate, q(ΔS,p).

When you set Orifice parameterization to Tabulated data - Mass flow rate vs. opening and pressure drop the block calculates the mass flow rate directly from the spool position and the pressure drop across the valve. The relationship between the three variables can be nonlinear and it is given by the tabulated data in the Spool travel vector, ds, Pressure drop vector, dp, and Mass flow rate table, mdot(ds,dp) parameters.

Ports

Conserving

A — Liquid port

thermal liquid

Thermal liquid conserving port.

B — Liquid port

thermal liquid

Thermal liquid conserving port.

Input

S — Spool displacement, m

physical signal

Physical signal associated with the spool displacement, in m. A positive value causes the valve to open.

Parameters

Model Parameterization

Orifice parameterization — Opening area relationship

Linear - Area vs. spool travel (default) | Tabulated data - Area vs. spool travel | Tabulated data - Volumetric flow rate vs. spool travel and pressure drop | Tabulated data - Mass flow rate vs. spool travel and pressure drop

Method the block uses to calculate the valve flow area.

Spool position at maximum orifice area — Spool offset at maximum area

5e-3 m (default) | positive scalar

Position of the spool travel member when the valve is fully open.

Spool travel between closed and open orifice — Maximum spool stroke

5e-3 m (default) | positive scalar

Spool offset at the maximum valve opened area.

Dependencies

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

Maximum orifice area — Area of fully open valve

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

Maximum valve area experienced during simulation.

Dependencies

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

Leakage area — Valve gap area when in fully closed position

1e-10 m^2 (default) | positive scalar

Sum of all gaps when the valve is in the fully closed position. The block maintains any area smaller than this value 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.

Smoothing factor — Numerical smoothing factor

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

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.

Spool travel vector — Spool opening distance values

[0, .002, .004, .007, .017] m (default) | vector

Vector of control member travel distances. A positive value opens the valve. The values in this vector correspond one-to-one to values in the Orifice area vector parameter. The values must ascend from 0. The block interpolates the points linearly.

Dependencies

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

Orifice area vector — Valve opening area values

[1e-09, 2.0352e-07, 4.0736e-05, .00011438, .00034356] m^2 (default) | vector

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. The block interpolates the points linearly.

Dependencies

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

Discharge coefficient — Discharge coefficient

0.7 (default) | positive scalar

Discharge loss for a hydraulic structure.

Dependencies

To enable this parameter, set Orifice parametrization to either:

• Tabulated data - Area vs. spool travel

• Linear - area vs. spool travel

Critical Reynolds number — Upper Reynolds number limit for laminar flow

12 (default) | positive scalar

Upper Reynolds number limit for laminar flow through the valve.

Dependencies

To enable this parameter, set Orifice parametrization to either:

• Tabulated data - Area vs. spool travel

• Linear - area vs. spool travel

Pressure recovery — Whether to account for pressure increase in area expansions

On (default) | Off

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.

Spool travel vector, ds — Tabular spool opening distance values

[0, .002, .004, .007, .017] m (default) | vector

Vector of control member travel distances. 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(ds,dp) parameter. A positive displacement corresponds to valve opening. The values ascend from 0. The block interpolates the points linearly.

Dependencies

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

Pressure drop vector, dp — Tabular pressure drop values

[.3, .5, .7] MPa (default) | vector

Vector of pressure drop values for the volumetric flow rate. The pressure drop vector forms an independent axis with the Spool travel vector, ds parameter for the 3-D dependent Volumetric flow rate table, q(ds,dp) parameter. The values must be ascending. The block interpolates the points linearly

Dependencies

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

Volumetric flow rate table, q(ds,dp) — Volumetric flow rate for given spool travel and pressure drop

[1.7e-05, 2e-05, 2.6e-05; .0035, .0045, .0053; .7, .9, 1.06; 1.96, 2.5, 3; 6, 7.7, 9.13] m^3/s (default) | matrix

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 elements in the Spool travel vector, ds parameter.

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

Dependencies

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

Mass flow rate table, mdot(ds,dp) — Mass flow rate for given spool travel and pressure drop

[1.7e-05, 2e-05, 2.6e-05; .0035, .0045, .0053; .7, .9, 1.06; 1.96, 2.5, 3; 6, 7.7, 9.13] kg/s (default) | matrix

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 elements in the Spool travel vector, ds parameter.

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

Dependencies

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

Reference inflow temperature — Temperature at which mass flow rate data is specified

293.15 K (default) | positive scalar

Temperature at which the tabulated mass flow rate data is specified.

Dependencies

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

Reference inflow pressure — Pressure at which mass flow tabulated data is specified

0.101325 MPa (default) | positive scalar

Pressure at which the tabulated mass flow rate data is specified. The block uses this parameter to calculate a third reference parameter, the reference density.

Dependencies

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

Cross-sectional area at ports A and B — Valve area at conserving ports

inf m^2 (default) | positive scalar

Cross-sectional area at ports A and B. The block uses this area in the pressure-flow rate equation to determine the volumetric flow rate through the valve.

Dependencies

To enable this parameter, set Orifice parametrization to either:

• Tabulated data - Area vs. spool travel

• Linear - area vs. spool travel

Model Examples

Aircraft Fuel Supply System with Three Tanks

The fuel supply system represented in the example consists of three tanks and an engine. The tanks are connected by the fuel lines and the pressure drop in the fuel lines depends on the bank angle of the aircraft or the relative elevation of the ends of the fuel lines. The central tank bottom is elevated by 36 in with respect to the reference plane, which is drawn horizontally through the entry point of the engine. The side tank bottoms are elevated by 4.2 in each at zero bank angle.

Open Model

Extended Capabilities

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

Version History

Introduced in R2016a