Documentation

3-Way Directional Valve (TL)

Three-port two-position directional control valve

Library

Thermal Liquid/Valves/Directional Control Valves

Description

The 3-Way Directional Valve (TL) block represents a three-port two-position directional control valve for the thermal liquid domain. Valve position 1 allows fluid flow between ports A and T. Valve position 2 allows fluid flow between ports A and P. The figure shows the two valve positions.

Physical signal input port S sets the valve position through a control member displacement signal. The valve is in position 1 at a zero control member displacement. It is in position 2 at the maximum allowable displacement specified through the Maximum valve opening block parameter.

This block is a composite component based on two Simscape™ Fluids™ Variable Area Orifice (TL) blocks. The figure shows the equivalent block diagram for this component. Each block corresponds to a valve flow path. The block names identify the associated flow paths. For example, the Variable Area Orifice (TL) P-A block corresponds to the flow path between ports P and A.

Composite Component Diagram

Physical signal S controls all Variable Area Orifice (TL) blocks, and therefore all flow paths, simultaneously. The control member position for a given orifice is a function of the Control member offset value specified in the block dialog box and the control member displacement specified through port S. The control member position for the P-A orifice is

lPA=lpA,0+dS,

while for the T-A orifice it is

lTA=lAT,0dS,

where:

  • lP-A and lT-A are the control member positions for the P-A and T-A orifices.

  • lP-A,0 and lT-A,0 are the initial control member offsets for the P-A and T-A orifices.

  • dS is the control member displacement specified through physical signal input port S.

Parameters

Parameters Tab

Valve area parameterization

Parameterization used to calculate the valve opening area. Select Linear area-opening relationship to calculate this area from the valve control member displacement. Select Tabulated data — Area vs. opening to specify the valve open area as a lookup table parameterized in terms of the valve control member displacement. The default setting is Linear area-opening relationship.

Maximum valve opening

Control member displacement at which the valve opening area reaches its maximum value. The physical signal input S saturates at this value. This parameter is active only when the Orifice area parameterization parameter is set to Analytical. The default value is 0.005 m.

Maximum opening area

Valve cross-sectional area in the fully open position. This area corresponds to the maximum control member displacement. This parameter is active only when the Orifice area parameterization parameter is set to Analytical. The default value is 1e-4 m^2.

Leakage area

Area through which fluid can flow in the fully closed valve position. This area accounts for leakage between the valve inlets. The default value is 1e-10 m^2.

Smoothing factor

Portion of the opening-area curve to smooth expressed as a fraction. Smoothing eliminates discontinuities at the minimum and maximum flow valve positions. The smoothing factor must be between 0 and 1.

Opening-Area Curve Smoothing

Enter a value of 0 for zero smoothing. Enter a value of 1 for full-curve smoothing. The default value is 0.01. This parameter is visible only when the Valve area parameterization parameter is set to Linear area-opening relationship.

Valve opening vector

Vector of control member displacements at which to specify the valve cross-sectional area. This parameter is visible only when the Orifice area parameterization parameter is set to Tabulated. The default vector is a five-element vector ranging from -0.002 to 0.015 m.

Opening area vector

Vector of valve opening areas corresponding to the control member displacements specified through the Valve opening vector parameter. This parameter is visible only when the Orifice area parameterization parameter is set to Tabulated. The default vector is a five-element vector ranging from 1.0e-9 to 0.00034356 m^2.

Cross-sectional area at ports A, P, and T

Area normal to the direction of flow at the valve inlets. This area is assumed the same for all the inlets. The default value is 0.01 m^2.

Characteristic longitudinal length

Approximate length of the valve. This parameter provides a measure of the longitudinal scale of the valve. The default value is 0.1 m^2.

Discharge coefficient

Semi-empirical parameter commonly used as a measure of valve performance. The discharge coefficient is defined as the ratio of the actual mass flow rate through the valve to its theoretical value.

The block uses this parameter to account for the effects of valve geometry on mass flow rates. Textbooks and valve data sheets are common sources of discharge coefficient values. By definition, all values must be greater than 0 and smaller than 1. The default value is 0.7.

Critical Reynolds number

Reynolds number corresponding to the transition between laminar and turbulent flow regimes. The flow through the valve is assumed laminar below this value and turbulent above it. The appropriate values to use depend on the specific valve geometry. The default value is 12.

Valve Opening Offsets Tab

Between ports P and A

Control member offset from the zero position between ports P and A. The control member position is the sum of the offset specified and the physical signal input S. The offset value does not affect the hard stop locations. The default value is 0 m.

Between ports A and T

Control member offset from the zero position between ports A and T. The control member position is the sum of the offset specified and the physical signal input S. The offset value does not affect the hard stop locations. The default value is 0 m.

Ports

  • A — Thermal liquid conserving port representing valve inlet A

  • P — Thermal liquid conserving port representing valve inlet P

  • T — Thermal liquid conserving port representing valve inlet T

  • S — Physical signal input port for the control member displacement

Introduced in R2016a

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