Translational Mechanical Converter (TL)

Interface between thermally conductive fluid and mechanical progressive networks.

translational mechanical converter (tl)

Description

The Translational Mechanical Converter (TL) block models the interface between a thermal liquid network and a translational mechanics network. The block converts thermal liquid pressure into mechanical force and vice versa. The block can be used as a basic component for linear actuators.

The inverter has a variable volume of fluid, and the change in fluid temperature is calculated by taking into account the heat capacity of this volume. If Fluid dynamic compressibility is checked, the pressure will also depend on the dynamic compressibility of the fluid. The Mechanical orientation parameters determine the direction of movement of the R port relative to the C port as the pressure increases.

Port A is the thermal liquid port corresponding to the inlet cross-section of the transducer. Port H is a thermal port representing the temperature of the fluid inside the transmitter. Ports R and C are mechanical progressive motion ports associated with the moving part (rod) and the transducer body, respectively.

Mass conservation

The mass conservation equation for a mechanical transducer is as follows:

where:

- is the mass flow rate of fluid in the transducer through port A.
- mechanical orientation of the transducer (1 if the increase in fluid pressure causes a positive displacement of R relative to C, -1 if the increase in fluid pressure causes a negative displacement of R relative to C).
- density of the fluid in the transducer.
- cross-sectional area of the working surface of the transducer stem.
- velocity of the transducer stem.
- volume of liquid inside the transducer.
- volume modulus of elasticity of the liquid in the transducer body.
- coefficient of thermal expansion of the liquid.
- pressure of the liquid inside the transducer body.
- temperature of the liquid inside the converter body.

In the block, the stem displacement is calculated from the relative port velocities according to the block equations. The rod position is zero when the fluid volume is equal to the uninvolved volume (value of the Dead Volume parameters). The direction of stem action is determined by the Mechanical orientation parameters:

If `Pressure at A causes positive displacement of R relative to C', then the rod displacement increases when the fluid volume increases compared to the idle volume.
If `Pressure at A causes negative displacement of R relative to C', the stem displacement decreases when the fluid volume increases compared to the unused volume.

Conservation of momentum

The conservation of momentum equation for a mechanical transducer is of the form:

where:

- is the force with which the liquid acts on the transducer stem.
- atmospheric pressure.

Conservation of energy

The conservation of energy equation for a mechanical transducer is as follows:

where:

- is the internal energy of the fluid.
- is the total energy flux through port A.
- value of heat flux through the port H.

Assumptions and limitations

The walls of the transducer are absolutely rigid. They are not deformed by internal pressure and temperature.
The inverter does not contain any mechanical rigid restraints. To add rigid restraints, use block Translational Hard Stop.
The hydraulic resistance to flow between the inlet port and the inside of the drive is negligible.
The thermal resistance between the thermal port and the inside of the converter is negligible.
The kinetic energy of the fluid in the converter is negligible.

Ports

Non-directional

A - input port to the transmitter
thermal liquid

Thermal liquid port, corresponds to the inlet to the inverter.

H is the temperature of the fluid in the transmitter
heat

Heat port related to the temperature of the liquid in the converter.

R - stem
` translational mechanics'

Mechanical progressive port, corresponds to the inverter stem.

C - housing
translational mechanics

Mechanical progressive port, corresponds to the inverter housing.

Parameters

Main

Mechanical orientation - orientation of the transducer

Pressure at A causes positive displacement of R relative to C (by default)|Pressure at A causes negative displacement of R relative to C

Parameters sets the direction of stem movement depending on the change of liquid volume:

`Pressure at A causes positive displacement of R relative to C' - an increase in fluid volume causes positive displacement of port R relative to port C.
`Pressure at A causes negative displacement of R relative to C' - an increase in fluid volume causes negative displacement of port R relative to port C.

Initial interface displacement - initial position of port R relative to port C
`m (By default)

Linear displacement of port R relative to port C at the beginning of the simulation. A value of 0 corresponds to an initial fluid volume equal to Dead volume.

Dependencies

If Mechanical orientation has the value Pressure at A causes positive displacement of R relative to C, the parameter value must be greater than or equal to 0.
If Mechanical orientation has the value Pressure at A causes negative displacement of R relative to C, then the parameter value must be less than or equal to 0.

Interface cross-sectional area is the cross-sectional area of the internal channel of the transmitter, or the working area of the stem, which is pressurised by the fluid to produce a force of
0.01 m^2 (by default).

The area that the fluid pressurises to create a translational force.

Dead volume - the volume of fluid at which the stem position is 0
1e-5 m^3 (by default).

The volume of liquid at which the stem position is 0.

Environmental pressure specification - method of determining the ambient pressure
Atmospheric pressure (by default) | Specified pressure.

Specifies the method for determining the ambient pressure:

Atmospheric pressure - uses the atmospheric pressure specified in the Thermal Liquid Settings (TL) or Thermal Liquid Properties (TL) blocks connected to the circuit.
Specified pressure - the pressure value specified in the Environment pressure parameters is used.

Environment pressure - pressure of the medium in the external part of the transmitter
0.101325 MPa (by default).

The pressure outside the inverter acting against the pressure inside. A value of 0 indicates that the transmitter is operating in vacuum.

Dependencies

Used when the Environment pressure specification parameters are set to Specified pressure.

Effects and Initial Conditions

Fluid dynamic compressibility - fluid dynamic compressibility modelling
On (By default) | Off

Tick the checkbox to enable dynamic compressibility modelling. During simulation, dynamic compressibility determines the dependence of fluid density on pressure and temperature, and affects transients in the system in small time intervals.

Initial liquid pressure - initial value of liquid pressure
`0.101325 MPa (by default)

Liquid pressure in the transmitter at the beginning of the simulation.

Dependencies

To enable this parameter, select the Fluid dynamic compressibility checkbox.

Initial liquid temperature - Initial liquid temperature value
`293.15 K (By default).

The temperature of the liquid in the transmitter at the beginning of the simulation.