Translational Mechanical Converter (IL)
Interface between isothermal liquid and mechanical progressive networks.
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Description
The Translational Mechanical Converter (IL) block represents the interface between an isothermal liquid network and a mechanical progressive network. The block converts fluid pressure into mechanical force and vice versa. It can be used as a basis for translational actuators.
The block icon changes depending on the value of the Mechanical orientation parameter.
The volume of fluid in the inverter changes during operation. If Fluid dynamic compressibility is enabled, the pressure is calculated based on the compressibility of the fluid (fluid dynamic compressibility).
The Mechanical orientation parameter determines whether an increase in fluid volume causes the R port to move towards or away from the C port.
Port A is the isothermal liquid port corresponding to the transducer input. Ports R and C are mechanical progressive ports corresponding to the stem and body of the transmitter, respectively.
Mass conservation
The mass conservation equations for the transducer are of the form:
Where:
-
- is the mass flow rate through the port A.
-
- mechanical orientation of the converter (
1if the increase in fluid pressure causes a positive displacement of R relative to C,-1if the increase in fluid pressure causes a negative displacement of R relative to C). -
- is the density of the liquid inside the converter.
-
- the bulk modulus of elasticity of the fluid in the transducer.
-
- cross-sectional area of the hydraulic part of the transducer.
-
- linear velocity of the mechanical part of the transducer.
-
and - linear velocities of ports R and C respectively.
-
- displacement of the mechanical part of the converter.
-
- volume of liquid inside the transducer.
-
- volume of liquid at which the position of the rod is equal to
0. -
- pressure inside the transmitter.
The stem position is zero when the fluid volume is equal to . Depending on the value of the Mechanical orientation parameter:
-
If the Mechanical orientation parameter is set to
Pressure at A causes positive displacement of R relative to C, the stem displacement increases when the fluid volume increases compared to . -
If Mechanical orientation is set to
Pressure at A causes negative displacement of R relative to C, the stem displacement decreases when the fluid volume increases compared to .
The equations used to calculate the density and bulk modulus of a mixture of fluids depend on the isothermal liquid model selected.
Assumptions and limitations
-
The walls of the inverter are perfectly rigid.
-
The inverter does not contain any mechanical hard stops. Use the Translational Hard Stop block to enable hard limiters.
-
The flow resistance between the inlet and the inside of the inverter is negligible.
-
The kinetic energy of the fluid in the transmitter is negligible.
Ports
Non-directional
A - inlet port of the transducer
isothermal liquid
isothermal liquid port, corresponds to the inlet of the transducer.
R - stem
translational mechanics
Mechanical progressive port, corresponds to the inverter stem.
C - housing
Mechanical progressive port
Mechanical progressive port, corresponds to the inverter housing.
Parameters
Mechanical orientation - orientation of the inverter
Pressure at A causes positive displacement of R relative to C (by default) | `Pressure at A causes negative displacement of R relative `
Sets the direction of stem movement relative to the fluid pressure:
-
`Pressure at A causes positive displacement of R relative to C' - increasing fluid pressure 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 pressure causes a negative displacement of R relative to port C.
Initial interface displacement - initial displacement of port R relative to port C
`0 (By default)
`0 (By default)
Linear displacement of port R relative to port C at the beginning of the simulation, m. The value 0 corresponds to the 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 value of the parameter 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, the parameter value must be less than or equal to0.
Interface cross-sectional area is the area pressurised by the fluid to produce the force
0.01 m² (By default).
The area that the fluid pressurises to create force.
Dead volume is the volume of fluid at which the stem position is 0
1e-5 m³ (by default).
Liquid volume at which the stem position is 0.
Environment pressure specification - method of specifying the ambient pressure
Atmospheric pressure (by default) | Specified pressure.
Specifies the method for specifying the ambient pressure:
-
Atmospheric pressure- use atmospheric pressure. -
Specified pressure- the pressure value specified in the Environment pressure parameter.
*Environment pressure - pressure outside the transmitter
101325 Pa (By default).
The pressure outside the inverter acting against the pressure inside. A value of 0 indicates that the inverter is operating in vacuum.
Dependencies
Used when Environment pressure specification is set to Specified pressure.
Fluid dynamic compressibility - determines whether to model the dynamic compressibility of the fluid
Enabled (By default) | Disabled.
Specifies whether the dynamic compressibility of the fluid should be considered. Dynamic compressibility makes the fluid density pressure dependent, which affects the transient response of the system on small time scales.
Initial liquid pressure is the pressure of the liquid at zero moment of time
`101325 Pa (by default).
Liquid pressure at the beginning of the simulation.
Dependencies
Used when Fluid dynamic compressibility is set to Enabled.