Rotational Mechanical Converter (IL)
Interface between isothermal liquid and mechanical rotational networks.
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Description
The Rotational Mechanical Converter (IL) block represents the interface between an isothermal liquid network and a mechanical rotational network. The block converts fluid pressure into torque and vice versa. It can be used as a basis for rotating hydraulic drives.
The fluid volume in the converter changes during operation. If the Fluid dynamic compressibility parameter is enabled, the pressure is calculated according to the compressibility of the fluid (fluid dynamic compressibility).
The Mechanical orientation parameter determines whether an increase in fluid volume causes the R port to rotate positively or negatively with respect to the C port.
Port A is the isothermal liquid port corresponding to the transducer input. Ports R and C are mechanical rotational ports corresponding to the shaft and housing, 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 transducer (
1if increasing fluid pressure causes positive rotation of R relative to C,-1if increasing fluid pressure causes negative rotation of R relative to C). -
- is the density of the liquid inside the transducer.
-
- the bulk modulus of elasticity of the fluid.
-
- volumetric displacement of the transducer, i.e. the volume of fluid required to rotate the shaft per unit angle.
-
- angular velocity of the transducer shaft rotation.
-
and * are angular velocities of ports R and C respectively.
-
- is the rotation angle of the inverter shaft.
-
- volume of liquid inside the converter.
-
- volume of liquid at which the shaft rotation angle is equal to
0. -
- pressure inside the converter.
The shaft rotation angle 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 rotation of R relative to C, the shaft rotation angle when the fluid volume is increased compared to . -
If the Mechanical orientation parameter is set to
Pressure at A causes negative rotation of R relative to C, the shaft angle decreases when the fluid volume increases compared to .
The equations used to calculate the density and bulk modulus of elasticity of a fluid mixture depend on the isothermal liquid model selected.
Impulse balance
The equation of conservation of momentum in the volume of a mechanical transducer is of the form:
,
where:
-
- is the torque on the inverter shaft.
-
- ambient pressure.
Assumptions and limitations
-
The walls of the inverter are perfectly rigid.
-
The inverter does not contain any mechanical hard stops. Use the Rotational 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
The isothermal liquid port corresponds to the inlet of the transmitter.
R is the shaft
`rotational mechanics
Mechanical rotational port, corresponds to the shaft of the inverter.
C - housing
`rotational mechanics
The mechanical rotary port corresponds to the inverter housing.
Parameters
Mechanical orientation - inverter orientation
Pressure at A causes positive rotation of R relative to C (by default) | `Pressure at A causes negative rotation of R relative `
Sets the direction of shaft rotation relative to the fluid pressure:
-
`Pressure at A causes positive rotation of R relative to C' - increasing fluid pressure causes positive rotation of port R relative to port C.
-
`Pressure at A causes negative rotation of R relative to C' - an increase in fluid pressure causes negative rotation of port R relative to port C.
Initial interface rotation - initial angular position of port R relative to port C at the beginning of the simulation
0.0 (by default)
Angular position 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 is set to `Pressure at A causes positive rotation of R relative to C', the value must be greater than or equal to `0'.
-
If Mechanical orientation has the value
Pressure at A causes negative rotation of R relative to C, the value of the parameter must be less than or equal to0.
Interface volume displacement - volume of fluid displaced per unit rotation angle
0.001 m³/rad (by default).
The volume of fluid displacement per unit angle of rotation of the shaft.
Dead volume - volume of liquid in the transmitter at which the shaft rotation angle is equal to zero
1e-5 m³ (by default)
The volume of liquid in the transmitter at which the shaft rotation angle is zero.
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- atmospheric pressure. -
Specified pressure- the exact value specified in the Environment pressure parameter.
Environment pressure - pressure outside 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
Available 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 the initial moment of time
`0.101325 MPa (by default).
Liquid pressure at the beginning of the simulation.
Dependencies
Used when Fluid dynamic compressibility is set to Enabled.