Fixed-Displacement Motor (IL)

Fixed-displacement motor in isothermal liquid system

Since R2020a

Libraries:
Simscape / Fluids / Isothermal Liquid / Pumps & Motors

Description

The Fixed-Displacement Motor (IL) block models a motor with constant-volume displacement. The fluid may move from port A to port B, called forward mode, or from port B to port A, called reverse mode. Motor mode operation occurs when there is a pressure drop in the direction of the flow. Pump mode operation occurs when there is a pressure gain in the direction of the flow.

Shaft rotation corresponds to the sign of the fluid volume moving through the motor. Positive fluid displacement at corresponds to positive shaft rotation in forward mode. Negative fluid displacement corresponds to negative shaft angular velocity in forward mode.

The block has eight modes of operation. The working mode depends on the pressure drop from port A to port B, Δp = pApB and the angular velocity, ω = ωRωC:

• Mode 1, Forward Motor: Flow from port A to port B causes a pressure decrease from A to B and a positive shaft angular velocity.

• Mode 2, Reverse Pump: Negative shaft angular velocity causes a pressure increase from port B to port A and flow from B to port A.

• Mode 3, Reverse Motor: Flow from port B to port A causes a pressure decrease from B to A and a negative shaft angular velocity.

• Mode 4, Forward Pump: Positive shaft angular velocity causes a pressure increase from port A to port B and flow from A to B.

The motor block has analytical, lookup table, and physical signal parameterizations. When using tabulated data or an input signal for parameterization, you can choose to characterize the motor operation based on efficiency or losses.

In the tabulated data and the input signal parameterization options, the threshold parameters Pressure drop threshold for motor-pump transition and Angular velocity threshold for motor-pump transition identify regions where numerically smoothed flow transition between the motor operational modes can occur. Choose a transition region that provides some margin for the transition term, but which is small enough relative to the pressure and angular velocity that it will not impact calculation results.

Analytical Leakage and Friction Parameterization

If you set Leakage and friction parameterization to `Analytical`, the block calculates leakage and friction from constant values of shaft velocity, pressure drop, and friction torque. The leakage flow rate, which is correlated with the pressure differential over the motor, is calculated as:

`${\stackrel{˙}{m}}_{leak}=K{\rho }_{avg}\Delta p,$`

where:

• Δp is pApB.

• ρavg is the average fluid density.

• K is the Hagen-Poiseuille coefficient for analytical loss,

`$K=\frac{D{\omega }_{nom}\left(\frac{1}{{\eta }_{v,}{}_{nom}}-1\right)}{\Delta {p}_{nom}},$`

where:

• D is the value of the Displacement parameter.

• ωnom is the value of the Nominal shaft angular velocity parameter.

• ηv, nom is the value of the Volumetric efficiency at nominal conditions parameter.

• Δpnom is the value of the Nominal pressure drop parameter.

The friction torque, which is correlated with shaft angular velocity, is calculated as:

`${\tau }_{fr}=\left({\tau }_{0}+k|\Delta p|\right)\mathrm{tanh}\left(\frac{4\omega }{5×{10}^{-5}{\omega }_{nom}}\right),$`

where:

• τ0 is the value of the No-load torque parameter.

• k is the friction torque vs. pressure gain coefficient at nominal displacement, which is determined from the value of the parameter, ηm:

`$k=\frac{{\tau }_{fr,nom}-{\tau }_{0}}{\Delta {p}_{nom}}.$`

τfric is the friction torque at nominal conditions:

`${\tau }_{fr,nom}=\left(1-{\eta }_{m,nom}\right)D\Delta {p}_{nom}.$`

• Δp is the pressure drop between ports A and B.

• ω is the relative shaft angular velocity, or ${\omega }_{R}-{\omega }_{C}$.

Tabulated Data Parameterizations

When using tabulated data for motor efficiencies or losses, you can provide data for one or more of the motor operational modes. The signs of the tabulated data determine the operational regime of the block. When data is provided for less than four operational modes, the block calculates the complementing data for the other mode(s) by extending the given data into the remaining quadrants.

Tabulated Data - Volumetric and Mechanical Efficiencies Parameterization

The leakage flow rate is

`${\stackrel{˙}{m}}_{leak}={\stackrel{˙}{m}}_{leak,motor}\left(\frac{1+\alpha }{2}\right)+{\stackrel{˙}{m}}_{leak,pump}\left(\frac{1-\alpha }{2}\right),$`

where:

• ${\stackrel{˙}{m}}_{leak,pump}=\left({\eta }_{\upsilon }-1\right){\stackrel{˙}{m}}_{ideal}$

• ${\stackrel{˙}{m}}_{leak,motor}=\left(1-{\eta }_{v}\right)\stackrel{˙}{m}$

and ηv is the volumetric efficiency, which is interpolated from the user-provided tabulated data. The transition term, α, is

`$\alpha =\mathrm{tanh}\left(\frac{4\Delta p}{\Delta {p}_{threshold}}\right)\mathrm{tanh}\left(\frac{4\omega }{{\omega }_{threshold}}\right),$`

where:

• Δp is pApB.

• pthreshold is the value of the Pressure drop threshold for motor-pump transition parameter.

• ω is ωRωC.

• ωthreshold is the value of the Angular velocity threshold for motor-pump transition parameter.

The friction torque is calculated as:

`${\tau }_{fr}={\tau }_{fr,pump}\left(\frac{1+\alpha }{2}\right)+{\tau }_{fr,motor}\left(\frac{1-\alpha }{2}\right),$`

where:

• ${\tau }_{fr,pump}=\left({\eta }_{m}-1\right)\tau$

• ${\tau }_{fr,motor}=\left(1-{\eta }_{m}\right){\tau }_{ideal}$

and ηm is the mechanical efficiency, which is interpolated from the user-provided tabulated data.

Tabulated Data - Volumetric and Mechanical Losses Parameterization

The leakage flow rate is

`${\stackrel{˙}{m}}_{leak}={\rho }_{avg}{q}_{loss}\left(\Delta p,\omega \right),$`

where qloss is interpolated from the Volumetric loss table, q_loss(dp,w) parameter, which is based on user-supplied data for pressure drop, shaft angular velocity, and fluid volumetric displacement.

The shaft friction torque is calculated as:

`${\tau }_{fr}={\tau }_{loss}\left(\Delta p,\omega \right),$`

where τloss is interpolated from the Mechanical loss table, torque_loss(dp,w) parameter, which is based on user-supplied data for pressure drop and shaft angular velocity.

Tabulated Data - Torque and Speed Parameterization

The block calculates the volumetric loss table, qloss,TLU and the mechanical loss table, τloss,TLU, as

`$\begin{array}{l}{\text{q}}_{loss,TLU}={q}_{TLU}-D{\omega }_{TLU}\\ {\tau }_{loss,TLU}=D\Delta {p}_{TLU}-{T}_{TLU}\end{array}$`

where:

• qTLU is the value of the Flow rate vector, q parameter.

• ωTLU is the value of the Shaft speed table, w(q,dp) parameter.

• ΔpTLU is the value of the Pressure drop vector, dp parameter.

• TTLU is the value of the Torque table, T(q,dp) parameter.

If the supplied values for the Shaft speed table, w(q,dp) and Torque table, T(q,dp) parameters do not cover all four quadrants, the block extends the data by

• Symmetrically mirroring the values of the Pressure drop vector, dp and Flow rate vector, q parameters to contain negative values.

• Symmetrically extending the values of the volumetric loss table, qloss,TLU, to additional quadrants. The signs of these extended values match the sign ΔpTLU in each quadrant.

• Calculating the extended values of the shaft speed vector, ωTLU, from the extended values of the flow rate vector and volumetric loss table, ${\omega }_{TLU}=\frac{{q}_{TLU}-{q}_{loss,TLU}}{D}.$

• Symmetrically extending the values of the mechanical loss table, τloss,TLU, to additional quadrants. The signs of these extended values match the sign ωTLU in each quadrant.

If your data tables have unknown data points in any of the four corners or the Shaft speed table, w(q,dp) or Torque table, T(q,dp) parameters, use `NaN` in place of these values. The block fills in the `NaN` elements in the resulting volumetric loss table and mechanical loss table with nearest extrapolation with respect to pressure drop. The block adjusts the signs in the extrapolated mechanical loss table to match the sign of the corresponding elements in the shaft speed vector, ωTLU, where ${\omega }_{TLU}=\frac{{q}_{TLU}-{q}_{loss,TLU}}{D}.$

After extending or filling in the unknown data, the block uses linear interpolation and nearest extrapolation to calculate the volumetric and mechanical loss tables during simulation

`$\begin{array}{l}{q}_{loss}=tablelookup\left({q}_{TLU},\Delta {p}_{TLU},{q}_{loss,TLU},Q,\Delta p,interpolation=linear,extrapolation=nearest\right)\\ {\tau }_{loss}=tablelookup\left({q}_{TLU},\Delta {p}_{TLU},{\tau }_{loss,TLU},Q,\Delta p,interpolation=linear,extrapolation=nearest\right)\end{array}$`

where $Q=\frac{{\stackrel{˙}{m}}_{A}}{{\rho }_{avg}}.$

Input Signal Parameterization

When Leakage and friction parameterization is set to```Input signal - volumetric and mechanical efficiencies```, ports EV and EM are enabled. The internal leakage and shaft friction are calculated in the same way as the ```Tabulated data - volumetric and mechanical efficiencies``` parameterization, except that ηv and ηm are received directly at ports EV and EM, respectively.

When Leakage and friction parameterization is set to`Input signal - volumetric and mechanical losses`, ports LV and LM are enabled. These ports receive leakage flow and friction torque as positive physical signals. The leakage flow rate is calculated as:

`${\stackrel{˙}{m}}_{leak}={\rho }_{avg}{q}_{LV}\mathrm{tanh}\left(\frac{4\Delta p}{{p}_{thresh}}\right),$`

where:

• qLV is the leakage flow received at port LV.

• pthresh is the value of the Pressure drop threshold for motor-pump transition parameter.

The friction torque is calculated as:

`${\tau }_{fr}={\tau }_{LM}\mathrm{tanh}\left(\frac{4\omega }{{\omega }_{thresh}}\right),$`

where

• τLM is the friction torque received at port LM.

• ωthresh is the value of the Angular velocity threshold for motor-pump transition parameter.

The volumetric and mechanical efficiencies range between the user-defined specified minimum and maximum values. Any values lower or higher than this range will take on the minimum and maximum specified values, respectively.

Pump Operation

The motor flow rate is:

`$\stackrel{˙}{m}={\stackrel{˙}{m}}_{ideal}+{\stackrel{˙}{m}}_{leak},$`

where ${\stackrel{˙}{m}}_{ideal}={\rho }_{avg}D\cdot \omega .$

The motor torque is:

`$\tau ={\tau }_{ideal}-{\tau }_{fr},$`

where ${\tau }_{ideal}=D\cdot \Delta p.$

The mechanical power extracted by the motor shaft is:

`${\phi }_{mech}=\tau \omega ,$`

and the motor hydraulic power is:

`${\phi }_{hyd}=\frac{\Delta p\stackrel{˙}{m}}{{\rho }_{avg}}.$`

If you would like to know if the block is operating beyond the supplied tabulated data, you can set Check if operating beyond the range of supplied tabulated data to `Warning` to receive a warning if this occurs, or `Error` to stop the simulation when this occurs. For parameterization by input signal for volumetric or mechanical losses, you can be notified if the simulation surpasses operating modes with the Check if operating outside of motor mode parameter.

You can also monitor motor functionality. Set Check if pressures are less than motor minimum pressure to `Warning` to receive a warning if this occurs, or `Error` to stop the simulation when this occurs.

Predefined Parameterization

Pre-parameterized manufacturer data is available for this block. This data allows you to model a specific supplier component.

1. Click the "Select a predefined parameterization" hyperlink in the block dialog description.

2. Select a part from the drop-down menu and click Update block with selected part.

3. If you change any parameter settings after loading a parameterization, you can check your changes by clicking Compare block settings with selected part. Any difference in settings between the block and pre-defined parameterization will display in the MATLAB command window.

Note

Predefined block parameterizations use available data sources to supply parameter values. The block substitutes engineering judgement and simplifying assumptions for missing data. As a result, expect some deviation between simulated and actual physical behavior. To ensure accuracy, validate the simulated behavior against experimental data and refine your component models as necessary.

Ports

Conserving

expand all

Entry or exit port to the motor.

Entry or exit port to the motor.

Rotating shaft angular velocity and torque.

Motor casing reference angular velocity and torque.

Input

expand all

Motor efficiency for fluid displacement, specified as a physical signal. The value must be between 0 and 1.

Dependencies

To enable this port, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Motor efficiency for the mechanical extraction of energy, specified as a physical signal. The value must be between 0 and 1.

Dependencies

To enable this port, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Motor losses associated with fluid displacement in m^3/s, specified as a physical signal.

Dependencies

To enable this port, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical losses```.

Motor losses associated with the mechanical extraction of energy in N*m, specified as a physical signal.

Dependencies

To enable this port, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical losses```.

Parameters

expand all

Parameterization of the leakage and friction characteristics of the pump.

• In the `Analytical` parameterization, the leakage flow rate and the friction torque are calculated by analytical equations.

• In the ```Tabulated data - volumetric and mechanical efficiencies``` parameterization, the volumetric and mechanical efficiencies are calculated from the user-supplied Pressure drop vector, dp and Shaft angular velocity vector, w parameters and interpolated from the 2-D dependent Volumetric efficiency table, e_v(dp,w) and Mechanical efficiency table, e_m(dp,w) tables.

• In the ```Tabulated data - volumetric and mechanical loss``` parameterization, the leakage flow rate and torque friction are calculated from user-supplied Pressure drop vector, dp and Shaft angular velocity vector, w parameters and interpolated from the 2-D dependent Volumetric loss table, q_loss(dp,w) and Mechanical loss table, torque_loss(dp,w) tables.

• In the ```Tabulated data - torque and speed``` parameterization, you can enter the torque and shaft speed as functions of flow rate and pressure drop by using the Torque table T(q,dp) and Shaft speed table w(q,dp) parameters.

• In the ```Input signal - volumetric and mechanical efficiencies``` parameterization, the volumetric and mechanical efficiencies are received as physical signals at ports EV and EM, respectively.

• In the ```Input signal - volumetric and mechanical loss``` parameterization, the leakage flow rate and torque friction are received as physical signals at ports LV and LM, respectively.

Amount of fixed-volume fluid displacement.

Angular velocity of the shaft under nominal operating conditions.

Dependencies

To enable this parameter, set Leakage and friction parameterization to `Analytical`.

Motor pressure drop between the fluid entry and exit under nominal operating conditions.

Dependencies

To enable this parameter, set Leakage and friction parameterization to `Analytical`.

Ratio of actual flow rate to ideal flow rate at nominal conditions.

Dependencies

To enable this parameter, set Leakage and friction parameterization to `Analytical`.

Minimum value of torque to overcome seal friction and induce shaft motion.

Dependencies

To enable this parameter, set Leakage and friction parameterization to `Analytical`.

Ratio of actual torque to ideal torque generated at nominal conditions.

Dependencies

To enable this parameter, set Leakage and friction parameterization to `Analytical`.

Vector of pressure differential values for the tabular parameterization of leakage and torque friction. This vector forms an independent axis with the Shaft angular velocity vector, w parameter or the Flow rate vector, q parameter for the 3-D dependent Volumetric efficiency table, e_v(dp,w), Mechanical efficiency table, e_m(dp,w), Torque table, T(q,dp), and Shaft speed table, w(q,dp) parameters. The vector elements must be listed in ascending order.

Dependencies

To enable this parameter, set Leakage and friction parameterization to either:

• ```Tabulated data - volumetric and mechanical efficiencies```

• ```Tabulated data - volumetric and mechanical losses```

• ```Tabulated data - torque and speed```

Vector of angular velocity data for the tabular parameterization of leakage and torque friction. This vector forms an independent axis with the Shaft angular velocity vector, w parameter for the 3-D dependent Volumetric efficiency table, e_v(dp,w) and Mechanical efficiency table, e_m(dp,w) parameters. The vector elements must be listed in ascending order.

Dependencies

To enable this parameter, set Leakage and friction parameterization to either:

• ```Tabulated data - volumetric and mechanical efficiencies```

• ```Tabulated data - volumetric and mechanical losses```

Vector of flow rate data for the tabular parameterization of torque and speed. This vector forms an independent axis with the Pressure drop vector, dp parameter for the 3-D dependent Torque table, T(q,dp) and Shaft speed table, w(q,dp) parameters. The vector elements must be listed in ascending order.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - torque and speed```.

M-by-N matrix of volumetric efficiencies at the specified fluid pressure drop and shaft angular velocity. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

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

• N is the number of vector elements in the parameter.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - volumetric and mechanical efficiencies```.

M-by-N matrix of mechanical efficiencies at the specified fluid pressure drop and shaft angular velocity. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

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

• N is the number of vector elements in the parameter.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - volumetric and mechanical efficiencies```.

M-by-N matrix of volumetric efficiencies at the specified fluid pressure drop and shaft angular velocity. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

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

• N is the number of vector elements in the parameter.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - volumetric and mechanical losses```.

M-by-N matrix of mechanical losses at the specified fluid pressure drop and shaft angular velocity. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

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

• N is the number of vector elements in the parameter.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - volumetric and mechanical losses```.

M-by-N matrix of torque values at the specified fluid pressure drop and flow rate. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

• M is the number of elements in the parameter.

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

If your table has unknown data points in any of the four corners, use `NaN` in place of these values.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - torque and speed```.

M-by-N matrix of shaft speed values at the specified fluid pressure drop and flow rate. The block employs linear interpolation between table elements. M and N are the sizes of the correlated vectors:

• M is the number of elements in the parameter.

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

If your table has unknown data points in any of the four corners, use `NaN` in place of these values.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Tabulated data - torque and speed```.

Minimum value of volumetric efficiency. If the input signal is below this value, the volumetric efficiency is set to the minimum volumetric efficiency.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Maximum value of volumetric efficiency. If the input signal is above this value, the volumetric efficiency is set to the maximum volumetric efficiency.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Minimum value of mechanical efficiency. If the input signal is below this value, the mechanical efficiency is set to the minimum mechanical efficiency.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Maximum value of mechanical efficiency. If the input signal is above this value, the mechanical efficiency is set to the maximum mechanical efficiency.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical efficiencies```.

Threshold pressure drop value for the transition between pump and motor functionality. A transition region is defined around 0 MPa between the positive and negative values of the pressure drop threshold. Within this transition region, the computed leakage flow rate and friction torque are adjusted according to the transition term α to ensure smooth transition from one mode to the other.

Dependencies

To enable this parameter, set Leakage and friction parameterization to either:

• ```Tabulated data - volumetric and mechanical efficiencies```

• ```Input signal - volumetric and mechanical efficiencies```

• ```Input signal - volumetric and mechanical losses```

Threshold angular velocity value for the transition between pump and motor functionality. A transition region is defined around 0 rpm between the positive and negative values of the angular velocity threshold. Within this transition region, the computed leakage flow rate and friction torque are adjusted according to the transition term α to ensure smooth transition from one mode to the other.

Dependencies

To enable this parameter, set Leakage and friction parameterization to either:

• ```Tabulated data - volumetric and mechanical efficiencies```

• ```Input signal - volumetric and mechanical efficiencies```

• ```Input signal - volumetric and mechanical losses```

Whether to notify if the extents of the supplied data are surpassed. Select `Warning` to be notified when the block uses values beyond the supplied data range. Select `Error` to stop the simulation when the block uses values beyond the supplied data range.

When Leakage and friction parameterization to ```Tabulated data - torque and speed```, this parameter also checks if the block is operating in a region of supplied `NaN` values.

Dependencies

To enable this parameter, set Leakage and friction parameterization to:

• ```Tabulated data - volumetric and mechanical efficiencies```

• ```Tabulated data - volumetric and mechanical losses```

• ```Tabulated data - torque and speed```

Whether to notify if block operates outside of the motor mode functionality. This block has four operation modes: forward motor, reverse motor, reverse pump, and forward pump. Select `Warning` to be notified when the block operates in the forward or reverse motor pump modes. Select `Error` to stop the simulation when the block operates in the forward or reverse pump modes.

Dependencies

To enable this parameter, set Leakage and friction parameterization to ```Input signal - volumetric and mechanical losses```.

Whether to notify if the fluid at port A or B experiences low pressure. Select `Warning` to be notified when the outlet pressure falls below a minimum specified value. Select `Error` to stop the simulation when the outlet pressure falls below a minimum specified value.

The parameter helps identify potential conditions for cavitation, when the fluid pressure falls below the fluid vapor pressure.

Lower threshold of acceptable pressure at the motor inlet or outlet.

Dependencies

To enable this parameter, set Check if pressures are less than motor minimum pressure to either:

• `Warning`

• `Error`

Version History

Introduced in R2020a

expand all