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Fixed-Displacement Motor (IL)

Fixed-displacement motor in isothermal liquid system

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  • Fixed-Displacement Motor (IL) block

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.

Operation Modes

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: Positive shaft angular velocity causes a pressure decrease from port A to port B and flow from port A to port B.

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

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

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

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 torque. The leakage flow rate, which is correlated with the pressure differential over the motor, is calculated as:

m˙leak=KρavgΔp,

where:

  • Δpnom is the Nominal pressure drop.

  • ρavg is the average fluid density.

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

    K=Dnomωnom(1ηv,nom1)Δpnom,

    where:

    • Dnom is the Displacement.

    • ωnom is the Nominal shaft angular velocity.

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

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

τfr=(τ0+k|Δp|)tanh(4ω5×105ωnom),

where:

  • τ0 is the No-load torque.

  • k is the Friction torque vs. pressure drop coefficient.

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

  • ω is the relative shaft angular velocity, or ωRωC.

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.

The Tabulated data - volumetric and mechanical efficiencies parameterization

The leakage flow rate is calculated as:

m˙leak=m˙leak,motor(1+α2)+m˙leak,pump(1α2),

where:

  • m˙leak,pump=(ηυ1)m˙ideal

  • m˙leak,motor=(1ηv)m˙

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

α=tanh(4ΔpΔpthreshold)tanh(4ωωthreshold),

where:

  • Δp is pApB.

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

  • ω is ωRωC.

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

The friction torque is calculated as:

τfr=τfr,pump(1+α2)+τfr,motor(1α2),

where:

  • τfr,pump=(ηm1)τ

  • τfr,motor=(1ηm)τideal

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

The Tabulated data - volumetric and mechanical losses parameterization

The leakage flow rate is calculated as:

m˙leak=ρavgqloss(Δp,ω),

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:

τfr=τloss(Δp,ω),

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.

Input Signal Parameterization

When Leakage and friction parameterization is set toInput 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 toInput 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:

m˙leak=ρavgqLVtanh(4Δppthresh),

where:

  • qLV is the leakage flow received at port LV.

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

The friction torque is calculated as:

τfr=τLMtanh(4ωωthresh),

where

  • τLM is the friction torque received at port LM.

  • ωthresh is 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:

m˙=m˙ideal+m˙leak,

where m˙ideal=ρavgDω.

The motor torque is:

τ=τidealτfr,

where τideal=DΔp.

The mechanical power extracted by the motor shaft is:

φmech=τω,

and the motor hydraulic power is:

φhyd=Δpm˙ρavg.

If you would like to know if the block is operating beyond the supplied tabulated data, you can set Check if operating beyond the quadrants 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.

Ports

Conserving

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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

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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

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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 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.

Constant of proportionality between friction torque and motor pressure drop.

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 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 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

M-by-N matrix of volumetric efficiencies at the specified fluid pressure drop and shaft angular velocity. Linear interpolation is employed 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 Shaft angular velocity vector, w 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. Linear interpolation is employed 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 Shaft angular velocity vector, w 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. Linear interpolation is employed 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 Shaft angular velocity vector, w 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. Linear interpolation is employed 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 Shaft angular velocity vector, w parameter.

Dependencies

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

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 rad/s 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.

Dependencies

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

  • Tabulated data - volumetric and mechanical efficiencies

  • Tabulated data - volumetric and mechanical losses

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

Introduced in R2020a