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Parameterizing Pumps and Motors

Pump and motor blocks in the Isothermal Liquid, Thermal Liquid, and Hydraulics (Isothermal Liquid) libraries model performance analytically or by lookup table with the Leakage and friction parameterization. A lookup table can be generated according to a data sheet or measurements. Manufacturer data sheet pre-parameterizations for gear, axial-piston, submersible, and centrifugal pump and motor blocks are also available in the Isothermal Liquid library.

Parameterize Performance with a Specification Sheet

To model pump performance according to a specific pump, you can supply capacity and pressure data for interpolation during simulation with the tabulated data parameterization option. If you do not want to manually input data from a data sheet, you can use the MATLAB File Exchange function grabit to extract data points from a plot image.

Fixed-Displacement Pumps and Motors

To parameterize a displacement pump with grabit:

  1. Enter grabit() at the MATLAB® command line.

  2. From the GUI that appears, click Load Image... to load a pump curve in PNG, TIF, JPG, GIF, or BMP format.

  3. Calibrate the image by selecting the axes ranges and entering the range values. Start by clicking on the x-axis origin, entering 0 in the box that appears, and pressing Enter.

  4. Click Grab Points to begin collecting data by clicking along the desired curve. To collect another set of data, press Enter and click Grab Points again.

  5. Enter the saved variables as the parameter setting:

If your datasheet does not provide mechanical efficiency, it can be calculated by dividing the overall efficiency by the volumetric efficiency.

Centrifugal Pumps

Centrifugal pump curves, like positive displacement pump curves, chart the pump capacity (flow rate) and head (pressure differential). The curves are organized by the number of stages associated with the delivered power. Additionally, the average efficiency curve and brake power curve per stage are provided. To determine the pump brake power, multiply the power for a given capacity by the number of pump stages

Depending on stage performance and model fidelity, a that a submersible pump can be modeled by a single centrifugal pump block or as multiple centrifugal pumps in series.

Parameterize Performance with Measurements

To parameterize a block with data from a text file or Excel sheet, you can assign a workplace variable to imported data with the Import Tool or the readtable function.

Parameterize Performance with Tabulated Losses and Efficiencies

In the Isothermal Liquid library, you can parameterize pump and motor block performance in varying conditions with tabulated data for losses and efficiencies.

If your pump or motor performance varies under certain conditions, you can use this parameterization to switch between points in a look-up table. This allows for more control over the block functionality in specific scenarios.

Parameterize Performance with Input Signals of Losses and Efficiencies

In the Isothermal Liquid library, you can parameterize pump and motor blocks according to physical signal inputs within a defined range of mechanical and volumetric efficiency or losses.

Use this option if you would like to use embedded Matlab scripts to set pump or motor performance, such as polynominal fitting of a pump curve.

Parameterize Centrifugal Pump Performance Analytically

You can parameterize the Centrifugal Pump (IL) and Centrifugal Pump (TL) blocks analytically by defining the pump nominal values at the no-flow and no-head conditions. The following plot of head, capacity, and brake power shows the analytical parameter assignment.

Generate Block Pump Curves

To generate a pump curve, a test harness simulates a set of operating conditions with a specified fluid inherited from your model. You can also adjust the parameters in the test harness prior to simulation. Any changes made in the test harness are not reflected in the source model. To open the harness and generate a plot for the Fixed-Displacement Pump and Fixed-Displacement Motor blocks in the Hydraulics (Isothermal) library, right-click the block and select Fluids > Plot Characteristic.

Hydrostatic Transmission Example

  1. Enter sh_hydrostatic_trans at the MATLAB command line.

  2. Right-click on the block labeled Motor and select Fluids > Plot Characteristic. This opens the test harness for the motor.

  3. The directions for modifying the test harness parameters are listed in the test harness:

    • You can modify the working fluid by clicking the hyperlink in step 1.

    • You can modify the harness simulation range for pressure and shaft speed by clicking the hyperlink in step 2.

    • You can define the output units by clicking the hyperlink in step 3.

    • To generate the motor curve, click Generate plots in step 4. This will start the test harness simulation for the source model Leakage and friction parameterization, which is set to Analytical.

  4. After the test simulation is complete, the curves for capacity (flow rate), power, and the power ratio are generated:

To also generate the motor efficiency curves, close the test harness, set the motor Leakage and friction parameterization parameter to Tabulated data - volumetric and mechanical efficiencies, and re-run the test harness simulation. You can similarly generate the loss curves with the Tabulated data - volumetric and mechanical losses parameterization.

See Also

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