Centrifugal Pump (IL)

Centrifugal pump in isothermal liquid network

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Description

The Centrifugal Pump (IL) block represents a centrifugal pump that transfers energy from the shaft to a fluid in an isothermal liquid network. The pressure differential and mechanical torque are functions of the pump head and brake power, which depend on pump capacity. You can parameterize the pump analytically or by linear interpolation of tabulated data. The pump affinity laws define the core physics of the block, which scale the pump performance to the ratio of the current to the reference values of the pump angular velocity and impeller diameter.

By default, the flow and pressure gain are from port A to port B. Port C represents the pump casing, and port R represents the pump shaft. You can specify the normal operating shaft direction in the Mechanical orientation parameter. If the shaft begins to spin in the opposite direction, the pressure difference across the block drops to zero.

Port Configuration

The figure shows the location of the block ports on a typical centrifugal pump.

Analytical Parameterization: Capacity, Head, and Brake Power

When you set, Pump parameterization to Capacity, head, and brake power at reference shaft speed, the block calculates the pressure gain over the pump as a function of the pump affinity laws and the reference pressure differential:

$$p_B-p_A=\Delta H_{ref}\rho g{\left(\frac{\omega }{{\omega }_{ref}}\right)}^2{\left(\frac{D}{D_{ref}}\right)}^2,$$

where:

• g is the gravitational acceleration.

• ΔH is the reference pump head, which the block derives from a quadratic fit of the pump pressure differential between the values of the Maximum head at zero capacity, Nominal head, and Maximum capacity at zero head parameters.

• ω is the shaft angular velocity, ω_R – ω_C.

• ω_ref is the value of the Reference shaft speed parameter.

• $$\frac{D}{D_{ref}}$$ is the value of the Impeller diameter scale factor parameter. This block does not reflect changes in pump efficiency due to pump size.

• ρ is the network fluid density.

The shaft torque is:

$$\tau =W_{brake,ref}\frac{{\omega }^2}{{\omega }_{ref}^3}{\left(\frac{D}{D_{ref}}\right)}^5.$$

The reference brake power, W_brake,ref, is calculated as capacity·head/efficiency. The pump efficiency curve is quadratic with its peak corresponding to the Nominal brake power parameter, and it falls to zero when capacity is zero or maximum as the pump curve figure demonstrates.

The block calculates the reference capacity as:

$$q_{ref}=\frac{\dot{m}}{\rho }\frac{{\omega }_{ref}}{\omega }{\left(\frac{D_{ref}}{D}\right)}^3.$$

You can choose to be warned when the block flow rate becomes negative or exceeds the maximum pump capacity by setting Check if operating beyond normal pump operation to On.

1-D Tabulated Data Parameterization: Head and Brake Power as a Function of Capacity

When you set Pump parameterization to 1D tabulated data - head and brake power vs. capacity at reference shaft speed, the pressure gain over the pump functions with the Reference head vector parameter, ΔH_ref, which is a function of the reference capacity, q_ref:

$$\Delta p=\rho g\Delta H_{ref}(q_{ref}){\left(\frac{\omega }{{\omega }_{ref}}\right)}^2{\left(\frac{D}{D_{ref}}\right)}^2,$$

where g is the gravitational acceleration.

The block bases the shaft torque on the Reference brake power vector parameter, W_ref, which is a function of the reference capacity:

$$\tau =W_{ref}(q_{ref})\frac{{\omega }^2}{{\omega }_{ref}^3}\left(\frac{\rho }{{\rho }_{ref}}\right){\left(\frac{D}{D_{ref}}\right)}^5,$$

where ρ_ref is the Reference density parameter. The reference capacity is:

$$q_{ref}=\frac{\dot{m}}{\rho }\left(\frac{{\omega }_{ref}}{\omega }\right){\left(\frac{D_{ref}}{D}\right)}^3,$$

which the block uses to interpolate the values of the Reference capacity vector, Reference head vector, and Reference brake power vector parameters as a function of q_ref.

When the simulation is outside of the normal pump operating conditions, the block extrapolates the pump head linearly and brake power to the nearest point.

2-D Tabulated Data Parameterization: Head and Brake Power as a Function of Capacity and Shaft Speed

When you set Pump parameterization to 2D tabulated data - head and brake power vs. capacity and shaft speed, the pressure gain over the pump is a function of the Head table, H(q,w) parameter, ΔH_ref, which is a function of the reference capacity, q_ref, and the shaft speed, ω:

$$\Delta p=\rho g\Delta H_{ref}(q_{ref},\omega ){\left(\frac{D}{D_{ref}}\right)}^2.$$

The shaft torque is a function of the Brake power table, Wb(q,w) parameter, W_ref, which is a function of the reference capacity, q_ref, and the shaft speed, ω:

$$\tau =\frac{W_{ref}(q_{ref},\omega )}{\omega }\left(\frac{\rho }{{\rho }_{ref}}\right){\left(\frac{D}{D_{ref}}\right)}^5.$$

The reference capacity is:

$$q_{ref}=\frac{\dot{m}}{\rho }{\left(\frac{D_{ref}}{D}\right)}^3.$$

When the simulation is outside of the normal pump operating conditions, the block extrapolates the pump head linearly and brake power to the nearest point.

Visualizing the Pump Curve

You can check the parameterized pump performance by plotting the head, power, efficiency, and torque as a function of the flow. To generate a plot of the current pump settings, right-click on the block and select Fluids > Plot Pump Characteristics. If you change settings or data, click Apply on the block parameters and click Reload Data on the pump curve figure.

The default block parameterization results in these plots:

Predefined Parameterization

You can model a specific supplier component by pre-parameterizing the Centrifugal Pump (IL) block with manufacturer data.

To load a predefined parameterization:

1. Double-click the block. Click the Select a predefined parameterization hyperlink in the Centrifugal Pump (IL) block dialog description.

2. Select a part from the Select manufacturer and Select part drop-down menus, then click Update block with selected part.

3. You can compare your current settings with a specific component by clicking Compare block settings with selected part. The differences between the current settings and the pre-defined parameterization display in the MATLAB Command Window.

Assumptions and Limitations

• Reverse flow or a pressure drop over the pump is not normal operation, and the simulation results in these situations may not be accurate.

• The block does not account for dynamic pressure in the pump. The block only considers pump head due to static pressure.

• Pre-defined parameterizations use available data and the block fills in missing data where necessary. Validate your model against expected results.

Ports

Conserving

A — Pump inlet

isothermal liquid

Isothermal liquid conserving port associated with the fluid inlet.

B — Pump outlet

isothermal liquid

Thermal liquid conserving port associated with the fluid outlet.

R — Impeller shaft

mechanical rotational

Mechanical rotational conserving port associated with the shaft.

C — Pump casing

mechanical rotational

Mechanical rotational conserving port associated with the case.

Parameters

Pump parameterization — Head and brake power parameterization

Capacity, head, and brake power at reference shaft speed (default) | 1D tabulated data - head and brake power vs. capacity at reference shaft speed | 2D tabulated data - head and brake power vs. capacity and shaft speed

Parameterization of the pump head and brake power.

• Capacity, head, and brake power at reference shaft speed: Parameterize pump pressure gain and shaft torque with an analytical formula.

• 1D tabulated data - head and brake power vs. capacity at reference shaft speed: Parameterize head and brake power from tabulated data of the head and brake power at a given capacity.

• 2D tabulated data - head and brake power vs. capacity and shaft speed: Parameterize head and brake power from tabulated data of the head and brake power at a given capacity and shaft speed.

Nominal capacity — Pump volumetric flow rate

45 lpm (default) | positive scalar

Nominal pump volumetric flow rate at a reference shaft angular velocity.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Nominal head — Pump head

40 m (default) | positive scalar

Nominal pump pressure differential, normalized by gravity and the fluid density, at a reference shaft angular velocity.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Nominal brake power — Pump power

0.85 kW (default) | positive scalar

Nominal mechanical shaft power at a reference angular velocity.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Maximum head at zero capacity — Maximum pump head with no flow

60 m (default) | positive scalar

Maximum pump head with no flow at a reference angular velocity. This parameter determines the reference pressure differential over the pump, which it uses to fit a quadratic equation for pressure in addition to the Nominal capacity, Nominal head, and Maximum capacity at zero head parameters.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Maximum capacity at zero head — Maximum flow rate with zero head

80 lpm (default) | positive scalar

Maximum fluid load with zero head at a reference angular velocity. This parameter determines the reference pressure differential over the pump, which it uses to fit a quadratic equation for pressure in addition to the Nominal capacity, Nominal head, and Maximum head at zero capacity parameters.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Reference shaft speed — Reference shaft angular velocity for affinity law calculations

1770 rpm | 3500 rpm | positive scalar

Reference angular velocity for affinity law calculations. The default value depends on the Pump parameterization setting.

Dependencies

To enable this parameter, set Pump parameterization to either:

• Capacity, head, and brake power at reference shaft speed.

• 1D tabulated data - head and brake power vs. capacity at reference shaft speed.

Reference capacity vector — Volumetric flow rate

[16.67, 30, 40, 53.33, 66.67, 83.33] lpm (default) | vector

Nonnegative vector of volumetric flow rates for the tabular parameterization of pump head or brake power. The elements in this vector correspond one-to-one with the elements in the Reference head vector and Reference brake power vector parameters.

Dependencies

To enable this parameter, set Pump parameterization to 1D tabulated data - head and brake power vs. capacity at reference shaft speed.

Reference head vector — Pump head vector

[50, 47.5, 45, 40, 35, 25] m (default) | vector

Nonnegative vector of pump head values for the 1-D tabular parameterization of pump head and brake power. This parameter corresponds one-to-one with the Reference capacity vector parameter

Dependencies

To enable this parameter, set Pump parameterization to 1D tabulated data - head and brake power vs. capacity at reference shaft speed.

Reference brake power vector — Pump brake power vector

[.6, .75, .85, .93, .98, .99] kW (default) | vector

Nonnegative vector of pump brake power values for the 1-D tabular parameterization of pump head and brake power. This parameter corresponds one-to-one with the Reference capacity vector parameter

Dependencies

To enable this parameter, set Pump parameterization to 1D tabulated data - head and brake power vs. capacity at reference shaft speed.

Capacity vector, q — Volumetric displacement vector

[16.67, 23.33, 30, 40, 53.33, 60] lpm (default) | vector

Vector of volumetric flow rates for the tabular parameterization of pump head. This vector forms an independent axis with the Shaft speed vector, w parameter for the 2-D Head table, H (q,w) and Brake power table, Wb(q,w) parameters. The vector elements must be listed in ascending order and must be greater than or equal to 0.

Dependencies

To enable this parameter, set Pump parameterization to 2D tabulated data - head and brake power vs. capacity and shaft speed.

Shaft speed vector, w — Angular velocity vector

[2450, 2800, 3150, 3500] rpm (default) | vector

Vector of shaft angular velocity values for the tabular parameterization of pump head. This vector forms an independent axis with the Capacity vector, q parameter for the 2-D Head table, H (q,w) and Brake power table, Wb(q,w) parameters. The vector elements must be listed in ascending order and must be greater than 0.

Dependencies

To enable this parameter, set Pump parameterization to 2D tabulated data - head and brake power vs. capacity and shaft speed.

Head table, H(q,w) — Pump head matrix

[25, 32.7, 42.5, 50; 24, 31.7, 41, 49; 22.7, 30.5, 39, 47.5; 20, 28, 36, 45; 15.7, 24, 32, 40; 12.5, 21, 29.5, 37.5] m (default) | M-by-N matrix

M-by-N matrix of pump head values at the specified volumetric flow rate and angular velocity. All table elements must be greater than or equal to 0. The block employs linear interpolation between table elements. M and N are the sizes of the corresponding vectors:

• M is the number of elements in the Capacity vector, q parameter.

• N is the number of elements in the Shaft speed vector, w parameter. All rows must be in strictly ascending order.

Dependencies

To enable this parameter, set Pump parameterization to 2D tabulated data - head and brake power vs. capacity and shaft speed.

Brake power table, Wb(q,w) — Pump brake power matrix

[.28, .38, .5, .6; .31, .41, .55, .68; .33, .44, .6, .75; .36, .48, .65, .83; .38, .53, .72, .93; .39, .55, .75, .97] kW (default) | M-by-N matrix

M-by-N matrix of pump brake power values at the specified volumetric flow rate and angular velocity. All values must be greater than 0. Linear interpolation is employed between table elements. M and N are the sizes of the corresponding vectors:

• M is the number of vector elements in the Capacity vector, q parameter.

• N is the number of vector elements in the Shaft speed vector, w parameter. All rows must be in strictly ascending order.

Dependencies

To enable this parameter, set Pump parameterization to 2D tabulated data - head and brake power vs. capacity and shaft speed.

Reference density — Fluid density for given pump performance data

998 kg/m^3 (default) | positive scalar

Fluid density specified by the reference or data sheet performance. This parameter scales the pump performance between different fluids.

Impeller diameter scale factor — Ratio of model diameter to reference diameter for affinity law calculations

1 (default) | positive scalar

Ratio of the model diameter to reference diameter for affinity law calculations. Modify this value if there is a difference between your reference and the system impeller diameters, such as when testing pump scaling. For system pumps smaller than the reference pump, use a value less than one. For system pumps larger than the reference pump, use a value grater than one. The block does not reflect changes in pump efficiency due to pump size.

Mechanical orientation — Shaft normal rotational direction

Positive angular velocity of port R relative to port C corresponds to normal pump operation (default) | Negative angular velocity of port R relative to port C corresponds to normal pump operation

Shaft rotational direction for flow from port A to B.

Check if operating beyond normal pump operation — Option to notify when block is beyond operating bounds

Warning (default) | None | Error

Option to notify if the block operates outside of the normal pump boundary. This occurs when the flow rate through the pump is negative or beyond the maximum capacity of the pump.

Dependencies

To enable this parameter, set Pump parameterization to Capacity, head, and brake power at reference shaft speed.

Model Examples

Lubrication System

A simplified version of a lubrication system fed with the centrifugal pump. The system consists of five major units: Pump Unit, Scavenge Unit, Heat Exchanger Manifold, Nozzle Manifold, and Control Unit. Both the pump and the scavenge unit are built around the centrifugal pump. The Scavenge Unit collects fluid discharged by nozzles and pumps it back into the reservoir of the Pump Unit. The Control Unit generates commands to bypass either the heat exchanger, represented as a local resistance, or the nozzles block. In a real system, these commands are generated by temperature sensors installed in lubrication cavities.

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Version History

Introduced in R2020a