Centrifugal Pump Magnetic Flow Measurement with Direct Impeller Speed
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Solution Overview
Problem
Existing methods for determining the delivery flow in centrifugal pumps are either complex to install or costly, often relying on indirect measurements that are not reliable due to motor slip or broken couplings, and require extra cabling and protocol mapping for variable-frequency drives (VFDs).
Innovation Solution
A centrifugal pump design that incorporates a rotatable disc with permanent magnets on the pump shaft, coupled with a magnetic flux sensor to directly measure the rotational speed of both the turbine wheel and impeller, eliminating the need for extra cabling and providing a direct, reliable measurement through separate magnetic flux sensors for each component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a turbine wheel is exposed to the delivery flow through the centrifugal pump to measure delivery flow, then the delivery flow can be measured, but the measurement must be corrected according to the rotational speed of the impeller which requires additional sensors and cabling
Solution Approach 1:
The patent combines the impeller speed measurement function with the existing turbine wheel flow measurement system by integrating a permanent magnet on the impeller that interacts with the same magnetic flux sensor. This merging allows the sensor to simultaneously detect both flow information from the turbine wheel and speed information from the impeller magnet, eliminating the need for separate speed sensors and cabling while improving measurement precision through direct speed correction.
2Measurement precision
If an rpm sensor is attached to the electric motor to measure rotation speed, then the rotational speed can be measured, but extra mounting and cabling are required and the measurement is indirect and not always reliable
Solution Approach 1:
The patent extracts the speed measurement function from the motor and places it directly on the impeller by mounting a permanent magnet on the impeller itself. This extraction eliminates the need for separate RPM sensors on the motor and removes the indirect measurement path through the motor, providing direct impeller speed measurement that is more reliable and requires no extra mounting or cabling beyond the existing flow measurement setup.
3Measurement precision
If the rotational speed is determined on the basis of a signal from a VFD for an AC motor, then the rotational speed can be determined, but extra cabling is needed and a huge mix of signals/communication protocols must be covered
Solution Approach 1:
The patent enables the pump system to self-determine its rotational speed by using the permanent magnet on the impeller to generate a magnetic field that is detected by the existing magnetic flux sensor. This self-service approach eliminates the need for external VFD signals and complex communication protocols, as the system uses its own operational parameters (the rotating magnet's field) to provide speed information directly to the flow measurement calculation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution offers a simple, reliable, and direct measurement of delivery flow without additional installation complexity or cost, allowing for accurate detection of turbine wheel alignment and impeller speed, using neodymium magnets for enhanced strength and minimizing signal interference.
Implementation Method 1
The rotatable disc (52) includes at least one permanent magnet (53)... the flow measuring device is adapted to include in the measurement of the delivery flow a second measurement signal generated by the at least one magnetic flux sensor (51) as a result of the rotation of the rotatable disc (52)
Implementation Method 2
the flow measuring device including at least one magnetic flux sensor (51), the flow measuring device being adapted to measure the delivery flow on the basis of at least a first measurement signal generated by the at least one magnetic flux sensor (50) as a result of the rotation of the turbine wheel (32)
Data Source
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AI summary
The centrifugal pump includes a flow measuring device (3) adapted to measure a delivery flow through the pump by means of a turbine wheel (32) including at least one permanent magnet (42). The flow measuring device includes at least one magnetic flux sensor (50, 51) arranged in a sensor housing (48) mounted in an outer wall of the pump casing (2). A rotatable disc (52) is fixed on a pump shaft and includes at least one permanent magnet (53). The flow measuring device is adapted to measure the delivery flow on the basis of a first measurement signal generated by the at least one magnetic flux sensor as a result of the rotation of the turbine wheel and to include in the measurement of the delivery flow a second measurement signal generated by the at least one magnetic flux sensor as a result of the rotation of the rotatable disc.