Pump Flow Rate Estimation Using Reverse Motor Power
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Solution Overview
Problem
Existing methods for determining flow rate through pumps, particularly centrifugal pumps, face challenges in accuracy and efficiency due to flat or non-monotonic power curves, especially in modern pumps designed for energy efficiency, making it difficult to estimate flow rates accurately over a wide range of speeds and rates without relying on expensive flow sensors.
Innovation Solution
The method involves temporarily operating the pump's impeller in a reverse direction to observe the motor's power, using the relationship between reverse power and forward flow rate to compute an accurate estimate of the forward flow rate, leveraging monotonically increasing reverse power curves for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flow sensors are used to determine flow rate, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the flow measurement function from physical flow sensors and relocates it to the motor control system by utilizing existing motor current and power measurements. This eliminates the need for separate flow sensors while maintaining measurement capability through computational methods that process motor electrical parameters to derive flow rate information.
Solution Approach 2:
The patent replaces mechanical flow sensors with an electrical/control-based measurement system. Instead of using physical sensors to directly detect flow, the system uses electrical measurements (current, power) from the motor control circuitry and computational algorithms to determine flow rate, substituting mechanical measurement hardware with electrical measurement and processing.
2Device complexity
If power curves are used for flow estimation, then device complexity is reduced, but measurement precision deteriorates due to flat or non-monotonic curves
Solution Approach 1:
The patent dynamically adapts the power curve data based on operating conditions. Instead of using a single static power curve, the system selects and interpolates between multiple power curves corresponding to different motor speeds and operating points. This dynamic approach allows the system to maintain accurate flow estimation across varying operating conditions where static power curves would be flat or non-monotonic.
Solution Approach 2:
The patent changes the parameters used for flow estimation by incorporating multiple variables beyond simple power consumption, including motor speed, current, and interpolated power curve data. By transforming the estimation approach to use multiple parameters and their relationships, the system overcomes the limitations of single-parameter power curve methods that produce flat or non-monotonic relationships.
3Use of energy by moving object
If pump efficiency is optimized, then energy consumption is reduced, but measurement precision of flow rate estimation deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the control system continuously monitors motor electrical parameters and uses this information to update flow rate estimates. The system compares estimated flow rates with actual operating conditions and adjusts its calculations accordingly, allowing it to maintain measurement precision even as pump efficiency varies with operating conditions.
Solution Approach 2:
The patent performs preliminary characterization of the pump's power curves under various operating conditions during manufacturing or commissioning. This preliminary data is stored and used during normal operation to enable accurate flow estimation without requiring real-time physical measurements. The preliminary action of characterizing the pump allows subsequent operation to benefit from both high efficiency and accurate measurement.
Data Source
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AI summary
A computer-implemented method for determining a forward flow rate of fluid flow through a pump, the pump comprising an impeller and a pump motor, the forward flow rate being responsive to the impeller being driven by the pump motor to rotate in a forward direction and at a forward speed, the method comprising: obtaining an observed reverse power of the pump motor when the pump motor is operated to drive the impeller in a reverse direction, opposite the forward direction, and at a reverse speed; computing an estimate of the forward flow rate from at least the observed reverse power.