Flywheel Cooling in Hermetic Motor-Pump Units
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Solution Overview
Problem
Motor-pump units with flywheels experience high power losses due to hydrodynamic friction, reducing overall efficiency, and existing solutions either rely on fault-prone shaft seals or inefficient cooling methods.
Innovation Solution
A flywheel with heavy metal inserts and a high-strength material, surrounded by a heat exchanger that minimizes friction losses through temperature reduction and efficient cooling, eliminating the need for shaft seals by using a pressure shell design with annular gaps and external cooling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flywheel rotates in the coolant-filled motor housing, then the motor-pump unit can be hermetically sealed without shaft seals, but high power losses occur due to hydrodynamic friction
Solution Approach 1:
The motor housing is divided into two separate chambers: a dry chamber for the motor and a liquid-filled chamber for the pump and flywheel. This segmentation eliminates hydrodynamic friction by preventing the flywheel from rotating in coolant, while maintaining hermetic sealing through the magnetic coupling interface between chambers.
Solution Approach 2:
A magnetic coupling mechanism acts as an intermediary to transmit rotational force from the motor to the pump impeller without direct mechanical contact. The magnetic field couples the dry motor chamber to the liquid-filled pump chamber, eliminating the need for shaft seals while preventing hydrodynamic friction.
2Temperature
If the flywheel is cooled by the pumped liquid flowing through it, then the temperature is reduced, but the hub-shaft connection is weakened
Solution Approach 1:
The cooling function is separated from the structural function by introducing a separate heat exchanger. The heat exchanger provides cooling pathways without requiring liquid flow through the flywheel's hub-shaft connection, thus maintaining structural integrity while achieving temperature control.
Solution Approach 2:
A heat exchanger acts as an intermediary cooling system, transferring heat from the flywheel to the coolant without requiring direct liquid flow through the flywheel's structural components. This maintains the hub-shaft connection strength while achieving effective cooling.
3Temperature
If a thermal barrier is introduced between pump and motor, then heat conduction is reduced, but the device complexity increases
Solution Approach 1:
The thermal barrier function is merged with the hermetic sealing function by making the separator wall between dry and liquid chambers serve both purposes. This single structural element provides both thermal insulation and hermetic sealing, eliminating the need for additional thermal barrier components.
Solution Approach 2:
The separator wall between motor and pump chambers is designed to perform multiple functions simultaneously: providing thermal insulation, ensuring hermetic sealing, and serving as a structural support element. This multi-functionality reduces overall device complexity while achieving thermal separation.
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
This design reduces power losses and maintains operational reliability by ensuring a defined temperature in the flywheel space, minimizing friction, and enhancing cooling efficiency, thus improving the motor-pump unit's overall performance and safety.
Implementation Method 1
surrounded by a heat exchanger that minimizes friction losses through temperature reduction and efficient cooling
Implementation Method 2
Due to the moment of inertia of a flywheel, such an electric motor continues to run even in the event of a power failure and the motor-pump unit delivers a quantity of coolant
Implementation Method 3
The motor and the pump are coupled to one another in a drive-motor fashion by means of a magnetic coupling, wherein the impeller is driven without shaft seals
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to an electric motor (1) having a coaxially arranged pump (6) for a coolant circuit, in particular in a system with temperature transfer or heat transfer. Within housing parts (7, 10) which are configured as a hermetically sealed pressure enclosure, a shaft assembly (5) transmits a torque from the electric motor (1) to at least one impeller (8) which is arranged in the pump housing (7), and a flywheel (12) is arranged between the electric motor (1) and the pump housing (7). All the rotating parts are arranged within a hermetically sealed motor/pump assembly, and the motor/pump assembly is filled with fluid. Here, the flywheel (12) comprises a flywheel body (13) having a multiplicity of cavities (16, 17) and having heavy-metal inserts (16, 17) which are arranged in the cavities. A heavy metal having a density of greater than 11.0 (kg/dm3) forms the heavy-metal inserts or is arranged therein, and the flywheel body (13) is composed of a high-strength material.