Stator Heat Exchanger With Isolated Coolant Paths for Generator Cooling
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Solution Overview
Problem
Aircraft engine electric generators face challenges in maintaining optimal operating temperatures due to high heat generation during idling, particularly with shared coolant systems, leading to potential engine failures and contamination risks, and require redundant cooling systems that are challenging in restricted spaces.
Innovation Solution
A fluidically isolated coolant system for electric generators, comprising a stator cooling path and a separate coolant circuit for rotatable components, with heat exchange occurring between the two fluids within the stator, eliminating the need for additional supply and return lines and enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single shared oil system is used to cool multiple parts of the aircraft engine, then the number of system components is reduced, but the reliability decreases because failure of this single system will lead to multiple parts overheating and potential engine failure
Solution Approach 1:
The cooling system is divided into two separate circuits: a first coolant circuit for the gearbox and a second coolant circuit for the generator. This segmentation allows independent operation of each cooling system, so that failure in one circuit does not affect the other, thereby improving reliability while maintaining reasonable system complexity.
2Reliability
If a self-contained coolant system with mechanical pump is provided for the electric generator, then the reliability is improved, but the device complexity increases due to additional components in restricted space
Solution Approach 1:
The generator cooling system is merged with the existing aircraft engine cooling system by using the same coolant type and integrating with the engine's coolant circulation infrastructure. This combining approach provides redundant cooling capability while avoiding the need for completely separate systems, thus reducing overall device complexity in restricted space.
3Temperature
If high cooling capacity coolant systems are designed to provide sufficient fluid flow at idling speeds, then the generator cooling is adequate during high heat generation, but the system complexity increases to maintain high cooling capacity at low speeds
Solution Approach 1:
The coolant pump is driven by the turbine, creating a dynamic system where pump speed varies with turbine speed. During idling, the turbine runs at lowest speeds, but the system maintains adequate cooling capacity through the direct coupling of pump and turbine speeds, avoiding the need for complex variable speed control mechanisms while ensuring sufficient coolant flow when heat generation is highest.
4Reliability
If multiple redundant coolant systems are installed in restricted space environments, then the reliability is improved, but the space requirements and drag increase
Solution Approach 1:
The generator cooling system is nested within the aircraft engine's existing cooling infrastructure by integrating the generator's second coolant circuit with the engine's cooling system. This nesting approach allows redundant cooling capability to be achieved within the existing space envelope, minimizing additional volume requirements and drag while maintaining reliability.
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 system effectively maintains generator temperatures within optimal ranges, reduces contamination risks, and simplifies integration with engine cooling systems by increasing modularity and reducing drag, while ensuring efficient cooling of both stator and rotor components.
Implementation Method 1
heat is exchanged between the first coolant fluid and the second coolant fluid at the stator
Implementation Method 2
a stator cooling path configured to provide a first coolant fluid to flow around the stator core and through the stator slots
Implementation Method 3
a coolant circuit configured to provide a second coolant fluid to at least one rotatable component of the electric machine
Data Source
AI summary
A heat exchanger for an electric machine. The electric machine includes a stator having a stator core and stator slots extending along a longitudinal axis of the stator, and a rotor assembly having a rotor configured to rotate about the longitudinal axis. The electric machine includes a coolant system having a stator cooling path providing a first coolant fluid in direct contact with the stator to flow around the stator core and through the stator slots. The coolant system also includes a coolant circuit providing a second coolant fluid to at least one rotatable component of the electric machine, such as at least one bearing. The coolant circuit and the stator cooling path are fluidically isolated from one another and arranged such that heat is exchanged between the first coolant fluid and the second coolant fluid at the stator.