Rotating Baffle Centrifugal Coolant Scavenging
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Solution Overview
Problem
Liquid cooled electrical machines, such as generators, suffer from poor coolant management leading to insufficient scavenging, resulting in coolant buildup in the air gap, which increases windage and friction losses, potentially causing rotor and stator failure.
Innovation Solution
The implementation of a hollow central shaft with radially extending baffles that direct liquid coolant flow via centrifugal force through coolant spray openings between the rotor and stator windings, and into baffle cavities, enhancing coolant distribution and scavenging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid coolant is flowed through the generator to cool components, then cooling effectiveness is improved, but coolant scavenging becomes insufficient leading to windage loss increase
Solution Approach 1:
The generator is divided into multiple cooling channels with dedicated coolant flow paths. Each channel includes spray nozzles positioned at specific locations to target different components, and scavenge ports arranged to efficiently collect coolant from respective zones, preventing accumulation in the air gap
Solution Approach 2:
A centrifugal scavenge wheel acts as an intermediary device between the coolant spray system and the sump. The wheel actively captures coolant droplets carried by airflow and redirects them to the sump, preventing coolant accumulation that would cause windage losses while maintaining effective cooling
2Temperature
If coolant flow rate is increased to improve cooling, then temperature control is improved, but coolant accumulation in sump increases leading to higher windage losses
Solution Approach 1:
The cooling system incorporates feedback through strategically positioned scavenge ports that detect and respond to coolant accumulation. When coolant levels rise in specific zones, the centrifugal scavenge wheel increases extraction, automatically balancing coolant distribution and preventing sump overflow that would cause windage losses
3Device complexity
If simple coolant circulation is used, then system complexity is reduced, but coolant distribution and scavenging efficiency deteriorate
Solution Approach 1:
The system employs a dynamically operating centrifugal scavenge wheel that rotates at variable speeds to match operating conditions. This dynamic element actively manages coolant removal throughout the generator, providing efficient scavenging across multiple zones without requiring proportionally complex static structures
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 solution effectively reduces coolant levels in the sump, minimizing windage and friction losses, thereby improving the operational efficiency and longevity of electrical machines by ensuring efficient coolant circulation and heat transfer.
Implementation Method 1
the first baffle directs a flow of liquid coolant radially, originating from the central shaft, through a plurality of coolant spray openings in the shaft, between the first baffle and a rotor winding, between the first baffle and a stator winding and into the baffle cavity via centrifugal force
Data Source
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AI summary
An electrical machine (10) includes a rotor (12) located at a central shaft (18) and a stator (14) located radially outboard of the rotor and secured at a back iron (26). A first baffle (46) is coupled to the central shaft at one axial end (44) of the rotor, the baffle extending radially outwardly from the shaft toward a baffle cavity (48) at the back iron. A flow of coolant is urged toward the baffle cavity along the baffle via centrifugal force. A method of flowing coolant through an electrical machine includes injecting a flow of coolant substantially radially into an electrical machine cavity (34). The flow of coolant is urged radially outwardly along a rotating baffle (46) located at one axial end (44) of a rotor (12) of the electrical machine via centrifugal force and into a baffle cavity (48) disposed at the back iron (26) at a radial end of the baffle.