Generator Rotor Cooling Flow Distribution for Variable Speed Operation
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Solution Overview
Problem
Aircraft generator cooling systems face inefficiencies due to high kinetic energy loss and mechanical power consumption from fluid ejected at varying rotor speeds, particularly in variable frequency generators, where balancing jet velocity with rotor velocity is challenging.
Innovation Solution
A fluid distribution arrangement in the rotor that selectively directs fluid to different sets of outlets based on operational parameters, such as rotational velocity, using varying radial positions and restrictors to maintain a constant flow rate, minimizing the impact on the stator and mechanical power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the jet holes are made large to evacuate sufficient fluid flow rate at minimum rotor speed, then the fluid flow rate is improved, but the jet velocity decreases resulting in higher residual kinetic energy and increased mechanical power consumption
Solution Approach 1:
The fluid distribution arrangement is divided into multiple cavities (first cavity, second cavity, third cavity) with separate inlet openings, allowing selective distribution of fluid to different outlet sets based on rotor speed. This segmentation enables optimization of jet characteristics for different operating conditions without requiring a single large jet hole that would compromise velocity.
Solution Approach 2:
The system dynamically adapts jet configuration by switching between different cavity outlet combinations based on rotor speed. At minimum speed, all cavities are activated to maximize flow rate. At higher speeds, fewer cavities are activated to reduce flow rate and increase jet velocity, thereby minimizing mechanical power consumption while maintaining effective cooling.
2Loss of energy
If the jet velocity is increased to reduce residual kinetic energy, then the mechanical power consumption is reduced, but the fluid flow rate decreases which is insufficient at minimum rotor speed
Solution Approach 1:
The system dynamically adjusts jet velocity and flow rate by selectively activating different cavity combinations based on rotor speed. At minimum speed, all three cavities are activated to maximize flow rate even with lower jet velocity. At higher speeds, fewer cavities are activated, reducing total flow rate but increasing jet velocity to minimize kinetic energy loss and mechanical power consumption.
Solution Approach 2:
The system changes operational parameters (which cavities are active, how many outlets receive fluid) based on rotor speed. This parameter change allows the system to optimize the balance between flow rate and jet velocity for different operating conditions, minimizing mechanical power consumption across the entire speed range.
3Temperature
If fluid is distributed to all outlets at all speeds, then sufficient cooling is maintained, but the mechanical power consumption increases due to high absolute velocities imparted to the fluid
Solution Approach 1:
The system dynamically selects which cavities and outlets receive fluid based on rotor speed. At minimum speed, all three cavities are activated to ensure sufficient cooling with lower jet velocities. At higher speeds, fewer cavities are activated, reducing the number of outlets receiving fluid and thereby reducing mechanical power consumption while maintaining adequate cooling through higher velocity jets.
Solution Approach 2:
The system changes the operational parameter of which cavities are active based on rotor speed. This allows optimization of the balance between cooling effectiveness and mechanical power consumption by adjusting fluid distribution to match the rotor speed conditions.
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
Regulates fluid ejection to match rotor speed, reducing kinetic energy loss and mechanical power consumption across varying speeds, ensuring efficient cooling and optimal operation.
Implementation Method 1
the rotor imparting large absolute velocities to the fluid... minimum centrifugal pumping force... velocity of the jets relative to the rotor
Data Source
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AI summary
The present invention provides a rotor for a generator arranged to be driven by an aircraft engine. The rotor comprises an inlet for receiving a fluid, a plurality of outlets configured to release the fluid from a radially outer region of the rotor, and a fluid distribution arrangement arranged to direct fluid from the inlet to one or more of the plurality of outlets. The fluid distribution arrangement is configured to selectively distribute fluid to one or more of the plurality of outlets in dependence on an operational parameter of the rotor.