Sprag-Clutch Variable Drive for Hybrid Turbine Power Split
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Solution Overview
Problem
Hybrid-electric gas turbine engines face increased complexity, mass, and expense due to the inclusion of generators, motors, and drive elements, which hinder efficient power redistribution and fault tolerance in aerospace applications.
Innovation Solution
The implementation of variable drive arrangements using sprag clutches to couple motors and generators to the engine's low spool, providing efficient load paths for hybrid power distribution with reduced mass and complexity, including epicyclic gear systems for enhanced compactness and passive operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If generators, motors, and drive elements are added to redistribute power in hybrid-electric architectures, then operating efficiencies are improved and component lifetimes are extended, but engine complexity, mass, and expense increase
Solution Approach 1:
The sprag clutch mechanism serves multiple functions simultaneously: it acts as a one-way coupling device, a passive disconnect mechanism, and a load path selector. This single component performs what would traditionally require multiple separate systems, thereby improving operating efficiency while limiting the increase in engine complexity.
Solution Approach 2:
The sprag clutch operates passively without requiring external control systems, actuators, or power sources. It automatically engages and disengages based on the direction of torque flow, eliminating the need for complex control mechanisms and reducing overall system complexity while maintaining the ability to redistribute power for improved efficiency.
2Duration of action of stationary object
If generators, motors, and drive elements are added to redistribute power, then operating efficiencies are improved and component lifetimes are extended, but mass and expense increase
Solution Approach 1:
The sprag clutch enables a single drive element to serve multiple functions: power redistribution for load balancing (extending component lifetime) and passive disconnect for fault protection. This multi-functionality allows lifetime extension without proportionally increasing mass, as the same hardware provides multiple benefits.
Solution Approach 2:
The passive operation of the sprag clutch eliminates the need for additional actuators, sensors, and control systems that would increase mass. The component automatically performs load balancing and fault protection functions without adding significant weight, thereby extending component lifetime with minimal mass penalty.
3Adaptability or versatility
If traditional drive arrangements are used for hybrid power distribution, then power redistribution is achieved, but device complexity and mass increase significantly
Solution Approach 1:
The sprag clutch provides a universal coupling mechanism that handles multiple drive configurations (series, parallel, hybrid) without requiring different hardware for each mode. This single component enables adaptable power redistribution across various operating modes while maintaining simple drivetrain architecture.
Solution Approach 2:
The passive, self-actuating nature of the sprag clutch allows the drivetrain to automatically adapt to different power distribution requirements without complex control systems. The component responds autonomously to torque direction changes, enabling versatile power redistribution while keeping drivetrain complexity low.
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 enables efficient hybrid power distribution with reduced mass and complexity, improving engine efficiency, extending component lifetimes, and providing fallback power without adding significant weight or cost, while maintaining compactness and simplicity in the drivetrain.
Implementation Method 1
variable drive arrangements using sprag clutches to couple motors and generators to the engine's low spool
Data Source
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AI summary
A gas turbine engine (10; 310; 510) includes an engine spool (24) with a turbine section (22), a propeller (12), a motor (34), and a variable drive arrangement (28; 328; 528). The variable drive arrangement (28; 328; 528) mechanically couples the engine spool (24) to the propeller (12), and includes a first gear connection (38; 338; 538) rotationally coupled to the propeller (12), a second gear connection (42; 342; 542) rotationally coupled to the engine spool (24), and a sprag clutch rotationally coupled to the first gear connection (38; 338; 538). The sprag clutch is configured to passively decouple the motor (34) from the first gear connection (38; 338; 538) when a torque input from the engine spool (24) exceeds a torque input from the motor (34), and is configured to passively couple the motor (34) to the first gear connection (38; 338; 538) when the torque input from motor (34) exceeds a torque input from the engine spool (24).