Hybrid-Electric Propulsion Coupler for Smooth Shaft Synchronization
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Solution Overview
Problem
Hybrid-electric propulsion systems face challenges in balancing and shifting power between the electric machine and gas turbine engine, and efficiently coupling/decoupling these components for safety and operational efficiency.
Innovation Solution
A coupler mechanism is introduced to selectively mechanically couple and decouple the propulsor, power turbine, and electric machine shafts, allowing for smooth transitions between different modes of operation by synchronizing speeds and torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent disconnection methods (cutting shafts) are used to decouple electric machines and turbines, then reliability is improved by ensuring complete separation, but ease of repair deteriorates because permanent damage requires replacement rather than reconnection
Solution Approach 1:
The coupling mechanism is segmented into discrete, separatable components including coupling elements on the turbine shaft and corresponding receptacles on the electric machine shaft. These segments can be independently engaged or disengaged without permanent damage, allowing the system to transition between connected and disconnected states while maintaining repairability.
Solution Approach 2:
The coupling system transitions from a static permanent connection to a dynamic reversible connection. The coupling elements are designed to be engageable and disengageable through controlled movement, enabling the system to adapt between operational modes (connected for power transmission, disconnected for maintenance or reconfiguration) without compromising reliability or ease of repair.
2Ease of repair
If complex coupling mechanisms are used to enable reversible connection, then ease of repair is improved by allowing reconnection, but device complexity increases due to additional coupling components and control systems
Solution Approach 1:
The coupling and decoupling functionality is extracted as a separate, dedicated mechanism rather than being integrated into the main drive train components. This allows the coupling elements to be simplified and specialized for their specific function, reducing the complexity burden on the overall system while maintaining ease of repair through reversible connection.
Solution Approach 2:
Coupling elements act as intermediary components between the turbine shaft and electric machine shaft. These intermediaries provide the reversible connection functionality without requiring complex integration into the primary components, simplifying the overall design by isolating the coupling function to dedicated, easily replaceable elements.
3Reliability
If synchronous speed matching is performed before coupling, then reliability is improved by preventing shock loads and mechanical damage, but time is increased due to the additional synchronization step
Solution Approach 1:
Speed synchronization is performed as a preliminary action before the actual coupling operation. The control system adjusts the rotational speeds of the turbine and electric machine to match within an acceptable tolerance range before engaging the coupling elements. This preliminary speed matching prevents shock loads and mechanical damage during coupling, improving reliability without requiring complex real-time control during the coupling itself.
Data Source
AI summary
A propulsion assembly includes a first torque source coupled with a first shaft and a second torque source coupled with a second shaft. A coupler selectively couples the first and second torque sources. When the first and second torque sources are coupled via the coupler, in response to a command to decouple the first torque source, an unloading operation is performed to decrease the torque output provided by the first torque source to a threshold, and when reached, the first shaft is decoupled from the coupler. When the first torque source is coupled with the coupler but the second torque source is not, in response to a command to couple the second torque source, a speed matching operation is performed to increase the speed of the second shaft to match a speed of the first shaft, and when the speeds are matched, the second shaft is coupled to the coupler.