Engine Coupling Arrangement for Aircraft Accessory Drive
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Solution Overview
Problem
Internal combustion engines face challenges in efficiently driving aircraft accessories independently of the main rotatable load, particularly due to high inertia requirements and the need for separate power sources like APUs and starter/generators.
Innovation Solution
A gearbox system is introduced that allows an intermittent internal combustion engine to be selectively engaged or disengaged with a turbine shaft, enabling independent rotation and combined power transmission to drive accessories and rotatable loads, with a clutch mechanism switching between engaged and disengaged configurations to manage rotational inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If accessories are driven by the main engine, then power is available for accessories, but the accessories cannot be driven independently of the rotatable load
Solution Approach 1:
The power transmission system is segmented into separate drivable paths: one path from the intermittent internal combustion engine to accessories, and another path from the turbine to the rotatable load. The gearbox is divided into first and second portions that can independently transmit power, allowing accessories to be driven separately from the main load through the first portion while the second portion handles turbine-to-load transmission.
Solution Approach 2:
The intermittent internal combustion engine serves multiple functions: it can drive accessories independently through the gearbox first portion, and when engaged with the turbine shaft, it can also contribute to driving the rotatable load. The gearbox itself is multi-functional, capable of transmitting power in both engaged and disengaged configurations, eliminating the need for separate dedicated systems for each function.
2Adaptability or versatility
If a separate APU is used to drive accessories, then independent accessory driving is achieved, but device complexity and weight increase
Solution Approach 1:
The intermittent internal combustion engine is designed to perform multiple roles: functioning as a standalone power source for accessories when the gearbox is disengaged, and functioning as a compounding power source with the turbine when engaged. This eliminates the need for a separate APU while maintaining the capability for independent accessory driving, thereby reducing overall system complexity and weight.
Solution Approach 2:
The patent merges the APU functionality with the main intermittent internal combustion engine. Instead of having separate systems for accessory power and main propulsion power, the engine and gearbox system is designed to provide both functions through selective engagement, consolidating what would traditionally require separate components into a unified system.
3Power
If the gearbox is in engaged configuration, then power from both engine and turbine is transmitted to the load, but accessories cannot be driven independently
Solution Approach 1:
The gearbox is segmented into functionally independent portions: the first portion transmits power from the intermittent internal combustion engine to accessories, while the second portion transmits power from the turbine to the output shaft. This segmentation allows the engaged configuration to simultaneously provide combined power transmission for the load while maintaining the capability for independent accessory driving, as each portion can operate semi-independently within the engaged state.
4Ease of operation
If clutch components engage at different rotational speeds, then engagement is achieved, but wear on clutch components increases
Solution Approach 1:
The control system synchronizes the rotational speeds of the engine shaft and turbine shaft before the clutch components engage. This preliminary speed matching ensures that when engagement occurs, both shafts are rotating at compatible speeds, minimizing shock loads and reducing wear on the clutch components. The synchronization happens in advance of the actual engagement action, preventing damage that would result from speed mismatch.
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 configuration allows for efficient operation of accessories without driving the rotatable load, reduces wear on clutch components by synchronizing rotational speeds, and enables the engine assembly to perform both main engine and APU functions, enhancing operational flexibility and reducing energy consumption.
Implementation Method 1
a turbine having a turbine shaft and having an inlet in fluid communication with an exhaust of the intermittent internal combustion engine
Data Source
AI summary
An engine assembly includes an intermittent internal combustion engine having an engine shaft, a turbine having a turbine shaft, an output shaft for driving a load, and a gearbox having a first portion and a second portion. The engine shaft is in engagement with an accessory via the first portion. The turbine shaft is in driving engagement with the output shaft via the second portion. The gearbox is configurable between an engaged and a disengaged configurations. In the disengaged configuration, the first and second portions are decoupled, and the engine shaft and the turbine shaft are rotatable independently from each other. In the engaged configuration, the first and second portions are coupled, and the engine shaft and the turbine shaft are drivingly engaged with each other via the coupled first and second portions.