Aircraft Turbine Fan Drive Gear Lubrication During Autorotation
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Solution Overview
Problem
Aircraft turbine engines with fan-driven reduction gears face challenges in lubrication during autorotation, as the high pressure shaft is either stopped or rotates at low speeds, making it difficult for the existing lubrication systems to provide sufficient lubricant flow, leading to inefficiencies and the need for additional complex and costly secondary oil circuits.
Innovation Solution
A lubrication system with a controlled lubricant dispenser that can switch between lubricant recovery and blocking configurations, using lubricant pressure control to manage lubricant flow and prevent vacuum creation, eliminating the need for additional pumps or tanks, and incorporating a mechanical or hydraulic actuator with elastic return elements to manage piston positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the existing lubrication system uses the high pressure shaft to drive the supply pump, then the system structure is simple during normal operation, but the lubricant flow rate becomes insufficient during autorotation when the shaft stops or rotates at low speed
Solution Approach 1:
The lubrication system dynamically switches between two operational modes: during normal operation, the supply pump driven by the high pressure shaft provides lubrication; during autorotation, when the shaft stops or rotates at low speed, the system automatically activates the recovery pump to suck lubricant from the enclosure and the controlled dispenser to block lubricant outlets, ensuring continuous adequate lubrication flow without structural complexity
Solution Approach 2:
The system uses the recovery pump to recycle lubricant from the reduction gear enclosure back to the tank, creating a self-sustaining lubrication cycle during autorotation. The controlled dispenser automatically blocks lubricant outlets to prevent loss, allowing the system to maintain lubrication using its own components without external assistance or additional complex machinery
2Quantity of substance
If a secondary oil circuit with auxiliary tank and auxiliary pump is added to ensure lubrication during autorotation, then the lubricant flow rate becomes sufficient, but the system mass, space requirement, complexity, cost and reliability deteriorate
Solution Approach 1:
The existing lubrication components are made multi-functional: the supply pump serves both normal operation and autorotation lubrication; the recovery pump, originally perhaps unused or for minor functions, becomes the primary lubrication source during autorotation; the controlled dispenser adds intelligent flow management to existing lubricant pathways. This eliminates the need for separate auxiliary tanks and pumps while maintaining sufficient lubricant flow rate during autorotation
Solution Approach 2:
The system changes operational parameters dynamically: during normal operation, the supply pump delivers lubricant at high flow rates; during autorotation, the recovery pump adjusts to provide appropriate flow rates, and the controlled dispenser modulates lubricant flow by blocking outlets. These parameter changes allow the same hardware to provide adequate lubrication across different operational conditions without adding secondary circuits
3Quantity of substance
If the controlled lubricant dispenser blocks the lubricant outlet during autorotation, then the lubricant is retained in the enclosure for continuous lubrication, but the risk of vacuum formation in the recovery circuit increases
Solution Approach 1:
The controlled lubricant dispenser acts as an intermediary device between the reduction gear enclosure and the recovery circuit. It selectively blocks lubricant outlets to retain lubricant in the enclosure while simultaneously managing the recovery pump's suction to prevent vacuum formation, mediating between lubricant retention needs and vacuum prevention requirements
Solution Approach 2:
The system implements feedback control where the controlled dispenser monitors lubricant levels and pressure conditions in real-time. When the recovery pump operates during autorotation, the dispenser adjusts blocking of lubricant outlets based on feedback signals, ensuring lubricant is retained sufficiently while preventing excessive pressure drops that would cause vacuum formation in the recovery circuit
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
Ensures reliable and efficient lubrication of the reduction gear during autorotation without additional components, maintaining gear assembly lubrication and preventing vacuum formation, thus simplifying and cost-reducing the lubrication management.
Implementation Method 1
a piston (70) movable in the cylinder (68), the piston (70) being subjected to a first force applied by an elastic return element
Implementation Method 2
a second force applied by the lubricant pressure
Data Source
AI summary
An assembly for an aircraft turbine engine includes a fan drive reduction gear and a lubrication system including: a reduction gear housing; a lubricant tank; a lubricant supply circuit including a feed pump; and a lubricant recovery circuit including a pump for recovering lubricant from the reduction gear housing. The recovery circuit includes a lubricant distributor, including: a lubricant inlet communicating with a lubricant outlet of the housing; an air inlet; and a distributor outlet, the distributor being able to adopt a lubricant recovery configuration and a configuration for retaining the lubricant in the housing.