Ring Gear Flange for Convective Cooling in Rotorcraft Drive Systems
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Solution Overview
Problem
Current rotorcraft drive systems are prone to failures due to single component failures, loss of lubrication, and high-speed gearing issues, which can lead to reduced flight performance and safety concerns.
Innovation Solution
The design incorporates dual engine reduction gearboxes isolated from the main rotor gearbox, a low-speed overhung planetary gear system, compartmentalized lubrication, and a ring gear with a circumferential flange for convective cooling, minimizing single load paths and enhancing redundancy and heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single load path component is used in the rotorcraft drive system, then the device complexity is reduced, but the reliability deteriorates due to single point failures
Solution Approach 1:
The drive system is segmented into multiple independent load paths with separate gearboxes and shafts. The dual engine reduction gearboxes are isolated from each other and from the main rotor gearbox, creating distinct functional segments that can operate independently. This segmentation allows the system to maintain reliability through redundancy while managing complexity through modular design.
Solution Approach 2:
Different parts of the drive system are given different functional qualities - some components are designed for torque transmission while others are optimized for cooling. The ring gear incorporates both gear teeth for torque transmission and a circumferential flange for convective cooling, allowing local optimization of both power transmission and thermal management functions within the same component.
2Device complexity
If high-speed gearing is used to reduce the number of components, then the device complexity is reduced, but the reliability deteriorates due to increased stress and failure risk
Solution Approach 1:
The design preemptively addresses potential gear failures by incorporating redundant load paths before failures occur. Instead of relying on high-speed gearing that pushes components to their limits, the system uses lower-speed gearing with multiple parallel paths that can accommodate component failures without catastrophic system failure.
Solution Approach 2:
The circumferential flange on the ring gear acts as a heat dissipation structure that prevents thermal buildup before it can cause gear failure. The flange provides continuous convective cooling to the ring gear, cushioning against thermal stress and preventing lubrication breakdown before it occurs.
3Reliability
If lubrication is used to reduce friction and heat, then the reliability is improved, but the vulnerability to lubrication loss deteriorates the system survivability
Solution Approach 1:
The circumferential flange acts as an intermediary cooling structure between the ring gear and the ambient environment. It provides an additional heat transfer path that reduces reliance on lubrication for thermal management, allowing the gear to survive longer during lubrication loss events by dissipating heat through the flange's convective surface.
4Temperature
If the ring gear is cooled by conduction through housings, then the heat management is improved, but the device complexity increases due to additional mounting requirements
Solution Approach 1:
The circumferential flange serves multiple functions simultaneously: it provides structural support for mounting the ring gear to the housings, and it acts as a heat dissipation surface for convective cooling. This multi-functionality allows the same component to address both mechanical mounting requirements and thermal management needs without increasing overall device complexity.
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 enhances the survivability of the drive system by reducing the impact of high-speed gear failures and lubrication losses, maintaining torque transmission, and improving maintenance efficiency while maximizing operational safety and reliability.
Implementation Method 1
the ring gear is cooled by convection of heat away from the ring gear to the ambient air outside the ring gear
Implementation Method 2
the ring gear is cooled by conduction of heat away from the ring gear through the first housing or the second housing or a combination thereof
Data Source
AI summary
A ring gear includes a ring having one or more sets of inwardly facing teeth, a circumferential flange extending outward from the ring, and the flange is mounted between a first housing and a second housing. In addition, the flange protrudes into an ambient air outside the first housing and second housing.