Epicyclic Gear Train Ring Gear Layout for Repeatable Fan Balance
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Solution Overview
Problem
The splined connection between the ring gear and spline ring in epicyclic gear trains of gas turbine engines experiences wear and deflection under high loads, leading to unreliable turbo fan assembly balance, which deteriorates over time.
Innovation Solution
The implementation of a tapered bearing on the fan shaft with passages that extend radially and a two-piece ring gear design with oppositely angled teeth and a radial interface, eliminating the need for a spline ring and reducing heat generation and windage, while allowing for direct radial oil flow and improved balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a splined connection is used between the ring gear and spline ring, then the turbo fan assembly can be connected and driven, but wear and deflection occur under high loads leading to unreliable balance that deteriorates over time
Solution Approach 1:
The patent removes the spline ring component entirely from the design. Instead of using a splined connection between a ring gear and spline ring, the invention directly connects the ring gear to the turbo fan assembly, eliminating the intermediate spline ring that was causing wear and balance issues.
Solution Approach 2:
The ring gear is divided into two separate portions with teeth facing in opposite directions. Each portion can be independently manufactured and balanced, then assembled together to form the complete ring gear assembly, improving overall balance reliability.
2Power
If a splined connection is used between the ring gear and spline ring, then torque transmission is achieved, but radial clearance is required making it difficult to get repeatable balance
Solution Approach 1:
The spline ring is removed from the system, eliminating the radial clearance issue inherent in splined connections. The direct connection approach allows for tighter tolerances and more repeatable balance.
Solution Approach 2:
By segmenting the ring gear into two portions that can be separately balanced and then assembled, the invention achieves better overall balance precision. Each portion can be manufactured and pre-balanced independently, reducing the impact of radial clearance.
3Productivity
If a splined connection is used between the ring gear and spline ring, then the gear train can operate, but wear occurs under high loads leading to balance deterioration over time
Solution Approach 1:
The spline ring is eliminated from the design, removing the wear-prone splined connection. The direct connection between the ring gear and turbo fan assembly eliminates the wear mechanism that caused balance deterioration over time.
Solution Approach 2:
The two-portion ring gear design allows each section to be optimized for its specific loading conditions, reducing overall wear. The segmented structure can better distribute and manage high loads, maintaining balance stability throughout the operational life.
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 structural rigidity and balance of the turbo fan assembly, reduces wear, and minimizes heat and windage losses, resulting in a more reliable and efficient operation of the gas turbine engine.
Implementation Method 1
at least one tapered bearing mounted on the fan shaft
Data Source
AI summary
A turbine engine according to an example of the present disclosure includes, among other things, a fan shaft, at least one tapered bearing mounted on the fan shaft, the fan shaft including at least one passage extending in a direction having at least a radial component, and adjacent the at least one tapered bearing, a fan mounted for rotation on the at least one tapered bearing. An epicyclic gear train is coupled to drive the fan, the epicyclic gear train including a carrier supporting intermediate gears that mesh with a sun gear, and a ring gear surrounding and meshing with the intermediate gears, wherein the epicyclic gear train defines a gear reduction ratio of greater than or equal to 2.3. A turbine section is coupled to drive the fan through the epicyclic gear train, the turbine section having a fan drive turbine that includes a pressure ratio that is greater than 5. The fan includes a pressure ratio that is less than 1.45, and the fan has a bypass ratio of greater than ten (10).