Contoured Planet Pin Geometry for Turbine Gearbox Clearance
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Solution Overview
Problem
Turbine engine gearbox assemblies face efficiency reduction due to planet gear deformation under torque, leading to reduced clearance and increased wear, especially as engine power and thrust increase, necessitating an improved planet pin design to maintain lubrication and prevent metal-to-metal contact.
Innovation Solution
A contoured planet pin shape is developed, characterized by specific deflections (minor axis, contoured portion, and major axis) that account for fan power, speed, and gearbox ratio, ensuring adequate clearance and reducing the risk of contact between the planet pin and gear rim, thereby enhancing gearbox efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard circular planet pin is used, then the structure is simple and easy to manufacture, but the clearance between the planet pin and gear rim reduces under torque leading to increased wear
Solution Approach 1:
The planet pin is designed with a contoured, non-circular cross-section featuring curved surfaces that match the deformation pattern of the planet gear rim under load. This curvature compensation ensures that the clearance between the planet pin and gear rim is maintained even when the gear rim deforms elastically under torque, preventing metal-to-metal contact and reducing wear.
Solution Approach 2:
The planet pin geometry is modified by changing its cross-sectional parameters from a standard circular shape to a contoured shape with specific radii of curvature. These parameter changes are calculated based on the expected elastic deformation of the planet gear rim under operating torque, allowing the pin to maintain optimal clearance throughout the gear deformation cycle.
2Power
If engine power and thrust are increased, then the turbine engine performance is improved, but the planet gear deformation increases leading to reduced clearance and increased wear
Solution Approach 1:
The planet pin contour parameters are specifically designed as a function of the turbine engine's power output and operating torque. As engine power increases, the contoured shape parameters are adjusted to provide greater clearance compensation for the increased elastic deformation of the planet gear rim, ensuring reliable lubrication and preventing wear across the full range of engine power ratings.
3Reliability
If a contoured planet pin shape is used, then clearance is maintained and wear is reduced, but the manufacturing complexity increases
Solution Approach 1:
The contoured planet pin shape, while more complex than a circular cross-section, can be manufactured using standard aerospace fabrication techniques such as precision forging or CNC machining. The curved surfaces are designed to match common elastic deformation patterns, allowing the use of established manufacturing processes rather than requiring entirely new fabrication methods.
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
The contoured planet pin design maintains clearance and improves gearbox efficiency by preventing contact, reducing wear, and enhancing the conversion of kinetic energy in turbine engines, even under increased torque conditions.
Implementation Method 1
planet gear deformation under torque, leading to reduced clearance and increased wear
Implementation Method 2
maintain lubrication and prevent metal-to-metal contact
Data Source
AI summary
A gearbox assembly for a turbine engine including a drive shaft and a fan shaft. The gearbox assembly includes a first gear, a second gear, and a planet pin. The first gear is coupled to the drive shaft. The second gear is supported by a planet carrier. The planet carrier is coupled to the fan shaft. Torque is transferred from the drive shaft to the fan shaft through the gearbox assembly. The planet pin is disposed within the second gear. A planet pin shape of the planet pin includes a contoured portion that is characterized by a contoured portion deflection that is greater than or equal to −4.2e-03 inches and less than or equal to −1.2e-05 inches.