Planetary Gear Journal Pin Grooves for Bearing Heat Control
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Solution Overview
Problem
Current planetary gear arrangements in gas turbine engines face challenges with heat management, leading to increased frictional losses and susceptibility to particle contamination due to inadequate handling of hot oil, which affects efficiency and structural rigidity.
Innovation Solution
Incorporating helical grooves on journal pins to guide hot oil from the converging gap to the diverging gap, preventing mixing with cold oil and enhancing heat management, thereby improving load-bearing capacity and structural rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cold oil is provided within the journal bearing to overcome temperature increase, then temperature management is attempted, but hot oil is not displaced and mixes with cold oil, further increasing temperature
Solution Approach 1:
The journal pin surface is segmented into different functional zones using grooves: a leading groove in the converging gap to channel cold oil, and a trailing groove in the diverging gap to channel hot oil. This segmentation separates the oil flow paths, preventing hot and cold oil mixing, and enables targeted temperature management in different regions of the journal bearing.
Solution Approach 2:
Cold oil is channeled to the leading groove before the minimum gap region where temperature begins to rise. This preliminary application of cold oil to the converging gap allows heat to be removed from the lubricant before it reaches the highest temperature zones, preventing excessive temperature buildup in advance.
2Reliability
If lubricant is used to carry load and reduce friction, then friction and wear are reduced, but temperature increases due to hot oil condensation in the middle of the journal bearing
Solution Approach 1:
The trailing groove in the diverging gap extracts hot oil from the journal bearing clearance. By providing a dedicated exit path for hot lubricant in the diverging gap region, the system removes heated oil before it can re-enter the minimum gap region, preventing temperature accumulation and maintaining reliable operating conditions.
Solution Approach 2:
Different regions of the journal pin are given different properties through the groove configuration: the leading groove region handles cold oil supply and cooling, while the trailing groove region handles hot oil discharge. This local differentiation of function allows each region to optimize its specific role in temperature management while maintaining overall bearing reliability.
3Manufacturing precision
If minimum gap is expected at bottom dead center, then lubrication is optimized at that point, but hot oil is condensed in the middle and temperature reaches maximum after minimum gap
Solution Approach 1:
Cold oil is channeled to the leading groove before the minimum gap region where temperature begins to rise. This preliminary application of cold oil to the converging gap allows heat to be removed from the lubricant before it reaches the highest temperature zones, preventing excessive temperature buildup in advance.
Solution Approach 2:
The trailing groove in the diverging gap extracts hot oil from the journal bearing clearance. By providing a dedicated exit path for hot lubricant in the diverging gap region, the system removes heated oil before it can re-enter the minimum gap region, preventing temperature accumulation and maintaining reliable operating conditions.
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 solution effectively manages heat, reduces frictional losses, and increases the robustness of the journal bearing, protecting the coating and reducing the risk of thermal seizures, while improving the efficiency and load-bearing capability of the planetary gear arrangement.
Implementation Method 1
the at least one longitudinal groove is configured to guide oil on the outer surface of the journal pin when the oil is carried from the converging gap towards the diverging gap due to a rotary movement between a planet gear around a corresponding journal pin
Implementation Method 2
When the planet gears rotate the lubricant develops a pressure gradient and heats up thereby increasing the temperature therebetween
Implementation Method 3
a lubricant is provided between the cylindrical pins and planet gears in a clearance region for lubrication thereof. The lubricants are used to carry the load, reduce friction, wear-tear
Implementation Method 4
the rise in temperature reaches maximum, after the minimum gap. Notably, the rise in temperature increases the frictional loss, and particle contamination due to wear and tear which occurs due to metal-to-metal contacts
Data Source
AI summary
A planetary gear arrangement including a sun gear configured to rotate about an axis of rotation, a plurality of planet gears driven by the sun gear, a ring gear engaged with the plurality of planet gears and a plurality of journal pins arranged in the plurality of planet gears forming a converging gap and a diverging gap therebetween. Each journal pin has at least one longitudinal groove along an outer surface thereof, configured to guide oil on the outer surface when the oil is carried from the converging gap towards the diverging gap due to a revolving movement between a planet gear around a corresponding journal pin. A journal pin for supporting a gear and a gas turbine engine.