Aircraft Propeller Guide Bearing Layout for Lower Hub Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing propeller designs for aircraft turbomachines face challenges in optimizing aerodynamic performance, mechanical strength, and weight due to the configuration of guide bearings, which are oversized and increase the hub ratio, affecting engine performance and efficiency.
Innovation Solution
The use of a double-row ball bearing with angular contact and different diameters for guide bearings, allowing the rows of balls to be superimposed without increasing the overall dimensions, thereby maintaining the mounting stroke and reducing the diameter of the balls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-row ball bearing with larger diameter balls is used to withstand centrifugal forces, then the bearing can handle the loads, but the mounting stroke increases and the hub ratio increases
Solution Approach 1:
The single-row bearing is segmented into two concentric rows of balls with different diameters. The first row has larger diameter balls to handle radial loads, while the second row has smaller diameter balls to reduce the mounting stroke. This segmentation allows the bearing to maintain load capacity while reducing the overall dimension that affects mounting stroke.
Solution Approach 2:
The solution transitions from a single-row configuration to a multi-row concentric configuration, adding a dimensional aspect (concentric arrangement) to the bearing structure. This allows smaller balls in the second row to be positioned within the space defined by the first row, effectively reducing the radial dimension without compromising load-bearing capability.
2Strength
If the number and diameter of balls in the inner bearing are increased to handle centrifugal forces, then the bearing can withstand the loads, but the hub ratio increases and aerodynamic performance decreases
Solution Approach 1:
The bearing ball population is segmented into two distinct groups with different diameters arranged in concentric rows. This segmentation allows the total load-bearing capacity to be distributed between larger balls (fewer in number) and smaller balls (more in number), reducing the overall volume occupied by the bearing while maintaining the ability to withstand centrifugal forces.
Solution Approach 2:
Different regions of the bearing (different rows) have different ball diameters optimized for different functions. The first row uses larger balls for primary load bearing, while the second row uses smaller balls for additional support with minimal volume increase. This local differentiation of quality allows the bearing to handle centrifugal forces without increasing the hub ratio.
3Strength
If larger diameter balls are used in the guide bearing, then the bearing can withstand operational loads, but the overall bearing dimensions and weight increase
Solution Approach 1:
The bearing is segmented into two rows with different ball sizes, allowing the load-bearing function to be distributed across multiple smaller balls rather than relying on fewer larger balls. This segmentation reduces the total weight while maintaining the necessary load capacity through the combined effect of both rows.
Solution Approach 2:
The bearing design changes the parameter of ball diameter from uniform to non-uniform, with two distinct diameter values used in different rows. This parameter change allows optimization of the weight-strength trade-off by using smaller balls where possible while maintaining adequate load capacity through the multi-row configuration.
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 optimizes the propeller's dimensions and weight, enhancing engine performance by reducing the impact on the hub ratio and maintaining mechanical strength while improving aerodynamic efficiency.
Implementation Method 1
said guide bearings comprising: a first ball bearing which extends around said pitch axis and said root, between a radially external end of said bowl and said hub, and a second ball bearing which extends around said pitch axis and said root, between a radially internal end of said bowl and said hub
Data Source
AI summary
A propeller for an aircraft turbomachine, the propeller having; a hub extending around a first axis including openings distributed around the first axis, each of the openings having a substantially radial orientation relative to the first axis and extending through the hub, a system for controlling the angular setting of a blade which is mounted in each of the openings, and bearings for guiding the control system, which are mounted in each of the openings, the guide bearings including two guide bearings, one of which includes two annular rows of angular contact coaxial balls having different diameters.