Fan Rotor Blade Root Thickening for Stress Reduction
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Solution Overview
Problem
Air cycle machine fan blades experience breakage due to high operational stress, leading to reduced fatigue life, and increasing thickness to enhance structural strength negatively impacts aerodynamic performance.
Innovation Solution
Designing fan blades with a thicker base portion and optimized chord length, defined by specific X, Y, and Z coordinates, to enhance structural strength while maintaining aerodynamic performance, using computational fluid dynamics and scaling factors as outlined in Tables T-1 and B-1/B-2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of fan blades is increased to enhance structural strength, then the fatigue life and reliability improve, but the aerodynamic performance deteriorates
Solution Approach 1:
The fan blade is designed with non-uniform thickness distribution, featuring a thicker root portion and a thinner distal portion. This local variation in geometry allows the blade root to have enhanced structural strength and fatigue resistance where stresses are highest, while the thinner distal portion maintains optimal aerodynamic performance. The thickness ratio between root and distal portions is specifically controlled to balance structural and aerodynamic requirements.
2Reliability
If the chord length of fan blade base portion is increased to reduce peak stress, then the reliability improves, but the device complexity increases
Solution Approach 1:
The fan blade is segmented into distinct geometric zones with different characteristics: a base portion with longer chord length for stress reduction, a transition portion with varying thickness, and a distal airfoil portion with uniform thickness. This segmentation allows each zone to be optimized independently for its specific function while maintaining overall blade integrity and simplifying the design process through modular geometric definition.
Data Source
AI summary
A fan rotor of an air cycle machine includes a hub with fan blades extending from the hub. Each of the plurality of fan blades includes a main airfoil portion located distally from the hub. The main airfoil portion generally has a uniform thickness along its span. A base portion located between the hub and the main airfoil portion of each of the fan blades has a chord length that is longer than a chord length of the main airfoil portion.