Guide Vanes for Rotary Wing Propeller Angle of Attack
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Solution Overview
Problem
Rotary wing aircraft tail rotors experience significant efficiency losses due to high propeller blade angles of attack caused by loading constraints, leading to reduced propulsive efficiency and increased weight.
Innovation Solution
A propulsor system with guide vanes positioned upstream of the propeller blades to reduce the angle of attack, combined with vortex generators to reenergize the boundary layer and reduce drag, allowing for lighter propeller blades and increased thrust efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the propeller diameter is constrained and shaft horsepower is increased to provide additional thrust, then the propeller becomes highly loaded requiring higher blade angles of attack, but this results in significant losses of cruise propulsive efficiency
Solution Approach 1:
Guide vanes are positioned upstream of the propeller blades to pre-condition the airflow before it reaches the blades. The guide vanes turn the incoming air to reduce the angle of attack of the propeller blades, optimizing the airflow conditions in advance and enabling efficient thrust generation without excessive blade angles of attack
Solution Approach 2:
The guide vanes act as an intermediary component between the free stream air and the propeller blades. They modify the airflow characteristics and redirect it appropriately, serving as a mediator that optimizes the interaction between the air and the propeller blades to improve propulsive efficiency
2Force
If the propeller blade angle of attack is increased to withstand higher loading, then thrust is maintained under constrained diameter, but weight increases and efficiency decreases
Solution Approach 1:
The guide vanes pre-condition the airflow upstream, reducing the angle of attack required at the propeller blades. This preliminary action on the airflow allows the blades to be designed with lighter construction while still generating the necessary thrust, thereby reducing propeller blade weight
3Force
If the propeller blade angle of attack is increased to withstand higher loading, then thrust is maintained under constrained diameter, but propulsive efficiency is significantly reduced
Solution Approach 1:
Guide vanes are positioned upstream to pre-turn the incoming airflow, reducing the angle of attack at the propeller blades. This preliminary conditioning of the air allows the propeller to operate at optimal angles of attack, significantly improving cruise propulsive efficiency while maintaining thrust
Solution Approach 2:
The guide vanes serve as an intermediary that optimizes the airflow before it reaches the propeller blades, enabling the propeller to operate in more efficient airflow conditions and thereby improving overall propulsive efficiency
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 reduces the angle of attack of propeller blades to 0-5 degrees, enhancing propulsive efficiency, increasing thrust output, and reducing load on propeller blades, enabling lighter construction and improved performance.
Implementation Method 1
The plurality of guide vanes are positioned to turn an airflow flowing into the plurality of propeller blades, thereby reducing an angle of attack of the plurality of propeller blades relative to the airflow
Implementation Method 2
A plurality of vortex generators are positioned upstream of the plurality of propeller blades
Implementation Method 3
vortex generators to reenergize the boundary layer and reduce drag
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A propulsor system (16) for a rotary winged aircraft (10) includes a propeller (30) including having a propeller hub (40) rotatable about a propeller axis (56) and a plurality of propeller blades (44) secured to and extending radially outwardly from the propeller hub (40). The propeller (30) is oriented on the rotary winged aircraft (10) to provide forward thrust for the rotary winged aircraft when the propeller is rotated about the propeller hub (40). A plurality of guide vanes (52) non rotatable about the propeller axis (56) are positioned upstream of the plurality of propeller blades (44). The plurality of guide vanes (52) are positioned to turn an airflow flowing into the plurality or propeller blades (44), thereby reducing an angle of attack of the plurality of propeller blades (44) relative to the airflow.