Variable Diameter Propeller Blades for Aircraft Noise Reduction
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Solution Overview
Problem
Aircraft turbine engines with counter-rotating propellers face a contradiction between maximizing downstream blade elongation for efficiency at cruising speed and minimizing noise during take-off, where high blade load causes vortex interaction noise issues.
Innovation Solution
The downstream propeller's diameter is varied using telescopically mounted blades with actuation means, such as pneumatic actuators, to adjust radial position and pitch, allowing the blades to retract under upstream propeller vortices during take-off while maintaining optimal aerodynamic profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the downstream propeller blade diameter is increased to maximize efficiency at cruising speed, then propeller efficiency is improved, but noise level increases during take-off due to vortex interaction
Solution Approach 1:
The downstream propeller blade diameter is made variable through telescopic adjustment mechanisms, allowing the blade length to be dynamically changed between take-off (retracted) and cruising (extended) configurations, thus adapting to different operational requirements
Solution Approach 2:
The physical parameter of blade diameter is changed between operational phases - reduced during take-off to minimize vortex interaction noise, and increased during cruising to maximize propeller efficiency and thrust
2Object-generated harmful factors
If the downstream propeller blade diameter is reduced to minimize noise during take-off, then noise level is reduced, but propeller efficiency decreases at cruising speed
Solution Approach 1:
The propeller system transitions from a static fixed-diameter design to a dynamic variable-diameter design, enabling optimal performance across different flight phases by adjusting blade extension state
Solution Approach 2:
The telescopic blades are extended and retracted periodically according to flight phase requirements - retracted during take-off for noise reduction, extended during cruising for efficiency optimization
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 solution optimizes propeller efficiency across flight conditions while reducing noise by allowing the downstream propeller to pass under upstream vortices, maintaining aerodynamic performance and thrust during take-off.
Implementation Method 1
the or each actuator is pneumatic and more preferably configured to be activated according to an ambient pressure
Implementation Method 2
Said actuator can comprise elastic means arranged to exert a return force on the blades opposite the centrifugal force exerted on the latter
Data Source
AI summary
An aircraft turbine engine has a pair of rotating and non-ducted propellers. An upstream propeller has an outer diameter D1 and a downstream propeller has an outer diameter D2. The engine further includes a system for varying the diameter D2. The downstream propeller includes an annular row of blades, each of which is configured to be mounted telescopically in the radial direction (R) in an outer fan duct.