Counterrotating Open Rotor Telescopic Blades Noise Reduction
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Solution Overview
Problem
Aircraft turbine engines with unducted twin propellers face significant noise issues due to the interaction of vortices between the propellers, which current noise reduction methods fail to adequately address without compromising thrust and aerodynamic performance.
Innovation Solution
The downstream propeller blades are designed to be retractable, featuring telescopic elements that can slide relative to each other, reducing their diameter during take-off and landing to minimize vortex interaction and noise, while maintaining optimal aerodynamic performance during cruising by compensating with increased blade load and pitch angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the downstream propeller diameter is reduced to avoid vortex interaction, then noise levels are reduced, but thrust production is reduced
Solution Approach 1:
The patent applies the dynamics principle by making the downstream propeller blades telescopic, allowing the diameter to be dynamically adjusted between extended and retracted positions. During take-off and landing phases, the blades are retracted to reduce diameter and avoid vortex interaction, thereby reducing noise. During cruising phases, the blades are extended to maximize thrust production. This dynamic adjustment resolves the contradiction by allowing the system to optimize for noise reduction when needed while maintaining full thrust capability when required.
2Object-generated harmful factors
If guide means are added to deflect vortices outward, then noise interaction is reduced, but device complexity is increased
Solution Approach 1:
The patent replaces the static guide means concept with a dynamic telescopic blade structure. Instead of adding complex guide elements to deflect vortices, the invention simply retracts the blade length to move the blade tips outside the vortex core region. This approach achieves vortex avoidance with a relatively simple telescopic mechanism rather than complex vortex-deflection geometry, thereby reducing overall device complexity while still effectively reducing noise interaction.
3Force
If blade load is increased to compensate for reduced diameter, then thrust is maintained, but aeromechanical design difficulty is increased
Solution Approach 1:
The patent applies parameter changes by adjusting the pitch angle of the telescopic blades when in the retracted position. By increasing the pitch angle, the aerodynamic efficiency of each blade element is enhanced, allowing the reduced-diameter propeller to generate sufficient thrust during take-off and landing. This parameter adjustment compensates for the smaller diameter without requiring excessive blade loading or complex aeromechanical designs, thereby maintaining thrust while controlling design complexity.
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 effectively reduces noise emissions during critical phases like take-off and landing, meeting stringent acoustic certification standards while preserving engine efficiency and performance during cruising.
Implementation Method 1
two blade elements which fit one inside the other and can slide relative to each other along the longitudinal axis of the blade
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a turbine engine including two outer coaxial counter-rotating unducted propellers, i.e. an upstream propeller and a downstream propeller, respectively. Said engine is characterized in that the blades of the downstream propeller (124) are retractable in the lengthwise direction thereof so as to reduce the diameter of the propeller. Said reduction in the diameter of the downstream propeller makes it possible to reduce the noise caused by the vortices generated by the upstream propeller.