Aircraft Pylon Orifice Air Injection for Jet Noise Reduction
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Solution Overview
Problem
The presence of a pylon on an aircraft engine increases noise levels during takeoff due to turbulence and velocity shear between hot and cold flows, limiting noise reduction effectiveness of existing devices like chevrons or mixers.
Innovation Solution
A pylon design with strategically positioned orifices for injecting or drawing air into the gas flow around the engine, reducing vortex formation and turbulent intensity, and controlling the initial jet growth and mixing to minimize noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pylon is used to support the engine, then the engine can be mounted on the aircraft wing, but noise levels increase due to turbulence and velocity shear between hot and cold flows
Solution Approach 1:
The patent introduces an intermediary substance (air or gas) that is injected between the hot exhaust flow and the cold ambient flow around the pylon. This intermediary flow acts as a buffer that reduces the velocity shear and turbulence at the pylon surface, thereby reducing noise generation while maintaining the structural support function of the pylon
Solution Approach 2:
The invention utilizes pneumatic principles by injecting compressed air or gas through nozzles positioned on the pylon. This pneumatic flow modifies the aerodynamic environment around the pylon, reducing turbulent mixing between hot and cold flows and consequently reducing the noise generated by the pylon-exhaust interaction
2Object-generated harmful factors
If chevrons or mixers are fitted to the exit nozzle, then jet noise is reduced, but the presence of the pylon considerably reduces the effectiveness of these devices
Solution Approach 1:
Instead of only modifying the jet flow at the exit nozzle (two-dimensional approach), the patent adds a third dimension by introducing flow modification nozzles on the pylon surface. This three-dimensional approach addresses the noise problem at multiple locations simultaneously, compensating for the pylon's interfering effect and restoring noise reduction effectiveness
3Shape
If the pylon protrudes beyond the plane in which the gases are ejected, then structural configuration is optimized, but turbulence and noise levels increase significantly
Solution Approach 1:
The patent changes the flow parameters (velocity, pressure, density) by injecting controlled amounts of air or gas through nozzles on the pylon. This modifies the flow characteristics around the protruding pylon structure, reducing turbulence intensity and noise generation while preserving the optimized structural 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
Significantly reduces lateral noise by modifying the airflow around the pylon, improving jet mixing and acoustic signatures, with the option to activate only during takeoff to avoid performance drops and fuel consumption increases.
Implementation Method 1
a jet of air is injected into, or drawn in from, the flow of gas flowing along its flanks
Implementation Method 2
modifying the flow around the pylon and thus, by directing this jet in a suitable direction, to reduce the formation of vortices between the engine and the pylon and thus reduce the wall noise
Implementation Method 3
the noise associated with the interaction between the jet of the engine and the flow of the air around the pylon
Implementation Method 4
controlling the initial growth of the jet and therefore the mixing thereof
Data Source
AI summary
An aircraft pylon for mounting a dual-flow or triple-flow jet engine, the pylon including an upper surface for connection to the aircraft, two side flanks, and a flange on the lower portion of the pylon. The pylon further includes at least one portion that extends downstream from the cold flow nozzle of the jet engine and lies in the cold flow and, on the portion thereof extending into the cold flow beyond the nozzle, at least one opening, positioned on one of the flanks of the pylon, by which an air stream is injected into or drawn from the gas flow that flows along the flanks of the pylon.