Microjet Ejection Gratings for Turbine Jet Noise Reduction
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Solution Overview
Problem
Existing solutions for reducing jet noise in turbine engines with separate streams often compromise engine performance and generate significant noise penalties at medium and high frequencies due to the presence of feed ducts and their aerodynamic noise.
Innovation Solution
The implementation of microjet circuits with ejection gratings that split the intake gas stream into smaller sections, injected at the trailing edge of the outer cover with optimized angles and spacing, to enhance mixing between the bypass stream and external air, minimizing parasitic noise and maintaining aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If feed ducts are used to eject air jets at the trailing edge of the outer cover, then jet noise is reduced through enhanced mixing, but engine performance is penalized and medium-high frequency noise increases
Solution Approach 1:
The invention divides the single feed duct into multiple microjet circuits, each with its own small feed duct opening directly onto the outer cover surface. This segmentation allows distributed air injection across multiple locations, enhancing mixing effectiveness while minimizing the total area blocked and reducing aerodynamic noise from individual duct structures.
Solution Approach 2:
The invention extracts the air injection function from the traditional feed duct structure and relocates it directly to the outer cover surface through multiple small openings. This extraction eliminates the need for large feed ducts and their associated aerodynamic noise problems while maintaining the air ejection function.
2Object-affected harmful factors
If air is taken from the bypass stream to form microjets, then jet noise is reduced, but engine performance impacts increase
Solution Approach 1:
The invention applies local quality by creating multiple localized microjet circuits distributed across the outer cover surface. Each microjet circuit operates independently with its own small feed duct, allowing localized air extraction and injection. This distribution ensures that the impact on the bypass stream is minimized while achieving effective noise reduction through cumulative mixing effects.
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 approach effectively reduces jet noise at medium and high frequencies while preserving engine performance by minimizing head losses and noise generation, with the ejection grating's design allowing for precise control of gas stream injection angles and flow rates.
Implementation Method 1
high frequency noise coming from small turbulent structures in the mixing between the streams
Implementation Method 2
act on the shear layers that form in the zone where mixing takes place between the bypass stream and the air stream outside the engine
Data Source
AI summary
A device for reducing the jet noise of a turbine engine includes an outer cover having an inside wall defining the outside of an annular passage for passing a bypass stream from the engine, the wall of the outer cover including a plurality of microjet circuits, each including intakes for taking a gas stream from the bypass stream flow passage and leading to a single feed duct, which in turn opens out into the trailing edge of the outer cover via at least one ejection grating suitable for splitting the intake gas stream into a plurality of gas streams of right sections of dimensions less than a right section of the feed duct.