Turbofan Primary Cowl Rotating Ring Micro-jets
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Solution Overview
Problem
Current noise reduction methods for turbofan engines, such as chevrons and micro-jets, are ineffective in reducing jet noise and negatively impact cruise performance.
Innovation Solution
A cowl with a rotating ring and perforations that inject pressurized gas into the secondary stream, creating an unsteady flow phenomenon along the primary cowl to reduce noise, while maintaining thrust and specific consumption performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chevrons are installed on the primary nozzle to reduce noise, then jet noise is reduced, but cruise performance deteriorates
Solution Approach 1:
The invention divides the noise control function into separate components: a fixed primary cowl and a rotating secondary cowl with micro-jets. This segmentation allows the secondary cowl to be optimized purely for noise reduction without compromising the primary nozzle's aerodynamic performance, thereby resolving the contradiction between noise reduction and cruise performance
Solution Approach 2:
The secondary cowl is designed to rotate about the engine axis, introducing dynamic motion to the noise control mechanism. This rotation creates time-varying flow disturbances that effectively reduce jet noise while the modular design ensures the primary nozzle remains fixed and optimized for cruise performance
2Object-affected harmful factors
If micro-jets are used on fixed cowls to reduce noise, then some noise reduction is achieved, but the control capacity is limited
Solution Approach 1:
The secondary cowl rotates to create time-varying flow disturbances, transforming the static micro-jet system into a dynamic one. This rotation enables the system to actively modulate the flow field and interact more effectively with coherent structures, significantly enhancing noise control capacity beyond what fixed micro-jets can achieve
Solution Approach 2:
The rotation of the secondary cowl introduces periodic action to the micro-jet injection, creating oscillating flow disturbances that resonate with and disrupt the coherent structures in the jet flow. This periodic modulation amplifies the noise reduction effect compared to continuous static injection
3Ease of operation
If disturbances are introduced at the nozzle lip, then flow control is applied, but the disturbance is quickly assimilated by turbulence
Solution Approach 1:
The rotating secondary cowl with micro-jets applies flow control actions upstream and within the jet flow before the turbulence has fully developed and assimilated disturbances. By acting earlier in the flow development process, the rotating structure maintains coherent disturbances longer, preventing their rapid assimilation by turbulence and thereby improving noise reduction effectiveness
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 jet noise by introducing an unsteady flow that persists along the primary cowl, minimizing turbulence assimilation and maintaining coherent flow dynamics, without affecting cruise performance or increasing onboard mass.
Implementation Method 1
at least one ring bearing said perforation(s), which is rotatable about said axis in relation to the external surface, and the external face of which is located in the extension of said cowl such as to recreate continuity with the external surface thereof
Implementation Method 2
by adjusting the conditions for injecting a pressurized gas in relation to the static pressure in the secondary stream, an unsteady flow phenomenon to be created along the primary cowl which continues along the entire length of this cowl and beyond
Data Source
AI summary
The invention relates to a primary cowl for a turbofan comprising a primary body generating a primary stream to be ejected through a primary nozzle, and a secondary body generating a secondary stream to be ejected through a secondary nozzle, the primary cowl being shaped so as to be positioned downstream from the primary body and to define, on the inside of the turbofan, the path followed by the primary stream downstream from the primary nozzle and, on the outside, the path followed by the secondary stream downstream from the secondary nozzle. The primary cowl comprises a coupling to a system for supplying a pressurized gas and at least one perforation for injecting the pressurized gas, through the perforation, into the secondary stream. The primary cowl preferably comprises a ring which has perforations and which is rotated about the axis of rotation of the turbofan.