Turbomachine Nozzle Chevrons with Non-Axisymmetric Inner Face
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing turbine engine nozzle designs that incorporate chevrons to reduce jet noise often compromise thrust performance and operability, particularly during take-off and cruising speeds, due to the need for pronounced inclination of chevrons which can lead to a reduction in the effective discharge cross-section and creation of recirculation zones.
Innovation Solution
A nozzle design featuring a cowl with a convergent internal wall and divergent external wall, incorporating indentations and re-entrant chevrons that allow for a larger equivalent discharge cross-section while promoting flow mixing, thereby optimizing noise reduction and operational performance without compromising thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chevrons are inclined towards the outlet jet to reduce jet noise, then noise reduction effectiveness is improved, but thrust performance and operability deteriorate due to reduced effective discharge cross-section
Solution Approach 1:
The chevron structure employs asymmetric geometry where the internal face is non-axisymmetric with different curvatures in upstream and downstream directions. The upstream face has a first curvature while the downstream face has a second curvature, creating asymmetric flow control that reduces noise without compromising thrust by optimizing the interaction between internal and external flows
Solution Approach 2:
Different portions of the chevron structure have different geometric properties tailored to specific functions. The upstream face geometry is optimized for flow convergence and mixing, while the downstream face geometry is optimized for noise reduction. This local differentiation allows simultaneous optimization of thrust and noise reduction performance
2Object-affected harmful factors
If chevrons are inclined towards the outlet jet to reduce jet noise, then noise reduction effectiveness is improved, but operability between take-off and cruising speeds deteriorates
Solution Approach 1:
The non-axisymmetric internal face geometry dynamically adapts to different flow conditions. The asymmetric curvatures create different flow control effects at different operating points, allowing the chevron structure to maintain effectiveness across the full range from take-off to cruising speeds without compromising operability
3Object-affected harmful factors
If pronounced inclination of chevrons is used to reduce jet noise, then noise reduction is improved, but recirculation zones are created that deteriorate flow quality
Solution Approach 1:
Instead of using conventional chevron inclination that creates recirculation zones, the invention inverts the approach by using a non-axisymmetric internal face with specific curvature characteristics. The upstream face curvature is designed to promote flow convergence rather than separation, eliminating recirculation zones while maintaining 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 design effectively reduces jet noise while maintaining or improving thrust performance across various operating conditions by separating geometric parameters for acoustic and operational performance, eliminating recirculation zones, and ensuring confluence of internal and external flows.
Implementation Method 1
The speed difference between the jet at the nozzle outlet and the other gaseous flow or flows which it encounters creates fluid shears penetrating between these gaseous flows, which causes noise... The use of chevrons placed in a ring at the outlet of the nozzle is a known means for substantially reducing the low-frequency components of this noise. The patent application EP1873389A1 describes chevrons which make it possible to reduce the turbulent intensity of large vortices constituting the major sources of noise.
Data Source
AI summary
In a cowl for a nozzle, an internal wall has a cross-section with a determined abscissa on the axis defining a neck line on the internal wall. The cowl has, downstream of the determined abscissa, indentations in the trailing edge which delimit chevrons distributed in the circumferential direction. The internal wall of the cowl diverges radially towards the interior, in a second axial half-plane passing through the tip of a chevron, from the upstream tangent on the point of the neck line in the second axial half-plane, and the lines defining the internal wall of the cowl in any axial half-plane do not have a turning point downstream of the determined abscissa of the neck line.