Scalloped Root Regions in Chevron Nozzle Housing
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Solution Overview
Problem
Existing chevron designs in gas turbine engine nozzles can increase duct drag, reducing engine efficiency while attempting to reduce low-frequency noise through mixing with freestream air.
Innovation Solution
A gas turbine engine exhaust nozzle with a housing that terminates in a row of chevrons, featuring scalloped root regions with reduced thickness, which vary in cross-sectional plane, to minimize drag and enhance noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chevrons are added to the nozzle to increase mixing between engine flow and freestream air, then low-frequency noise is reduced, but duct drag increases and engine efficiency decreases
Solution Approach 1:
The patent applies local quality by creating scalloped root regions with varying thickness at specific locations where chevrons are positioned. The housing thickness is reduced in cross-sectional planes drawn through the scalloped root regions, creating localized geometric variations that optimize flow characteristics. This allows the chevrons to effectively mix engine flow with freestream air for noise reduction while the scalloped regions minimize the drag penalty by creating favorable pressure gradients and reducing flow separation.
2Object-affected harmful factors
If chevrons are added to the nozzle to increase mixing between engine flow and freestream air, then low-frequency noise is reduced, but duct drag increases
Solution Approach 1:
The patent applies local quality by creating scalloped root regions with varying thickness at specific locations where chevrons are positioned. The housing thickness is reduced in cross-sectional planes drawn through the scalloped root regions, creating localized geometric variations that optimize flow characteristics. This allows the chevrons to effectively mix engine flow with freestream air for noise reduction while the scalloped regions minimize the drag penalty by creating favorable pressure gradients and reducing flow separation.
Solution Approach 2:
The patent applies dimensionality change by introducing scalloped root regions that create three-dimensional geometric variations in the housing thickness. The scalloped regions are defined by varying the housing thickness in cross-sectional planes drawn through the scalloped root regions, adding a dimensional complexity that optimizes both noise reduction and drag characteristics simultaneously.
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 reduces the drag coefficient of the nozzle, thereby increasing engine efficiency and effectively reducing low-frequency noise by optimizing the mixing of engine flow with surrounding air.
Implementation Method 1
increase the amount of mixing between the high velocity gases exiting the engine, and the surrounding freestream air
Implementation Method 2
reduces the drag coefficient of the nozzle, thereby increasing engine efficiency
Data Source
AI summary
A gas turbine engine exhaust nozzle comprises a housing having an aft end that terminates in a row of chevrons. At least one surface of the housing has scalloped root regions proximate bases of adjacent chevrons. The scalloped root regions have a reduced thickness relative to the rest of the aft end.