Concave Core Cowling Jet Engine Exhaust Shock Wave Reduction
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Solution Overview
Problem
Current gas turbine engine exhaust systems suffer from reduced aerodynamic efficiency due to the generation of shock waves caused by convex nozzle edges, leading to increased aerodynamic losses and decreased thrust performance.
Innovation Solution
The implementation of a concave cross-sectional geometry in the core cowling, particularly in the transition region between subsonic and supersonic areas, reduces the strength and effect of shock waves by decelerating airflow and minimizing friction drag, thereby enhancing exhaust airflow streamline and overall engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a convex nozzle edge geometry is used in the core cowling, then the manufacturing is simpler, but shock waves are generated causing increased aerodynamic losses and decreased thrust performance
Solution Approach 1:
The patent inverts the conventional convex nozzle edge geometry to a concave geometry. This inversion fundamentally changes the airflow behavior at the nozzle edge, preventing shock wave formation by creating a gradual expansion rather than a sudden contraction, thereby reducing aerodynamic losses while maintaining manufacturing feasibility
Solution Approach 2:
The patent introduces a curved concave surface at the nozzle edge instead of a sharp convex angle. This curvature allows for smooth airflow transition and gradual pressure equalization, eliminating the abrupt flow separation that causes shock waves in convex geometries, thus reducing aerodynamic energy losses
2Loss of energy
If a concave cross-sectional geometry is implemented in the core cowling, then aerodynamic efficiency is improved by reducing shock waves, but the device complexity increases
Solution Approach 1:
The patent applies the concave geometry only at the specific location where it is most effective - the nozzle edge region of the core cowling. This localized application achieves the aerodynamic benefits of shock wave reduction without requiring a complete redesign of the entire cowling structure, thereby limiting the increase in device complexity to only the necessary local area
3Loss of energy
If the core cowling is spaced from the exhaust section to define a core outlet, then aerodynamic streamline is enhanced, but the engine size and weight increase
Solution Approach 1:
The patent employs a concave curved surface in the core cowling that gradually guides the airflow from the exhaust section to the core outlet. This curved geometry creates a streamlined flow path that maintains aerodynamic efficiency while allowing for a more compact spacing between the core cowling and exhaust section, thereby reducing the overall engine size and weight compared to straight-line configurations
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 concave core cowling structure significantly reduces the strength of shock waves, increases airflow streamline, and enhances engine efficiency by minimizing aerodynamic losses and friction drag, resulting in improved thrust performance and reduced engine size and weight.
Implementation Method 1
the generation of shock waves caused by convex nozzle edges
Implementation Method 2
reduces the strength and effect of shock waves by decelerating airflow
Implementation Method 3
minimizing friction drag, thereby enhancing exhaust airflow streamline
Data Source
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AI summary
A compression inner core cowling 76 for a jet engine 10 can have a concave annular section 90 of the core cowling 76. The concave section 76 can begin within the expanse of an outer fan cowl 40 and extend aft of the fan cowl 40 toward the tail cone 94, defining an annular bypass section 80 between the fan cowling 40 and the core cowling 76. The concave geometry of the core cowling 76 reduces the strength of supersonic shock waves generated at the corners 140, 142 of the cowlings 40, 76 adjacent a supersonic airflow stream to increase overall efficiency of the engine 10.