Ovalized Secondary-Air Nozzle for Underwing Engine Clearance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in mounting turbofan engines with large fan diameters under an aircraft wing while maintaining sufficient ground clearance and minimizing drag, as the rear part of the engine nacelle interacts with the wing surface, requiring a reduction in the vertical height and overall diameter of the cold flow nozzle.
Innovation Solution
The solution involves varying the radial positioning of the thrust reversal grids in the azimuth direction to ovalize or deform the cowl element, allowing for aerodynamic adjustment of the cold air flow during thrust reversal, thereby reducing the vertical bulk of the nacelle and maintaining the fan diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan diameter is increased to improve thrust performance and fuel efficiency, then the engine's specific fuel consumption decreases and thrust increases, but the vertical height of the nacelle increases, reducing ground clearance and increasing drag when installed under the wing
Solution Approach 1:
The patent applies asymmetry by deforming the cold flow nozzle from a circular cross-section to an oval cross-section. The oval shape has a reduced vertical dimension while maintaining or increasing the horizontal diameter, allowing larger fan diameters without proportionally increasing the vertical height. This asymmetric deformation of the nozzle geometry enables the contradiction between thrust performance (related to fan diameter) and vertical height to be resolved.
Solution Approach 2:
The patent transitions from a circular (isotropic) nozzle geometry to an oval (anisotropic) geometry, effectively changing the dimensional characteristics. By redistributing the diameter in different directions (reducing vertical dimension while maintaining horizontal dimension), the solution operates in multiple dimensional directions simultaneously, allowing the fan diameter to be large without proportionally increasing the vertical height that would interfere with ground clearance.
2Length of moving object
If the nacelle vertical height is reduced to improve ground clearance and reduce drag, then ground clearance increases and drag decreases, but the fan diameter must be reduced, lowering thrust performance
Solution Approach 1:
The oval-shaped cold flow nozzle creates an asymmetric geometry where the vertical and horizontal dimensions are different. This allows the vertical height to be reduced independently from the horizontal diameter, enabling better ground clearance and reduced drag without sacrificing the fan diameter needed for thrust performance. The asymmetric shape decouples the relationship between vertical height and thrust capability.
Solution Approach 2:
The patent applies local quality by varying the nozzle dimensions in different spatial directions. The horizontal dimension (affecting thrust) is maintained or increased, while the vertical dimension (affecting ground clearance) is reduced. This directional differentiation of dimensional qualities allows simultaneous optimization of both thrust performance and ground clearance characteristics.
3Length of moving object
If the cold flow nozzle is deformed to oval shape to reduce vertical height, then the nacelle fits better under the wing with improved ground clearance, but aerodynamic performance may be compromised
Solution Approach 1:
The patent deliberately introduces asymmetry in the nozzle geometry to resolve the contradiction between vertical height reduction and aerodynamic performance. The oval shape is not merely a compromise but a designed asymmetric configuration that maintains proper flow characteristics while achieving the required dimensional constraints for underwing installation.
Solution Approach 2:
The patent incorporates a thrust reverser system with movable flaps and deflectors that can dynamically adjust the flow path and pressure distribution within the deformed nozzle. This dynamic capability allows the system to compensate for the static geometric deformation, maintaining aerodynamic performance across different operating conditions despite the oval cross-section.
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 enables the installation of engines with larger fan diameters under the wing without sacrificing performance, reducing drag and ensuring adequate ground clearance, while minimizing aerodynamic issues associated with nozzle deformation.
Implementation Method 1
The cold flow is guided along these deflection edges. A plurality of ring-shaped grids 8 are arranged across the passages, around the periphery of the cold flow 17. The grids are formed of ring-shaped fins 81, oriented radially with respect to the engine axis and creating channels between them to guide the flow passing through them outwards with a component upstream of the engine to provide reverse thrust.
Implementation Method 2
The solution involves varying the radial positioning of the thrust reversal grids in the azimuth direction to ovalize or deform the cowl element, allowing for aerodynamic adjustment of the cold air flow during thrust reversal, thereby reducing the vertical bulk of the nacelle and maintaining the fan diameter.
Data Source
Figure 1~2
Figure 3~5
Figure 6~10
AI summary
The present invention relates to a secondary-air nozzle of a two-flow jet engine having separated flows including an annular cowl element (27, 127, 227) translatably mobile in an axial direction between an upstream retracted position allowing the engine to operate under direct thrust and a downstream extended position, and a grid thrust reverser (28, 128, 228) in the form of cylindrical ring sectors coaxial with said cowl element, made up of blades with a radial setting, and axially separated such as to provide radial guide passages therebetween, the cowl element opening said radial guide passages in the downstream extended position through the thrust reverser grids. The nozzle is characterised in that the radius of the ring sectors forming the grids (28, 128, 228) is not constant around the circumference of the cowl element (27, 127, 227), and in that said annular cowl element (27, 127, 227) includes an inner wall (27int, 127int, 227int) delimiting the periphery of the secondary-air stream and an outer wall (27ext, 127ext 227ext) housing the nacelle, the radius of the transverse cuts of at least one of the walls not being constant, when moving around the circumference of the cowl element, the cuts being made between the upstream edge of the cowl element and the downstream edge thereof.