Variable Area Flow Duct With Helical Vanes for Throat Control
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Solution Overview
Problem
Existing nozzle designs with fixed geometry struggle to simultaneously achieve throat area control, thrust vectoring, and efficient mixing, often requiring separate systems that increase cost, weight, and complexity, while existing fluidic vectoring designs are inefficient for supersonic flows and only applicable to low area ratio nozzles, and previous systems do not address the need for cross-sectional area control during the cruise segment without using bleed air.
Innovation Solution
A variable area flow duct with helical vanes that generate secondary flows to reduce the cross-sectional area, optionally using fluidic injection to suppress these flows and maintain a maximum area, and a dissipative coating that exposes the vanes to alter the effective throat area based on operational phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical linkage systems are used to control throat area, then throat area control is achieved, but device complexity and weight increase
Solution Approach 1:
The patent replaces mechanical linkage systems with a fluidic injection system that uses fluid dynamics to control throat area. Fluid jets are injected into the flow path to generate secondary flows that effectively reduce the throat area, eliminating the need for mechanical moving parts and linkages while achieving the same control function.
Solution Approach 2:
The patent employs fluid injection (pneumatics/hydraulics) to control the effective throat area of the nozzle. By injecting fluid into the flow path and utilizing secondary flow generation, the system achieves throat area control through fluid dynamic effects rather than mechanical means, reducing complexity and weight.
2Ease of operation
If fluid property manipulation systems are used to alter effective throat area, then throat area control is achieved, but bleed air is required which reduces engine efficiency
Solution Approach 1:
The patent makes the fluid injection system self-sufficient by using the engine's own exhaust flow as the injection medium. The system utilizes a portion of the primary exhaust flow itself to generate the secondary flows needed for throat area control, rather than requiring separate bleed air sources, thereby maintaining engine efficiency while achieving control functionality.
3Force
If existing fluidic vectoring designs are used, then thrust vectoring is achieved, but compressive shock waves are developed which inefficiently turn supersonic flow
Solution Approach 1:
The patent changes the flow parameters and injection timing to prevent the formation of compressive shock waves. By carefully controlling the fluid injection parameters and using the specific geometry of the injection holes, the system achieves thrust vectoring through gradual flow turning rather than shock wave-induced abrupt turning, thereby maintaining flow efficiency.
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
Enables efficient throat area control, thrust vectoring, and mixing without moving parts, reducing system weight and cost, and maintaining efficiency across various flight phases without using bleed air, while allowing for adaptability across different platforms.
Implementation Method 1
The projection generates a secondary flow adjacent the inner surface as the primary flow flows through the duct
Implementation Method 2
The fluid jet suppresses the formation of the secondary flow by the projection, thus maintaining the effective cross-sectional area at a maximum area
Data Source
AI summary
A variable area flow duct and method. In one embodiment the flow duct includes a plurality of helical vanes arranged around an interior surface wall of the flow duct. The vanes cause secondary flow vortices to be developed in the vicinity of each of the vanes that effectively reduce the interior cross-sectional area of the duct that a primary flow sees as it flows through the duct. In various embodiments fluidic injection is employed to suppress the formation of the secondary flow vortices during certain phases of operation, for example, during an afterburn phase of operation of a jet aircraft engine which the flow duct is being used with. In another embodiment, an ablative coating is used over the vanes to suppress the formation of the secondary flow vortices. The ablative material is removed by the hot fluid flow during an afterburn phase of operation, thus exposing the vanes and enabling the subsequent formation of secondary flow vortices to narrow the cross-sectional area of the throat.