Vortex Generator Array Sizing in Offset Diffusers
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Solution Overview
Problem
Aircraft engine inlet diffusers with aggressive curvatures and offset designs often experience secondary flow issues, leading to inefficient air redirection and potential engine operability problems due to distortions caused by low energy boundary layers and high pressure gradients, necessitating a method to determine optimal vortex generator placement without costly trial and error processes.
Innovation Solution
A method employing Navier-Stokes computational fluid dynamic analysis to determine the size, position, orientation, and spacing of vortex generator blades within an offset inlet diffuser, using boundary layer height and flow velocity vectors to set blade parameters such as height, length, and angle, and staggering them to manage secondary flows effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If aggressive inlet diffuser curvatures are used to reduce diffuser length, then the diffuser length is reduced, but secondary flow and air vortices are generated causing engine operability issues
Solution Approach 1:
The patent converts the harmful secondary flow and boundary layer separation caused by aggressive diffuser curvatures into beneficial controlled vortices through vortex generators. These generators intentionally create vortices that energize the boundary layer and prevent detrimental flow separation, thus converting the harmful effect of high curvature into a beneficial flow control mechanism that maintains engine operability while achieving compact diffuser length.
Solution Approach 2:
Vortex generators act as intermediary devices placed within the diffuser to mediate between the aggressive curvature geometry and the airflow. These generators introduce controlled vortices that serve as an intermediate mechanism to manage the boundary layer and prevent direct harmful interaction between the high curvature and the low-energy boundary layer, thereby eliminating air vortices that would otherwise enter the engine.
2Reliability
If vortex generators are added to control secondary flow, then engine operability is improved, but device complexity increases
Solution Approach 1:
The patent employs parameter changes by systematically varying vortex generator characteristics (size, spacing, orientation, and position) based on local flow conditions analyzed through computational fluid dynamics. This allows optimization of the vortex generator array to control secondary flow effectively while minimizing the number of generators needed, thus improving engine operability without excessive complexity.
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 eliminates the need for trial and error, providing a systematic design for vortex generator arrays that reduce distortion and improve airflow efficiency by counteracting secondary flows, enhancing engine performance and reducing the risk of surge or stall.
Implementation Method 1
The present invention discloses and describes a method for effectively determining the size, position and orientation of an array of vortex generator blades positioned within an offset inlet diffuser
Implementation Method 2
conducting a Navier-Stokes computational fluid dynamic analysis of air flowing through the diffuser that identifies a height of a local boundary layer
Implementation Method 3
a low velocity, low pressure boundary layer of air builds up on the fuselage of the aircraft. The boundary layer is generated as a result of friction forces on the aircraft fuselage
Implementation Method 4
the low energy boundary layer's inability to negotiate the large pressure gradient induced by the high curvature of the diffuser
Data Source
AI summary
A method for optimizing size and position parameters of an array of vortex generator blades configured on an offset diffuser in an inlet of an aircraft engine. The method includes providing a computational fluid dynamic analysis of air flowing through the diffuser that identifies a height of a local boundary layer at a plurality of positions across the diffuser substantially parallel to the flow of air and a flow velocity vector at each of the plurality of positions at one half of a height of the local boundary layer. The method also includes determining an angle orientation of the blades using the boundary layer height and the flow vector, determining the length and height of the blades using the boundary layer height, and determining the number and spacing of the blades using the width of the diffuser.