ZNMF Actuators for Suppression of Shock-Induced Airflow Separation
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Solution Overview
Problem
High-speed jet inlets operating at supersonic speeds develop shock waves that cause flow separation of boundary layer air, leading to low-energy separated air bubbles forming around inlet walls, resulting in blockage, pressure losses, and potential engine unstart.
Innovation Solution
An apparatus and method using phased zero-net-mass-flux (ZNMF) actuators to alternately inhale and exhale fluid, positioning them to direct exhaled fluid back into the boundary layer in a downstream direction, phasing their operation cycles to ensure continuous fluid management, and optimizing inhalation and exhalation durations to diminish and collapse separation bubbles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If shock waves are allowed to propagate in the inlet, then supersonic flow control is achieved, but flow separation occurs causing blockage and pressure losses
Solution Approach 1:
The patent employs oscillating actuators that periodically draw and discharge fluid to interact with shock-induced separation bubbles. The periodic action creates unsteady flow structures that prevent bubble formation and maintain boundary layer attachment, resolving the contradiction between maintaining supersonic flow control and preventing flow separation.
Solution Approach 2:
The patent changes the flow parameters by introducing oscillating fluid injections that modify the boundary layer energy and shock wave structure. This parameter change allows the system to maintain supersonic flow while preventing separation through controlled fluid addition and removal.
2Reliability
If fluid is drawn from and directed back into the boundary layer, then separation bubbles are collapsed, but device complexity increases
Solution Approach 1:
The patent uses zero-net-mass-flux actuators that draw fluid from the boundary layer and discharge it back downstream, creating a self-contained system that doesn't require external fluid sources. The actuators serve multiple functions: they sense separation, draw fluid, and discharge it to collapse bubbles, reducing overall system complexity.
Solution Approach 2:
The patent employs pneumatic actuators that use pressure differentials to draw and discharge fluid. This pneumatic approach simplifies the actuator design compared to mechanical pumps or complex control systems, as the pressure gradients naturally drive the fluid motion needed to collapse separation bubbles.
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
Effectively suppresses shock-induced separation, preventing blockage, pressure losses, and engine unstart by energizing and collapsing boundary layer separation bubbles, ensuring stable and efficient high-speed jet inlet airflow.
Implementation Method 1
Each actuator is configured to alternately inhale and exhale fluid, such as air, at a rapid rate in an operation cycle. The actuators are positioned to alternately inhale fluid from and exhale fluid into a relatively low-energy boundary layer of a fluid mass flowing along the wall.
Implementation Method 2
suppressing shock-induced separation of high speed jet inlet airflow from a relatively low-energy boundary layer
Data Source
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AI summary
An apparatus for suppressing shock-induced separation of high speed airflow from a relatively low-energy boundary layer. The apparatus may include an actuator or array of actuators configured to alternately inhale and exhale fluid and positioned to alternately inhale fluid from and exhale fluid into a boundary layer of a fluid mass flowing along the wall. The actuator may be positioned to inhale fluid from a boundary layer separation bubble induced by a supersonic shock wave propagated in the fluid mass.