Swept-Back Wedge Isolator for Supersonic Engine Flow Control

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Solution Overview

Problem

Supersonic and hypersonic air-breathing engines face issues with flow distortion and separation in isolators, leading to reduced combustion efficiency, engine stall, and potential burn-through due to strong shock-boundary layer interactions, which limit the engine's range and acceleration capabilities.

Innovation Solution

Incorporating an inner-mold-line swept-back ramp or wedge in the isolator that anchors shocks and improves flow mixing by diverting boundary-layer and core flow radially and circumferentially, reducing flow separations and allowing the isolator to reach higher back pressures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If strong shock-boundary layer interactions occur in the isolator, then pressure rise capability is improved, but flow separation and distortion increase

Engineering Contradiction:

Improvepressure rise capabilityVSAvoidflow profile distortion

Core Design Contradiction:

Stress or pressureVSStability of the object's composition

Solution Approach 1:

The isolator is divided into multiple sections with different shock train configurations. The forward section has a longer isolator length to accommodate a more upstream shock train, while the aft section has a shorter length for a downstream shock train. This segmentation allows different regions to handle pressure rise and flow quality requirements separately, resolving the contradiction between pressure rise capability and flow profile distortion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the isolator are designed with different characteristics optimized for their specific functions. The forward region is designed to generate strong shocks for pressure rise, while the aft region is designed to minimize flow distortion. This local optimization allows each section to perform its specific function without compromising the other, resolving the contradiction between pressure rise and flow quality.

Inventive Principle:

Principle #3Local quality

2Reliability

If isolator length is increased to improve shock anchoring, then maximum back pressure capability is improved, but flow separation risk increases

Engineering Contradiction:

Improvemaximum back pressure capabilityVSAvoidflow separation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The isolator is segmented into forward and aft sections with different length characteristics. The forward section has sufficient length to anchor shocks and achieve high back pressure capability, while the aft section is optimized to minimize flow separation. This segmentation allows the system to achieve high back pressure capability without excessive overall length that would cause flow separation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The forward section of the isolator is designed with excessive length relative to what would be needed for shock anchoring alone, creating a buffer zone that prevents flow separation from propagating upstream. This partial excess length in the forward section protects the overall system from flow separation issues while maintaining high back pressure capability.

Inventive Principle:

Principle #16Partial or excessive action

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 solution enhances flow mixing and reduces separation regions, enabling the isolator to achieve higher back pressure capabilities and improved combustion efficiency, thereby increasing the engine's range and acceleration performance while minimizing the risk of burn-through.

Implementation Method 1

In operation a forward part of the wedge produces an oblique shock

Methodology Applied

Scientific EffectOblique shock: Oblique Shock Wave

Implementation Method 2

features of the wedge divert boundary-layer and core flow that is close to the surface of the wedge, radially outboard and circumferentially along the walls of the isolator as the flow proceeds axially downstream through the isolator, to improve flow mixing

Methodology Applied

Scientific EffectFlow mixing: Turbulence

Data Source

PatentUS11473500B2Method of reducing low energy flow in an isolator of a flight vehicle air breathing engine

Publication Date: 2022.10.18 RAYTHEON CO

AI summary

A method of reducing low-energy flow in a flight vehicle engine includes an isolator of the engine having a swept-back wedge to improve flow mixing. The wedge includes forward shock-anchoring locations, such as edges or rapidly-curved portions, that anchor oblique shocks in situations where the isolator has sufficient back pressure. The swept-back wedge may also create swept oblique shocks along its length. Boundary layer flow streamlines are diverted running parallel to or parallel but moving outward conically to the swept-wedge leading edge moving outboard and upward. The non-viscous flow outside the boundary layer is processed through the swept-back ramp shock and diverted outboard and upward as well. The outboard aft portion of the wedge at the sidewall intersection may also induce shocks and divert flow near the walls closer toward the walls and upward, and/or improve flow mixing.