Supersonic Injectors for Aircraft Engine Shock Noise Reduction
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Solution Overview
Problem
Supersonic jet engine exhaust generates significant noise due to shock cell structures, which are difficult to mitigate with existing technologies, especially when the engine nozzle is in an under-expanded or over-expanded state, leading to inefficiencies and performance penalties.
Innovation Solution
Creating a virtual aerodynamic surface, or aero-lobe, by injecting supersonic flow from multiple supersonic injectors into the primary engine flow path, which controls the shock front and reduces shock cell strength through adjustable parameters such as injector shape, size, and speed, without permanent structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive devices such as mechanical lobe mixers are used to reduce shock cell noise, then noise reduction is achieved, but system weight increases and reliability decreases due to permanent structures in the hot flowpath
Solution Approach 1:
The patent employs active flow control through supersonic injectors that can be dynamically activated or deactivated based on operational conditions. This replaces static passive structures with dynamic active control, allowing the system to achieve noise reduction only when needed, thereby eliminating the continuous weight and reliability penalties of permanent structures in the hot flowpath.
Solution Approach 2:
The invention uses pneumatic injection of supersonic flows from multiple injectors to create virtual aerodynamic lobes. This pneumatic approach replaces solid mechanical structures with fluid-based control, achieving the same noise mitigation function without the weight and reliability issues associated with physical structures exposed to hot exhaust gases.
2Object-affected harmful factors
If variable iris nozzles are used to control nozzle expansion, then some shock cell control is achieved, but thrust and actuation limits restrict their effectiveness
Solution Approach 1:
The invention segments the flow control function by using multiple independent supersonic injectors distributed around the nozzle periphery. Each injector can be controlled independently, allowing precise local flow manipulation to control shock cells without requiring large-scale nozzle geometry changes that would affect thrust. This segmented approach enables fine-grained control of shock cell structures while preserving overall engine performance.
Solution Approach 2:
The supersonic injectors act as intermediary devices that mediate between the engine core flow and the exhaust plume. By introducing controlled injection flows that penetrate the primary exhaust, these intermediaries create virtual lobes that control shock cell development without directly modifying the nozzle geometry or restricting the main thrust-generating flow path.
3Object-affected harmful factors
If traditional noise reduction means are applied to subsonic exhausts, then noise is reduced, but mixing is suppressed and system penalties increase
Solution Approach 1:
The invention changes the fundamental parameters of the injection flow by using supersonic velocities rather than subsonic flows. This parameter change allows the injection to penetrate the primary exhaust flow and create constructive interference patterns that control shock cells while simultaneously enhancing mixing through the high-speed interaction. The supersonic parameter enables both noise control and mixing enhancement, avoiding the trade-off present in subsonic systems.
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 allows for on-demand reduction of shock-cell noise and enhances mixing, reducing system penalties like weight, drag, and thrust loss, while maintaining engine performance and extending the life of components.
Implementation Method 1
The injected flow creates a virtual obstacle for the primary flow, thus creating an aero-lobe or virtual surface which, in turn, creates a shock front
Implementation Method 2
a series of repeating detonations (or deflagrations) within the device cause a pressure rise and subsequent acceleration of the combustion products
Data Source
AI summary
An aircraft engine is provided with at least one pulse detonation device connected to an engine exhaust nozzle portion with a plurality of supersonic injectors. The flow from the pulse detonation device is passed through the supersonic injectors into the primary engine flow path. The injector flow is injected at a velocity such that the injected flow penetrates into the primary flow path. This injected flow creates a virtual obstacle for the primary flow, and their interaction creates a virtual surface or an aero-lobe, thus controlling the nozzle exit area to reduce engine noise.