Slidable Plug-Cowl Nozzle for Supersonic Aircraft Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Supersonic aircraft face challenges in meeting stringent noise regulations due to high jet noise from exhaust nozzles, which existing technologies have not adequately addressed, especially at low speed operations around airports.
Innovation Solution
A slidable plug-cowl assembly within the nozzle is used, where the plug slides to change the nozzle throat area and expansion ratio, optimizing noise reduction during takeoff and supersonic cruise while maintaining engine efficiency, by positioning the plug aft of the cowl exit plane during takeoff and forward during supersonic flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed nozzle design is used, then the structure is simple, but it cannot adapt to different flight conditions (takeoff vs supersonic cruise) and results in high noise emissions
Solution Approach 1:
The nozzle employs a slidable plug assembly that can move between different positions (aft position for takeoff, forward position for supersonic cruise) to dynamically adjust the throat area and expansion ratio, allowing the same nozzle structure to adapt to multiple flight conditions without requiring multiple separate nozzles
2Productivity
If the nozzle throat area is increased for supersonic cruise, then thrust efficiency improves, but noise emissions increase during takeoff operations
Solution Approach 1:
The slidable plug assembly allows dynamic adjustment of the throat area: during takeoff, the plug is positioned aft to reduce throat area and noise emissions, while during supersonic cruise, the plug is positioned forward to increase throat area and thrust efficiency, thus resolving the contradiction between thrust efficiency and noise emissions
Solution Approach 2:
The nozzle design changes the geometric parameters (throat area and expansion ratio) by moving the plug assembly between positions, thereby optimizing performance for different flight conditions - larger throat area for supersonic cruise thrust efficiency, smaller throat area for takeoff noise reduction
3Productivity
If a convergent-divergent nozzle is used for supersonic flight, then thrust efficiency at high NPR improves, but jet noise increases at low NPR during takeoff
Solution Approach 1:
The slidable plug assembly dynamically adjusts the effective throat area and expansion characteristics of the nozzle. During supersonic cruise with high NPR, the plug is positioned to create an effective C-D nozzle configuration for high thrust coefficient. During takeoff with low NPR, the plug is positioned to reduce the effective throat area and minimize jet noise, thus resolving the contradiction between thrust coefficient and jet noise
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 configuration reduces noise emissions while maintaining thrust efficiency, achieving optimal noise reduction for both low-speed takeoff and supersonic conditions, thereby complying with stringent noise regulations.
Implementation Method 1
A slidable plug-cowl assembly within the nozzle is used, where the plug slides to change the nozzle throat area and expansion ratio
Data Source
AI summary
The present disclosure relates to a method of operating a supersonic aircraft comprising the steps of: at takeoff, positioning a slidable plug-cowl assembly disposed within a nozzle and behind an engine in an aft position such that a front surface of a plug is aft of an exit plane of a cowl, to thereby reduce noise during takeoff and maintain engine efficiency; and after takeoff, re-positioning the slidable plug-cowl assembly to a forward position such that the front surface of the plug is not disposed aft the exit plane of the cowl.