Heating System for Convergent-Divergent Nozzle Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Convergent-divergent nozzles in mixed-flow turbomachines experience high-frequency noise due to turbulence interactions and Mach pockets, which are acoustically disadvantageous despite performance improvements.
Innovation Solution
A heating system, including a heating radiator or hot-air diffuser, is integrated into the secondary nozzle to locally heat the airflow at the neck region, reducing noise by reheating the slipstream and minimizing acoustic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a convergent-divergent secondary nozzle is used to improve engine performance, then the nozzle performance is improved, but high-frequency noise increases due to Mach pockets and turbulence interactions
Solution Approach 1:
The patent applies parameter changes by modifying the temperature parameter of the airflow through heating elements. The heating system raises the temperature of the air in the neck region, which changes the local speed of sound and reduces the Mach number, thereby eliminating Mach pockets and reducing turbulence-induced noise while maintaining the convergent-divergent nozzle's performance benefits
Solution Approach 2:
The patent converts the harmful effect of cold air (which creates Mach pockets and noise) into a benefit by deliberately heating it. The heating system transforms the problematic cold airflow into a controlled thermal field that reduces noise generation, turning the originally harmful temperature condition into a useful control parameter for noise reduction
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 heating system effectively reduces noise levels by up to 1 EPNdB, addressing the acoustic disadvantages of convergent-divergent nozzles while maintaining engine performance.
Implementation Method 1
A heating system, including a heating radiator or hot-air diffuser, is integrated into the secondary nozzle to locally heat the airflow at the neck region, reducing noise by reheating the slipstream and minimizing acoustic effects
Data Source
AI summary
An assembly for a rear of a dual-flow turbomachine having a longitudinal axis includes a secondary nozzle and a heating system. The secondary nozzle is defined about the longitudinal axis and ejects a mixture of the flows coming from a secondary vein and a primary vein of the turbomachine. The secondary nozzle is of a convergent-divergent form with a neck corresponding to a minimal cross-cross-section of the secondary nozzle. The heating system is located on a portion of the internal circumference of the secondary nozzle longitudinally in the region of the neck or upstream from the neck.