Variable Slope Exhaust Nozzle for Turbofan Engines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The circumferential interruptions caused by the upper and lower bifurcations in turbofan engines reduce the aerodynamic performance and efficiency of the exhaust nozzle, as they disrupt the continuity of velocity and pressure distributions in the fan air discharge.
Innovation Solution
The exhaust nozzle design is modified by varying the axial slope or cone angle of the inner shell circumferentially around the fan duct, increasing the cone angle away from the pylon and beam to redistribute pressure and velocity distributions, and adjusting the outer shell radius to maintain total flow area, thereby improving thrust coefficient and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the exhaust nozzle is designed with upper and lower bifurcations to accommodate the pylon and beam structure, then the engine can be properly mounted in the aircraft, but the circumferential continuity of the fan duct is interrupted and aerodynamic performance is reduced
Solution Approach 1:
The patent applies local quality by varying the cone angle locally in different circumferential regions of the fan duct. Specifically, the cone angle is increased in regions away from the pylon and beam to compensate for the flow disruption caused by these structures, while maintaining the original design in other regions. This localized modification optimizes the velocity and pressure distributions specifically where needed without changing the entire nozzle geometry.
Solution Approach 2:
The patent introduces asymmetry by making the cone angle variation circumferentially non-uniform. The cone angle is selectively increased in specific circumferential positions (away from pylon and beam) rather than being constant around the entire duct. This asymmetric design compensates for the asymmetric placement of the pylon and beam structures, restoring aerodynamic balance to the flow field.
2Loss of energy
If the cone angle is increased away from the pylon and beam, then the velocity and pressure distributions are improved and thrust coefficient is increased, but the device complexity increases due to variable geometry
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameter (cone angle) of the fan duct in a controlled manner. Instead of changing the overall nozzle design or adding complex active control systems, the solution varies a single geometric parameter (cone angle) circumferentially to optimize performance. This approach improves thrust coefficient while keeping the complexity manageable, as it only requires modifying the duct shape rather than adding mechanical or electronic systems.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A turbine exhaust nozzle (36) includes an inner shell (30) disposed coaxially inside an outer shell (32) to define a flow duct (34) terminating in an outlet (38) at a trailing edge (40) of the outer shell (32). The inner shell (30) is non-axisymmetric and varies in axial slope angle circumferentially around the duct (34).