Auxiliary Lobes and Capture Ducts for Turbofan Mixer Obstruction
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Solution Overview
Problem
The presence of engine mounting struts and fairings in turbofan engines obstructs the mixing of primary and secondary fluid streams, leading to diminished propulsive efficiency and increased acoustic emissions due to the absence of effective secondary chutes in the mixer lobes.
Innovation Solution
Incorporating auxiliary lobes and fluid capture ducts that convey secondary fluid to secondary chutes, with the ducts' intake ends projecting into the secondary fluid stream to capture and convey air, enhancing mixing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If engine mounting struts and fairings are installed to support the engine, then structural support and aerodynamic fairing are provided, but the mixing of primary and secondary fluid streams is obstructed leading to diminished propulsive efficiency and increased acoustic emissions
Solution Approach 1:
The mixer is segmented into multiple lobes (first lobe, second lobe, third lobe, fourth lobe) that are distributed around the circumference. Each lobe contains internal passages that guide fluid flow independently, allowing the mixing function to be maintained even when certain regions are obstructed by fairings or struts
Solution Approach 2:
Different lobes are positioned at different circumferential locations to account for local obstructions. The first and second lobes are positioned in regions less affected by the fairing, while the third and fourth lobes are positioned in other regions, ensuring that mixing functionality is preserved locally throughout the circumference despite the presence of obstructions in specific areas
2Ease of manufacture
If fairing intrudes axially into the mixer occupying lobe space, then engine mounting structure is supported, but secondary chutes cannot be provided in the vicinity of the fairing compromising mixing uniformity
Solution Approach 1:
The mixer is divided into multiple discrete lobes with internal passages, allowing the mixing function to be distributed around the circumference. This segmentation enables mixing to occur in multiple locations simultaneously, maintaining overall mixing uniformity even when certain lobes or regions are obstructed by fairings
Solution Approach 2:
The mixer utilizes the circumferential dimension by distributing lobes around the entire circumference of the exhaust stream. This circumferential distribution adds a dimensional aspect to mixing, ensuring that mixing occurs uniformly around all directions rather than being limited to a single plane, thereby compensating for axial intrusions by fairings
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 auxiliary lobes and ducts improve fluid mixing uniformity and propulsive efficiency, reducing noise emissions by effectively capturing and conveying secondary fluid past obstructions, thereby enhancing the mixer's performance.
Implementation Method 1
The auxiliary lobes are defined, at least in part, by the discharge ends of the ducts. In operation, the ducts convey secondary fluid to secondary chutes defined by the lobes
Implementation Method 2
the forward ends of the auxiliary fluid capture ducts project into a secondary fluid stream to promote effective air capture and total pressure recovery
Data Source
AI summary
A fluid mixer for mixing two fluid streams 40, 42 includes a set of main lobes 26 defining alternating primary and secondary main chutes 30, 32, one or more auxiliary lobes 28 intermediate two of the main lobes, and an auxiliary fluid capture duct 62. The auxiliary lobes are defined, at least in part, by the discharge end of the duct. In operation, the duct conveys secondary fluid to secondary chutes 36 defined by the lobes thereby improving the performance of the mixer despite the presence of an obstruction 18 that would otherwise impede thorough mixing of two fluid streams.