Lobed Exhaust Mixer Protrusions for Gas Turbine Mixing
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Solution Overview
Problem
Current exhaust mixer configurations in turbofan engines do not adequately enhance the mixing of high and low velocity fluid flows, limiting engine performance and thrust generation.
Innovation Solution
A lobed exhaust mixer assembly with a lobed annular wall and axially extending protrusions at the trailing edge, promoting three-dimensional instability modes and vortex formation to improve mixing efficiency by increasing the contact area and shear layer deformation between core and bypass gas flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional exhaust mixer configurations are used, then the structure is simple, but the mixing efficiency of high and low velocity fluid flows is insufficient
Solution Approach 1:
The patent introduces axially extending protrusions at the trailing edge of the lobed annular wall, adding a third dimension (axial direction) to the traditional lobed structure. This dimensional enhancement creates additional flow interaction surfaces and promotes three-dimensional instability modes, significantly improving mixing efficiency without fundamentally redesigning the entire mixer architecture
Solution Approach 2:
The trailing edge is segmented into multiple discrete protrusions distributed circumferentially around the mixer. This segmentation allows each protrusion to independently generate vortices and promote local mixing, while the collective arrangement provides comprehensive flow enhancement throughout the exhaust stream
2Productivity
If lobed-shaped exhaust mixers are used to increase contact area and create vortices, then mixing performance improves, but the trailing edge geometry becomes more complex
Solution Approach 1:
The protrusions extend in the axial direction from the lobed annular wall, transforming the traditional two-dimensional lobed trailing edge into a three-dimensional structure. This adds axial depth to the flow interaction surfaces, enhancing vortex generation and mixing performance while maintaining the beneficial lobed configuration
3Shape
If the protrusions are closely spaced, then the trailing edge appears continuous, but manufacturing precision requirements increase
Solution Approach 1:
The protrusions are spaced at intervals rather than being continuously distributed, providing sufficient flow interaction and mixing enhancement without requiring continuous precision manufacturing. The discrete arrangement maintains adequate spacing to simplify fabrication while still achieving the desired flow control effects
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 solution effectively enhances the mixing of core and bypass gas flows, leading to improved engine performance, thrust generation, and reduced specific fuel consumption by accelerating vortex growth and stability downstream of the mixer.
Implementation Method 1
promoting three-dimensional instability modes and vortex formation to improve mixing efficiency
Implementation Method 2
increasing the contact area and shear layer deformation between core and bypass gas flows
Data Source
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AI summary
An exhaust mixer assembly for a gas turbine engine (10) includes a core passage (26) directing a core flow. An outer annular passage (24) directing a bypass flow surrounds the core passage (26). A lobed exhaust mixer (32) communicating with the passages has upstream and downstream ends (36, 38) and a lobed annular wall (34) therebetween. The annular wall (34) defines alternating inner and outer radial lobes (42, 44) having exits defining a mixing plane for the core and bypass flows. The outer lobes (44) protrude into the outer passage (24) and the inner lobes (42) protrude into the core passage (26). The inner lobes (42) include troughs (46) and the outer lobes (44) include crests (48). Adjacent inner and outer lobes (42, 44) have radial walls (50) interconnecting adjacent troughs (46) and crests (48). Protrusions (52) extend axially from a downstream end (38) of the annular wall (34) to form a mixer jagged trailing edge (54). Each protrusion (52) is spaced apart from one another and protrudes independently from one along the annular wall (34).