Turbine Exhaust Case Mixer Strut Axial Positioning
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Solution Overview
Problem
Conventional turbofan engine configurations with deswirling struts and mixers suffer from inefficiencies in mixing exhaust gases and bypass airstreams, leading to suboptimal performance and pressure losses.
Innovation Solution
An improved turbine exhaust case with an annular mixer featuring axially extending lobes and circumferentially spaced deswirling struts, where the struts are positioned upstream of the mixer lobes' trailing edge root to deswirl and mix gases within a shorter axial length, optimizing the mixing action and reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deswirling struts are positioned upstream of the mixer lobes' trailing edge root, then mixing efficiency is enhanced and axial length is reduced, but the complexity of strut positioning and alignment increases
Solution Approach 1:
The deswirling struts are integrated with the mixer assembly, merging the deswirling function into the existing mixer structure. This integration allows the struts to be positioned upstream of the trailing edge root while maintaining compact overall dimensions and avoiding the need for separate deswirling components, thus improving mixing efficiency without proportionally increasing device complexity
Solution Approach 2:
The deswirling struts perform the deswirling action preliminarily, before the flow enters the main mixing section of the lobes. By positioning the struts upstream of the trailing edge root, the exhaust flow is deswirling in advance, which prepares the flow for more efficient mixing in the subsequent lobe structure, thereby enhancing overall mixing efficiency while allowing for compact axial arrangement
2Weight of moving object
If the axial length of the mixer is reduced, then weight is minimized and engine compactness is improved, but the mixing performance may be compromised
Solution Approach 1:
The mixer lobes are designed with specific geometric parameters including the positioning of the trailing edge root and the arrangement of deswirling struts. By optimizing these parameters, the design achieves effective mixing within a reduced axial length, thereby minimizing weight while maintaining or improving mixing performance through enhanced flow control and mixing efficiency
Solution Approach 2:
The mixer employs localized features such as the trailing edge root positioning and deswirling strut placement at specific locations within the axial length. These local structural qualities are optimized to maximize mixing efficiency in the available space, allowing reduced overall axial length and weight while maintaining effective mixing performance through concentrated flow manipulation at critical locations
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 configuration enhances mixing efficiency and performance, achieving equivalent or better results than conventional setups while minimizing weight and pressure losses, thus improving thrust and engine efficiency.
Implementation Method 1
A swirling flow of exhaust gases from the turbine exit is conventionally deswirled by a plurality of deswirling struts located within the TEC
Implementation Method 2
Hot gases exhausted from the engine core and the bypass airstream are mixed together before expulsion through a single nozzle
Data Source
AI summary
A turbine exhaust case (TEC) of a turbofan aeroengine includes a mixer for mixing exhaust gases with a bypass air stream, the TEC comprising an annular hub and the mixer surrounding the hub, and a plurality of deswirling struts circumferentially spaced apart with respect to a central axis of the TEC and located entirely within an axial length of the mixer. The mixer defines a trailing edge having one or more upstream-most locations thereof where the mixing of the exhausted gases and the bypass air stream begins to take place. The deswirling struts each extend radially across the annular exhaust gas duct and interconnect the mixer and the hub, defining a trailing edge positioned upstream of and axially spaced away from the one or more upstream-most locations of the trailing edge of the mixer.