Auxiliary Power Unit Exhaust Diffuser Step Design
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Solution Overview
Problem
The collision between bypass and main flows at the turbine outlet in auxiliary power units generates turbulence, leading to reduced exhaust efficiency and energy efficiency due to the lack of radius change in the exhaust diffuser before and after the bypass flow joins the main flow.
Innovation Solution
An auxiliary power unit design featuring a turbine outlet with an exhaust diffuser and a guide portion, where the radius of the exhaust diffuser increases from the inlet to the outlet, forming a step difference to guide the bypass flow and reduce turbulence, thereby minimizing flow loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the radius of the exhaust diffuser is kept constant before and after the bypass flow joins the main flow, then the structure is simple, but turbulence occurs due to collision between flows, reducing exhaust efficiency
Solution Approach 1:
The exhaust diffuser applies local quality by changing the radius only in the specific region where the bypass flow joins the main flow, while keeping other sections unchanged. This localized modification reduces turbulence at the critical junction point without requiring complete restructuring of the entire diffuser, thus balancing energy efficiency improvement with structural simplicity.
Solution Approach 2:
The invention introduces a radial dimension change to the exhaust diffuser structure by varying the radius in the direction perpendicular to the flow direction. This dimensional modification creates a stepped configuration that guides the bypass flow to join the main flow more smoothly, reducing collision-induced turbulence and improving exhaust efficiency.
2Productivity
If the radius of the exhaust diffuser is increased to reduce turbulence, then exhaust efficiency improves, but the device complexity increases
Solution Approach 1:
The exhaust diffuser applies local quality by changing the radius only in the specific region where the bypass flow joins the main flow, while keeping other sections unchanged. This localized modification reduces turbulence at the critical junction point without requiring complete restructuring of the entire diffuser, thus balancing energy efficiency improvement with structural simplicity.
Solution Approach 2:
The exhaust diffuser is segmented into multiple sections with different radii: a first section with a smaller radius before the bypass flow joins, and a second section with a larger radius after the junction. This segmentation allows the diffuser to optimize flow characteristics at the critical junction point while maintaining simplicity in other regions, thereby improving exhaust efficiency without excessive structural complexity.
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
This design reduces turbulence and enhances exhaust and energy efficiency by allowing the bypass and main flows to join more parallel, resulting in improved turbine output and energy efficiency.
Implementation Method 1
the bypass flow and the main flow collide with each other to generate turbulence, which lowers an exhaust efficiency of the turbine
Implementation Method 2
reducing a flow loss generated from collision between a bypass flow and a main flow
Data Source
AI summary
An auxiliary power unit that can reduce a flow loss of gas includes: a compressor, a combustion chamber, a turbine, a turbine outlet, and a bypass duct, wherein the turbine outlet comprises an exhaust diffuser and a guide portion, wherein the bypass duct connects the compressor with the guide portion, wherein the guide portion is a channel for an air or gas and is extended radially from an outer circumferential surface of the exhaust diffuser and communicates with an inside of the exhaust diffuser via an opening, and wherein the exhaust diffuser has a first portion adjacent to a front end of the opening and a second portion adjacent to a rear end of the opening, and a radius of the second portion is larger than a radius of the first portion so that there is formed a step difference between the first portion and the second portion.