Turbo-shaft Ejector Flow Guide Ring for Stiffness and Mixing
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Solution Overview
Problem
Gas turbine engine exhaust mixers/ejectors face challenges with thermal variations, radial deflection, and vibrations due to high and low velocity flows, which affect their stiffness and aerodynamic performance, limiting their ability to effectively mix exhaust gases and pump secondary mass flow.
Innovation Solution
An ejector design featuring a primary nozzle with annular walls and circumferentially distributed lobes, combined with a flow guide ring that minimizes diffusion of the primary flow, enhances the engine's stiffness and aerodynamic performance by guiding high-velocity flows and improving secondary flow entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the ejector is exposed to high and low velocity flows, then the mixing function is achieved, but thermal variation and radial deflection occur reducing stiffness
Solution Approach 1:
The ejector is divided into multiple lobes (typically 6-12 lobes) around the circumference, with each lobe handling a portion of the flow. This segmentation allows thermal expansion to occur locally in each lobe rather than causing overall structural distortion, maintaining the stiffness of the entire ejector assembly while enabling the mixing function.
2Ease of manufacture
If the ejector structure is simplified, then manufacturing is easier, but vibration resistance and structural integrity deteriorate
Solution Approach 1:
The ejector features lobes with different local geometries optimized for their specific functions: some lobes have thicker walls for structural support and vibration resistance, while others have optimized flow passages for efficient mixing. This local quality differentiation allows the structure to meet reliability requirements without unnecessary overall complexity.
3Productivity
If the primary flow velocity is increased, then mixing capability improves, but diffusion towards the main axis increases reducing aerodynamic performance
Solution Approach 1:
The lobes act as intermediary structures that guide and contain the high-velocity primary flow, preventing it from diffusing towards the main axis. The lobes redirect the flow laterally to mix with the secondary flow in the annular region, maintaining aerodynamic efficiency while achieving effective mixing through controlled flow interaction.
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 design increases the rigidity of the exhaust case, reduces vibrations and thermal stresses, and enhances aerodynamic performance by effectively mixing high and low velocity flows, thereby improving the engine's efficiency and longevity.
Implementation Method 1
the flow guide ring having an aerodynamic surface configured to minimize diffusion of the primary flow towards the main axis of the engine
Implementation Method 2
the primary nozzle and the secondary nozzle defining a mixing zone downstream of an exit of the primary nozzle where the high velocity primary flow and the secondary flow mix together
Implementation Method 3
the aerodynamic performance of ejectors is often limited by the ability of the primary flow to entrain the secondary cooling flow
Data Source
AI summary
An ejector comprises a primary nozzle having an annular wall forming part of an outer boundary of an exhaust portion of a primary flow path of a gas turbine engine. The annular wall has a downstream end defining a plurality of circumferentially distributed lobes. The ejector further comprises a secondary nozzle having an annular wall disposed about the primary nozzle, the primary nozzle and the secondary nozzle defining a secondary flow passage therebetween for channeling a secondary flow. The secondary nozzle defines a mixing zone downstream of an exit of the primary nozzle. A flow guide ring is mounted to the primary nozzle lobes. The ring has an aerodynamic surface extending from a leading edge to a trailing edge respectively disposed upstream and downstream of the exit of the primary nozzle. The aerodynamic surface of the ring is oriented to guide the high velocity primary flow into the mixing zone.