Boundary Layer Ejector for Gas Turbine Drag Reduction
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Solution Overview
Problem
Existing aircraft propulsion systems face challenges in producing high thrust while minimizing jet noise, installation drag, and fuel consumption, and ensuring optimal fuel and lubrication temperatures.
Innovation Solution
The integration of a boundary layer ejector system that utilizes boundary layer bleed flow to enhance entrainment and convert boundary layer fluid into a useful source for increasing system efficiency and thermal management, reducing drag and noise by removing the boundary layer through bleed ports and ejector pumping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If boundary layer is removed through bleed ports and ejector pumping, then drag is reduced and thrust is increased, but device complexity increases due to additional ejector system components
Solution Approach 1:
The ejector system is integrated with the engine exhaust flow path, merging the boundary layer removal function with the existing exhaust system. The ejector utilizes the engine's exhaust gases as the primary flow to entrain and remove the boundary layer, combining multiple functions into a unified system that reduces drag while leveraging existing engine components.
Solution Approach 2:
The ejector system employs pneumatic principles by using high-velocity exhaust gases to create a low-pressure region that entrains and removes the boundary layer through suction. This hydraulic/pneumatic approach allows for passive boundary layer control without requiring additional mechanical moving parts, reducing complexity while achieving drag reduction.
2Object-affected harmful factors
If boundary layer is removed through bleed ports and ejector pumping, then installation drag is minimized, but loss of useful flow occurs through the bleed ports
Solution Approach 1:
The system converts the potentially harmful boundary layer, which causes drag, into a beneficial flow by entraining it with the ejector and mixing it with the exhaust stream. The removed boundary layer is not simply discarded but integrated into the exhaust flow, transforming a harmful factor into part of the useful exhaust plume.
Solution Approach 2:
The ejector acts as an intermediary device that captures the boundary layer through bleed ports and transports it to the exhaust stream. This intermediary function allows the boundary layer to be removed from the critical inlet region while being disposed of in a location where it no longer causes drag, mediating between the boundary layer removal need and the exhaust flow system.
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 approach increases thrust, reduces fuel consumption, minimizes jet noise, and decreases installation drag by effectively removing the boundary layer, improving overall engine efficiency and performance.
Implementation Method 1
The integration of a boundary layer ejector system that utilizes boundary layer bleed flow to enhance entrainment and convert boundary layer fluid into a useful source for increasing system efficiency
Implementation Method 2
removing the boundary layer through bleed ports and ejector pumping
Data Source
Figure 1~2
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Figure 4b~4c
AI summary
The present inventions include a boundary layer ejector fluidically connecting boundary layer bleed slots from an external surface of an aircraft to reduce aircraft/nacelle/pylon drag, reduce jet noise and decrease thrust specific fuel consumption. In one embodiment a boundary layer withdrawn through the boundary layer bleed slots is entrained with an exhaust flow of a gas turbine engine. In another embodiment a boundary layer withdrawn through the boundary layer bleed slots is entrained with a flow stream internal to the gas turbine engine, such as a fan stream of a turbofan. Members can be provided near an outlet of a passageway conveying the withdrawn boundary layer air to locally reduce the pressure of the fluid in which the withdrawn boundary layer air is to be entrained. A lobed mixer can be used in some embodiments to effect mixing between the boundary layer and a primary fluid of the ejector.