Open Fan Boundary Layer Suction for Inlet Distortion
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Solution Overview
Problem
Turbofan engines with unducted fans face challenges in achieving efficiency across a wide range of operations while maintaining acceptable stall margin due to boundary layer induced distortion, which affects the uniformity of airflow entering the engine inlet.
Innovation Solution
An airflow diverting assembly is implemented downstream of the fan section and upstream of the engine inlet, utilizing passive or active flow suction to divert the boundary layer away from the hub, reducing distortion and improving airflow uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an unducted fan is used to reduce weight and increase efficiency, then engine efficiency is improved, but boundary layer induced distortion increases
Solution Approach 1:
The patent extracts and removes the boundary layer flow from the hub surface using suction ports, preventing it from causing distortion downstream. This directly addresses the harmful effect while preserving the unducted fan configuration for efficiency.
Solution Approach 2:
The patent introduces an intermediary device (boundary layer control system with suction ports and dividers) between the hub surface and the downstream flow path to intercept and manage the boundary layer before it causes distortion.
2Productivity
If fan speed is increased to improve thrust, then productivity is improved, but noise levels increase
Solution Approach 1:
The patent changes the flow parameters by removing the boundary layer, which allows for optimized fan operation at lower speeds while maintaining thrust, thereby reducing noise levels.
3Adaptability or versatility
If operating at high angles of attack is required for versatility, then adaptability is improved, but stall margin decreases
Solution Approach 1:
The patent applies preliminary action by removing the boundary layer before it can cause adverse effects at high angles of attack, thereby maintaining stall margin even when operating in high-angle regimes for improved adaptability.
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 solution enhances engine efficiency by minimizing boundary layer induced distortion, reducing fan speeds, lowering noise levels, and improving stall margin, while allowing for design flexibility and operation at high angles of attack.
Implementation Method 1
utilizing passive or active flow suction to divert the boundary layer away from the hub
Data Source
AI summary
An engine includes a fan section having an open fan defining an axial centerline and a rotor. The rotor includes a plurality of fan blades mounted to a hub and being rotatable about the axial centerline. The engine also includes a turbomachine downstream of the fan section. The turbomachine includes a core cowl that defines an engine inlet and encloses turbomachinery. Further, the engine includes an airflow diverting assembly downstream of the fan section and upstream of the engine inlet. The airflow diverting assembly includes at least one fluid passageway formed into at least a portion of the hub for diverting at least a portion of a boundary layer on a surface of the hub away from the surface of the hub to reduce distortion caused by the boundary layer in the turbomachinery.