Fan Assembly Flow Recirculation Circuit Guide Vanes
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Solution Overview
Problem
The high slope of fan blades in turbofan gas turbine engines leads to compromised airflow downstream, resulting in large circumferential wakes and thick end wall boundary layers, which impair the performance of downstream components like the compressor section due to minimized chord lengths or increased blade thicknesses for weight or structural reasons.
Innovation Solution
A flow recirculation circuit with a recirculation stator comprising stationary guide vanes is introduced, which draws airflow from downstream of the fan stator, changes its angle, and injects it upstream, reducing flow separation and improving momentum near the radially inner ends of the fan stator vanes, thereby enhancing the performance of downstream components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If fan blade chord lengths are minimized to reduce overall weight, then weight is reduced, but flow quality downstream deteriorates with large circumferential wakes and thick boundary layers
Solution Approach 1:
The invention extracts the harmful flow features (circumferential wake and thick boundary layers) from the main airflow path by creating a separate recirculation circuit. This circuit draws out the low-momentum flow from downstream of the fan stator and redirects it upstream, effectively removing the harmful factors from the downstream path without changing the fan blade geometry or weight.
Solution Approach 2:
The recirculation circuit acts as an intermediary system between the fan rotor and downstream components. It mediates the harmful effect of high-slope fan blades by capturing the degraded flow, processing it through guide vanes that change its angle, and re-injecting it upstream to improve the overall flow quality reaching downstream components.
2Strength
If fan blade thicknesses are increased for structural reasons, then structural strength is improved, but flow quality downstream deteriorates with compromised airflow and increased blockage
Solution Approach 1:
The recirculation circuit extracts the thick boundary layers and blocked flow regions from downstream of the fan stator. By drawing these harmful flow features into a separate recirculation path, the system removes the blockage effects from the main airflow path, allowing downstream components to receive improved flow quality despite the increased fan blade thickness.
Solution Approach 2:
The recirculation circuit serves as an intermediary that processes the flow degraded by thick fan blades. It captures the blocked and low-momentum flow, redirects it through guide vanes that alter its angle and improve its momentum, and re-injects it upstream to compensate for the flow degradation caused by the structurally necessary thick blades.
3Weight of moving object
If high slope fan blades are used with minimized chord lengths, then weight is reduced and certain aerodynamic advantages are gained, but downstream component performance is impaired due to compromised flow
Solution Approach 1:
The recirculation circuit implements a feedback mechanism where flow from downstream of the fan stator is continuously drawn and re-injected upstream. This closed-loop system monitors the flow quality downstream and actively corrects it by redirecting processed flow back into the inlet, ensuring that downstream components consistently receive high-quality flow despite the use of lightweight high-slope fan blades.
Solution Approach 2:
The recirculation circuit acts as an intermediary system that bridges the gap between the lightweight high-slope fan blades and the downstream components. It processes the flow degraded by these blades and delivers improved flow quality to downstream components, enabling the system to simultaneously achieve weight reduction and maintain downstream performance.
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 flow recirculation circuit improves the stall range and reduces losses in downstream components by re-injecting high-momentum airflow, increasing pressure near the fan stator vanes and reducing blockage, ultimately enhancing the overall performance of the gas turbine engine.
Implementation Method 1
A flow recirculation circuit having an inlet downstream of radially inner ends of the vanes of the fan stator and an outlet upstream of radially inner ends of the vanes
Implementation Method 2
reducing flow separation and improving momentum near the radially inner ends of the fan stator vanes
Implementation Method 3
changing an angle of the drawn portion of the airflow
Implementation Method 4
increasing pressure near the fan stator vanes and reducing blockage
Data Source
AI summary
There is disclosed a fan assembly including a fan rotor including a hub and fan blades. The fan blades have a leading edge and a trailing edge. A fan stator downstream of the fan rotor relative to a direction of an airflow through the fan assembly. The fan stator includes vanes extending between radially inner ends and radially outer ends. A flow recirculation circuit has an inlet downstream of radially inner ends of the vanes of the fan stator and an outlet upstream of radially inner ends of the vanes. A recirculation stator has a plurality of stationary guide vanes circumferentially distributed around the axis and located in the flow recirculation circuit between the inlet and the outlet A method of operating the fan assembly is also disclosed.