Circumferential Fan Casing Treatments for Fan Noise and Stall Margin
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Solution Overview
Problem
Gas turbine engines experience noise issues due to fan-outlet-guide-vane interaction, fan self-noise, and fan inlet distortion, which affect efficiency and operability, particularly under conditions of crosswinds and high angle-of-attack.
Innovation Solution
Implementing circumferentially varying fan casing treatments with tailored design parameters, such as slots and grooves, to reduce noise by aligning low noise wakes with outlet guide vane leading edges and attenuating noise with acoustic liners, addressing both mean and distorted inflow responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan operates under high angle-of-attack or crosswind conditions, then thrust production is maintained, but fan noise increases due to inlet distortion and wake-guide vane interaction
Solution Approach 1:
The patent applies local quality by implementing circumferentially varying casing treatments with different slot depths at different angular positions around the fan inlet. The slot depth is optimized at specific locations where wake-guide vane interaction occurs, while other areas maintain different treatment characteristics. This localized optimization reduces noise at critical positions without compromising overall thrust production capability.
Solution Approach 2:
The patent changes the geometric parameters of the casing treatment, specifically the slot depth, to optimize noise reduction. By varying the slot depth parameter circumferentially and adjusting it based on operating conditions (such as angle-of-attack and crosswind effects), the system maintains thrust while reducing fan noise generated under distorted inflow conditions.
2Object-generated harmful factors
If circumferentially varying casing treatments are implemented, then fan noise is reduced, but device complexity increases
Solution Approach 1:
The patent segments the fan casing treatment into multiple discrete slots arranged circumferentially around the inlet. Each slot can be independently designed with specific depth and spacing parameters. This segmentation allows the complex noise reduction function to be achieved through multiple simple, manufacturable features rather than a single complex structure.
Solution Approach 2:
The patent employs asymmetric slot depth distribution around the circumferential direction, with different slot depths at different angular positions. This asymmetric configuration is optimized to address the specific noise generation mechanisms at particular locations, providing effective noise reduction while maintaining manufacturing feasibility through standardized slot geometries.
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
Reduces fan noise and extends stall limits, improving engine efficiency and operability by mitigating aeromechanics risks and noise propagation.
Implementation Method 1
attenuating noise with acoustic liners
Implementation Method 2
circumferentially varying fan casing treatments with tailored design parameters, such as slots and grooves, to reduce noise by aligning low noise wakes with outlet guide vane leading edges
Data Source
AI summary
A rotary component for a gas turbine engine includes a plurality of rotor blades operably coupled to a rotating shaft extending along the central axis and an outer casing arranged exterior to the plurality of rotor blades in a radial direction of the gas turbine engine. The outer casing defines a gap between a blade tip of each of the plurality of rotor blades and the outer casing. The outer casing includes a plurality of features formed into an interior surface thereof. Each of the plurality of features includes one or more design parameters that are perturbed about a mean design parameter for stall performance so as to provide a circumferential variation in wake strengths associated with the plurality of rotor blades, thereby reducing operational noise of the gas turbine engine.