Fan Case Slot Depth Adjustment for Gas Turbine Stall Margin
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Solution Overview
Problem
Gas turbine engines experience high pressure and swirl distortions, leading to engine stall and undesirable aeromechanical behavior, making it challenging to maintain performance across various flight conditions while minimizing stall margin.
Innovation Solution
A fan case assembly with an inlet distortion mitigation system, featuring a movable band and control unit that adjusts the depth of slots between vanes in response to preselected operating conditions, including aircraft maneuvers and sensor measurements, to minimize the negative effects of pressure and swirl distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the fan operates under high pressure and swirl distortions, then the engine can maintain power output, but engine stall and undesirable aeromechanical behavior occur
Solution Approach 1:
The patent applies a movable band that can dynamically adjust the slot depth in the fan case assembly. The band is positioned to cooperate with vanes and define slots, where the slot depth can be changed by moving the band axially. This dynamic adjustment allows the system to adapt to different operating conditions, maintaining stall margin while preserving power output capability.
Solution Approach 2:
The invention changes the geometric parameter of slot depth to control airflow characteristics. By varying the slot depth (a physical dimension), the system modifies the interaction between distorted airflow and fan blades, thereby improving stall margin without sacrificing power output. This parameter change is achieved through axial movement of the movable band.
2Reliability
If the slot depth is increased to improve stall margin, then pressure and swirl distortions are mitigated, but the device complexity increases
Solution Approach 1:
Rather than providing multiple fixed slot depth configurations, the patent uses a single movable band that can dynamically adjust slot depth. This dynamic approach replaces what would otherwise require multiple static components or complex adjustment mechanisms, thereby improving stall margin while limiting the increase in device complexity.
Solution Approach 2:
The movable band serves multiple functions: it defines the slots, adjusts slot depth, and cooperates with the vanes to control airflow. This multi-functionality reduces the need for separate components for each function, thereby achieving improved stall margin without proportionally increasing device complexity.
3Ease of manufacture
If a fixed slot depth is used in the fan case assembly, then the manufacturing is simpler, but the engine cannot adapt to different flight conditions
Solution Approach 1:
The patent replaces fixed slot depth with a movable band that enables dynamic adjustment. The band can be actuated to change slot depth in response to different flight conditions, providing adaptability while maintaining a relatively simple manufacturing process compared to providing multiple fixed-depth slot configurations.
Solution Approach 2:
The fan case assembly is segmented into movable and stationary components. The movable band is separated from the fixed fan case structure, allowing independent adjustment of slot depth without redesigning the entire assembly. This segmentation enables adaptability while keeping individual components manufacturable.
Data Source
AI summary
A fan case assembly adapted for use with a gas turbine engine includes a case at extends circumferentially at least partway about an axis of the gas turbine engine and a plurality of vanes. The case is formed to define a channel that extends circumferentially at least partway about the axis. The plurality of vanes are arranged in the channel and spaced apart circumferentially about the axis.