Compressor Casing Sliding Ring for Stall Margin and Resonance Control
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Solution Overview
Problem
Turbine engine compressors face efficiency degradation and compressor stall due to clearance between blade tips and the casing, with existing non-axisymmetric casing treatments (NACT) potentially causing acoustic resonance and varying efficiency at different operating speeds.
Innovation Solution
A turbine engine compressor casing with a movable sliding ring in the annular cavity, allowing controlled communication between slots and the plenum, adjustable via an actuating device such as a pressurized air injection system, to optimize NACT treatment based on operational needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular cavity (plenum) is added to amplify NACT capability, then stall margin is increased, but acoustic resonance may occur leading to compressor stall
Solution Approach 1:
The patent makes the annular cavity dynamically controllable by introducing a movable partition that can shift between positions. This allows the cavity volume and its acoustic characteristics to be adjusted in real-time according to operating conditions, transforming a static structure into a dynamic one that adapts to prevent resonance while maintaining stall margin benefits.
Solution Approach 2:
The patent changes the physical parameters of the annular cavity by allowing the partition to move, thereby altering the cavity volume, shape, and communication characteristics with the slots. This parameter adjustment enables optimization of both aerodynamic performance (stall margin) and acoustic properties (resonance prevention) under different operating conditions.
2Reliability
If NACT with annular cavity is used at all speeds, then stall margin is improved, but efficiency decreases at speeds where slots alone are sufficient
Solution Approach 1:
The movable partition enables dynamic adjustment of the annular cavity configuration based on compressor operating speed. At low speeds where slots alone suffice, the partition closes off the cavity to maintain high efficiency. At high speeds requiring enhanced stall margin, the partition opens to activate the NACT with plenum, thus optimizing productivity across the full operating range.
Solution Approach 2:
The system employs periodic or conditional activation of the annular cavity based on operating conditions. The partition responds to changing speed requirements by periodically opening or closing the cavity connection, ensuring NACT is activated only when necessary for stall prevention, thereby maintaining optimal efficiency at varying operating points.
3Productivity
If slots are opened into the annular cavity, then aerodynamic blockage is reduced, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The movable partition is designed to operate autonomously based on pressure differentials or aerodynamic forces that naturally arise during compressor operation. The system self-regulates the opening/closing of the cavity connection without requiring complex external control systems, sensors, or actuators, thereby reducing device complexity while maintaining the ability to optimize aerodynamic efficiency.
Solution Approach 2:
The partition movement is driven by pneumatic pressure differentials created during compressor operation. The pressure distribution across the partition naturally causes it to shift positions that optimize flow management, eliminating the need for mechanical actuators or complex control mechanisms while achieving the desired aerodynamic blockage reduction.
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
Enhances compressor operability by delaying stall onset, reduces aerodynamic blockage, and prevents acoustic resonance, while maintaining structural integrity and minimizing mass increase.
Implementation Method 1
the cavity necessarily has its own acoustic modes. If these own modes are excited, phenomena of acoustic resonance may appear leading to compressor stall.
Implementation Method 2
an actuating device to move the sliding ring between the open and closed positions
Data Source
AI summary
A casing of a turbine engine compressor including an inner annular wall and an outer annular wall delimiting therebetween an annular cavity. The inner annular wall includes a plurality of slots hollowed out in the thickness of the wall, the slots being arranged next to one another in a circumferential direction and each extending in an axial direction. The casing further includes a sliding ring present in the annular cavity of the casing. The sliding ring is movable in the axial direction between an open position in which the slots in the inner annular wall of the casing open into the annular cavity and a closed position in which the sliding ring covers at least some slots.