Axial Compressor Stall Prevention via Movable Casing Slots
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Solution Overview
Problem
Axial-flow compressors face performance deterioration due to stall occurrences, with existing casing treatments either compromising efficiency or having limited effectiveness in preventing stall, especially when the slope of slots varies with rotor rotation.
Innovation Solution
An apparatus with a movable inner casing and drive mechanism that opens or closes slots in the outer casing to control airflow, allowing high-pressure air recirculation without requiring a separate energy source, and is applicable to casings with constant or varying slot slopes, thereby maintaining compressor efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive control with casing treatment is used to prevent stall, then operational stability is improved, but compressor efficiency deteriorates
Solution Approach 1:
The invention makes the casing treatment structure dynamic by allowing the inner casing to move axially relative to the outer casing. This enables the slots to be opened or closed based on operating conditions, transforming a static passive control structure into a dynamic one that can adapt to different flow conditions while maintaining both stability and efficiency.
Solution Approach 2:
The invention changes the operational parameters of the casing treatment by varying the axial position of the inner casing, which controls the opening area of the slots. By adjusting this geometric parameter dynamically, the system can optimize the balance between stall prevention and efficiency maintenance according to real-time operating conditions.
2Ease of manufacture
If fixed slope slots are used in casing treatment, then manufacturing is simplified, but effectiveness in preventing stall deteriorates when rotor rotates
Solution Approach 1:
The invention introduces dynamic adjustment capability to the casing treatment structure. By making the inner casing movable axially, the system can compensate for the fixed slot geometry and maintain effectiveness across different rotor positions and operating conditions, resolving the contradiction between manufacturing simplicity and operational effectiveness.
3Reliability
If active control with high pressure air injection is used, then stall prevention is effective, but device complexity increases
Solution Approach 1:
The invention extracts the essential function of active control (high pressure air injection) and implements it through a simplified passive structure. The movable inner casing with slots achieves similar stall prevention effects through geometric design and flow recirculation, eliminating the need for complex injection systems while maintaining effectiveness.
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
Prevents stall occurrences without compromising compressor efficiency, extends the operating region, and improves overall stability by adaptively managing airflow through the casing treatment, regardless of rotor position or slot orientation.
Implementation Method 1
a way of forming various forms of recesses such as grooves or slots and re-circulating high pressure air at the downstream to upstream through casing treatment
Implementation Method 2
allowing high-pressure air recirculation without requiring a separate energy source
Data Source
AI summary
An apparatus for preventing an axial-flow compressor from stalling by employing a casing treatment includes an outer casing having an inner wall with a slot formed to face a rotor blade, an inner casing moveable so as to open the slot in an unstable operating region and close the slot of the outer casing in a stable operating region, and a drive means for moving the inner casing along the axial direction of the outer casing. Thus, the apparatus can be applied not only to a casing treatment structure where the slope of a slot does not vary with the rotational position of the rotor, but also to a casing with a variously shaped slot such as a radial slot or an axial skewed slot.