Axial Compressor Stator Vane Asymmetry for Vibration Control
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Solution Overview
Problem
Conventional axial compressors experience harmful vibrations in rotor blades and stator vanes due to cyclic pressure distribution and rotor-stator interaction, leading to durability issues.
Innovation Solution
The axial compressor design features rotor blades extending radially and stator vanes inclined circumferentially, creating a time delay in excitation force application along the length of the vanes, which prevents resonance vibrations by offsetting the radially outer end of each stator vane from the inner end by at least half the pitch, thereby canceling out excitation forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rotor blades and stator vanes extend radially with respect to the axial center line, then the structure is simple and easy to manufacture, but cyclic pressure distribution causes harmful vibrations and reduces durability
Solution Approach 1:
The stator vanes are designed with an asymmetric configuration where the suction surface and pressure surface are positioned at different radial distances from the axis of rotation. Specifically, the suction surface is located at a greater radial distance than the pressure surface, creating an asymmetric geometry that disrupts the cyclic pressure distribution and reduces harmful vibrations while maintaining manufacturing feasibility
2Stability of the object's composition
If rotor blades cyclically overlap with stator blades substantially entirely at certain angular positions, then the pressure distribution is uniform along the radial direction, but this arrangement generates strong excitation forces that cause vibrations
Solution Approach 1:
The asymmetric vane configuration causes the overlap region between rotor blades and stator vanes to be distributed unevenly along the radial direction. This asymmetric overlap distribution spreads out the excitation force application in time and space, preventing concentrated excitation forces while maintaining relatively uniform pressure distribution across the blade spans
3Device complexity
If stator vanes extend radially, then the flow path is simple, but wake generation downstream and potential flow upstream cause significant circumferential pressure fluctuation
Solution Approach 1:
The asymmetric positioning of suction and pressure surfaces creates an optimized flow path that reduces wake generation and potential flow effects. The suction surface at greater radial distance allows for smoother flow attachment and reduced separation, while the pressure surface configuration minimizes circumferential pressure fluctuations, achieving better flow characteristics without significantly complicating the overall flow path geometry
Data Source
AI summary
In an axial compressor including a row of rotor blades (70) provided on a rotational shaft (20) around a central axial line of the rotational shaft at a prescribed pitch, and a row of stator vanes (40) provided on a casing around the central axial line at a prescribed pitch so as to adjoin the row of rotor blades on an upstream or downstream side thereof, the rotor blades each extend along a radial line (R) emanating from the central axial line, and the stator vanes each extend along a slanted line (I) that is slanted with respect to a corresponding radial line in a circumferential direction.