Axial Compressor Extraction Impeller for Vortex Whistle Reduction
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Solution Overview
Problem
Axial compressors in gas turbine systems experience vortex whistle and flow unsteadiness due to high swirling air flow, which amplifies acoustic modes and causes vibrations, particularly when extracting air for cooling purposes.
Innovation Solution
An extraction impeller with specific vane configurations, including elongated S-shaped first vanes, radially longer second vanes, and shorter third vanes, along with a domed portion, directs air flow to reduce circumferential velocity and enhance axial velocity, minimizing vortex whistle and flow unsteadiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air is extracted radially inwardly through an axial passage, then cooling function is achieved, but vortex whistle and flow unsteadiness increase
Solution Approach 1:
The impeller vanes are segmented into multiple types (first vanes, second vanes, third vanes) with different radial lengths and configurations. This segmentation allows each vane type to perform specific functions in controlling airflow patterns, reducing vortex whistle while maintaining cooling effectiveness.
Solution Approach 2:
Different portions of the impeller have different vane configurations. The first vanes extend to the outer diameter, second vanes extend to intermediate radius, and third vanes extend to inner radius. This local differentiation optimizes airflow control at different radial positions, reducing swirling flow and vortex whistle generation.
2Speed
If circumferential velocity is high in the axial passage, then airflow speed is maintained, but acoustic vibrations and flow unsteadiness increase
Solution Approach 1:
The patent transitions the airflow from primarily circumferential motion to primarily axial motion by using impeller vanes that guide the flow in the axial direction. This dimensional change reduces the swirling component that causes vortex whistle and acoustic vibrations while maintaining effective cooling airflow.
Solution Approach 2:
The impeller vane geometry parameters (radial length, angular orientation, spacing) are optimized to change the flow parameters. By adjusting these geometric parameters, the airflow is transformed from high-swirl circumferential flow to low-swirl axial flow, reducing acoustic vibrations while maintaining cooling 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
The impeller design effectively reduces vortex whistle and flow unsteadiness by converting circumferential velocity to axial velocity, enhancing airflow stability and reducing acoustic vibrations in axial passages.
Implementation Method 1
directs air flow to reduce circumferential velocity and enhance axial velocity
Data Source
AI summary
An extraction impeller for an axial compressor includes first vanes having an elongated S-shape arranged on the surface of an impeller body. The first vanes extend radially from an outer flow inlet edge of the body to a flow outlet hub centered on the surface at the rotation axis. A radially inner end of each of the first vanes connects at the flow outlet hub in a direction perpendicular to a rotation axis. Second vane(s) are arranged between adjacent first vanes, and third vanes are arranged between second vanes and between first vanes and second vanes. Second vanes are radially longer than third vanes. The impeller extracts air from the axial compressor and forms an axial flow with reduced vortex whistle. When used in an axial compressor of a gas turbine system, the impeller reduces flow unsteadiness.