Hub-Swept Impeller Blades for Secondary Flow Reduction
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Solution Overview
Problem
Secondary flow, or three-dimensional vortical flow structures, in centrifugal compressors reduce the energy available for transfer to the working fluid, leading to undesirable effects such as tip leakage flow and premature flow blockage, which negatively impact the performance of downstream components.
Innovation Solution
The impeller design incorporates a cutback section on the splitter blades, with a sweep angle ranging from 5 to 70 degrees, extending in both spanwise and chordwise directions, to minimize secondary flow by redirecting cross flows and reducing interaction with the tip leakage flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional impeller design without hub sweep is used, then manufacturing is simpler, but secondary flow vortices increase energy loss and reduce compressor performance
Solution Approach 1:
The invention applies a cutback section specifically to the hub region of the splitter blades, creating local geometric modification rather than changing the entire blade structure. This localized sweep angle modification (5-70 degrees) targets the specific area where secondary flow originates, reducing energy loss without requiring complex changes throughout the entire blade geometry
Solution Approach 2:
The cutback section introduces a curved or swept leading edge geometry at the hub region, replacing the conventional straight or uniform blade leading edge. This curvature modification redirects the flow more effectively, reducing the formation of three-dimensional vortical structures and secondary flow, thereby decreasing energy loss while maintaining manufacturability
2Reliability
If conventional blade design is used, then manufacturing is easier, but tip leakage flow and flow blockage increase, reducing diffuser performance
Solution Approach 1:
The cutback section is applied locally to the hub region of splitter blades rather than modifying the entire blade structure. This localized geometric change with sweep angles of 5-70 degrees specifically addresses flow control at the critical hub area, reducing tip leakage and flow blockage effects that impact diffuser performance, while keeping the rest of the blade geometry relatively simple for manufacturing
Solution Approach 2:
The cutback section pre-redirects the flow at the leading edge hub region before the flow enters the main blade passage. By modifying the flow direction and reducing secondary flow generation at the source, the design prevents subsequent tip leakage and flow blockage issues, improving diffuser performance while maintaining ease of manufacture through localized geometry modification
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 cutback section reduces secondary flow vortices, enhances energy transfer efficiency, and improves diffuser performance by minimizing flow blockage and mixing losses, resulting in improved engine performance.
Implementation Method 1
a secondary flow that includes three-dimensional vortical flow structures develops in blade passages due to the rotation of the flow and to the non-uniform inlet pressure profiles
Implementation Method 2
When the impeller rotates about its rotational axis, a secondary flow that includes three-dimensional vortical flow structures develops in blade passages due to the rotation of the flow
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An impeller (20) having a hub (22), blades (42, 44, 144, 244) extending from the hub (22) along respective spans (S) from roots (35) to tips (36), the blades (42, 44, 144, 244) extending along respective chords (C) from leading edges (42a, 44a, 144a, 244a) to trailing edges (42b, 44b), the leading edge (42a, 44a, 144a, 244a) of at least one of the blades (42, 44, 144, 244) having a cutback section (150, 250) defining a sweep at the root (35), the cutback section (150, 250) extending in a spanwise direction (D1) from the hub (22) to a location (L1) at least about 5% of the span (S) from the hub (22) of the at least one of the blades (42, 44, 144, 244), and the cutback section (150, 250) extending in a chordwise direction (D2) along at least about 5% of the chord (C) of the at least one of the blades (42, 44, 144, 244).