Centrifugal Blower Scroll Chamber Noise Reduction
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Solution Overview
Problem
Conventional centrifugal blowers for automobile air-conditioning systems face challenges in reducing noise levels due to backflow and eddy formation, which affect efficiency and noise levels, despite previous attempts to mitigate these issues.
Innovation Solution
The design incorporates a multi-blade fan with a spiral-shaped scroll chamber featuring a gradually expanding bottom part and a backflow prevention rib, optimizing the fan outlet angle, chamber expansion angles, and rib placement to guide airflow and prevent backflow between blades, thereby reducing noise and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a step structure is used to sharply expand the scroll chamber passage, then the noise reduction effect is limited, but the structure becomes simpler
Solution Approach 1:
The scroll chamber bottom is divided into multiple sections with different expansion characteristics. The first section has a first expansion angle and the second section has a second expansion angle, allowing each section to be optimized independently for noise reduction while maintaining manufacturing feasibility
Solution Approach 2:
Different sections of the scroll chamber bottom are given different expansion angles tailored to their specific functional requirements. The first section uses a first expansion angle optimized for one aspect of flow control, while the second section uses a second expansion angle optimized for another aspect, achieving localized optimization for noise reduction
2Object-generated harmful factors
If a plate is provided to prevent backflow near the nose portion, then backflow is suppressed, but suction resistance increases and flow rate decreases
Solution Approach 1:
The expansion angles of the scroll chamber bottom are optimized to specific ranges (first expansion angle and second expansion angle within defined ranges) to control backflow through geometric parameters rather than physical barriers, maintaining flow rate while reducing backflow
Solution Approach 2:
The plate structure used in conventional designs to prevent backflow is completely removed. Instead, the scroll chamber bottom geometry itself is designed with specific expansion angles to prevent backflow, eliminating the need for additional components that would obstruct flow
3Device complexity
If the scroll chamber is sharply expanded, then the structure is simpler, but eddy formation increases and noise increases
Solution Approach 1:
The scroll chamber expansion is segmented into multiple sections with different expansion angles. The first section expands at a first angle and the second section expands at a second angle, preventing sudden sharp expansions that would cause eddy formation while avoiding overly complex single-stage designs
Solution Approach 2:
The scroll chamber bottom uses curved surfaces with specific expansion angles rather than sharp angular transitions. The continuous curved geometry with controlled expansion angles smooths airflow, preventing eddy formation and noise while maintaining structural simplicity
Data Source
AI summary
A centrifugal blower provided with a spiral shaped scroll chamber where a bottom part of the scroll chamber gradually expands downward in the axial direction of the fan well along with expansion of the spiral and where a flow area gradually expands toward an air outlet from a spiral start part of the casing, the centrifugal blower having an initial slant angle θ0 at the spiral start part of the bottom part of the scroll chamber of a range of angle of 5.2° to 27.5° or setting a backflow prevention rib at the fan outlet.