Centrifugal Blower Labyrinth Sealing Gap Optimization
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Solution Overview
Problem
Centrifugal blower devices experience increased noise due to disturbed airflow in blade passages caused by reverse flow, which is exacerbated by the minimized gap dimension at the outlet portion between the shroud ring and the cover portion, leading to higher reverse flow speeds.
Innovation Solution
The centrifugal blower device incorporates a labyrinth sealing structure with specific radial and axial gaps between the shroud ring and the cover portion, where the minimum gap dimension of the radial gap is smaller than the axial gap, and the lengths of these gaps are arranged to increase the sealing length, thereby reducing the reverse flow and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gap dimension of the outlet portion between the shroud ring and the cover portion is minimized, then the flow amount of reverse flow is reduced, but the speed of reverse flow increases causing disturbance in blade passages and increased noise
Solution Approach 1:
The outlet portion gap is segmented into two distinct regions: a first region with a minimized gap dimension to reduce reverse flow quantity, and a second region with a larger gap dimension to reduce reverse flow speed. This segmentation allows each region to address different aspects of the contradiction independently.
Solution Approach 2:
Different gap dimensions are applied at different locations within the outlet portion. The first region (closer to the shroud ring) has a smaller gap dimension optimized for reducing flow amount, while the second region (closer to the cover portion) has a larger gap dimension optimized for reducing flow speed. This local differentiation resolves the contradiction by optimizing each location for its specific function.
2Object-affected harmful factors
If the gap dimension is increased to reduce reverse flow speed, then noise is reduced, but the flow amount of reverse flow increases
Solution Approach 1:
The outlet portion is divided into two regions with different gap dimensions. The first region maintains a minimized gap to keep reverse flow quantity low, while the second region has an increased gap to reduce reverse flow speed and associated noise. This segmentation allows both requirements to be satisfied simultaneously in different locations.
Solution Approach 2:
The solution transitions from a single uniform gap dimension to a two-dimensional gap structure with varying dimensions across the outlet portion. By introducing dimensional variation in the gap structure, the system can optimize for both flow quantity and flow speed control.
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
This configuration effectively suppresses airflow disturbance in the blade passages and reduces the reverse flow, resulting in lower noise levels by optimizing the gap dimensions and lengths within the labyrinth sealing structure.
Implementation Method 1
pressure loss can be increased when air flows through the space between the shroud ring and the cover portion
Data Source
AI summary
A centrifugal blower device includes a rotating shaft, a turbo fan unit and a casing. A shroud ring of the turbo fan unit and a cover portion of the casing form a gap between them. The gap includes a radial gap formed between the cover portion and the shroud ring in a radial direction and an axial gap formed between the cover portion and the shroud ring in an axial direction. The radial gap is located at a position outside of a shroud-side inner peripheral end in the radial direction. The axial gap is located at a position inside of the radial direction in the radial direction. A minimum gap dimension of the radial gap is smaller than a minimum gap dimension of the axial gap. A shortest distance between the shroud-side inner peripheral end and the cover portion is larger than the minimum gap dimension of the radial gap.