Centrifugal Blower Blade Leading Edge Segmentation for Airflow Separation

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Solution Overview

Problem

Centrifugal blowers with stepped portions throughout the leading edge of blades experience decreased airflow efficiency and increased noise due to airflow separation from the negative pressure surface near the shroud ring, requiring higher rotation speeds which further increase noise.

Innovation Solution

Forming stepped portions only in the first side region of the leading edge of the blades, where the first side region is on the first side in the rotation axis direction compared to the trailing edge, to reduce airflow separation and noise, while maintaining airflow efficiency by aligning the mold-separation direction with the fan axial direction during molding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If stepped portions are formed throughout the entire leading edge of the blades, then airflow separation from the negative pressure surface is reduced, but airflow efficiency decreases and noise increases

Engineering Contradiction:

Improveairflow separationVSAvoidairflow efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The leading edge of the blade is divided into multiple regions: a first region where stepped portions are formed to reduce airflow separation, and a second region where the surface remains smooth to maintain airflow efficiency. This segmentation allows different portions of the leading edge to serve different functions, resolving the contradiction between reducing airflow separation and maintaining airflow efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Stepped portions are applied locally only to the first region of the leading edge where they are most effective at preventing airflow separation, rather than uniformly across the entire leading edge. This localized application maintains airflow efficiency in the second region while still achieving the benefit of reduced airflow separation in the critical first region.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If stepped portions are formed throughout the entire leading edge of the blades, then airflow separation is reduced, but noise increases

Engineering Contradiction:

Improveairflow separationVSAvoidnoise

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The leading edge is segmented into a first region with stepped portions and a second region without stepped portions. This segmentation reduces noise by limiting the stepped portions to only where they are necessary for controlling airflow separation, rather than extending them across the entire leading edge which would generate excessive noise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Stepped portions are applied locally to the first region of the leading edge where airflow separation occurs, while the second region maintains a smooth surface to minimize noise generation. This localized application achieves the dual benefit of reducing airflow separation and controlling noise.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If stepped portions are formed in the second side region of the leading edge, then airflow separation is reduced, but the amount of work performed by each blade increases

Engineering Contradiction:

Improveairflow separationVSAvoidwork performed by blade

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The leading edge is divided into a first region where stepped portions are formed and a second region where they are not. This segmentation ensures that stepped portions are placed only where they effectively reduce airflow separation without unnecessarily increasing the work performed by the blade, optimizing the energy-work balance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Stepped portions are applied locally to the first region of the leading edge where they provide the most benefit for reducing airflow separation with minimal impact on the work performed by the blade. The second region remains smooth to avoid excessive energy consumption.

Inventive Principle:

Principle #3Local quality

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 reduces noise by 1 dB and maintains airflow efficiency by forming stepped portions only where necessary, minimizing the amount of work performed by each blade while effectively reducing airflow separation from the shroud ring side.

Implementation Method 1

airflow separation from the negative pressure surface near the shroud ring

Methodology Applied

Scientific EffectAirflow separation: Flow Separation

Data Source

PatentUS11255334B2Centrifugal blower

Publication Date: 2022.02.22 DENSO CORP

AI summary

A centrifugal blower includes a turbofan. The turbofan includes blades, a shroud ring, and a main panel. Each blade includes a leading edge that is located inward of the shroud ring in a radial direction of the turbofan, and a trailing edge that is located on an outer side in the radial direction of the turbofan. The leading edge includes a second side region located on the second side in the rotation axis direction, and a first side region located on the first side of the second side region in the rotation axis direction. The first side region is located on the first side in the rotation axis direction compared with the trailing edge. Stepped portions are formed only in a part of the leading edge, the stepped portions being formed in the first side region or in the first side region and the second side region.