Impeller Blade Concave-Convex Shaping to Reduce Tip Vortex Noise

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Solution Overview

Problem

Existing impellers face challenges in achieving both high efficiency and low noise due to air leakage from the outboard edge part of the blade, which prevents an increase in static pressure and turbulence from blade tip vortices.

Innovation Solution

The impeller design features a blade shape with a specific concave-convex-concave sequence in span-wise cross-section, promoting blade tip vortex generation while reducing turbulence and air leakage, and is surrounded by a bellmouth to enhance airflow directionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If more airflow is directed toward the outboard part of the blade, then work output and efficiency are improved, but strong vortices are generated causing noise

Engineering Contradiction:

Improvework outputVSAvoidnoise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The blade cross-sectional shape is specifically designed with different curvature characteristics at different radial positions. The outboard part has a convex shape on the suction side while the inboard part has a concave shape, creating localized flow control that directs airflow to the outboard region without generating strong vortices.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The blade employs curved surfaces with specific convex and concave portions to control airflow patterns. The convex shape at the outboard part and concave shape at the inboard part create smooth flow transitions that enhance work output while minimizing vortex generation and associated noise.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Productivity

If the blade has a convex shape at the outboard part to direct airflow outward, then work output increases, but air leakage occurs reducing static pressure

Engineering Contradiction:

Improvework outputVSAvoidair leakage

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

Different cross-sectional shapes are applied at different radial positions: the outboard part uses a convex shape to direct airflow outward for work production, while the inboard part uses a concave shape to prevent air leakage and maintain static pressure, optimizing both work output and pressure retention.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The blade is divided into functional zones along its span, with the outboard region optimized for work production through convex shaping and the inboard region optimized for pressure retention through concave shaping, allowing each segment to perform its specific function effectively.

Inventive Principle:

Principle #1Segmentation

3Productivity

If the blade tip vortex is strengthened to increase work output, then efficiency improves, but turbulence increases causing noise

Engineering Contradiction:

ImproveefficiencyVSAvoidnoise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The blade employs carefully designed convex and concave curved surfaces that promote controlled vortex formation for work production while maintaining smooth flow transitions that prevent turbulent collapse, thereby generating useful vortices without the associated noise.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 design increases work output at the outboard part of the blade, reduces noise by minimizing strong vortices, and improves efficiency by minimizing air leakage and turbulence.

Implementation Method 1

promoting blade tip vortex generation while reducing turbulence and air leakage

Methodology Applied

Scientific EffectVortex generation: Vortex Ring

Implementation Method 2

reducing turbulence and air leakage

Methodology Applied

Scientific EffectTurbulence reduction: Turbulence

Implementation Method 3

surrounded by a bellmouth to enhance airflow directionality

Methodology Applied

Scientific EffectFlow direction control:

Data Source

PatentUS12510095B2Impeller, fan, and air-conditioning apparatus

Publication Date: 2025.12.30 MITSUBISHI ELECTRIC CORP

AI summary

An impeller includes a blade including, at its leading edge part, a first leading-edge-side concavity, a leading-edge-side convexity, and a second leading-edge-side concavity, which are positioned in sequence from a radially middle part to an outboard edge part. The first leading-edge-side concavity is a part where the suction side of the impeller is concave. The leading-edge-side convexity is a part where the suction side is convex. The second leading-edge-side concavity is a part where the suction side is concave. At the leading edge part of the blade, the blade has a blade height defined in a direction along the rotational axis of the impeller toward the suction side. The blade height decreases monotonically from the radially middle part toward a first leading-edge-side stationary point, and increases monotonically from the first leading-edge-side stationary point toward a second leading-edge-side inflection point.