Impeller, fan, and air-conditioning apparatus
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Solution Overview
Problem
The existing impeller design with a concave shape at the blade's outer periphery promotes blade tip vortices, leading to reduced efficiency and insufficient static pressure of air, as the load on the outer periphery is small, resulting in reduced work and pressure.
Innovation Solution
The impeller design features blades with a leading edge that is concave between the radially middle portion and the outer circumferential edge and a trailing edge that is convex in the same area, reducing air leakage and promoting blade tip vortices, thereby increasing the static pressure and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the blade's outer periphery is shaped concave toward the suction side, then blade tip vortices are promoted and fan efficiency is improved, but the load on the outer periphery is reduced and static pressure of air cannot be sufficiently raised
Solution Approach 1:
The invention applies different cross-sectional shapes to different regions of the blade. The part adjoining the leading edge has a concave cross-section to promote blade tip vortices and improve efficiency, while the part adjoining the trailing edge has a convex cross-section to increase load and raise static pressure. This local differentiation allows each region to fulfill its specific functional requirement.
Solution Approach 2:
The blade is segmented into at least two distinct parts along the span direction: a leading edge part with concave cross-section and a trailing edge part with convex cross-section. This segmentation allows independent optimization of each part's geometry to achieve conflicting performance goals simultaneously.
2Stress or pressure
If the blade height is increased to increase the amount of work and static pressure, then more noise is generated
Solution Approach 1:
Instead of changing the blade height parameter, the invention changes the cross-sectional shape parameters of the blade parts. By modifying the concave/convex geometry and inflection point positions, the blade achieves higher static pressure generation without increasing height, thereby avoiding noise generation from larger blade dimensions.
3Loss of energy
If the blade's outer periphery is shaped concave toward the suction side, then the load on the outer periphery is reduced, but the amount of work by the entire blade is reduced
Solution Approach 1:
The invention creates local quality differences in blade loading by applying concave cross-sections to the leading edge part (reducing load locally to improve efficiency) and convex cross-sections to the trailing edge part (increasing load locally to maintain power). This allows the blade to achieve both high efficiency and sufficient power output.
Solution Approach 2:
The blade exhibits asymmetric cross-sectional shapes along its span, with the leading edge part being concave and the trailing edge part being convex. This asymmetry optimizes the aerodynamic performance by creating different flow characteristics in different regions, improving overall efficiency while maintaining work capacity.
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 design enhances the impeller's efficiency and increases the static pressure of air by reducing air leakage and promoting blade tip vortices, allowing for higher performance without increasing blade height, which reduces noise in air-conditioning applications.
Implementation Method 1
generation of blade tip vortices is promoted at part of a suction surface of each blade that is located in the vicinity of the outer periphery of the blade
Data Source
AI summary
An impeller includes a boss provided on a rotation axis and a blade provided on an outer circumferential side of the boss. The blade has a radially middle portion that is located midway between an outer circumferential edge and an inner circumferential edge in a radial direction of the blade from the rotation axis. A span-direction section of part of the blade that adjoins the leading edge is shaped such that part of a suction side of the blade that is located in an area between the radially middle portion and the outer circumferential edge is concave, and a span-direction section of part of the blade that adjoins the trailing edge is shaped such that part of the suction side of the blade that is located in the area between the radially middle portion and the outer circumferential edge is convex.