Through-flow fan, and indoor unit for air conditioner
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Solution Overview
Problem
Cross flow fans in air-conditioning units experience non-uniform air velocity distribution at the outlet, leading to increased energy loss and noise levels due to localized high-speed airflow, which is not effectively addressed by existing designs with V-shaped notches or other blade configurations.
Innovation Solution
The cross flow fan incorporates impeller blades divided into long-chord and short-chord sections, where the long-chord section has a longer chord length than the short-chord section, with the long-chord section protruding inward, to disperse airflow widely across the outlet region, reducing localized high-speed flow areas and enhancing air velocity uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cross flow fan blades with uniform chord length are used, then the structure is simple and easy to manufacture, but the air velocity distribution at the outlet is non-uniform, leading to localized high-speed flow areas that increase energy loss and noise
Solution Approach 1:
The blade is segmented into multiple blade sections along the rotational axis direction, where each section has a different chord length. Specifically, at least one blade section has a longer chord length than others, creating a stepped configuration. This segmentation allows different portions of the blade to contribute differently to airflow generation, expanding the high-speed flow region and improving air velocity uniformity at the outlet, thereby reducing energy loss.
Solution Approach 2:
Different blade sections are designed with different chord lengths to create localized variations in blade geometry. The longer chord length sections are positioned to specifically expand the high-speed flow region and improve air velocity distribution in critical areas. This local quality modification addresses the non-uniform air velocity distribution problem without requiring complete redesign of the entire blade structure.
2Device complexity
If conventional cross flow fan blades with uniform chord length are used, then the structure is simple, but the noise level increases due to localized high-speed airflow
Solution Approach 1:
The blade is divided into multiple blade sections with different chord lengths along the rotational axis direction. This segmentation creates a stepped blade configuration where longer chord sections strategically expand the high-speed flow region, promoting more uniform air velocity distribution at the outlet. The resulting reduction in localized high-speed flow areas directly decreases noise generation while maintaining relatively simple manufacturing processes.
3Device complexity
If the air velocity distribution at the outlet is non-uniform, then the fan structure can be simpler, but the maximum air velocity increases leading to higher energy loss
Solution Approach 1:
The blade is segmented into multiple blade sections with different chord lengths, where at least one section has a longer chord than others. This segmentation strategically expands the high-speed flow region and improves air velocity uniformity across the outlet, effectively reducing the maximum air velocity while maintaining the relatively simple stepped blade structure.
Solution Approach 2:
Different blade sections with varying chord lengths are positioned to locally modify airflow characteristics. The longer chord sections specifically target areas needing velocity distribution improvement, reducing peak velocities in localized high-speed flow regions while maintaining overall fan performance.
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 expands the high-speed flow region, reduces maximum air velocity, and decreases energy loss and noise levels by dispersing airflow uniformly across the outlet, thereby improving the efficiency and quiet operation of the air-conditioning unit.
Implementation Method 1
the long-chord section has a longer chord length than the short-chord section, with the long-chord section protruding inward, to disperse airflow widely across the outlet region
Implementation Method 2
The blade of the cross flow fan has a blade pressure surface at the rotational direction side on which pressure is made greater by the rotation of the cross flow fan than that during rest, a blade pressure suction surface in a counter-rotational direction on which pressure is made less by the rotation of the cross flow fan than that during rest
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An impeller element 14 includes a plurality of blades 13 disposed along an outer circumference of a circular support plate 12. Each blade 13 is divided into a plurality of blade sections in a rotational axis direction AX. At least one of the divided blade sections as a long-chord blade section 20 is configured such that a chord 28a as a line segment connecting a blade outer-circumferential edge 20b and a blade inner-circumferential edge 20a of the blade 13 in a cross section perpendicular to a rotational axis 17 of the blade 13 has a greater length than a chord 28b of another one of the blade sections as a short-chord blade section 21. The blade inner-circumferential edge 20a of the at least one long-chord blade section 20 having the longer chord 28a protrudes toward the inner circumferential side, relative to the blade inner-circumferential edge 21 a of the at least other one of the blade sections as the short-chord blade section 21 having the shorter chord 28b.