Indoor Unit Fan Inlet Bars for Quieter Axial-Flow Air Intake
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In indoor air-conditioning units with axial-flow fans, bars provided for casing strength create ventilation resistance, leading to speed loss areas and sudden pressure fluctuations, resulting in noise generation when the fan blades interact with the slipstream behind these bars.
Innovation Solution
The indoor unit design includes axial-flow fans with blades whose leading edges are inclined towards the outer peripheral side, and bars are positioned upstream or downstream of the filters, with their own inclination opposite to the fan's rotation direction, reducing interference with the slipstream and thus noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bars are provided to the air inlet to ensure casing strength, then the strength of the casing is improved, but ventilation resistance increases causing noise generation
Solution Approach 1:
The bars are designed with asymmetric inclination angles relative to the axial direction. Specifically, the inclination angle on the upstream side differs from the inclination angle on the downstream side, creating an asymmetric structure that reduces interference with the slipstream while maintaining structural strength. This asymmetric configuration prevents the formation of speed loss areas that would otherwise cause noise when interacted with by fan blades.
Solution Approach 2:
The patent optimizes specific parameters including the inclination angles of the bars (making them non-zero and asymmetric), the spacing between bars, and the dimensions of the speed loss areas. By carefully controlling these parameters, the design minimizes the interference between bars and slipstream, thereby reducing noise generation while preserving the necessary structural strength of the casing.
2Strength
If bars are provided at the air inlet, then structural support is improved, but speed loss areas are generated in the slipstream
Solution Approach 1:
The asymmetric inclination of bars reduces the formation and extent of speed loss areas in the slipstream. By positioning bars at different inclination angles on upstream and downstream sides, the design minimizes flow separation and maintains more uniform air flow through the inlet, thereby preserving productivity while providing structural support.
Solution Approach 2:
Optimization of bar spacing, inclination angles, and dimensional parameters reduces the size and impact of speed loss areas. The patent specifies particular parameter ranges that minimize flow resistance and maintain efficient air flow, ensuring that structural reinforcement does not compromise productivity.
3Stress or pressure
If leading edge portions of fan blades interfere with slipstream behind bars, then pressure fluctuation occurs, but noise is generated
Solution Approach 1:
The asymmetric bar configuration modifies the slipstream pattern behind the bars, reducing the intensity and extent of speed loss areas. This modification decreases the interference between fan blade leading edges and the slipstream, thereby reducing pressure fluctuations and the associated noise generation.
Solution Approach 2:
By optimizing parameters such as bar inclination angles and spacing, the patent minimizes the interaction between fan blades and slipstream. The optimized parameters reduce sudden pressure fluctuations that occur during blade-slipstream interference, thereby suppressing noise while maintaining necessary structural support.
Data Source
AI summary
An indoor unit includes axial-flow fans, which are provided on downstream of an air inlet. Further, a plurality of first bars are provided to the air inlet. In plan view, leading edge portions of blades of the axial-flow fan are inclined in a direction of rotation of the axial-flow fan from a rotary shaft side of the axial-flow fan to an outer peripheral side. Further, in plan view, the plurality of the first bars are inclined in a direction opposite to the direction of rotation of the axial-flow fan from the rotary shaft side of the axial-flow fan to the outer peripheral side.