Propeller Fan Blade Design for Uniform Air Velocity
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Solution Overview
Problem
The existing propeller fans in outdoor units of air conditioners suffer from non-uniform air velocity distribution, leading to surging phenomena, noise, and damage due to the significant difference in air velocity between the outer and inner peripheral portions of the blades, resulting in inefficient air blowing and reduced air volume.
Innovation Solution
A propeller fan design with a hub and blades where the radius ratio between the inner and outer peripheral portions is limited to 0.4 or less, and the air velocity ratio is maintained below 1.3, ensuring a more uniform air velocity distribution and reducing the likelihood of surging, thereby enhancing air volume and operational stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size and rotation speed of the propeller fan are increased to improve air volume, then the air velocity at the outer peripheral portion increases, but the air velocity difference between outer and inner peripheral portions becomes larger, causing surging and noise
Solution Approach 1:
The patent applies local quality by differentiating the blade design into two distinct regions: an outer peripheral portion with optimized chord length and angle of attack for high velocity, and an inner peripheral portion with specifically designed chord length and angle of attack to prevent surging. This localized differentiation allows each region to perform its function optimally without compromising the other, resolving the contradiction between maximizing air volume and preventing surging-induced noise.
Solution Approach 2:
The patent changes critical parameters including the radius ratio (setting it to 0.4 or less), chord length ratios, and angle of attack values for different blade portions. By systematically adjusting these parameters, the design achieves uniform air velocity distribution across the blade span, thereby increasing air volume while suppressing surging phenomena and associated noise.
2Stability of the object's composition
If the radius ratio is reduced to 0.4 or less to uniform air velocity distribution, then the air velocity difference decreases, but the blade design becomes more complex
Solution Approach 1:
The patent segments the blade into distinct functional zones (outer peripheral portion and inner peripheral portion) with clearly defined boundaries at the radius ratio of 0.4. Each segment has optimized geometric parameters, which simplifies the design process by allowing independent optimization of each zone while maintaining overall blade performance and reducing design complexity.
3Productivity
If the air velocity at the inner peripheral portion is increased to reduce surging, then the air volume improves, but the angle of attack and chord length must be precisely controlled
Solution Approach 1:
The patent specifies precise parameter ranges for the inner peripheral portion, including chord length ratios and angle of attack values, which when properly controlled, enable the blade to achieve optimal air velocity distribution. These parameter specifications provide clear manufacturing guidelines that balance the need for precision with achievable production tolerances, ensuring both high air volume and reduced surging.
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 reduces the air velocity difference between the outer and inner peripheral portions, minimizing surging and noise, and increases the air volume while improving the efficiency and stability of the propeller fan operation.
Implementation Method 1
a propeller fan includes a hub having a side surface about a center axis; and a plurality of blades provided on the side surface of the hub
Data Source
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AI summary
A propeller fan includes: a hub having a side surface about a center axis; and a plurality of blades provided on the side surface of the hub. Each blade includes an inner peripheral portion positioned closer to a base portion of the each blade connected to the hub, and an outer peripheral portion positioned closer to an outer edge of the each blade. A ratio r/R between a radius r as a distance from the center axis to a boundary between the inner peripheral portion and the outer peripheral portion and a radius R as a distance from the center axis to the outer edge of each blade is equal to or lower than 0.4. A relational expression of V1 < V2 × 1.3 is satisfied, where an air velocity at the outer peripheral portion is V1 and an air velocity at the inner peripheral portion is V2.