Propeller Fan Blade Outlet Angle Design for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional propeller fans do not adequately reduce noise due to the occurrence of wing tip vortices, which are caused by airflow leakage and result in increased noise levels.
Innovation Solution
The propeller fan design features a hub and blades with specific outlet angles at the trailing edge, where one peak outlet angle is located radially outer and another radially inner than the representative square mean radius position, along with concave curve surfaces on the pressure surfaces, guiding airflow to prevent leakage and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a bent portion is provided in the outer peripheral portion of a blade to stabilize wing tip vortex, then noise reduction is attempted, but sufficient noise reduction effect is not obtained
Solution Approach 1:
The invention applies different outlet angle characteristics to different radial regions of the blade. The outer region (radially outer than representative square mean radius position) has a peak outlet angle, while the inner region (radially inner than representative square mean radius position) has another peak outlet angle. This local differentiation of blade geometry allows optimized airflow control in each region, effectively reducing wing tip vortices and noise without requiring complex additional structures.
Solution Approach 2:
The invention changes the outlet angle parameter distribution along the radial direction of the blade. By positioning peak outlet angles at specific radial locations (one in the outer region and one in the inner region), the airflow characteristics are modified to prevent leakage flow and reduce vortex formation. This parameter optimization achieves noise reduction while maintaining simple blade structure.
2Productivity
If multiple bent surface-shaped recesses are formed on the positive pressure surface at trailing edge of each blade, then air blowing performance is improved, but sufficient noise reduction effect is not obtained
Solution Approach 1:
The invention differentiates the blade structure into outer region and inner region with distinct outlet angle characteristics. The outer region peak outlet angle optimizes air blowing performance, while the inner region peak outlet angle specifically addresses noise reduction by controlling airflow near the hub. This local quality differentiation achieves both high air blowing performance and effective noise reduction simultaneously.
Solution Approach 2:
The blade is functionally segmented into outer region (radially outer than representative square mean radius position) and inner region (radially inner than representative square mean radius position). Each segment has its own peak outlet angle optimization, allowing independent control of air blowing performance and noise characteristics. This segmentation enables simultaneous achievement of both performance goals.
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 effectively reduces noise while maintaining air blowing performance by preventing airflow from reaching the outer peripheral portion, thus minimizing wing tip vortices and leakage, resulting in a lighter and more efficient fan.
Implementation Method 1
Rotation of the propeller fan generates airflow (leakage flow) in the vicinity of an outer peripheral portion of a blade, the airflow passing from a pressure surface side of the blade where pressure is high to a suction surface side of the blade where pressure is low
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A propeller fan (4) includes a blade (12). The blade (12) has a shape in which a peak outlet angle (θ) at a trailing edge (15) thereof exists in an outer region (12B) of the blade that is located radially outer than the representative square mean radius position (Rr), and an another peak outlet angle (θ) at a trailing edge (15) thereof exists in an inner region (12A) of the blade that is located radially inner than the representative square mean radius position (Rr).