Propeller Fan Blade Branching for Surging Reduction
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Solution Overview
Problem
The distribution of wind speed in a radial direction becomes non-uniform in propeller fans, leading to a surging phenomenon such as suction of air from the downstream side, resulting in abnormal operation states, noise, and potential damage.
Innovation Solution
A propeller fan design featuring a hub with integrally formed blades that branch from the outer peripheral portion to the inner peripheral portion, with specific blade elements and holes forming flow paths to manage airflow and reduce surging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diameter and speed of the propeller fan are increased to improve energy-saving performance, then the air volume increases, but the wind speed distribution in radial direction becomes non-uniform causing surging phenomenon
Solution Approach 1:
The blade is divided into multiple blade elements with different pitch angles along the radial direction. The inner peripheral portion has a smaller pitch angle while the outer peripheral portion has a larger pitch angle, creating local quality variations that optimize wind speed distribution and prevent surging while maintaining high air volume
Solution Approach 2:
The blade is segmented into multiple blade elements (first, second, third, and fourth blade elements) with different configurations. Each blade element has specific pitch angles and dimensions tailored to its radial position, allowing independent optimization of different regions to resolve the contradiction between high air volume and uniform wind speed distribution
2Productivity
If the inner peripheral portion of the blade is used for air blowing, then the air volume increases, but the low wind speed in this region causes airflow disturbance and ineffective blade surface utilization
Solution Approach 1:
The inner peripheral blade elements are designed with smaller pitch angles and optimized dimensions suitable for low wind speed conditions. This local adaptation allows the inner peripheral portion to effectively contribute to air blowing without causing airflow disturbance, thereby improving overall blade surface utilization
Solution Approach 2:
The pitch angle parameter is varied along the radial direction of the blade. Inner peripheral portions have smaller pitch angles while outer peripheral portions have larger pitch angles. This parameter change optimizes the performance of each region according to its wind speed characteristics, enabling stable airflow and effective utilization of the entire blade surface
3Device complexity
If the blade has a simple structure without multiple blade elements, then the device complexity is low, but the wind speed distribution becomes non-uniform causing abnormal operation
Solution Approach 1:
The blade is divided into multiple blade elements with different pitch angles and dimensions. This segmentation creates a more complex structure that enables better wind speed distribution across the radial direction, preventing surging and abnormal operation while maintaining reasonable device complexity
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
The design increases air volume while suppressing the occurrence of surging phenomena, enhancing operational stability and reducing noise and potential damage.
Implementation Method 1
the plurality of blade elements have a trailing edge on a downstream side of rotation with the central axis as a rotation center, and a leading edge on an upstream side of the rotation, are connected to the side surface at a pitch angle with respect to the central axis, and form a hole which is a flow path for airflow, between the adjacent blade elements
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A propeller fan (5) includes a hub (11) and a plurality of blades (12). The blade (12) has a plurality of blade elements (12-11, 12-12, 12-13) branching on a way from an outer peripheral portion (12b) to an inner peripheral portion (12a). The plurality of blade elements (12-11, 12-12, 12-13) form a hole (12-21) which is a flow path for airflow, between the adjacent blade elements, have a first blade element (12-11) on an upstream side of rotation and a second blade element (12-12) on a downstream side of the rotation to be adjacent to the first blade element (12-11) which branch at a branch point (12p), and include an extension portion (12-11B) as a part of the first blade element (12-11), on a trailing edge (12-11-1) of the first blade element (12-11) from the branch point (12p) to a side surface (11a) of the hub (11). At least a part of a leading edge (12-12-2) of the second blade element (12-12) overlaps with a rotation orbit of the extension portion (12-11B) with a central axis (O) as a rotation center.