Bidirectional Axial Fan With Multi-Stage Casing For Reverse Flow
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Solution Overview
Problem
Bidirectional axial fan devices face challenges in maintaining satisfactory ventilation properties during reverse rotation, leading to increased air-blowing sound and reduced static pressure, due to airflow disturbances caused by spokes during normal rotation.
Innovation Solution
The bidirectional axial fan device features a motor rotatable in both directions, a moving blade member with vanes, and a casing with a multiple stage inner peripheral surface shape, where the exhaust air side has a larger diameter than the air intake side during normal rotation, expanding intervals between vanes and the frame, and incorporating an intermediate tapered portion to reduce pressure variations and airflow disturbances during reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan device uses spokes to support the motor during normal rotation, then the motor is stably supported, but airflow disturbances occur during reverse rotation causing increased air-blowing sound and reduced static pressure
Solution Approach 1:
The frame's inner peripheral surface is segmented into multiple sections with different diameters: a large diameter portion at the exhaust air side, a small diameter portion at the air intake side, and an intermediate tapered portion connecting them. This segmentation allows the frame to provide stable support during normal rotation while reducing airflow disturbances during reverse rotation.
Solution Approach 2:
The frame is designed with an asymmetric cross-sectional shape where the inner peripheral surface has different diameters at different axial positions. The large diameter portion and small diameter portion create an asymmetric structure that optimizes airflow characteristics for bidirectional operation, reducing the harmful effects of spoke interference during reverse rotation.
2Device complexity
If the frame has a uniform diameter, then the structure is simple, but airflow disturbances occur during reverse rotation reducing ventilation properties
Solution Approach 1:
Different sections of the frame's inner peripheral surface are given different local qualities in terms of diameter. The large diameter portion at the exhaust air side and the small diameter portion at the air intake side create localized variations that optimize airflow patterns during reverse rotation, improving ventilation performance without requiring complete structural redesign.
Solution Approach 2:
The frame's multiple stage shape creates dynamic airflow characteristics that adapt to different rotation directions. During reverse rotation, the intermediate tapered portion and diameter variations dynamically guide airflow to minimize disturbances, enhancing ventilation performance while maintaining structural simplicity.
3Volume of moving object
If the interval between vanes and frame is small, then the device size is compact, but static pressure decreases during reverse rotation
Solution Approach 1:
The frame's inner peripheral surface utilizes the axial dimension to create diameter variations, transitioning from a two-dimensional cross-sectional view to a three-dimensional multiple stage structure. This dimensional approach allows the device to maintain compact radial dimensions while improving axial airflow characteristics during reverse rotation to maintain static pressure.
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 improves static pressure characteristics during reverse rotation to match those during normal rotation, while reducing air-blowing sound and maintaining high ventilation properties in both directions.
Implementation Method 1
the intermediate tapered portion is positioned outside the tops on the exhaust air side during the normal rotation at the outer peripheral edges of the plurality of vanes. The inner peripheral surface of the intermediate tapered portion is linearly inclined such that the radius decreases from the large diameter portion (44) side to the small diameter portion side
Data Source
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AI summary
A bidirectional axial fan device includes: a moving blade member with a plurality of vanes; and a casing that includes a mounting portion, a frame, and a plurality of spokes, a motor being mounted to the mounting portion, the frame forming a ventilation hole. The plurality of spokes couple the mounting portion to the frame at an exhaust air side during a normal rotation of the motor. An inner peripheral surface of the frame has a multiple stage shape, in which a part on the exhaust air side during the normal rotation has a diameter larger than a diameter of a part on an air intake side during the normal rotation, such that intervals between tops on the exhaust air side during the normal rotation at outer peripheral edges of the plurality of vanes and the inner peripheral surface of the frame are expanded.