Plenum Fan Secondary Inlet Cone Vibration Isolation
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Solution Overview
Problem
Plenum fans face challenges in maintaining smooth and quiet operation due to vibration issues between the fan wheel and inlet cone, which can lead to noise emission and disrupted airflow, as existing vibration dampening devices often compromise alignment and airflow efficiency.
Innovation Solution
A plenum fan design featuring two concentric inlet cones, where one cone is fixed to the frame supporting the fan wheel and the other to the enclosure, with a flexible duct allowing relative movement to isolate vibrations and maintain smooth airflow, while a secondary cone covers irregular surfaces of a flexible duct to ensure efficient air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If vibration dampening devices are provided in the plenum fan, then vibration transmission to the enclosure is reduced, but the inlet cone's alignment to the fan wheel is adversely affected and smooth inlet airflow is disrupted
Solution Approach 1:
The inlet cone system is segmented into two separate cones: a primary inlet cone attached to the fan wheel assembly and a secondary inlet cone attached to the enclosure. This segmentation allows each cone to be independently positioned - the primary cone maintains alignment with the fan wheel while the secondary cone provides a vibration-isolated interface with the enclosure, thus resolving the contradiction between vibration reduction and airflow efficiency
Solution Approach 2:
The secondary inlet cone acts as an intermediary element between the primary inlet cone and the enclosure. It provides a smooth, fixed surface that interfaces with the enclosure while allowing the primary cone to move with the fan wheel assembly, thereby mediating between the conflicting requirements of vibration isolation and precise alignment
2Manufacturing precision
If the radial and axial position of the inlet cone is fixed relative to the fan wheel, then alignment is maintained, but the fan wheel and inlet cone vibrate as a unit transmitting noise to the enclosure
Solution Approach 1:
The inlet cone system is divided into two separate cones attached to different components. The primary inlet cone is attached to the fan wheel assembly while the secondary inlet cone is attached to the enclosure. This segmentation breaks the rigid connection that causes unit vibration, allowing each cone to move independently with its attached component while maintaining proper alignment through careful design
3Object-affected harmful factors
If a flexible duct is used to couple the primary inlet cone to the enclosure, then vibration transmission is prevented, but the surface becomes irregular disrupting smooth inlet airflow
Solution Approach 1:
The inlet system is segmented into three functional elements: the flexible duct for vibration isolation, the primary inlet cone attached to the fan wheel assembly, and the secondary inlet cone attached to the enclosure. This segmentation allows each element to perform its specific function - the flexible duct isolates vibration while the two rigid cones provide smooth airflow surfaces
Solution Approach 2:
The secondary inlet cone serves as an intermediary that covers the irregular surface created by the flexible duct. It provides a smooth, fixed surface that interfaces with the enclosure while allowing the flexible duct to perform its vibration isolation function, thus mediating between the conflicting requirements of vibration isolation and smooth airflow
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 isolates vibrations from the enclosure, maintaining smooth inlet airflow and reducing noise, while allowing for efficient operation by accommodating movement and pressure differentials between the cones.
Implementation Method 1
the flexibility of the flexible duct permits relative movement between the primary inlet cone and the enclosure... effectively isolates vibrations from the enclosure
Implementation Method 2
The fan wheel is rotatable to force air sequentially through the inlet opening, through the fan mouth, through the plenum, and out through the outlet
Data Source
AI summary
A plenum fan comprising a fan wheel disposed within a box-like enclosure includes a secondary inlet cone, a primary inlet cone, and a flexible duct. The two inlet cones convey air to the mouth of the fan wheel. A frame supports the fan wheel and the primary inlet cone such that the frame, the fan wheel and the primary inlet cone comprise a fan assembly. If the fan assembly shifts due to fan thrust or vibration, the fan assembly moves as a unit. The flexible duct connects the primary inlet cone to an inlet of the enclosure while isolating the fan assembly's vibration from the enclosure. The secondary inlet cone extends from the inlet of the enclosure, protrudes into or toward the primary inlet cone and provides a smooth airflow path over the abrupt shape of the flexible duct.