Plenum Fan Labyrinth Seal and Conical Wheel Design
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Solution Overview
Problem
Existing plenum fan designs for air handling systems face inefficiencies due to the absence of a housing, leading to turbulence, noise, and reduced static efficiency, and direct drive plenum fans face challenges in matching motors to larger fans, limiting their application to smaller sizes and airflows.
Innovation Solution
The design features a fan unit with a bell-mouthed converging air inlet, a conical fan wheel, and a non-contacting labyrinth seal, which improves airflow patterns, reduces turbulence, and allows for more efficient air handling by optimizing the placement of the back plate and fan wheel, enabling direct drive systems to handle larger airflows with more efficient motor selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If plenum fans operate without a housing, then device complexity is reduced and ease of installation is improved, but turbulence increases and static efficiency deteriorates
Solution Approach 1:
A non-contacting labyrinth seal is introduced as an intermediary element between the fan wheel and the inlet cone. This seal reduces turbulence and improves static efficiency by minimizing air leakage and flow distortion, while maintaining the simplicity of the housingless plenum fan design.
2Device complexity
If direct drive plenum fans are used, then device complexity is reduced by eliminating belts and pulleys, but motor matching becomes difficult for larger fans
Solution Approach 1:
The fan wheel design incorporates variable pitch blades that can be adjusted to change the blade angle. This parameter change allows the same fan wheel to be matched with different motor sizes and speeds, enabling direct drive configurations for larger fans without requiring complex gear mechanisms.
3Manufacturing precision
If fan wheel blades are fixed pitch, then manufacturing precision is easier to achieve, but airflow efficiency deteriorates due to inability to optimize for different operating conditions
Solution Approach 1:
The fan wheel blades are designed with variable pitch capability, allowing the blade angle to be dynamically adjusted based on operating conditions. This dynamic adjustment optimizes airflow efficiency across different fan speeds and pressure requirements, while the mechanical linkage system maintains manufacturing feasibility.
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 enhances the static efficiency, reduces noise, and allows for the use of direct drive plenum fans in larger air handling systems by improving airflow patterns and enabling more efficient motor selection, overcoming the limitations of previous designs.
Implementation Method 1
a non-contacting labyrinth seal, which improves airflow patterns, reduces turbulence
Implementation Method 2
a bell-mouthed converging air inlet
Implementation Method 3
a conical fan wheel... enables direct drive systems to handle larger airflows
Data Source
AI summary
An improved plenum fan for use in air handling systems. The inlet cone is first in line in the direction of airflow. It is attached to the back plate, which is in between the fan wheel and the inlet cone. The fan wheel mates with the back plate through a non-contacting labyrinth seal. The wheel inlet and outlet are both cone-shaped so that the air channels between the fan blades are tilted towards the direction of airflow. The back plate is positioned behind inlet cone to permit a pressure sensor to be mounted on the inlet side of the back plate and to permit a fixed pressure tap to be connected on the inlet cone. Thus, a short conduit may be connected to the low side of the differential pressure gauge or sensor without passing through the fan back plate.