Blower Assembly Vortex Breaker for Noise Reduction
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Solution Overview
Problem
Blower assemblies with tangential or cross flow fans experience unstable airflow patterns, leading to aerodynamic noise, motor inefficiency, and undesirable speed variations, causing high-pitch whining and low-pitch revving sounds due to eccentric vortices and changing air loads.
Innovation Solution
The blower assembly incorporates a cross flow fan with circular blade supports featuring interrupters to stabilize airflow by breaking up eccentric vortices and uneven blade spacing to reduce velocity gradients, along with a high-resistance motor rotor for consistent speed and torque operation, and a strategically positioned cutoff to enhance airflow stability and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cross flow fans are used in blower assemblies, then air can be drawn in and discharged with rotation of the fan, but unstable airflow patterns and eccentric vortices are generated causing aerodynamic noise and motor inefficiency
Solution Approach 1:
A vortex breaker is introduced as an intermediary component between the fan blades and the housing cutoff. This vortex breaker intercepts and dissipates eccentric vortices before they can complete their circulation pattern and generate noise. The vortex breaker acts as a mediator that transforms the harmful vortex flow into more stable airflow patterns, reducing aerodynamic noise while preserving the fan's air moving capability
Solution Approach 2:
The harmful eccentric vortices are extracted or removed from the main airflow path by the vortex breaker. The vortex breaker is positioned to specifically target and remove these unstable flow patterns from the cutoff region, separating the harmful vortexes from the useful airflow that needs to be moved through the blower assembly
2Adaptability or versatility
If cross flow fans operate with changing air load, then the fan responds to airflow variations, but the motor speed and torque fluctuate causing low-pitch revving noise
Solution Approach 1:
The vortex breaker serves as a flow stabilizing intermediary that dampens rapid airflow variations before they reach the fan and motor. By breaking up eccentric vortices and stabilizing the airflow pattern in the cutoff region, the vortex breaker reduces the magnitude and frequency of air load changes on the fan, thereby minimizing motor speed fluctuations and eliminating revving noise while preserving the system's ability to respond to legitimate airflow demands
3Productivity
If fan blades travel past the housing cutoff, then air is discharged from the blower, but sharp velocity gradients are generated producing high-pitch whining noise
Solution Approach 1:
The vortex breaker is positioned as an intermediary element between the fan blades and the housing cutoff. It intercepts the airflow before it passes the cutoff, breaking up eccentric vortices and smoothing velocity gradients. This mediator component allows air discharge to continue while preventing the formation of sharp velocity gradients that cause high-pitch whining noise
4Adaptability or versatility
If the motor operates on a saddle-shaped speed-torque curve, then the motor can satisfy varying air load requirements, but the motor searches between multiple operating points causing speed fluctuations
Solution Approach 1:
The vortex breaker acts as a flow stabilizing intermediary that reduces the variability of air load presented to the fan-motor system. By damping eccentric vortices and stabilizing airflow patterns, the vortex breaker creates a more consistent operating condition that reduces the frequency and magnitude of motor operating point transitions along the speed-torque curve, thereby stabilizing fan speed while preserving the motor's ability to adapt to varying air load requirements
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 solution results in more stable airflow, reduced noise levels, and a quieter operation by minimizing the frequency and magnitude of speed changes in the fan, eliminating undesirable revving sounds and improving motor efficiency.
Implementation Method 1
at least one interrupter of the circular blade support disposed radially outwardly from a center of the circular blade support... configured to break up an interaction between an eccentric vortex within the cross flow fan and flow induced by rotation of the circular blade support
Implementation Method 2
a motor for rotating the fan
Data Source
AI summary
A blower assembly having a housing and a cross flow fan rotatably mounted to the housing. Rotation of the fan drives fluid flow through the housing and produces an eccentric vortex of fluid flow in the housing. The fan has a circular blade support that induces fluid flow with rotation of the fan which interacts with the eccentric vortex. The circular blade support has at least one flow interrupter configured and arranged to rotate through the interaction of the eccentric vortex and the flow induced by the circular blade support to disrupt the interaction between the eccentric vortex and the flow induced by the circular blade support. In this manner, the at least one flow interrupter reduces the effect of the unstable vortex-blade support interaction on the airflow through the blower assembly which stabilizes the air loading on the blower assembly motor and reduces noise.