Synthetic Jet Noise Reduction via Phase-Shifted Actuation
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Solution Overview
Problem
Synthetic jets produce high levels of acoustic noise due to the overlap of structural and acoustic resonance frequencies, limiting their use in applications where noise is a concern.
Innovation Solution
Using a pair of synthetic jets actuated with sinusoidal signals having a phase difference, such as 180°, to reduce acoustic noise, with the jets being thermally coupled to a heat sink to cool heat-producing components like LED lighting systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synthetic jets are operated at natural frequencies for optimal cooling performance, then cooling efficiency is improved, but acoustic noise increases
Solution Approach 1:
The invention divides a single synthetic jet into multiple synthetic jets (at least two) that are spatially separated and operate with different phase angles. This segmentation allows the acoustic noise from individual jets to interfere destructively, reducing overall noise levels while maintaining cooling effectiveness through distributed heat removal.
Solution Approach 2:
The invention employs periodic actuation of multiple synthetic jets with controlled phase differences between their actuation cycles. By operating jets at different phases of their periodic cycles, the system achieves noise cancellation through destructive interference while maintaining continuous cooling performance.
2Productivity
If multiple synthetic jets are used to improve cooling coverage, then cooling performance is improved, but device complexity increases
Solution Approach 1:
The invention combines multiple synthetic jets into a unified noise reduction system where the jets work cooperatively with phase-controlled actuation. By merging the acoustic fields of multiple jets with appropriate phase relationships, the system achieves noise cancellation while the combined cooling effect provides enhanced heat removal coverage.
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 out-of-phase operation of synthetic jets significantly reduces peak noise levels across various frequency spectra, making them more suitable for noise-sensitive applications.
Implementation Method 1
The flexible diaphragm is typically actuated by a piezoelectric actuator or other appropriate means
Implementation Method 2
A volume changing mechanism for periodically changing the volume within the internal chamber may include a flexible diaphragm constructed as a wall of the housing
Implementation Method 3
As the fluid passes through the orifice, vortices of fluid are formed. These vortices move away from the edges of the orifice under their own self-induced velocity
Implementation Method 4
As the vortices travel away from the orifice, they synthesize a jet of fluid, thus called a 'synthetic jet,' through entrainment of the ambient fluid
Implementation Method 5
The out-of-phase operation of synthetic jets significantly reduces peak noise levels across various frequency spectra
Data Source
AI summary
Apparatus and method are provided for reducing acoustical noise when cooling a device, such as a lamp system. The apparatus includes at least a set of a first synthetic jet and a second synthetic jet. The first and second synthetic jets are responsive to respective actuating signals having a phase difference (e.g., 180°) between one another chosen to reduce acoustic noise produced by the first and second synthetic jets when cooling the device.