Thermoacoustic device
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Solution Overview
Problem
Thermoacoustic devices face a trade-off between achieving high efficiency and high power density, as increasing gas volume velocities lead to larger power losses and higher costs, while maintaining low gas velocities results in lower power density.
Innovation Solution
Incorporating a spring-type partitioning element in the acoustic circuit near the regenerator unit to enforce larger volume flows without adding gas volume, improving phasing between pressure and velocity, and suppressing DC flow, thereby enhancing efficiency and power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compliance of the gas volume is increased to achieve higher volume velocities, then power density is improved, but acoustic losses increase proportionally to the square of the velocity
Solution Approach 1:
The acoustic circuit is segmented into two separate paths connecting the thermoacoustic core to the passage, with the spring-type partitioning element dividing the compliance volume. This segmentation allows independent optimization of each path's acoustic impedance, enabling higher volume velocities through the regenerator while distributing and reducing overall acoustic losses in the system.
Solution Approach 2:
The spring-type partitioning element introduces a dynamic, movable boundary within the compliance volume that can adjust its position in response to acoustic pressure variations. This dynamic adjustment optimizes the acoustic impedance matching throughout the cycle, allowing the system to achieve higher volume velocities and power density while minimizing acoustic losses through adaptive impedance control.
2Reliability
If a jet pump or membrane is added to suppress DC flow and improve efficiency, then conversion efficiency is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for separate DC flow suppression devices such as jet pumps or membranes. The spring-type partitioning element inherently performs the DC flow suppression function through its elastic properties and positioning within the acoustic circuit, while simultaneously providing compliance volume division. This integration removes unnecessary components, reducing device complexity and cost while maintaining or improving conversion efficiency.
Solution Approach 2:
The spring-type partitioning element serves multiple functions simultaneously: it suppresses DC flow, divides the compliance volume, and provides acoustic impedance matching. This multi-functionality replaces what would traditionally require separate components (jet pump for DC flow suppression, compliance volumes for acoustic storage), thereby reducing device complexity while maintaining conversion efficiency.
3Reliability
If the magnitude of impedance of the gas in the feedback inertance is increased to achieve traveling wave phasing, then conversion efficiency is improved, but the phase difference between velocity and pressure increases
Solution Approach 1:
The spring-type partitioning element creates local variations in acoustic impedance within the compliance volume, with different regions having different effective compliances. This local quality differentiation allows precise control of the phase relationship between velocity and pressure at the regenerator, achieving optimal traveling wave phasing (small phase difference) while maintaining the required impedance magnitude for high conversion efficiency.
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 increases volume velocities and power density while maintaining efficiency, reduces convective heat losses, and simplifies the system by eliminating the need for a jet pump or membrane, leading to a more compact and cost-effective thermoacoustic device.
Implementation Method 1
a spring-type partitioning element within the loop; the spring-type partitioning element being configured to close off the cross-section of the tube and to be impermeable for the working fluid while allowing transmission of pressure waves in the working fluid through the spring-type partitioning element
Implementation Method 2
Within the thermoacoustic device a conversion process between acoustic power and thermal power, and vice versa, takes place in the regenerator
Implementation Method 3
The heat exchangers are configured to transfer heat to or from the thermoacoustic device
Data Source
AI summary
A thermoacoustic device includes a process volume which is filled with a working fluid through which the acoustic wave propagates. The thermoacoustic device further includes an acoustic network comprising a tubular loop configured with a passage providing an opening in the loop and configured as acoustic circuit provided with a compliance volume, a thermo-acoustic core and an inertance volume. Within the loop, the thermoacoustic core is at a first side thereof adjacent to the passage at a first path length through the loop, and at its second side, opposite to the first side, the thermoacoustic core is at a second path length from the passage. The thermoacoustic device includes within the loop a spring-type partitioning element that is configured to close off the cross-section of the tube and to be impermeable for the working fluid while allowing transmission of pressure waves in the working fluid through the spring-type partitioning element.