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AssigneeThe Penn State Research Foundation
InventorsMathew E. Poese, Robert W. M. Smith, Ray S. Wakeland, Steven L. Garrett
Estimating the term…
According to one embodiment of the present invention, a thermoacoustic device has a complaint enclosure which includes a rigid portion and a compliant portion. The compliant portion includes an oscillating member and a flexure seal with a pair of ends and a flexure body extending between the ends. One of the ends is sealed to the rigid portion and the other end is sealed to the oscillating member. The flexure seal has an average cross-sectional area and an end-to-end equilibrium length. A flexure volume is defined as the product of the average cross-sectional area and the end-to-end equilibrium length. A thermal core is disposed in the complaint enclosure and includes at least a first and a second heat exchanger. A working volume of gaseous working fluid fills the complaint enclosure. The working volume of gaseous working fluid has an equilibrium pressure. A motor is operable to oscillate the oscillating member such that the end-to-end length of the flexure seal is increased and decreased with respect to the equilibrium length. Therefore, the pressure of the working volume of gaseous working fluid is oscillated between a peak pressure greater than the equilibrium pressure and a minimum pressure less than the equilibrium pressure. In some embodiments, the working volume is less than or equal to four times the flexure volume, while in other embodiments, the working volume is less than or equal to two times or one times the flexure volume.
A thermoacoustic device comprising:
A thermoacoustic device comprising:
A thermoacoustic device comprising:
A thermoacoustic device comprising:
A thermoacoustic device comprising:
Dependencies are inferred from the claim text.
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Characterised by the cycle used, e.g. Stirling cycle: pulse-tube cycle
The engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly…:…
Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for: using the energy of…
Having resonance tubes: thermo-acoustic
Term end not estimated
The present invention relates generally to thermoacoustic devices and, more specifically, to thermoacoustic engines, heat pumps, and refrigeration devices. However, the present invention has applicability outside the field of thermoacoustics, and is therefore not limited to thermoacoustic devices.
During the past two decades, there has been an increasing interest in the development of thermoacoustic cooling engines (pumps) for a variety of commercial, military and industrial applications. Interest in thermoacoustic cooling has accelerated rapidly with the production ban of chlorofluorocarbons (CFC's). Thermoacoustic refrigerators can be constructed such that they use only inert gases, which are non-toxic and do not contribute to ozone depletion, nor to global warming. Exemplary prior art designs for thermoacoustic engines and refrigerators are shown in the following patents: U.S. Pat. Nos. 4,489,553, 4,722,201, 5,303,555, 5,647,216, 5,953,921, 6,032,464, and 6,314,740.
Most of the thermoacoustic engines and refrigerators that consume or produce electrical power require the containment of the thermoacoustic components and the gaseous working fluid within a rigid-walled enclosure (pressure vessel). The pressure vessel is typically either a rigid-walled adiabatic compression volume or a rigid-walled acoustic resonator of either the standing-wave or Helmholtz type. Within these rigid enclosures, oscillatory pressures are produced. If one is building an electrically-driven thermoacoustic refrigerator, there is usually a piston that is actuated by some electro-mechanical transducer (e.g., loudspeaker or other motor mechanism) contained within, or attached to the rigid enclosure. Motion of that piston produces the required pressure oscillations. The piston is coupled to the rigid enclosure, containing the thermoacoustic components, by some means that provides a dynamic pressure seal against leakage of the gaseous working fluid around the piston. In all known cases except one, this dynamic pressure seal is either a clearance seal (e.g., a close-fitting surface that surrounds the piston) or a flexure seal, such as a bellows or diaphragm. The only exception is the Torsionally-Resonant Toroidal Thermoacoustic Refrigerator (T-RTTAR) (see U.S. Pat. No. 5,953,921). The T-RTTAR approach does not employ a dynamic pressure seal, but requires that the entire rigid enclosure be oscillated at the operating frequency.
FIG. 1 is a cross-sectional view of a prior art thermoacoustic device;
FIG. 2 is a cross-sectional front view of a first embodiment of a thermoacoustic device according to the present invention;
FIG. 3 is a cross-sectional front view of a second embodiment of a thermoacoustic device according to the present invention;
The present invention provides a thermoacoustic device with a compliant enclosure that contains the gaseous working fluid and the thermoacoustic components. In one embodiment, a bellows or other flexible structure that provides a dynamic gas seal defines substantially the entire sidewall of the compliant enclosure. In this approach, the volume of the gaseous working fluid contained within the compliant enclosure, Vo, may be close to, approximately the same as, or less than the volume of the bellows, Vbel. In some embodiments, the bellows is assumed to be a thin-walled cylindrical-shaped shell that has convolutions in some portion of its walls. The outer radius of the convolutions is rout and the inner radius is rin. The equilibrium length of the bellows is Lbel. The bellows volume Vbel is then taken to be the product of the mean cross-sectional area of the bellows, Abel=π((rin+rout)/2)2, and the bellows length Lbel, so that Vbel=AbelLbel. In one preferred embodiment, Vo, may be less than Vbel, due to the exclusion of some of the enclosure volume from the intrusion of the piston into the bellows volume Vbel, the volume displaced by the thermoacoustic components that are within the bellows, and the intentional inclusion of rigid (but not necessarily solid) bodies placed within the bellows volume specifically to reduce the effective enclosure volume Vo.
For purposes of illustration, one embodiment may be assumed to have a compliant enclosure with an effective volume that is 15% less than the volume of the bellows, Vo=0.85Vbel. If again it is assumed that δV=0.10 Vbel, for the reasons described earlier, then the magnitude of the compression ratio becomes δV/Vo=0.10Vbel/0.85Vbel≅12%. Assuming that an inert gas with polytropic coefficient γ=5/3 is used for the working fluid, then Equation 4 suggests that the compliant cavity could produce a maximum ratio of peak-to-mean pressure, p1/pm, of nearly 20 percent, while still maintaining a bellows excursion within the range required for infinite bellows lifetime (Nmax=∞). Such a pressure ratio is more than adequate for any contemplated thermoacoustic refrigeration or prime mover (engine) application.
First Preferred Embodiment