| Project/Area Number |
12555045
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Fluid engineering
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| Research Institution | SAITAMA UNIVERSITY |
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Principal Investigator |
KAWAHASHI Masaaki Saitama University, Faculty of Engineering, Professor, 工学部, 教授 (70008853)
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| Co-Investigator(Kenkyū-buntansha) |
FURUSHOU Kazuhiro Daikin Co. , Ltd., Researcher, 空調技術研究所, 研究員
SHIOZAKI Kouju Saitama University, Faculty of Engineering, Assistant, 工学部, 助手 (40008933)
HIRAHARA Hiroyuki Saitama University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20201733)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥12,700,000 (Direct Cost: ¥12,700,000)
Fiscal Year 2002: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2001: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2000: ¥6,900,000 (Direct Cost: ¥6,900,000)
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| Keywords | Finite amplitude wave motion / Nonlinear wave motion / Acoustic streaming / Thermo-acoustic effect / Acoustic compressor / アコースティックコンプレッサ / ソニックコンプレッサ |
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| Research Abstract |
Finite amplitude wave motion in closed tubes are classic but interesting research field for the applications in recent advanced technology. When the gas column in a closed tube is driven by a piston at one end at the resonant frequency, large amplitude standing wave is induced in the tube. The mode of the standing wave, the pressure waveform and its amplitude at the closed end strongly depend on the geometry of the tube shape. In the case of cylindrical tube, the amplitude of the waveform is restricted due to the nonlinear effect in propagating shock-wave generation by the steepenig of wave front. Acoustic saturation comes quickly because the energy supplied to generate standing wave at exiting frequency mode is dissipated to higher harmonics instead of increasing the amplitude of the pressure waveform. On the other hand, in varying cross-sectional area tube, a large amplitude standing wave can be achieved and shock waves disappear with the wave motion. This large amplitude pressure fl
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uctuation has a practical application in the development of acoustic compressor which can consist an oil-less compression system of gases. The large amplitude standing wave in closed tube also induces non zero mean pressure distribution along the tube axis, steady circulating streaming at every 1/4 wave length section, and thermoacoustic effect of cooling at the node of pressure fluctuation and heating at the loop. The coupling of acoustic streaming with unstable convection not only transforms it into stable convection with cellular structure characterized by the wavelength of the sound wave but also increases the velocity of the convection current. Thermoacoustic effect induced by the air column oscillation can be applied to design thermoacoustic engine and refrigerator.
The geometry of the tube shape is conical, exponential or half cosine function cross-sectional area contraction towards the closed end. The cylindrical tube is used as reference tube. The length of each tube is same. All the tubes area symmetric with regards to axis of the tube. The finite amplitude wave motion is induced in tube by sinusoidal oscillation of piston at big end of each tube. Linear and nonlinear theories have been derived by using the basic fluid dynamics equation. By the linear theory, the resonant frequency can be evaluated for different shaped tubes with different area contraction ratios. And it can be used to estimate the node position which is necessary to place the stack plate in tubes to design thermoacoustic engine and refrigerator. The nonlinear theory based on Chester' theory reveals that changing the shape of the tube can reduce the discontinuity of the waveform appeared in closed cylindrical tube. The result obtained by the nonlinear calculation agrees well with previous investigation.
Finite difference MacCormack scheme keeping accuracy with second order in time and fourth order in space was used for numerical simulation of wave motion in closed tube. One-dimensional fluid dynamic equations are solved taking viscous and frictional dissipation into considerations. The limit of cross-sectional area contraction ratio to which shock wave appears, the effect of tube lengths, and effect of gas properties is investigated by numerical simulation. Numerical result revealed the possibility of getting shockless high amplitude pressure waveform by changing cross-sectional area of the tube.
An experimental setup was made to investigate the characteristics of wave motion in different tube geometries. Conical, exponential and half cosine area contraction tube was used to compare the hardening, hysteresis and frequency shift in each tube geometries. Experiments were conducted for different piston acceleration and results are compared with the results obtained by numerical simulation.
The finite amplitude standing wave in closed area change tubes was studied theoretically, numerically and by experiment. Experimental result agrees well with the numerical and theoretical result. The high amplitude shockless pressure waveform as well as high compression ratio in closed area change tube was developed. And the characteristic of the compressor mode operation for each shaped tube has been investigated for different gases.
As the results, it has been revealed that the geometry of the tube shape is the most important factor in determining shock free high amplitude pressure waveform and obtaining the stability of the resonant frequency. And the half cosine shaped area change tube is the best tube shape to design acoustic compressor in this investigation. Less
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