共查询到19条相似文献,搜索用时 78 毫秒
1.
2.
再次强调了大规模液体中超声处理、以及为此目的研究声空化的重要性。提出了对这项应用中声空化行为的几点思考,重点是关于声空化的"强度"以及关于电动力式和流体动力式两类产生空化系统所产生空化的不同特性。 相似文献
3.
再次强调了大规模液体中超声处理、以及为此目的研究声空化的重要性.提出了对这项应用中声空化行为的几点思考,重点是关于声空化的"强度"以及关于电动力式和流体动力式两类产生空化系统所产生空化的不同特性. 相似文献
4.
该文介绍了声空化液体中声波被反常吸收的现象,即驱动声压越大,吸收越强,远场声压越低。研究给出其物理机理是高声压导致强空化,空化泡吸收驱动能量辐射高次谐波,高频声波更易被液体吸收,最终形成更低的远场声压。为了克服空化屏蔽,改善声空化的均匀性,提出了改变工作液体的空化阈值的思路。并就简单的双层液体系统进行了计算和实验,结果证实这种思路的正确性。 相似文献
5.
6.
声空化气泡内的高温、高压和高密度是声空化工程的机理和基础。该文简要回顾了国内外声空化理论和实验研究的进展,针对当前在液体中进行工业规模声处理等声能应用方面的现状和存在的问题,提出了扩大声能应用的一种可能途径——声空化空间分布控制并在实验室内进行了实验研究。结果表明该方法具有可行性。在此基础上,文中给出了基于空化空间分布控制方法在稠油井口辅助降粘和高固污泥预处理方面取得声空化工程初步应用的两个例子。现场的试验结果表明,这两种声空化工程化样机在实际现场工况条件下,均取得了较好的应用效果。最后,对当前声空化工程应用前景进行了初步探讨。 相似文献
7.
简要概述了20世纪20年代起多泡声空化的发现、研究和应用,随后重点介绍了20世纪90年代初实现的稳态单一气泡;由于它的实现,对声空化的实验研究和理论研究迅速取得进展,特别是在对气泡内部的极端条件(高温、高压、高密度)以及对气泡内声致发光的机理研究方面,同时还介绍了我国早在20世纪60年代实现的瞬态单一泡以及近期的一些实验结果。文章最后提到2002年3月美国报道的声空化核辐射实验,这个实验正在激发人们对声空化的更多关注。 相似文献
8.
9.
10.
在超声快速制取组织细胞病理切片的过程中,发现激励信号对切片制取效果有明显的影响.为了掌握超声激励信号对组织细胞的影响规律,达到快速制取病理切片的最佳状态,从气泡空化模型入手,通过改变激励信号频率、声压、气泡初始半径和液体黏滞系数等参量,研究了声孔效应中气泡动力学激励机制.数值计算表明:空化泡振动随激励声压增强而升高,随液体黏滞系数增强而减弱;一定频率范围内空化泡振动能保持在膨胀、收缩和振荡的稳定空化状态,存在空化泡稳态振动的最佳激励频率;一定初始半径能保证空化泡产生稳定的振动,存在空化泡稳态振动幅度最大的初始半径.实际操作中,在频率、声压、初始半径和黏滞系数综合作用的若干空化阈内,声孔效应使超声快速法制取细胞组织切片获得最佳效果.
关键词:
声孔效应
超声空化
气泡振动
稳态空化域 相似文献
11.
Inertial cavitation thresholds, which are defined as bubble growth by 2-fold from the equilibrium radius, by two types of ultrasonic excitation (at the classical single-frequency mode and dual-frequency mode) were calculated. The effect of the dual-frequency excitation on the inertial cavitation threshold in the different surrounding media (fluid and tissue) was studied, and the paramount parameters (driving frequency, amplitude ratio, phase difference, and frequency ratio) were also optimized to maximize the inertial cavitation. The numerical prediction confirms the previous experimental results that the dual-frequency excitation is capable of reducing the inertial cavitation threshold in comparison to the single-frequency one at the same output power. The dual-frequency excitation at the high frequency (i.e., 3.1 + 3.5 MHz vs. 1.1 + 1.3 MHz) is preferred in this study. The simulation results suggest that the same amplitudes of individual components, zero phase difference, and large frequency difference are beneficial for enhancing the bubble cavitation. Overall, this work may provide a theoretical model for further investigation of dual-frequency excitation and guidance of its applications for a better outcome. 相似文献
12.
13.
超声空化及其声流效应在医学、化工和能源等领域得到广泛应用。本文采用高速摄像和粒子图像测速系统分别研究了超声场下的空化形态和声流场结构的时空演化规律。实验研究了50W,100W,200W和250W等四种不同输入功率对18kHz的超声变幅杆附近空化及其声流场的影响。研究结果表明:(1)在变幅杆下端面处观察到由大量空化气泡均匀分布组成的倒置锥形空泡结构,并且锥形空泡结构为稳态流动结构。(2)在超声变幅杆附近产生了两种不同的声流形式,第一种是变幅杆底端的射流型声流,第二种是变幅杆两侧的回旋流。此外,通过研究空泡与声流场中最大速度点之间的空间对应关系,发现声流是因为空泡流动带动而产生的。(3)空间位置和输入功率能显著影响射流型声流的流场结构,但是对回旋流的影响十分微弱。 相似文献
14.
Dynamics and measurement of cavitation bubble 总被引:1,自引:1,他引:0
Based on the introduction of international progress, our investigations on acoustic cavitation have been reported. Firstly
we considered the cavity’s dynamics under the drive of the asymmetrical acoustic pressure. An aspheric dynamical model was
proposed and a new stable and aspheric solution was found in numerical simulation of the theoretical framework of the aspheric
model. Then, a dual Mie-scattering technique was developed to measure the cavity’s aspheric pulsation. A significant asynchronous
pulsation signal between two Mie-scattering channels was caught in the case of large cavity driven by low acoustic pressure.
As a direct deduction, we observed an evidence of cavity’s aspheric pulsation. Furthermore, we studied the dependency of the
asynchronous pulsation signal on the various parameters, such as the amplitude and frequency of the driving acoustic pressure,
and the surface tension, viscosity and gas concentration of the liquid. Finally, we introduced a new numeric imaging technique
to measure the shapes of the periodic pulsation cavities. The time-resolution was in the order of 20 ns, one order of magnitude
lower than that in the previous work, say, 200 ns. 相似文献
15.
The new electrical hypothesis proposed by Degrois and Baldo has been reviewed. The results show that the hypothesis is incompatible with the experimental observations. 相似文献
16.
17.
《Ultrasonics sonochemistry》2014,21(5):1696-1706
The generation and control of acoustic cavitation structure are a prerequisite for application of cavitation in the field of ultrasonic sonochemistry and ultrasonic cleaning. The generation and control of several typical acoustic cavitation structures (conical bubble structure, smoker, acoustic Lichtenberg figure, tailing bubble structure, jet-induced bubble structures) in a 20–50 kHz ultrasonic field are investigated. Cavitation bubbles tend to move along the direction of pressure drop in the region in front of radiating surface, which are the premise and the foundation of some strong acoustic cavitation structure formation. The nuclei source of above-mentioned acoustic cavitation structures is analyzed. The relationship and mutual transformation of these acoustic cavitation structures are discussed. 相似文献
18.
Cavitation mechanism of ultrasonic melt degassing 总被引:8,自引:0,他引:8
G. I. Eskin 《Ultrasonics sonochemistry》1995,2(2):S137-S141
The real melt always contains non-wettable fine inclusions which are potential nuclei for cavitation and degassing. This paper deals with the nature of ultrasonic degassing and the industrial application of a relevant technology. 相似文献
19.
Lawrence A. Crum 《Ultrasonics sonochemistry》1995,2(2):S147-S152
Sonochemistry is an evolving field that has shown recent rapid growth and increasing interest. Although this field concentrates on chemistry and uses acoustics principally as a tool, the basic mechanism that gives rise to sonochemistry — acoustic cavitation — is often ignored or given little attention. This paper addresses some of the relevant aspects of cavitation and physical acoustics that apply to sonochemistry. 相似文献