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1.
换热器内超声空化效应影响因素数值研究   总被引:2,自引:0,他引:2  
对超声波参数和换热器参数对超声波空化效应影响的研究,能够找出最佳的超声波参数使其防除垢效果更好。本文利用数值计算方法研究了超声波功率、频率和换热器内介质温度以及换热管的型式对超声空化的影响。结果表明,随着超声波功率的增大,水中汽含率也增大,而且变化也相对激烈;随着频率的增加汽含率先增大后降低,20 kHz为最佳频率;介质温度越高,空化效应越强烈;管径波动较多的波纹管更有利于空化效应的产生和发展。  相似文献   

2.
利用超声外场作用实现强化传热的技术越来越受到人们的关注。本文开展超声波强化传热技术的作用机理分析及数值模拟研究。在理论方面,提出了超声波强化传热机理的新解释——"空化链式反应";在数值模拟方面,建立了超声波强化换热的数值模型,验证了超声波对换热的强化作用。理论分析显示超声空化核心的链式破裂具有减薄边界层、增强换热的效果;模拟给出了不同波动压力和频率下的强化换热情况,当驱动压力为7 kPa和频率为20 kHz时,超声波对流体传热的强化效果最好。  相似文献   

3.
许龙  汪尧 《物理学报》2023,(2):159-165
为了对双泡耦合的声空化过程进行模拟,本文从流体动力学控制方程和流体体积分数模型出发,在Fluent软件中构建双泡耦合超声空化三维有限元仿真模型,对超声波驱动下流体中双泡耦合声空化动力学过程进行数值模拟,并通过对空化气泡周围声场的变化进行分析研究双泡耦合声空化的非线性动力学特性.结果显示:在超声波驱动下,球形气泡先缓慢扩张,扩张到最大半径后迅速收缩直至溃灭;耦合双气泡间存在相互作用力,使得空化气泡的扩张受到抑制、气泡收缩时间增长;空化气泡在收缩阶段的能量转换能力增强,相比单气泡声空化,耦合双气泡溃灭时气泡内部的压强更大.本文分析结果将为超声空化泡群的动力学过程模拟提供参考.  相似文献   

4.
介绍了螺旋锥齿轮超声研磨加工的方法,利用声学和超声空化的相关理论分析了超声研齿的材料去除方式,在齿面接触区具有旋转超声加工的特点,在非接触区,超声空化对齿面产生空蚀或者直接激励磨粒撞击和滑擦齿面,引起材料的去除。进行了超声研齿和普通研齿的对比试验,结果表明超声研齿的材料去除率可达到普通研磨的3倍,齿面粗糙度低至Ra0.2μm,水平截距c1.2μm。齿面研磨后的SEM照片证实,齿面质量明显提高。  相似文献   

5.
超声振动珩磨作用下空化泡动力学及影响参数   总被引:1,自引:0,他引:1       下载免费PDF全文
为了合理利用超声振动珩磨作用下的空化效应,以磨削区单个空化泡为研究对象,考虑珩磨头合成扰动速度和珩磨压力的作用建立了磨削区空化泡的动力学模型。数值模拟了空化泡初始半径,珩磨压力,液体静压力和超声声压幅值对磨削区空化效应的影响。研究表明考虑超声振动珩磨作用时,空化泡膨胀的幅值会受到抑制,其溃灭时间也会缩短,而且较容易出现稳态空化。珩磨压力和液体静压力对磨削区空化主要起抑制作用,超声波声压幅值在一定范围内能够促进磨削区空化效果的提升。本文的研究为进一步理解超声振动珩磨的空化机理提供了理论支持。  相似文献   

6.
声场中水力空化泡的动力学特性   总被引:4,自引:0,他引:4       下载免费PDF全文
沈壮志  林书玉 《物理学报》2011,60(8):84302-084302
以水为工作介质,考虑了液体黏性、表面张力、可压缩性及湍流作用等情况,对文丘里管反应器中空化泡在声场作用下的动力学行为特性进行了数值研究.分析了超声波频率、声压及喉径比对空化泡运动特性以及空化泡崩溃时所形成泡温以及压力脉冲的影响.结果表明,超声将水力空化泡运动调制成稳态空化,有利于增强空化效果. 关键词: 超声波 水力空化 湍流 气泡动力学  相似文献   

7.
在超声滚压加工中引入切削液后可能会产生空化现象,由此产生的微射流和冲击波对超声表面强化将有积极作用。为研究超声滚压加工中空化现象是否存在及空化效应在超声滚压中的作用,本文首先分析了超声滚压中的空化阈值,然后进行了染色法试验和超声滚压后试样氧元素能谱分析,最后通过超声滚压加工对比试验研究了空化效应对加工后材料表面粗糙度和显微硬度的影响。研究发现,超声滚压加工中的声压幅值远大于空化阈值,满足空化存在的必要条件;超声滚压中发生了明显的卡纸染色现象,引入切削液后工件超声滚压加工表面氧元素含量显著提高,表明超声滚压中发生了空化现象。超声滚压加工中的空化效应能进一步降低工件表面粗糙度和提高表面显微硬度,有利于提高工件表面强化质量。本研究为空化效应在超声滚压中的积极利用提供了依据。  相似文献   

8.
在超声波降解有机物溶液过程中,超声空化产生的高温高压以及空化泡振荡产生的激波在有机物溶液的降解中发挥重要作用.本文通过对超声波作用下气泡动力学的研究,讨论了超声波声压、频率、气泡初始半径等参量对有机物溶液降解效率的影响.研究发现.存在使降解效率极大的声压和频率.在空化稳定的情况下,存在一个使降解效率极大的气泡初始半径,降解效率随着黏滞系数的增大而减小.研究还发现,双频超声作用的空化效果比单频超声作用时强,与双频超声作用下有机物溶液降解率较大这一实验结果一致.  相似文献   

9.
对利用超声波去除或分离悬液中微小颗粒过程中频率和时均声能密度等声学参数对微粒凝聚的影响作了分析研究。利用前人的数学模型对不同声对比因数下悬浮液中微粒达到平衡状态时所需要的时间及凝聚位置进行了计算。在水模型实验,实验中所施加超声波的频率为24.1kHz,微粒的粒径为0-60um、密度940kg/m^3的高密度聚乙烯,实验液为脱气软化水,实验结果与部分理论分析结果是一致的。  相似文献   

10.
通过对超声波泵现象进行预实验,判断出毛细管内液面反常上升的高度与毛细管、液体和超声波的诸多性质相关.从挤压模效应和空化效应分别对超声毛细效应进行理论分析,判断出了影响超声波作用下毛细管内液面反常上升的因素,并通过实验测量结果验证了此理论的自洽性.  相似文献   

11.
With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology.With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology  相似文献   

12.
韦永梅  彭虎 《物理学报》2014,63(19):198702-198702
基于非衍射波的高帧率(high frame rate,HFR)超声成像的前提是发射阵列波(array beam)声场,但由于阵列波的正弦函数特征使对超声发射信号加权处理变得比较困难,导致了发射系统复杂.针对这一问题,本文提出一种有效的解决方案.基于傅里叶变换理论,从方波的能量成分主要集中在基波这一特性出发,采用单值方波对超声传感器发射信号进行加权,用一个功率信号源和简单的电子开关网络实现了HFR系统中所需要的发射电路.实验表明,这种方案对HFR的成像质量几乎没有什么影响,但大大简化了HFR成像系统,这为HFR超声成像方法在现有B超声系统上的实现提供了一个可行的方法.  相似文献   

13.
基于FPGA和DSP的超声波风向风速测量系统   总被引:2,自引:1,他引:1       下载免费PDF全文
丁向辉  李平 《应用声学》2011,30(1):46-52
本文研究了数字化超声风速测量系统,提出并实现了完整的系统设计方案。该方案的核心是基于现场可编程门阵列(FPGA)和数字信号处理器(DSP)的硬件系统架构和基于包络重心法的信号处理算法。该设计可实现超声信号的高速数据采集和复杂的信号处理算法。测试结果表明所实现的超声风速测量系统具有体积小、反应速度快、抗干扰能力强和分辨率高等优点,且具有成本优势,并保持较低的功耗。  相似文献   

14.
Solid foods include fish, shrimp, shellfish, and other aquatic products, fruits, and vegetables. These products are commonly used for food freezing, cooling, and thawing. However, traditional freezing, cooling, and thawing of solid food technologies have limitations in quality, such as protein denaturation and water loss in food. Ultrasound-assisted technology has become a useful method in solid food processing due to improved preservation quality of solid food. This paper comprehensively reviews the mechanism and application of ultrasonic in solid food processing technology. Although the application of ultrasound-assisted ultrasound in solid food processing is relatively comprehensive, the energy saving of food cold processing is essential for practical application. This paper analyzes the optimization of ultrasonic in solid food processing, including orthogonal/multi-frequency technology and the combination of ultrasonic and other technologies, which provides new ideas for freezing, cooling, and thawing of solid food processing.  相似文献   

15.
A vehicle guidance system has been developed using ultrasonic sensing. The ultrasonic technology is presented in this paper with reference to how it links in with the complete system. The ultrasonic unit is based on electrostatic transducer technology and comprises a separate linear array and curved divergent transmitter which gives it an effective field of view of 60° and a range of more than 5 m. The unit has been designed primarily for use on an unmanned vehicle travelling over rough, unknown terrain.  相似文献   

16.
王彦  赵洪亮 《应用声学》2019,38(1):114-119
为了满足超声换能器快速筛选的要求,在对超声换能器参数导纳圆法测量原理进行分析的基础上,利用NI ELVIS平台搭建了一种结构简单的超声换能器参数测量系统。采用点频法实现高精度、快速的导纳测量,采用最小二乘法拟合得到导纳圆,进而完成超声换能器诸参数的计算。基于LabVIEW软件平台编写了相应的软件系统。针对40 kHz超声换能器的测试表明,所设计的超声换能器参数测量系统精度高、处理速度快,且结构简单、便于使用。  相似文献   

17.
郭占玲  沈斌  赵志钢  刘瑶 《应用声学》2024,43(1):223-236
复合材料普遍具有高比强度、高比刚度、高模量、耐腐蚀等优异性能广泛应用于飞机机翼、导弹外壳、航空发动机壳体等部位。制造和服役过程中各类缺陷影响复合材料的力学性能和服役性能,必须采用有效的方法准确检测和评估复合材料中各类缺陷。空气耦合式超声检测具有完全非接触、非侵入、无损伤的特点能够更好地运用于传统超声检测难以适应的情形具有极为广阔的发展前景 本文就近年来空气耦合超声检测技术的研究现状进行了系统综述简明扼要地分析和介绍了当前空气耦合超声检测的研究热点及进展,重点介绍了1-3型压电复合材料换能器、信号处理技术、相控聚焦式空气耦合超声检测、超声在复合材料的传播特性及其与缺陷交互作用的研究现状,探讨了空气耦合超声无损检测技术与仪器的发展方向。总结了目前空气耦合超声检测的研究热点问题,最后展望了空气耦合超声检测的发展趋势和应用前景。  相似文献   

18.
Song SP  Que PW 《Ultrasonics》2006,44(2):188-193
The noise suppression techniques with wavelet transform (WT) are widely used in non-destructive testing and evaluation (NDT&E), especially in ultrasonics. Complete reconstruction theory with hard or soft thresholds, reconstruction technique based on the singularities of noise and signal, matched filter with an impulse response, and optimal frequency-to-bandwidth ratio of wavelet technique have all been used to analyze ultrasonic signals for noise suppression. But a more simple and effective technique has been pursued for decades. This paper develops a new technique using WT for the right purpose. In this work, WT is treated as a band-pass filter whose central frequency and frequency bandwidth (CF&FB) are determined by the spectra distribution of an ultrasonic signal captured from real testing situation. For the purpose of matching their CF&FB well, a technique for evaluating the optimal scale of a daughter wavelet is carried out too. By acting this daughter wavelet as a band-pass filter, we can obtain excellent de-noising results, even when the signal to noise ratio (SNR) is below -18 dB. The performance of the technique has been done by ultrasonic signals with computer generated white noises. Finally, the experimental verification is performed on a pipeline specimen with man-made small flaws with good results obtained. The results show that the technique is more suitable for processing heavy noised ultrasonic signals, and it can also be used in automatic flaw detection.  相似文献   

19.
Although the phenomenon of light diffraction by ultrasound has been studied very extensively during the last 40 years, almost all investigations were concentrated on the individual far field (Fraunhofer) diffraction orders. In the present paper, the basic theory is developed for studying the near field (Fresnel region) of light diffracted by an arbitrary plane ultrasonic wave and the fundamental periodicity properties are stated. The general plane-wave theory of Raman-Nath has been taken as a starting point. From the analysis, the near field of the diffracted light is seen to be highly sensitive to variations of the ultrasonic amplitude and this feature provides a useful technique for observing weak ultrasonic waves. In particular, for the specific case of Raman-Nath-type diffraction, a procedure is presented allowing the reconstruction of the time waveform of the ultrasonic wave from the diffracted light intensity signal.  相似文献   

20.
Near-well ultrasonic processing technology attracts more attention due to its simple operation, high adaptability, low cost and no pollution to the formation. Although this technology has been investigated in detail through laboratory experiments and field tests, systematic and intensive researches are absent for certain major aspects, such as whether ultrasonic excitation is better than chemical agent for any plugs removal; whether ultrasound-chemical combination plug removal technology has the best plugs removal effect. In this paper, the comparison of removing drilling fluid plug, paraffin deposition plug, polymer plug and inorganic scale plug using ultrasonic excitation, chemical agent and ultrasound-chemical combination plug removal technology is investigated. Results show that the initial core permeability and ultrasonic frequency play a significant role in plug removal. Ultrasonic excitation and chemical agent have different impact on different plugs. The comparison results show that the effect of removing any plugs using ultrasound-chemicals composite plug removal technology is obviously better than that using ultrasonic excitation or chemical agent alone. Such conclusion proves that ultrasonic excitation and chemical agent can cause synergetic effects.  相似文献   

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