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Augmentation of natural convective heat transfer by acoustic cavitation

Jun CAI, Xiulan HUAI, Shiqiang LIANG, Xunfeng LI,

《能源前沿（英文）》 2010年第4卷第3期页码 313-318 doi: 10.1007/s11708-009-0064-3

摘要： An experimental study was conducted to investigate the effects of acoustic cavitation on natural convective heat transfer from a horizontal circular tube. The experimental results indicated that heat transfer could be enhanced by acoustic cavitation and had the best effect when the head of the ultrasonic transducer was over the midpoint of the circular tube, and the distance between the head and the tube equaled 15 mm. The augmentation at low heat flux was better than that in the case of high heat flux. Based on experimental results, the correlation formula of Nusselt number for water was obtained.

关键词： heat transfer enhancement augmentation acoustic cavitation acoustic streaming convective heat transfer

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水力空化反应器的最新进展——空化机理、反应器设计与应用 Review

Haoxuan Zheng, Ying Zheng, Jesse Zhu

《工程（英文）》 2022年第19卷第12期页码 180-198 doi: 10.1016/j.eng.2022.04.027

摘要：

水力空化因其能效高、操作成本低、能够诱导化学反应并可规模化等优势，被认为是一种很有前途的工艺强化技术。近十年来，人们对水力空化及其主要变量的基本认识取得了一些进展，为水力空化在自由基诱导化学反应过程中的应用提供了基础。在这里，我们对这些研究工作进行了广泛回顾，包括水力空化的基本原理、空化反应器的设计、空化诱导的反应增强及相关的工业应用。比较了两种类型的水力空化反应器，即固定式和旋转式水力空化反应器。讨论了水力空化反应器的设计参数及其在实验室和中试尺度上的反应器性能，并就其最佳操作和几何条件提出了建议。本文首次回顾了目前市场上的商业空化反应器。水力空化的独特特点已广泛应用于各种化学反应，如氧化反应和废水处理，以及如乳化液生成和组分提取等物理过程。文中也详细讨论了自由基和气泡内爆的作用。

关键词：水动力空化作用空化核羟基自由基固定/旋转水动力空化反应器反应增强空化应用

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Ultrasonic emulsification: basic characteristics, cavitation, mechanism, devices and application

《化学科学与工程前沿（英文）》 2023年第17卷第10期页码 1560-1583 doi: 10.1007/s11705-022-2160-4

摘要： Emulsion systems are widely applied in agriculture, food, cosmetic, pharmaceutical and biomedical industries. Ultrasound has attracted much attention in emulsion preparation, especially for nanoemulsion, due to its advantages of being eco-friendly, cost-effective and energy-efficient. This review provides an overview for readers to the area of ultrasonic emulsification technology. It briefly introduces and summarizes knowledge of ultrasonic emulsification, including emulsion characteristics, acoustic cavitation, emulsification mechanism, ultrasonic devices and applications. The combination of microfluidics and ultrasound is highlighted with huge advantages in controlling cavitation phenomena and emulsification intensification. A novel scale of dμ_C^0.6/μ_D^0.33−E_V is proposed to be able to compare the energy efficiency of emulsion preparation in different devices.

关键词： nanoemulsion ultrasound microreactor multiphase energy

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水轮机抗磨蚀金属材料的优化设计

王飚,张自华,王宇栋

《中国工程科学》 2000年第2卷第2期页码 64-67

摘要：

对抗磨蚀金属材料的基础研究表明，在10种常用结构材料的金属中，以钨、钴、铬的抗气蚀性最佳；生产应用研究结果表明，钨系材料中的火焰喷焊WC-M硬面陶瓷材料，铬系材料中的电镀稀土铬硬面材料，钴系材料中的等离子喷焊CoCrWC硬面材料，都是抗磨蚀性能较优，成本较低，并可进入工业应用的水轮机抗磨蚀结构材料。

关键词：水轮机磨蚀材料设计

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The cavitation erosion damage process of dynamically loaded journal bearings

MA Yan-yan, CHENG Xian-hua

《机械工程前沿（英文）》 2006年第1卷第4期页码 461-464 doi: 10.1007/s11465-006-0059-2

摘要： The cavitation damage model was built using finite element analysis software MSC.Marc. This paper attempted to numerically analyze the action process based on damage mechanics when a jet created by bubble collapse acted on the bearing surface in the process of cavitation erosion. The numerical results show that the values of equivalent plastic strain and void volume fraction increase with time. The values of damage scalar are higher on the bearing surface and subsurface, and decrease when it approaches the interface of overlay and nickel layer. The strain history and damage evolvement of bearing material acted on by jet impact load can be calculated efficiently using the proposed method, which develops a new method of analyzing cavitation erosion failure of the bearing surface.

关键词： bearing fraction increase collapse process evolvement

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Numerical modeling of cavitation on spillway’s flip bucket

Abbas PARSAIE,Sadegh DEHDAR-BEHBAHANI,Amir Hamzeh HAGHIABI

《结构与土木工程前沿（英文）》 2016年第10卷第4期页码 438-444 doi: 10.1007/s11709-016-0337-y

摘要： Numerical modeling of hydraulic phenomenon by computational fluid dynamic (CFD) approaches is one of the main parts in the high cost hydraulic structure studies. In this paper, using Flow 3D as CFD commercial tool, the cavitation phenomenon was assessed along spillway's flip bucket of the Balaroud dam. Performance of numerical modeling was compared to the physical model, which was constructed to this purpose. During numerical modeling, it was found that RNG turbulence model is a suitable performance for modeling the cavitation. Physical modeling shows that minimum cavitation index is about 0.85 and minimum cavitation index based on Flow 3D results is about 0.665, which was related to the flood discharge with return period of 10000 years. The main difference between numerical and physical modeling is related to the head of velocity, which is considered in physical modeling. Results of numerical simulation show that occurrence of cavitation based on cavitation index equal to 0.25 is not possible along the spillway.

关键词： cavitation Index numerical simulation spillway’s flip Bucket CFD Balaroud Dam physical modeling

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Acoustic fault signal extraction via the line-defect phononic crystals

《机械工程前沿（英文）》 2022年第17卷第1期页码 10-10 doi: 10.1007/s11465-021-0666-y

摘要： Rotating machine fault signal extraction becomes increasingly important in practical engineering applications. However, fault signals with low signal-to-noise ratios (SNRs) are difficult to extract, especially at the early stage of fault diagnosis. In this paper, 2D line-defect phononic crystals (PCs) consisting of periodic acrylic tubes with slit are proposed for weak signal detection. The defect band, namely, the formed resonance band of line-defect PCs enables the incident acoustic wave at the resonance frequency to be trapped and enhanced at the resonance cavity. The noise can be filtered by the band gap. As a result, fault signals with high SNRs can be obtained for fault feature extraction. The effectiveness of weak harmonic and periodic impulse signal detection via line-defect PCs are investigated in numerical and experimental studies. All the numerical and experimental results indicate that line-defect PCs can be well used for extracting weak harmonic and periodic impulse signals. This work will provide potential for extracting weak signals in many practical engineering applications.

关键词： phononic crystals line-defect fault signal extraction acoustic enhancement

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水机材料的抗磨蚀性判据研究

王飚,王宇栋,张自华,叶献国

《中国工程科学》 2003年第5卷第7期页码 58-61

摘要：

为了证实水机材料的抗磨蚀和抗空蚀性能与材料的常规宏观性能之间的相依关系，选取4种具代表性的材料（碳化钨涂层、NiCr合金涂层、硼不锈钢涂层和钛），进行空蚀和磨蚀试验，并测试了它们的硬度和抗腐蚀性。试验结果表明，材料的空蚀和磨蚀抗力与硬度和抗腐蚀性有着紧密的相依关系：高硬度是抗磨蚀性优的第一判据，较强的抗腐蚀性是第二判据；高抗腐蚀性是抗空蚀性优的第一判据，较高的硬度是第二判据。

关键词：水机材料磨蚀判据

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Experimental study on wire breakage detection by acoustic emission

Limin SUN, Ji QIAN

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 503-509 doi: 10.1007/s11709-011-0132-8

摘要： This paper experimentally investigated wire breakage detection in a steel cable by acoustic emission (AE) waveform. In the experiments, the attenuation laws of waveform amplitudes were discussed based on stress wave propagation in the wire, which was generated by kNocking and wire breakage. Then the wave velocity was calculated based on the reach time of the stress wave from each sensor. Finally, based on the waveform attenuation laws and the linear position method, the amplitude and energy of the source were confirmed through the measured waveform to identify the source category. The experimental results illustrated that the stress wave from different sources has a different frequency spectrum, and the amplitude attenuation factor varied with the stress wave frequency; high frequency waves had a greater attenuation factor. Compared with the other source, the wire breakage source contained a much higher energy, and thus, the wire breakage signal can be distinguished from the other source by comparing the non-attenuation energy at the source position.

关键词： acoustic emission (AE) waveform wire breakage attenuation factor wave velocity

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Simulation and experimental improvement on a small-scale Stirling thermo-acoustic engine

Mao CHEN,Yonglin JU

《能源前沿（英文）》 2016年第10卷第1期页码 37-45 doi: 10.1007/s11708-015-0390-6

摘要： Compared with the traditional engines, the thermo-acoustic engines are relatively new and can act as the linear compressors for refrigerators. Many institutes have shown great interest in this kind of machine for its absence of moving mechanical part. In this paper, the influence of the dimensions of the main parts of the small-scale Stirling thermo-acoustic engine was numerically simulated using a computer code called DeltaEC. The resonator and the resonator cavity were found to be the most convenient and effective in improving the performance of the engine. Based on the numerical simulation, a small-scale Stirling thermo-acoustic engine were constructed and experimentally investigated. Currently, with a resonator length of only 1 m, the working frequency of the engine was decreased to 90 Hz and the onset temperature difference was decreased to 198.2 K.

关键词： thermo-acoustic Stirling engine small-scale simulation experiment

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Fast scaling approach based on cavitation conditions to estimate the speed limitation for axial piston

Qun CHAO, Jianfeng TAO, Junbo LEI, Xiaoliang WEI, Chengliang LIU, Yuanhang WANG, Linghui MENG

《机械工程前沿（英文）》 2021年第16卷第1期页码 176-185 doi: 10.1007/s11465-020-0616-0

摘要： The power density of axial piston pumps can benefit greatly from increased rotational speeds. However, the maximum rotational speed of axial piston machines is limited by the cavitation phenomenon for a given volumetric displacement. This paper presents a scaling law derived from an analytical cavitation model to estimate the speed limitations for the same series of axial piston pumps. The cavitation model is experimentally verified using a high-speed axial piston pump, and the scaling law is validated with open specification data in product brochures. Results show that the speed limitation is approximately proportional to the square root of the inlet pressure and inversely proportional to the cube root of volumetric displacement. Furthermore, a characteristic constant is defined based on the presented scaling law. This constant can represent the comprehensive capacity of axial piston pumps free from cavitation.

关键词： axial piston pump cavitation speed limitation scaling law

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Acoustic characteristics of bi-directional turbines for thermoacoustic generators

Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO

《能源前沿（英文）》 2022年第16卷第6期页码 1027-1036 doi: 10.1007/s11708-020-0702-3

摘要： Bi-directional turbines combined with rotary motors may be a feasible option for developing high power thermoacoustic generators with low cost. A general expression for the acoustic characteristics of the bi-directional turbine was proposed based on theoretical derivation, which was validated by computational fluid dynamics modeling of an impulse turbine with fixed guide vanes. The structure of the turbine was optimized primarily using steady flow with an efficiency of near 70% (the shaft power divided by the total energy consumed by the turbine). The turbine in the oscillating flow was treated in a lumped-parameter model to extract the acoustic impedance characteristics from the simulation results. The key acoustic impedance characteristic of the turbine was the resistance and inertance due to complex flow condition in the turbine, whereas the capacitance was treated as an adiabatic case because of the large-scale flow channel relative to the heat penetration depth. Correlations for the impedance were obtained from both theoretical predictions and numerical fittings. The good fit of the correlations shows that these characteristics are valid for describing the bi-directional turbine, providing the basis for optimization of the coupling between the thermoacoustic engine and the turbine using quasi-one-dimensional theory in the frequency domain.

关键词： thermoacoustic power generator acoustic characteristics bi-directional impulse turbine energy conversion

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Research on acoustic-structure sensitivity using FEM and BEM

ZHANG Jun, ZHAO Wenzhong, ZHANG Weiying

《机械工程前沿（英文）》 2007年第2卷第1期页码 62-67 doi: 10.1007/s11465-007-0010-1

摘要： Acoustic-structure sensitivity is used to predict the change of acoustic pressure when a structure design variable is changed. The sensitivity is significant for reducing noise of structure. Using FEM (finite element method) and BEM (boundary element method) acoustic-structure sensitivity was formulated and presented. The dynamic response and response velocity sensitivity with respect to structure design variable were carried out by using structural FEM, the acoustic response and acoustic pressure sensitivity with respect to structure velocity were carried out by using acoustic BEM. Then, acoustic-structure sensitivity was computed by linking velocity sensitivity in FEM and acoustic sensitivity in BEM. This method was applied to an empty box as an example. Acoustic pressure sensitivity with respect to structure thickness achieved in frequency ranges 1 100 Hz, and its change rule along with stimulating frequency and design variable were analyzed. Results show that acoustic-structure sensitivity method linked with FEM and BEM is effective and correct.

关键词： sensitivity method BEM acoustic pressure pressure sensitivity frequency

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Acoustic emissions evaluation of the dynamic splitting tensile properties of steel fiber reinforced concrete

《结构与土木工程前沿（英文）》页码 1341-1356 doi: 10.1007/s11709-023-0988-4

摘要： This study empirically investigated the influence of freeze–thaw cycling on the dynamic splitting tensile properties of steel fiber reinforced concrete (SFRC). Brazilian disc splitting tests were conducted using four loading rates (0.002, 0.02, 0.2, and 2 mm/s) on specimens with four steel fiber contents (0%, 0.6%, 1.2%, and 1.8%) subjected to 0 and 50 freeze–thaw cycles. The dynamic splitting tensile damage characteristics were evaluated using acoustic emission (AE) parameter analysis and Fourier transform spectral analysis. The results quantified using the freeze–thaw damage factor defined in this paper indicate that the degree of damage to SFRC caused by freeze–thaw cycling was aggravated with increasing loading rate but mitigated by increasing fiber content. The percentage of low-frequency AE signals produced by the SFRC specimens during loading decreased with increasing loading rate, whereas that of high-frequency AE signals increased. Freeze–thaw action had little effect on the crack types observed during the early and middle stages of the loading process; however, the primary crack type observed during the later stage of loading changed from shear to tensile after the SFRC specimens were subjected to freeze–thaw cycling. Notably, the results of this study indicate that the freeze–thaw damage to SFRC reduces AE signal activity at low frequencies.

关键词： steel fiber reinforced concrete freeze–thaw cycling Brazilian disc splitting test acoustic emission technique dynamic splitting tensile acoustic emission properties

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evolution behavior of polypropylene fiber reinforced concrete subjected to sulfate attack based on acoustic

Ninghui LIANG; Jinwang MAO; Ru YAN; Xinrong LIU; Xiaohan ZHOU

《结构与土木工程前沿（英文）》 2022年第16卷第3期页码 316-328 doi: 10.1007/s11709-022-0810-8

摘要： To study the damage evolution behavior of polypropylene fiber reinforced concrete (PFRC) subjected to sulfate attack, a uniaxial compression test was carried out based on acoustic emission (AE). The effect of sulfate attack relative to time and fiber hybridization were analyzed and the compression damage factor was calculated using a mathematical model. The changes to AE ringing counts during the compression could be divided into compaction, elastic, and AE signal hyperactivity stages. In the initial stage of sulfate attack, the concrete micropores and microcracks were compacted gradually under external load and a corrosion products filling effect, and this corresponded with detection of few AE signals and with concrete compression strength enhancement. With increasing sulfate attack time, AE activity decreased. The cumulative AE ringing counts of PFRC at all corrosion ages were much higher than those for plain concrete. PFRC could still produce AE signals after peak load due to drawing effect of polypropylene fiber. After 150 d of sulfate attack, the cumulative AE ringing counts of plain concrete went down by about an order of magnitude, while that for PFRC remained at a high level. The initial damage factor of hybrid PFRC was −0.042 and −0.056 respectively after 150 d of corrosion, indicating that the advantage of hybrid polypropylene fiber was more obvious than plain concrete and single-doped PFRC. Based on a deterioration equation, the corrosion resistance coefficient of hybrid PFRC would be less than 0.75 after 42 drying−wetting sulfate attack cycles, which was 40% longer than that of plain concrete.

关键词： polypropylene fiber reinforced concrete sulfate attack damage evolution behavior acoustic emission damage factor