超声空化效应及其应用

介绍了超声空化的原理,并对超声空化在化工、水处理方面和污泥处理方面的应用进行了综述,着重介绍了在降解难降解废水和促进污泥厌氧消化中的应用.     

超声辐照降解水中氯苯的研究

研究了超声辐照工艺技术降解水中氯苯的效果和影响因素 ,包括声强、溶液pH值、初始浓度、溶解气体和自由基清除剂 ,并探讨了氯苯超声降解的机理。试验结果表明氯苯的超声降解主要在空化泡内热解 ,降解效果好     

低强度超声提高污泥活性的运行条件优化

为优化超声处理提高污泥活性的运行条件,考察了超声波的频率、强度、作用时间和污泥浓度等因素的影响.结果表明,采用35 kHz和61 kHz两种低频率超声波先后对污泥进行强化处理时,在总处理时间一致的条件下,超声波的顺序和时间分配对污泥活性的提高程度及活性的延续时间无显著差别;采用固定频率的超声波处理时,提高超声波的功率和延长超声作用时间都可以显著提高污泥活性;在功率和作用时间恒定的条件下,增大MLSS对单位质量污泥活性的提高程度影响较小,因此,对污泥先进行浓缩再超声处理可大大提高超声效率.     

超声辐照降解水中氯苯的研究

研究了超声辐照工艺技术降解水中氯苯的效果和影响因素，包括声强、溶液pH值、初始浓度、溶解气体和自由基清除剂，并探讨了氯苯超声降解的机理。试验结果表明氯苯的超声降解主要在空化泡内热解，降解效果好。     

基于小波包变换和关联维数的空化信号特征提取

在详细阐述了声发射监测技术及空化声发射信号的特征基础上,采用小波包变换方法对空化信号进行处理.引入小波包特征频段分析法,以特征频段的能量和关联维数作为特征量来表征空化信号特征.最后根据选择的特征量对不同工况下的空化进行分类.仿真实验结果表明,该方法能够有效的表征空化强弱程度,具有一定的科学意义及工程价值.     

低强度超声场促进剩余污泥好氧消化

为了提高剩余污泥好氧消化效率,在消化过程中对剩余污泥进行超声辐射,声强为0.53 W/cm2,频率28 kHz,分别选用0.045 W/mL、0.09 W/mL两个功率密度,每次超声辐射时间20 min或10 min,辐射频次选用4次或2次,组成4个组合.研究表明,未经超声处理的污泥在消化第17天达到稳定,而经超声作用的污泥消化稳定时间较前者提前3～7 d.在相同好氧消化时间内,经超声波处理后污泥能获得更高的有机物降解率.同时对超声波促进污泥好氧消化工艺进行了工程经济评价.     

超声波处理蚊卵反应机制及效果研究

自来水厂沉淀池壁为蚊产卵提供了较好的生存环境，给供水安全带来隐患，需要有效的方法来控制蚊卵的暴发。研究评估了超声波对蚊卵的抑制效果，检测超声处理后蚊卵的死亡率，分析超声处理前后参与超声诱导应激反应的蛋白质含量和酶活性的变化。使用COMSOL软件模拟分析超声波场的特征，包括频率、功率、暴露距离和时间。在较低的频率下观察到较高的卵死亡率。在28 kHz的频率、450 W/h的功率、5 mm的暴露距离和120 s的暴露时间下，蚊卵的死亡率为100%,均声压强度为4.0 W/m²,而在较高的频率(68 kHz)下，死亡率则降至78%,均声压强度为0.9 W/m²。此外，暴露时间和距离对蚊卵的死亡率也有显著影响。从几何模型上可以看出，暴露在28 kHz下的蚊卵承受的声压(2 379 Pa)远大于暴露在68 kHz下的声压(422 Pa);但是频率越高，传播距离越大。超声波辐射的振动效应可能是导致蚊卵死亡的主要因素。研究发现，超声波作为一种有效的处理方法，对于预防自来水厂沉淀池蚊卵孽生具有较大潜力。     

超声空化清洗机理的研究

从理论上分析空化泡的形成与发展,并在研究与分析空化泡破裂时压力的基础上,分析空化与超声空化的清洗与冲蚀机理,阐明超声空化清洗的优越性,并对超声空化清洗的研究中需要考虑的因素进行了分析与探讨.     

水轮发电机功率摆动的分析和处理

某机组在偏离最优工况运行时,进入尾水管的水流夹带着空化气泡在离心力的作用下形成同水流共同旋进的尾水涡带,并在周期性非平衡因素的影响下产生偏心。尾水管压力脉动频率和发电机在电网中的自然振荡频率相近引起输出功率剧烈摆动。采用CFD分析确定尾水管内安装导流板方案以及有限元方法分析导流板的刚强度,最终圆满处理功率摆动问题。     

NACA 66_2-415水翼空化梢涡几何特征及涡唱频率分析

在一定的流动条件下,螺旋桨和水翼梢涡空化会伴随着涡唱现象。为了探究涡唱现象的产生机理与梢涡几何特征的关系,该文通过对NACA 66_2-415水翼空化梢涡高速摄像图像的定量处理分析,获得了涡唱发生前后空化梢涡的几何形态特征。发现未发生涡唱梢涡空化区域的形态不随时间而发生变化,呈现稳定的双螺旋形态;而涡唱产生时,梢涡空化区域在双螺旋结构基础上伴随一定频率的径向膨胀和收缩。通过高速摄像图像处理得到的空化梢涡振动频率、梢涡空化色散关系得到的理论拍振频率和圆柱泡本征频率与涡唱噪声频率之间的对比分析,发现梢涡径向振动频率与涡唱频率接近,表明空化梢涡径向膨胀收缩是涡唱产生的直接原因。     

Modelling of sonochemical processes in water treatment.

The mechanisms and kinetics of the sonochemical degradation of organic molecules in water are relatively complex since several parameters such as physicochemical properties, substrate concentration, water matrix, reactor geometry, ultrasound properties (frequency, power, emission system) all typically affect the process. In this work, simple kinetic models were used to predict the degradation of 2-chlorophenol and sodium dodecylbenzene sulphonate in aqueous solutions and verified against experimental data taken from previous studies. A pseudo-first order kinetic expression can adequately describe the degradation of the phenolic substrate, while a heterogeneous model based on the Langmuir-Hinshelwood equation is suitable for the surfactant degradation.     

Intensification of sonochemical degradation of phenol using additives at pilot scale operation

The present work reports the use of sonochemical reactors for the degradation of phenol in the presence of additives with an objective of enhancing the rates of degradation at a pilot scale operation. Process intensification studies have been carried out using additives such as hydrogen peroxide (H2O2) (0.5-2.0 g/L), sodium chloride (0.5-1.5 g/L) and solid particles viz. cupric oxide (CuO) and titanium dioxide (TiO2) (0.5-2.5 g/L). Optimum concentration for H2O2 and sodium chloride has been observed beyond which no beneficial effects are obtained even with additional loadings. Maximum extent of degradation has been observed by using ultrasound/H2O2/CuO approach at a solid loading of 1.5 g/L followed by ultrasound/H2O2/TiO2 approach at a loading of 2.0 g/L. The obtained results at pilot scale operation in the current work are very important especially due to the fact that the majority of earlier studies are at laboratory scale which cannot provide the design related information for large scale operation as required scale up ratios are quite high adding a degree of uncertainty in the design. The novelty of the present work lies in the fact that it highlights successful application of sonochemical reactors for wastewater treatment at pilot scale operation.     

Frequency effect on p-nitrophenol degradation under conditions of strict acoustic and electric control

The process of decomposing p-nitrophenol (PNP) with power ultrasound requires strict control of acoustic and electric conditions. In this study, the conditions, including acoustic power and acoustic intensity, but not ultrasonic frequency, were controlled strictly at constant levels. The absorbency and the COD concentrations of the samples were measured in order to show the variation of the sample concentration. The results show significant differences in the trend of the solution degradation rate as acoustic power increases after the PNP solution (with a concentration of 114 mg/L and a pH value of 5.4) is irradiated for 60 min with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1130.0 kHz. The degradation rate of the solution increases with time and acoustic power (acoustic intensity). On the other hand, the degradation rate of the solution is distinctly dependent on frequency when the acoustic power and intensity are strictly controlled and maintained at constant levels. The degradation rate of the PNP solution declines with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1130.0 kHz;the COD concentration, on the contrary, increase.     

Progress in numerical simulation of cavitating water jets

This paper reviews recent progress made toward modeling of cavitation and numerical simulation of cavitating water jets. Properties of existing cavitation models are discussed and a compressible mixture flow method for the numerical simulation of highspeed water jets accompanied by intensive cavitation is introduced. Two-phase fluids media of cavitating flow are treated as a homogeneous bubbly mixture and the mean flow is computed by solving Reynolds-Averaged Navier-Stokes (RANS) equations for compressible fluid. The intensity of cavitation is evaluated by the gas volume fraction, which is governed by the compressibility of bubble-liquid mixture corresponding to the status of mean flow field. Numerical results of cavitating water jet issuing from an orifice nozzle are presented and its applicability to intensively cavitating jets is demonstrated. However, the effect of impact pressure caused by collapsing of bubbles is neglected, and effectively coupling of the present compressible mixture flow method with the dynamics of bubbles remains to be a challenge.     

空化噪声量测结构的声学性能研究

本文从理论上分析了在水流空化声测研究中空化噪声量测结构的声学性能。提出了判断空化噪声传声窗声学性能的两个条件,第一,工作液体和传声窗特性阻抗匹配条件:ρ_1C_1=ρ_2C_2;第二,空化噪声谱频域的最大频率f_(max)(或最小波长λ_(min))条件:f_(max)≤C/(60D)(或λ_(min)/D≥60)。若传声窗满足其中任一条件,就可以获得较好的声测效果。同时,对此结果进行了试验验证,试验结果和理论分析结果吻合很好。 根据这两个条件,本文对目前常规使用的有机玻璃传声窗的声学性能进行了分析。结果表明:对于清水空化的声测研究而言,其阻抗比r_(21)=2.18,不满足ρ_1C_1=ρ_2C_2条件,而且实际空化噪声谱频域很难满足f_(max)≤V/(60D)条件。因此,有机玻璃材料传声窗的传声效果并不理想,其声学性能不如聚乙烯材料更好。     

INFLUENCE OF OCEAN INTERNAL WAVE ON PROPAGATION OF UNDERWATER RADIATION NOISE

The underwater acoustic field influenced by a selected ocean internal wave was computed using the Parabolic Equation (PE) method and split-step difference algorithm in this paper. Acoustic field is formed by sound source with different frequency covering the range of radiation noise of ships and submarines. Owing to the adoption of complex variables,sparse matrix, Gaussian source and analysis on the grid size.numerical results are achieved smoothly. The results show that internal wave‘s influence on underwater sound can‘t be neglected, especially for higher sound frequency. So it‘s necessary to take internal wave into account in identifying radiation noise of ships and submarines, namely for sound intensity, transmission loss and spectra shape.     

超声强化臭氧降解高浓度苯酚废水研究

超声及其组合技术对有机物废水降解是一种新兴的污水处理技术,有着广阔的发展前景和应用市场.对超声强声动力强化臭氧降解高浓度苯酚废水过程中的臭氧通气量、溶液的pH值、反应时间及溶液的初始浓度进行了实验研究,并对单一臭氧和超声强化臭氧降解效果进行了比较.结果表明:由于超声独特的物理、化学效应为臭氧降解提供了极端的物理、化学环境,二者协同作用使得反应进行彻底,COD去除率可达100%.     

超声协同Fenton法与类Fenton法预处理莠去津农药废水研究

针对莠去津农药废水有机物浓度高、含盐量高、有机物难降解等问题,提出了辅以超声协同的Fenton和类Fenton技术进行废水的预处理研究。分别研究了中性条件和酸性条件下,超声协同的Fenton以及类Fenton技术对废水有机物的去除率,并对比单独超声、Fenton以及类Fenton技术。结果表明:辅以超声作用后,TOC去除效果优于单独Fenton和类Fenton技术;针对超声Fenton和超声类Fenton协同技术,相比于中性条件下,酸性条件下能得到更高的TOC去除率,并且超声Fenton技术优于超声类Fenton技术,最高TOC去除率达到48.5%。因此,酸性条件下的超声辅助的芬顿法可作为莠去津农药废水的预处理方法。     

Soundpeaking – Hydropeaking induced changes in river soundscapes

Underwater soundscapes and their unique acoustic signatures are mainly generated through movement of streambed sediment, subsequent particle collisions, and turbulence created by water flowing over submerged obstructions such as rocks and woody debris. This study characterized river soundscapes in Alpine rivers of Trentino, (North East Italy) with the combined use of hydrophones and a new microelectricalmechanical systems based device (Hydroflown) that is capable of measuring particle velocity components of the sound field. Pool and riffle habitats affected and unaffected by hydropeaking were characterized in terms of their particle velocity and sound pressure levels across 10 octave bands (acoustic signature) to assess temporal variations in overall sound levels, changes in frequency composition, and relationship to hydromorphological habitat parameters. Data revealed that soundscapes affected by hydropeaking are highly homogenized, and sound pressure levels are strongly correlated with turbine discharge, which results in rapid, multiple‐fold spikes in low frequency amplitude levels within the typical hearing range of common teleost fish species. The outcomes of this study provide the basis for further examination of the resulting behavioural and physiological responses of organisms to anthropogenic changes in river soundscapes.