动载滑动轴承瞬态油膜的全景实验研究

在搭建的滑动轴承实验台上,对大扰动工况下油膜全景空穴分布图像及油膜压力进行瞬态同步采集,并对图像进行后处理,以便于观察并与基于质量守恒边界条件的理论仿真结果对比,并对同一旋转周期内油膜空穴分布和不同工况下油膜压力进行对比分析。结果表明：油膜全景图像经过后处理转化为油膜原形展开图像后,图像直观,且更易于对比分析;在大扰动工况下,油膜空穴区域随最大动偏心位置迁移而迁移。     

Control of sonoluminescence signal in deionized water using carbon dioxide

Megasonic cleaning is routinely employed in semiconductor industry for cleaning of wafers. However, the method also results in damage to wafer features and such damage has been proposed to arise from transient, imploding cavities formed during megasonic processing. Transient cavitation is associated with the release of light, a phenomenon called sonoluminescence (SL) and the extent of damage has been shown to correlate with the intensity of SL. Control of sonoluminescence may therefore allow control of damage during megasonic processing of wafers. In this study, the ability of carbon dioxide to quench sonoluminescence generation in deionized water exposed to megasonic field of varying power density and duty cycle has been systematically investigated. It has been found that CO₂ is not only incapable but also a potent inhibitor of sonoluminescence, providing a potential means for selective alleviation of the violent effects of transient cavitation in process fluids. A novel chemical method has been established for in situ release of CO₂ from NH₄HCO₃ through a pH induced shift in the carbonic acid equilibria in deionized water. Using this method, a precisely controlled, progressive decrease in SL of air saturated deionized water through addition of NH₄HCO₃ has been demonstrated. It has been determined that 130 ppm of released CO₂ is sufficient for complete inhibition of sonoluminescence generated in air saturated deionized water.     

泄水建筑物过流壁面不平整体初生空化与空蚀研究述评

泄水建筑物过流壁面不平整体初生空化与空蚀的研究进展，本文作了扼要的综述与评论。内容包括不平整度的定义及其初生空化与空蚀的理论分析、试验研究、比尺效应和理论预测，以及尚存在的问题。文中也包括了作者在上述工作中所作的研究和相应的看法。     

漫湾电站溢流表孔掺气减蚀的试验研究

漫湾水电站溢流表孔的掺气减蚀设施，通过不同比尺的模型试验研究，优化出以坎、槽组合型较好。根据试验成果分析，并结合施工现场实况，为设计推荐掺气设施的布置型式、位置、体型尺寸均为工程采用井已建成。从１９９４年汛期原型观测的成果表明：掺气浓度沿程分布、通气孔风速、进气量、空胶负压及气水比等项成果与模型试验规律基本一致，均满足规范要求。说明设计的掺气设施的体型、尺寸是合理的、有效的。     

紊动剪切流中气核振荡对空化的作用

为了解压力脉动对泡动力学和空化现象的作用，可将压力脉动的不同随机量与气核在流场中的动态响应联系一起进行分析。结果认为：在水流强烈的紊动下，由于压力脉动的影响，气核交替地膨胀和收缩，脉动负峰值可使瞬时压力降低。气核发育时间明显缩短，促使空化提前发生。     

超声强化过氧化氢-维生素C体系糖汁脱色的研究

研究超声强化过氧化氢-维生素C复合脱色剂体系对糖汁脱色的规律,考察了超声功率、复合脱色剂用量、超声温度和时间对糖汁脱色率的影响。试验结果表明:超声空化强化过氧化氢-维生素C对糖汁具有良好的脱色效果,当处理糖汁量为100 mL,超声功率为260 W,过氧化氢与维生素C的用量均为1.6 mL,空化温度为70℃,超声时间为6 min时,脱色率达到53.4%。通过正交试验分析,得到各个因素对糖汁脱色率影响的主次关系为:超声功率>复合脱色剂用量>超声时间>空化温度。     

基于滚筒摩擦和超声振荡的蚕丝含胶率测试方法研究

针对现有蚕丝含胶率测试方法所存在的缺陷,设计了蚕丝含胶率快速测试仪器,该仪器主要的脱胶机构为滚筒和超声振荡器,滚筒内壁呈凹凸状,上面均匀分布着小孔,在滚筒旋转过程中,蚕丝与滚筒内壁反复摩擦,加速丝胶与丝素的分离。利用超声波空化作用对蚕丝进行快速高效脱胶,最终使丝胶丝素彻底分离,进而测试蚕丝含胶率。经实践证明:测试仪器设计合理、结构简单,实验操作简便,测试结果准确、可靠,可以替代现有的蚕丝含胶率的测试仪器和方法,应用及推广价值高。     

An experimental study on the impact behavior of cavitation inside tip clearance of a hydrofoil

Tip clearance cavitation is one of the most common cavitation phenomena exist on duct propellers,pumps and some hydraulic turbines,which may lead to erosion of the components.Due to the influence of the nearby wall,cavitation inside the tip clearance is more complicated than other cases without interaction.So far,the understanding about the impact mechanism of tip clearance cavitation is still limited.In this paper,to obtain the impact behavior of tip clearance cavitation,a high-speed camera was used to capture the cavitation behavior inside the tip clearance of a hydrofoil,and surface paint coating peeling method was applied to show the impact region.Results indicated that cavitation around the tip of the hydrofoil was composed of a tip separation cavity and a tip leakage vortex cavity,and the one with contribution to impact was the tip separation cavity.Through the comprehensive analysis of the paint peeling region and dynamic behavior of tip separation cavity,the impact was found to be related to the local collapse and rebound of the cloud cavitation shed from the attached part.In addition,the influence of tip clearance size on the behavior of tip clearance cavitation was also investigated.As the tip clearance size increased,the tip separation cavity tended to transfer from sheet cavitation to vortex cavitation.These findings can provide a sound basis for evaluating the erosion risk arising from the tip clearance cavitation.