共查询到19条相似文献,搜索用时 468 毫秒
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提出了一种将外加气体与液压油结合起来的气液耦合激振方式,通过控制气脉冲与液压油形成的空化泡发生生长和破灭,从而产生空化作用对液压系统内部污染物进行分散与剥离;开发了以气液耦合波动为激振方式的气液激振试验系统,建立了波动发生器作用下的气泡运动学方程;数值模拟了波动发生器与超声波作用下空化泡的运动学过程,并进行了对比分析,发现低频的波动发生器作为激振源使气泡产生的空化作用是显著的,为气液耦合激振作用下气泡空化过程的可控性研究提供了部分理论依据。 相似文献
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基于水力空化相关原理和壅塞管的特性,对壅塞管空化器空化流场特性进行数值模拟研究,确认影响空化器空化效果的因素。通过研究确认,入口压力与入口直径对壅塞管空化器的空化强度有决定性影响。入口压力增大,空化器内压力梯度增大,表明入口压力越大,壅塞管空化器空化效果越好。入口直径增大,壅塞管内最大含气率升高,可在更大范围水体内产生空化泡,进而加强空化效果。在壅塞管空化器内产生比较均匀的气液混合两相流时,沿轴心线方向,从壅塞管中部位置至壅塞截面位置,气液两相流动的马赫数缓慢增大,在压力梯度到达极值时马赫数达到最大,为0.97,接近于1。 相似文献
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利用气液两相作用力和自激振荡效应产生的脉冲压力能够有效提高喷嘴雾化效果。基于气液二相流原理和自激振荡脉冲射流发生机理,将气液二相流原理和自激振荡雾化效应相结合,创新性地提出了气液同轴自激振荡式喷雾方式,设计出了气液同轴自激振荡式雾化喷嘴模型,并分析了新型喷嘴的射流脉动效果和雾化性能。研究结果表明:增加气液同轴后自激振荡雾化喷嘴内部的能量聚集与释放相比以前更加稳定;在相同条件下,相比原始自激振荡雾化喷嘴,气液同轴自激振荡雾化喷嘴出口轴线上速度脉动增长大约13.9%~31%,出口平均速度峰值提高了约24.3%,流场内部气相体积分数增长约23%~30%;气液同轴自激振荡雾化喷嘴内空化现象明显,流场内的紊流和扰动剧烈,具有良好的雾化性能。 相似文献
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针对气液固三相磨粒流抛光研究中流场分布不均问题,对气液固三相磨粒流中的湍流分布、湍流峰值分布、能量分布、温度分布和加工质量等方面进行了研究,对气液固三相磨粒流的抛光方法和抛光问题进行了归纳,提出了一种耦合超声场的气液固三相磨粒多物理场数值模拟方法,利用超声场的交变声压增加了气液固三相磨粒流流场的扰动,改变了流场分布。研究结果表明:不同的超声频率和声压幅值会带来不同的流场分布,其中频率为20 k Hz、声压幅值为30 k Pa的超声场所得的流场分布最优。该研究成果对气液固三相磨粒流抛光方法的推广与实际运用具有重要意义。 相似文献
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润滑膜的空化效应对流体动压型机械密封的密封性能影响显著。以煤油基磁流体润滑斜线槽上游泵送机械密封为研究对象,考虑空化热效应以及黏温效应,建立润滑液膜特性的数值分析模型,以液膜中的气相体积分数为指标,研究工况和结构参数对密封性能的影响规律,并与仅考虑黏温效应的模型进行对比。结果表明:因空化热模型考虑液膜介质饱和蒸汽压力随温度变化,考虑空化热效应时的开启力、泄漏率和气相体积分数均小于仅考虑黏温效应下的对应值,但2种条件下各参数的变化趋势基本一致;转速和槽径比增大,空化效应增强,而进口压力、膜厚、径向夹角和槽数的增大会削弱空化效应;转速、槽深、径向夹角、槽径比增加,会导致泄漏率增加,而进口压力和槽数的增加能够提升密封性能。 相似文献
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Even though most published results detailing damper behavior consider only the liquid phase, the cavitation process in the lubricant film, when it happens, is critical for the damper's performance. A number of modeling approaches, such as the half-Sommerfeld and Elrod models, were proposed in order to account for the effects of cavitation on the pressure generation, without directly simulating the cavitation process. Based on the experimental data, a few other homogeneous cavitation models have also been developed. All these models are based on the classical Reynolds equation. In this article, a three-dimensional numerical model is developed and validated in connection with the operation of a two-phase squeeze-film damper. The full Navier-Stokes equations (NSE), coupled with a homogeneous cavitation model, is solved to simulate the flow of the two-phase lubricant film and the associated pressures. The pressure variation on the journal surface and the gas concentration distribution in the lubricating fluid (cavitated region) will be presented. The damping coefficients predicted by the NSE model are compared to the ones that resulted from the application of the Reynolds equation. 相似文献
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Cavitation phenomenon is commonly known as a cause of deterioration of hydraulic components and a source of noise. In a proportional spool control valve for fluid power applications, the reduction of the cross section area at small openings can lead to the growth of gas bubbles inside the fluid phase. This phenomenon modifies the operating efficiency of the valve and can damage the material over time. The oil flow has been visualised through an experimental activity by using a 2-way 2-position spool valve with a plexiglass case and analysed by a CMOS type camera, with a high sampling rate. The recorded images focus the interaction between gas and liquid phases and highlights how the shape of cavitation bubbles is modified when the surface stress increases. In the present work, the interaction between liquid and gas phase has been studied by applying a non-linear method on the numerical matrices, derived from the acquired images. A cavitation instability index has been proposed, which is able to describe the cavitation behaviour and to define the instability of the equilibrium between the two phases. The trend of this index gives information about the two phase flow conditions, in order to reduce the cavitation phenomenon. 相似文献
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随着动压型非接触式机械密封应用领域的扩展和运行工况的复杂化,液膜相变成为影响其工作稳定性和可靠性的关键因素之一。针对端面液膜汽化和液膜空化2种相变类型,分析汽化和空化现象的产生机制,介绍常见的几类相变模型,如Thermal Lattice Boltzmann模型和Zwart-Gerber-Belanri模型等,综述端面型槽结构参数和工况参数对液膜相变程度影响规律的研究进展。指出在相变影响的研究方面,目前的研究主要集中在单因素对槽结构参数或工况参数的影响上,而对多因素综合影响的研究还不够深入。提出液膜相变问题未来可能的发展方向:汽化与空化综合作用理论计算模型的创新、极端工况下液膜相变与密封稳定性的关联、相变监测技术的突破。 相似文献
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C. K. Toh 《The International Journal of Advanced Manufacturing Technology》2007,31(7-8):688-693
Advances in machining technology, particularly in the field of micro-machining, have led to the design and creation of miniature
components suitable for use in the precision engineering industry. However, the need to contain ubiquitous burrs still exists
and has to be addressed. Previous studies on deburring have mostly focused on the parametric investigations of orientation,
temperature, type of liquid media and abrasives, frequency, deburring time and power. It is hypothesized that by inducing
compressive residual stresses on a pre-machined workpiece surface, the resulting burrs caused by machining can be minimized
or even eliminated. The paper presents the findings of an investigative study into the possibility of inducing compressive
residual stresses on machined surfaces by the use of ultrasonic cavitation, with the aim of reducing or eliminating burr formation.
The paper also briefly reviews the development of ultrasonic cavitation and covers published work on deburring by ultrasonic
cavitation. Experimental results are presented on the performance of ultrasonic cavitation peening on the residual stress
in Stavax stainless steels and on micro-burr formation. 相似文献