A study on the effects of wall contact angle makes it more flexible to predict and control the size of droplets generated in step emulsification.

Sufficient pulsation is important for physiologic perfusion if adequate flow is to be guaranteed. A fuzzy control method for rotary blood pumps using active speed modulation is proposed in this article. It maintains the mean aortic pressure to provide sufficient perfusion while it simultaneously enhances the pulse pressure. The controller uses the indices extracted from the aortic pressure as feedback to determine the amplitude and offset of the rectangular speed modulation waveform, which is synchronous with the cardiac cycle. An additional algorithm is included to prevent regurgitation. The controller is tested both in a baroreflex-cardiovascular model and in a preliminary in vitro experiment. Simulation results demonstrate that the controller is able to increase the pulse pressure to approximately 20 mm Hg and at the same time maintains the mean pressure at 100 mm Hg, when heart failure occurs. It is also quite robust under various physiologic disturbances. Experimental results show that the speed modulation can be implemented in real pumps and that the controller is feasible in practice.

Cavitation of centrifugal blood pump is a serious problem accompany with the blocking failure of short inlet cannula. However, hardly any work has been seen in published literature on this complex cavitation phenomenon caused by the coupling effect of inlet cannula blocking and pumps suction. Even for cavitation studies on ordinary centrifugal pumps, similar researches on this issue are rare. In this paper, the roles of throttling, rotation speed and fluid viscosity on bubble inception and intensity in a centrifugal blood pump are studied, on the basis of experimental observations. An adjustable throttle valve installed just upstream blood pump inlet is used to simulate the throttling effect of the narrowed inlet cannula. The rotation speed is adjusted from 2 600 r/min to 3 200 r/min. Glycerin water solutions are used to investigate the influences of kinetic viscosity. Bubbles are recorded with a high-speed video camera. Direct observation shows that different from cavitation in industrial centrifugal pumps, gas nuclei appears at the nearby of vane leading edges while throttling is light, then moves upstream to the joint position of inlet pipe and pump with the closing of the valve. It’s found that the critical inlet pressure, obtained when bubbles are first observed, decreases linearly with viscosity and the slope is independent with rotation speeds; the critical inlet pressure and the inlet extreme pressure which is obtained when the throttle valve is nearly closed, fall linearly with rotation speed respectively and the relative pressure between them is independent with rotation speed and fluid viscosity. This paper studies experimentally on cavitation in centrifugal blood pump that caused by the failure of assembled short inlet cannula, which may beneficial the design of centrifugal blood pump with inlet cannula.

目 的 固化变形问题是纤维增强复合材料结构件固化成形及应用过程中的一大阻碍。本文旨在综述引起 固化变形的原因和机理, 归纳和评价固化变形的 控制方法, 以及指出目前存在的问题与不足。

Gate valves, which are widely applied in pneumatic conveying systems, are vulnerable to erosion by particles. It is thus important to investigate the erosion in gate valves from the perspective of fluid analysis, and then to predict and improve their lifetimes. The effects of valve geometry and gas–solid flow conditions on valve erosion are investigated. Since a gate valve usually operates fully open to let fluid pass through, the geometry is simplified as a cavity. As gate valves are always placed horizontally in industrial situations, investigated cavities are placed horizontally, and the erosion damage to the bottom half of the aft wall (surface T), which is most likely to be eroded, is studied. A computational fluid dynamics (CFD) based two-way Eulerian–Lagrangian procedue is used to predict the erosion severity. The simulation procedure is validated by comparing the CFD results with those obtained from experiments of a pipe and an elbow, and also with the erosion region of a damaged valve. For convenience, the total erosion ratio, defined as the ratio of the mass eroded on a particular surface to the total particle mass passing through the pipe inlet during the same time, is introduced. The results show that the total erosion ratio of surface T is largely independent of the mass flux ratio, pipe diameter and cavity depth. Meanwhile, the total erosion ratio increases with cavity width and particle diameter, while it decreases with inlet velocity. According to the fitted results, a simple erosion formula is proposed and validated by the CFD results in another 16 orthogonal experiments. Furthermore, the formula is improved for various values of Brinell hardness of carbon steel and sharpness factors of particles.