A novel approach for determining the flow patterns in centrifuges by means of Laser-Doppler-Anemometry
A novel approach for determining the flow patterns in centrifuges by means of Laser-Doppler-Anemometry
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一种通过激光多普勒风速测定法确定离心机中流动模式的新方法
DOI：
10.1016/j.ces.2011.05.022
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发表时间：
2011
影响因子：
4.7
通讯作者：
H. Nirschl
中科院分区：
文献类型：
--
作者：
L. Spelter;J. Schirner;H. Nirschl
加工机械中的流动模式对产品质量具有重大影响，因为它影响停留时间、组分混合和化学反应的稳定性。因此，停留时间的确定和流动模式的测量一直是许多研究的重点。所提出的工作展示了一种确定管式转鼓离心机中切向和轴向速度分布的新方法。首次使用激光多普勒风速测量法测量快速旋转离心机内的流速。离心机转子采用碳纤维增强塑料制成，内径100mm，长度200mm。最大转速为20,000rpm，产生地球引力22,400倍的倍数。在任何工艺参数下均未检测到材料失效。离心机通过两种不同的设置进行操作。一种装置采用两个同轴圆柱体的组件，其中它们之间的空隙完全充满水。在第二种布置中，仅组装外转子并且离心机像溢流离心机一样操作。通过确定各种参数下的停留时间分布来确认轴向流体速度的激光多普勒测量。获得的结果显示了有效的切向加速度；该液体表现出刚体旋转，转速高达 8000rpm，吞吐量在 0.5 至 1.8l/min 之间。轴流模式取决于体积通量和转速。大多数情况下，液体流过的横截面占总面积的 60% 至 100%。入口的影响向出口方向减弱，入口区域占转子长度的 15%。在溢流装置中未检测到边界层流，这是由于插入式入口和进入液体的有效切向加速度所致。
The flow pattern in process machinery has a significant impact on the product quality, because it influences the residence time, the mixing of components and the stability of chemical reactions. Hence the determination of the residence time and the measurement of the flow patterns have been the emphasis of many studies. The work presented shows a novel approach for the determination of the tangential and axial velocity profiles in a tubular bowl centrifuge. For the first time, flow velocities inside a fast rotating centrifuge have been measured using Laser-Doppler-Anemometry. The rotor of the centrifuge is made of carbon fibre reinforced plastic with an inner diameter of 100mm and a length of 200mm. The maximum rotational speed is 20,000rpm, creating the multiple of 22,400 times the earth gravitational force. No failure of the material was detected at any process parameters. The centrifuge is operated with two different setups. One setup employs an assembly of two coaxial cylinders, in which the void between them is entirely filled with water. In the second arrangement, only the outer rotor is assembled and the centrifuge is operated like an overflow centrifuge. The Laser-Doppler measurements of the axial fluid velocity are confirmed by determining the residence time distribution at various parameters. The results obtained show an effective tangential acceleration; the liquid exhibits a rigid body rotation for rotational speeds up to 8000rpm for throughputs between 0.5 and 1.8l/min. The axial flow pattern depend on the volume flux and the rotational speed. The cross-section through which the liquid flows was in most cases between 60% and 100% of the overall area. The influence of the inlet subsides towards the outlet with an inlet zone of 15% of the length of the rotor. No boundary layer flow was detected in the overflow setup, which is due to the plunged inlet and the effective tangential acceleration of the incoming liquid.