| The research makes sure that fluid flow may lose stability in rotary tubular micro-filtration membrane separators when inner cylinder rotates and outer cylinder rests. If rotational velocity reaches a certain critical value, fluid flow will lose its stability. And the result of that is to form Taylor vortexes. The Taylor vortexes are propitious to intensify membrane separation. In the same conditions, comparing experiment results of rotational velocity varying from low to high with experiment results of rotational velocity varying from high to low, the author finds the flow pattern in lower rotational velocity is got when rotational velocity is changed from high to low. So it is benefit to study how flow patterns influence on separation of the tubular membrane that rotational velocity is changed from high to low. Separated suspension produces different shearing forces on tubular membrane in the different patterns. And shearing forces break in transform of flow patterns. And the result of shearing force breaking is that rotational velocity changes. So there is rotational speed difference between the input electromagnetism field in the asynchronous electric motor and membrane tube which is directly drive by the motor, and the difference is used to take as a token for various flow patterns between tow cylinders during the experiment. If neither axial flow nor radial flow exist, the flow patterns can be separated into Couette laminar flow, laminar flow plus Taylor vortexes, laminar flow plus wavy vortex, laminar flow plus modulated waves, turbulent Taylor vortices and turbulence flow. Using the same method, the flow patterns can be separated into Couette laminar flow, laminar flow plus Taylor vortexes, turbulent flow plus Taylor vortexes and purely turbulent flow if axial flow exists and radial flow doesn't exist. And the same flow patterns appear in the annular gap if both axial flow and radial flow exist. Moreover, it is found that axial flow and radial flow both are in favor of stability of flow. The separated suspensions are SiO2 and CaCO3 in the experiment. And a dimensionless parameter N has been named by an enhancement coefficient J0N = J and is used to indicate separate capability of membrane tubes. The definition gets rid of that the different initial condition may affect separate capability of membrane tubes. Then the effect of different operation-pressure, concentration and flow patterns may produce for the enhancement coefficient is studied in the experiment, when the separated suspension is SiO2. The operation-pressure effect can be concluded as follows: At the same concentration, when rotational speed is much lower, the enhancement coefficient is close to each other and enhancing effect is similar at the different operation-pressure. With rotational speed increasing gradually to turbulent flow, the higher operation-pressure is, the bigger enhancing is, and the better enhancing effect is. And the higher operation-pressure is, the higher rotational velocity is in which separate effect gets to be best. Under the low operation-pressure, the curves of enhancement coefficient versus practical rotational speed are similar to a parabola. And under the high operation-pressures, they are similar to a part of exponential. The concentration effect can be concluded as follows: The higher the concentration is, the bigger the change of enhancement coefficient is, and the better the enhancing separate effect is. At the same operation-pressure there is always critical rotational velocity Vc, which is about 1300rpm. When rotational velocity is lower than Vc, N in different concentration changes little with rotational velocity increasing. However, when rotational velocity is higher than Vc, N in different concentration changes great with rotational velocity increasing. The flow patterns (rotational speed) effect can be concluded as following, during the laminar flow, N increases with rotational velocity rising, and N is close to each other in different operation-pressures. During the laminar flow plus Taylor, N goes on increasing withrotational velocity rising, but the rate is speeding up than during the laminar flow, and N is much different to each other in different operation-pressure. During the turbulent Taylor flow, N goes on to increase with rotational velocity rising, and a majority of peak value appears here if curves exist peak value in the author's experiment. During the turbulent flow, N begins to minish with rotational velocity rising if curves exist peak value in the author experiment, but N goes on to minish with rotational velocity rising if curves don't appear peak value in the author's experiment. Moreover, the higher the operation-pressure is, the bigger the enhancement coefficient is, and the better the enhancing separate effect is. Furthermore, some suggestion on optimizing operation conditions of separating SiO2 is put forward that if concentration is 0.025%, it is better that using operation-pressures of 0.065MPa and rotational speed over 1700rpm, which is benefit to increase enhancement coefficient to 1.4～1.6; and if concentration varies from 0.05% to 0.085%, it is better that using operation-pressures of 0.05MPa～0.07MPa and rotational speed over 1700rpm, which is benefit to increase enhancement coefficient to 2～6. At last, two mathematic models about N, operation-pressure, concentration and rotational velocity are set up in different conditions. Comparing the experiment result of separating CaCO3 with that of separating SiO2, the author got these conclusions: Rotary tubular membrane can separate granules of different size, and membrane tube rotating is propitious to separate, but selecting aperture of membrane tube is very important. The pores'size of membrane tube must be consistent with separated granules'size. If the aperture much smaller than separated granules'size, penetration flux is too low; but if the aperture bigger than separated granules'size, the purity of filtrate will be affected and rotation will be useless to improving separation.
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