Study On The Dynamic Characteristics And Micro-Filtration Enhancement Mechanism In Rotary Tubular Membrane Separators

Rotary tubular micro-filtration membrane separators can be able to repress the effect from concentration-polarization and membrane fouling by the aid of Taylor vortex, but so far the study on its dynamic characteristics and micro-filtration enhancement mechanism is not only limited at qualitative stage, but also only research the separation performance effected by operation parameter and suspension properties. In this dissertation supported by the Doctorate Foundation of the Education Ministry of China (Grant No.2000061016), the micro-filtration enhancement mechanism is further ascertained through the study on its fundamental theory, dynamic characteristics and separation performance.During the study on its fundamental theory: first of all, the control equation of fluid-element deformation is induced under the coordinate system which has the same direction as the mean stresses of fluid-element based on the Stokes constitutive equation of Newtonian fluids. That the pulsation performance of fluid come from the inner of fluid is made clear by applied this equation to the plane Couette flow, which is the base of turbulent theory, and this equation can also account for why the Taylor vortex always appear in twins; this is a contribution to fluid mechanics. Secondly, the probability of the fluid to form the Taylor vortex between two co-axial cylinders is proved: the secondary flow is a spontaneous process when the inner cylinder is rotating; otherwise, the secondary flow is not a spontaneous process when the outer cylinder is rotating. And then, the necessity to form the Taylor vortex is also made clear by analyzing the structure of one group of Beltrami flow solution of the non-dimensional Navier-Stokes equation in inertial control area, where there is the heteroclinic orbit to circumscribe the secondary flow; this makes the generatingmechanism of Taylor vortex understood deeply. Finally, symmetrical disturbance with the structure that Taylor has assumed is always existence as a part of truncation-error in the process of computer simulating laminar Taylor vortex from the closed Navier-Stokes equations. If only the turbulent mode equations do not remove the development of disturbance cased by the nonlinearity of control equations, the turbulent Taylor vortex can also be simulated out successfully.During the study on its dynamic characteristics: first of all, that the tendency of the rotational speed difference between the electromagnetism field that is input in the asynchronous electric motor and the membrane tube which is directly drive by the motor varies with the rotation Taylor number is proposed out to take as a token for the various flow pattern, dynamic characteristics between the two cylinders; moreover combining the picture observed in process, the flow patterns with net axial flow can be made out into laminar helix flow, laminar random wavy vortex, turbulent wavy vortex, turbulent modulated vortex and turbulent random vortex; and the similar patterns can appear in the annular gap with net axial flow and permeate flow, but the flow regimes are different; by this way, the dynamic-characteristics difference between the processes from high speed to low speed gradually, from low speed to high speed gradually and from static state to given speed instantaneously is compared. Secondly, the relative error of velocity gradient on out-wall simulated from closed Navier-Stokes equations compared with the results from measurement is about 10% under laminar Taylor vortex state. Under turbulent Taylor vortex State, the relative error of axial velocity simulated from Reynolds stress mode (RSM) equations compared with the results from measurement is 28.7%, and the relative error of the azimuthal turbulence intensity is 5%. Finally, the flow-field panoramas of laminar Taylor vortex and turbulent Taylor vortex are quantitatively given out respectively according to the flow simulation; based on the flow field, the dynamic characteristics such as the pressure distribution, shear stress distribution, turbulence intensive distribution,...