Effect of magnetic lens on the electrospinning whipping instability, fiber diameter and its distribution

Electrospinning is an efficient and straightforward method for producing thin fibers from various materials. Although such thin fibers have diverse potential applications, the remaining problems with electrospinning are the whipping instability (also known as bending instability) of electrically charged liquid jets of polymer nanofibers and uneven fiber diameter distribution. In this study, we report a novel magnetic lens electrospinning system and discuss the principle of reducing the fiber diameter and width of the whipping circle in this electrospinning process. The effects of three types of electrospinning devices, needle-to-plate, needle-exciting coil-to-plate, and needle-magnetic lens-to-plate types, were studied through numerical simulation to analyze the electrospinning fiber collection state. For the 12 wt% polyacrylonitrile solution, when the applied voltage was 14–20 kV, the feed rate was 0.4–0.7 ml/h, and the current applied to the excitation coil or magnetic lens was 1 A, the experimental results demonstrated that, compared with needle-to-plate-type and needle-exciting coil-to-plate-type electrospinning, needle-magnetic lens-to-plate-type electrospinning produced smaller whipping circles with thinner and more uniform fibers.

Determination of Boussinesq and Coriolis coefficients for pipelines operating with discharge connection along the path

Peculiarities of the diagrams of averaged fluid velocities in the cross-sections of pressure collecting perforated pipelines were determined on the basis of the experimental studies conducted by the authors. The most characteristic typical diagrams of averaged velocities in the pipelines cross-sections with their different design characteristics were given. A comparative analysis of the obtained diagrams with the diagrams of velocities that occur during uniform motion in pressure pipelines with solid walls was carried out. It is shown that the main difference between them occurs in the flow zones, which are located near the pipeline walls. It was explained by the connected liquid jets effect on the main flow. The degree of diagrams deformation was estimated by the value of the momentum coefficient α0 (Boussinesq coefficient) and the coefficient of kinetic energy α (Coriolis coefficient). It was determined that in the general case these coefficients will be variable in magnitude along the length of the studied pipes. Nevertheless, these coefficients are recommended to be constant in magnitude in engineering calculations. The limits of the structural characteristics of collecting perforated pipes for which this non-uniformity of the diagrams must be taken into account, and for which it can be neglected were determined on the basis of the analysis of the equation of fluid motion with a variable flow rate.