The process of coating textiles with a blade coater has been investigated with CFD (Computational Fluid Dynamics) software. The simulations have uncovered a pressure drop in the area between the edge of the knife and the textile. This drop can be explained by the varying height of the flow channel which is made of the knife and the textile in conjunction with the no slip condition that is applied to the walls. In the simulations this drop became arbitrarily deep with increasing viscosity leading to negative absolute pressure levels. This may be a hint that the no slip condition is not valid in this scenario that involves shear rates of the order of 103/s and dynamic viscosities of around 10 to 100Pas. With a proposed slip condition for the textile the pressure drop became less pronounced. At the same time the flow rate through the gap between knife and textile was reduced leading to a thinner coating. This can be a hint that a slip between coating material and textile can cause distortions in the coating up to a complete disruption which is reported frequently by the industry. This could eventually be avoided by reducing the varying height of the flow channel. Alternatively a vertical lift of the textile due to the negative pressure was taken into account. This lift appeared only with low tensions of the textile of about 1N/m and showed no influence on coating thickness and pressure drop.
For the measurement of flow-induced microrotations in flows utilizing the depolarization of phosphorescence anisotropy, suitable luminophores are crucial. The present work examines dyes of the xanthene family, namely Rhodamine B, Eosin Y and Erythrosine B. Both in solution and incorporated in particles, the dyes are examined regarding their luminescent lifetimes and their quantum yield. In an oxygen-rich environment at room temperature, all dyes exhibit lifetimes in the sub-microsecond range and a low intensity signal, making them suitable for sensing fast rotations with sensitive acquisition systems.
Integration of wind power stations in primary control of the grid can be necessary in future. One solution to solve this problem is the emulation of a turbine and a generator such as in conventional power plants. The model is split into two parts: The grid-side inverter is controlled by a model of a separately excited synchronous machine with amortisseur in combination with torque and excitation voltage control. On the other side the physical generator is controlled by a virtual turbine that has to keep the voltage of the dc-link on a fixed level. The dc-link represents a virtual shaft between both models. Over droops the wind power station is now able to take part in primary control. Simulation includes all electrical parts of wind power station from wind wheel to grid supplying. Implementation of both models is shown and discussed with results of simulation.
Keywords-wind power station; virtual conventional power plant; synchronous machine, turbine; dc-link control; droop based control structure; primary controlI.
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