Papers by Keyword: Impurities

Abstract: For the question of difficult to control discharge process between the electrodes in WEDM, Systematic analysis of the relationship breakdown and the distance between poles、the relationship of the breakdown voltage and pulse duration、the relationship breakdown and impurity、the relationship breakdown and the temperature、Summed up the WEDM in the general laws of the electrode gap breakdown、So as to better control of WEDM process in the very room provides a theoretical basis for discharge.

Abstract: Direct Methanol Fuel Cells (DMFC) are an attractive power source for applications in the low kW-range like pallet trucks or uninterruptable power supplies. A significant problem during the past years, however, was the limited durability of DMFC systems. While single cells could be operated for thousands of hours, DMFC systems degraded significantly often within less than 1,000 hours.In an evolution of six generations of DMFC systems in the kW power range over the past decade, we identified the main reasons for degradation. Causes for fast degradation had to be removed first in order to identify what leads to slower degradation over several hundreds or thousands of hours. Interactions of cells and system components also had to be considered.As a result, the operating conditions of all cells must be carefully controlled by suitable operating algorithms and reproducible manufacturing technologies, in order to avoid high potentials on the anode, which would lead to ruthenium corrosion and subsequent poisoning of the cathode catalyst. All components of the stack and the peripheral system must be corrosion-proof and free from contaminants that might leach into the membranes. Finally, a DMFC system for a pallet truck was operated in a realistic load cycle for 20,000 hours.

Abstract: Fluids in the heat-supply pipelines have a small amount of impurities. Impurities can easily settle down on the ultrasonic heat meters’ reflecting faces. It caused measurement inaccuracy. Vortex generator is placed in ultrasonic heat meter in this paper, which can generate vortex in the reflect fields. Vortex toke away impurities on the bottom of heat meter. Reflecting surface keeps clean. A v-shaped ultrasonic heat meter is taken for example. Numerical study of the flow field near the Reflecting surface vortex generator is carried out. Results show certain strength of vortex is caused in the reflective surface, while other palaces influenced little.