Detailed comments on governing equations and boundary conditions on which numerical results of gas flow in porous media should rely are presented. Numerical results are shown for the gas flow through a large blast furnace with designed layered structure of burdens. Not only the effects of radial and vertical distributions of resistance to flow but also the effects of different top profiles of burden, such as V-, M-shapes and V-shape with a side terrace, on the resultant gas flow are discussed in relation to the properties of burden, such as repose angle, particle size, voidage and different charging sequence. For the gas flow in a coaxial annulus bed, which is expected to appear in the lower part of blast furnace during a start-up or a blow-out operation, numerical predictions are compared with analytical ones based on a simple yet convenient gas flow model.

Ahstract-A 5 MWp PV solar power station will be installed in a remote area of China. This new system may contribute to addressing the area's serious electricity shortage, while also minimizing damage to the environment. The PV station consists of photovoltaic generation system and battery energy storage system, which combine with the existing small-hydro facility to form an autonomous hybrid generation system. In this system, the small-hydro works in V/f control mode, the PV and battery storage systems work in P/Q control mode to make full use of solar energy and reduce the amount of water and diesel used. In this paper we analyze and evaluate the stability of the hybrid system using a PSCAD simulation. Reasonable measures and recommendations are proposed based on these results.