Some methods of establishing a new optimal shape of the shell for an energy concentrator system

摘要

The present work, setting its target on drawing up some methods of establishing a new optimal shape of energy concentrator, contains original contributions which can be rendered as follows: a) optimizing the shape of the shell for one type of energy concentrator system; b) finding a new profilled shell with a symmetrical profile or an assymmetrical one, in specific hypothesys for direction of flow, movement of profile on the variable surfaces; c) calculus and experimental analyses for profiled shells. The original methods developed may extended to the study of the bulb-shape or for the shape bulb-shell system, to the study of boundary layer in different types of flows for an energy concentrating systems. The fluid is incompressible, in permanent axial-symmetrical movement. The calculus of boundary layer on the profiled shells are starting with E.Boltze's equations with boundary conditions, and became the Prandtl's equations with the same boundary conditions. For better approximation of the flow's border, the boundary was considered as a sum of plane slabs of small dimensions. For each of this was calculated: Re number, the thickness of boundary layer, a tangent tension at the wall, a medium tangent tension on axial direction and a friction resistence. The obtained values for boundary layer and tangent tension from the calculus program are representative of the shels with symmetrical or asymmetrical profiles. The method used was F.E.M.. There are analized and calculated friction resistence for five types of shells with symmetrical profile and five types with asymmetrical profile, in the hypothessis of a constant velocity in the minimal section for variable angle of inclination (from -2.513~0 to +8.37~0) , depending on the length of the boundary. The best obtained values where for profiled shell NACA 4418 (-1.31~0) and NACA 0021 (+4.894~0).