Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled an...Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.展开更多
Many research results have revealed that vaporization pressure has important effects on the formation of the keyhole and molten pool during laser welding. In this paper, based on law of conservation of energy, an inno...Many research results have revealed that vaporization pressure has important effects on the formation of the keyhole and molten pool during laser welding. In this paper, based on law of conservation of energy, an innovative physical model is found to calculate the vaporization pressure during laser welding. In this model, vaporization pressure can be calculated according to some characteristics of the spatter particle. These features include the size, velocity and displacement. They can be measured through images taken by high-speed camera. The periods of this pressure also measured by counting opening and closing time of the bottom keyholes. At this welding condition, the typical vaporization pressure is about 20 203 Pa and the period is about 6. 9 ms. The average opening time of bottom keyholes is about 4. 3 ms, and the closing time is about 2. 6 ms.展开更多
文摘Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.
文摘Many research results have revealed that vaporization pressure has important effects on the formation of the keyhole and molten pool during laser welding. In this paper, based on law of conservation of energy, an innovative physical model is found to calculate the vaporization pressure during laser welding. In this model, vaporization pressure can be calculated according to some characteristics of the spatter particle. These features include the size, velocity and displacement. They can be measured through images taken by high-speed camera. The periods of this pressure also measured by counting opening and closing time of the bottom keyholes. At this welding condition, the typical vaporization pressure is about 20 203 Pa and the period is about 6. 9 ms. The average opening time of bottom keyholes is about 4. 3 ms, and the closing time is about 2. 6 ms.
