Numerical Study on Flow Length in Injection Molding Process with High-Speed Injection Molding
Pham Son Minh,
Tran Minh The Uyen
Issue:
Volume 2, Issue 5, October 2014
Pages:
58-63
Received:
1 October 2014
Accepted:
16 October 2014
Published:
30 October 2014
Abstract: In thin-wall injection molding, due to the very fast polymer melt heat transfer to the mold wall, the freeze layer appears quickly during the filling stage. In this study, high-speed injection molding (up to 1400 mm/s injection speed) was studied. A mold of spiral shape, 0.4 mm thick, is used to verify the ability of melt filling under different injection speeds. Simulation by Moldflow software was also performed for verification. The result shows that when injection speeds vary for 100 mm/s, 500 mm/s, 1000 mm/s, and 1400 mm/s, the flow length to thickness ratio was increased with the value of 335, 467.5, 605, and 640, respectively. The simulation results also show that the heat transfer coefficient between hot melt and mold wall has a strong influence on the flow length, especially with the high-speed injection molding. In general, slower injection speed requires a higher heat transfer coefficient, whereas higher injection speed require only a lower heat transfer coefficient.
Abstract: In thin-wall injection molding, due to the very fast polymer melt heat transfer to the mold wall, the freeze layer appears quickly during the filling stage. In this study, high-speed injection molding (up to 1400 mm/s injection speed) was studied. A mold of spiral shape, 0.4 mm thick, is used to verify the ability of melt filling under different in...
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Heat Release Rate in a Reduced-Scale Model of a Subway Car on Fire
Issue:
Volume 2, Issue 5, October 2014
Pages:
64-69
Received:
30 July 2014
Accepted:
28 October 2014
Published:
30 October 2014
Abstract: The heat release rate of a subway car on fire is measured for various positions of an ignition source and simulated materials differing in combustibility by using a reduced-scale model. Although the maximum HRR value is nearly independent of the position of the ignition source, the time required to reach this value varies greatly for different ignition positions. The open area of a subway car is a key factor that determines the maximum HRR value, although material combustibility also has an effect. Finally, the HRR curve is compared with that of a fire test in a real-scale subway car.
Abstract: The heat release rate of a subway car on fire is measured for various positions of an ignition source and simulated materials differing in combustibility by using a reduced-scale model. Although the maximum HRR value is nearly independent of the position of the ignition source, the time required to reach this value varies greatly for different igni...
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Experimental Study by Visualisation of Behavioural Properties of Vortex Structures on the Upper Surface of an Ogive of Revolution ß 52°
Issue:
Volume 2, Issue 5, October 2014
Pages:
70-77
Received:
20 October 2014
Accepted:
3 November 2014
Published:
10 November 2014
Abstract: A large number of studies of flow visualisations, developed on the upper surface of delta or gothic wings and on that of ogives of revolution, have been carried out in the wind tunnel of the Valenciennes University aerodynamics and hydrodynamics laboratory (LAH). These studies have provided a better understanding of the development and the positioning of vortex structures and have enabled, in particular, the preferential nature of intervortex angles, thereby defined, to be determined on a wide range of Reynolds. This paper concerns in particular the study by visualisations of the behavioural properties on the upper surface of an ogive of revolution having an apex angle of 68.6° at a low angle of attack and conducted at variable speeds. It has been noted that variations in speed have no influence at all on the behavioural properties of the development of vortex structures whereas, by contrast, changes to the angles of incidence do indeed strongly influence that development. The study of the ascent of the vortex breakdown at high angles of attack has revealed original behavioural properties which find expression notably in the discontinuous evolution, in terms of the apex angle, of those angles of attack which define the beginning and the end of the ascent of this vortex breakdown. These properties undoubtedly reflect those already observed in similar studies carried out on delta and gothic wings and on cones. However, no current theory seems to be able to provide a straightforward explanation of these phenomena.
Abstract: A large number of studies of flow visualisations, developed on the upper surface of delta or gothic wings and on that of ogives of revolution, have been carried out in the wind tunnel of the Valenciennes University aerodynamics and hydrodynamics laboratory (LAH). These studies have provided a better understanding of the development and the position...
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