Computer Simulation for Barrier Screw with double flights

• Main Authors: Shang-Bor Wang, 王善柏
• Other Authors: Jiann-Shing Wu
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/39111398907411945321

碩士 === 國立交通大學 === 應用化學系 === 83 === One of the most troublesome aspects in the use of plasticating single-screw extruders , which has long been recognized , is fluctuations of flow rate in the extruder , commonly referred to as ''surging''. The cause of ''surging'' has been debated for a long time. Today , it is widely accepted that the breakup of solid bed in the melting section of a plasticating extruder is the primary source of the surging. The reason for breakup of solid bed is due to the circulation flow of melt pool , which melting zone of a traditional single screw , would continuously push the solid bed , thus leading to the solid bed breakup . Once the solid bed breakup , it would cause the unmelted particulate solid to suspend in the melt. Consequently , this would cause the decrease of melting rate and unstable output rate . The basic idea for barrier screw is to design a plasticating screw in such a way , that the solid bed can be separated from the melt pool by a secondary barrier flight. For the design of a barrier screws , channel width , channel depth , helical angle and compression ratio etc. would directly affect the melting rate , pressure distribution and bulk temperature of the screw . The work aims to develop the computer simulation with LDPE as the processing material for the four different types of barrier screws . The solid bed velocity , melt film thickness , melting rate , pressure distribution and bulk temperature were investigated under various processing conditions and geometry of the screw , and compared the difference for single-flight and double-flights of the four barrier screws.