The three-dimensional isothermal flow fields of single screws with different values of tip-clearance (0.4, 0.8, 1.2 mm)were simulated by POLYFLOW software. Combined with the particle tracing technique, the effect of different tip- clearance on the flow field and mixing ability of the food melt was also explored. The results show that: the shear rate near the top of the screw flight increases, the average viscosity of food melt decreases, and the conveying capacity of the screw weakens with the decrease of the tip-clearance. On the contrary, with the increase of the tip-clearance, the residence time of the food melt increases first, then decreases subsequently, and the dispersion mixing effect becomes poorer. When the tip-clearance increases to value of 1.2 mm, the residence time of the food melt is even longer than the one with the value of 0.4 mm. It also shows that if the tip-clearance is too large, the residence time of the food material might become hard to be controlled and the mixing effect of these food material components would also become worse. As a result, the tip-clearance between screw and barrel could significantly influence both the flow field and mixing characteristics of food materials, when the tip-clearance is 0.8 mm, it can not only ensure the transport capacity to the food melt, but also behave the good flow field distribution and mixing effect. Therefore, it is the optimal tip-clearance value deduced by the numerical simulation.
Huanhuan, LI; Haiying, CHEN; and Zhengwei, CUI
"Numerical simulation on effect of tip-clearance between screw flight and barrel on performance of food melt conveying section in single screw extruder for expanding,"
Food and Machinery: Vol. 32:
1, Article 16.
Available at: https://www.ifoodmm.cn/journal/vol32/iss1/16
 韩国亮, 杨成德. 塑料挤出机螺杆与机筒间隙的影响[J]. 塑料制造, 2015(4): 62-64.
 Ramos-De Valle L F. Principles of Polymer Processing[M]// Handbook of Polymer Synthesis, Characterization, and Processing. Hoboken, New Jersey: John Wiley & Sons, Inc., 2013: 451-461.
 Sastrohartono T, Jaluria Y, Esseghir M, et al. A numerical and experimental study of three-dimensional transport in the channel of an extruder for polymeric materials[J]. International Journal of Heat & Mass Transfer, 1995, 38(38): 1 957-1 973.
 Peng Jiong, Chen Jin-nan. Numerical simulations of polymer melt conveying in Co-rotating twin screw extruder[J]. Journal of Beijing Institute of Technology, 2004, 11(2):189-192.
 Ghoshdastidar P S, Ghai G, Chhabra R P. Computer simulation of three-dimensional transport during moistened defatted soy flour processing in the metering section of a single-screw extruder[J]. Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science, 2000, 214(2): 335-349.
 Emin M A, Schuchmann H P. Droplet breakup and coalescence in a twin-screw extrusion processing of starch based matrix[J]. Journal of Food Engineering, 2013, 116(1): 118-129.
 王洪武, 林炳鉴. 大豆蛋白质单螺杆挤压熔体输送段的数值模拟[J]. 农业机械学报, 2005, 36(9): 75-78.
 朱向哲, 谢禹钧. 食品加工用三螺杆挤压机三维流场数值模拟[J]. 食品与机械, 2005, 21(3): 45-48.
 吴明星. 微型挤出熔体流变行为分析及螺杆优化设计研究[D]. 广州: 华南理工大学, 2010: 42-55.
 Winter H H. Temperature-induced pressure gradient in the clearance between screw flight and barrel of a single screw extruder[J]. Polymer Engineering & Science, 1980, 20(6): 406-412.
 王俊山, 王小龙, 任家骏. 单螺杆螺棱间隙漏流数值模拟[J].机械科学与技术, 2010(11): 86-89.
 Ishikawa T, Nagano F, Kajiwara T, et al. Tip-clearance effect on mixing performance of twin screw extruders[J]. International Polymer Processing Journal of the Polymer Processing Society, 2006, 21(4): 354-360.
 杨绮云, 赵静静. 食品双螺杆挤出机内物料停留时间及其分布研究[J]. 农业机械学报, 2006,37(8): 175-186.
 喻慧文, 徐百平, 何亮, 等. 非对称同向双螺杆端面造型对混合行为影响数值模拟[J]. 化工学报, 2012, 63(5): 1 622-1 629.
 Shearer G, Tzoganakis C. Relationship between local residence time and distributive mixing in sections of a twin-screw extruder[J]. Polymer Engineering & Science, 2001, 41(12): 2 206-2 215.
 Danckwerts P V. The definition and measurement of some characteristics of mixtures[J]. Applied Scientific Research, Section A, 1952, 3(4): 279-296.
 Cheng J, Manas-Zloczower I. Hydrodynamic analysis of a banbury mixer 2-D flow simulations for the entire mixing chamber[J]. Polymer Engineering & Science, 1989, 29(15): 1 059-1 065.
 王建, 郭迪, 陈晋南. 数值模拟研究螺筒结构对单螺杆挤出机性能的影响[J]. 塑料科技, 2012, 40(10): 74-78.