共查询到18条相似文献,搜索用时 140 毫秒
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潘龙;贾明印;薛平;金志明;唐广利 《中国塑料》2011,25(4):102-106
通过在固体输送段机筒内壁开设螺旋沟槽,同时将嵌入机筒沟槽与螺杆螺槽中的物料视为固体塞,建立了一个机筒与螺杆对物料协同作用的整体系统。充分考虑固体塞运动过程中的可压缩性及其受到的加速度的影响,建立数学模型,进而求解固体塞的压力及速度方程式。结果表明,固体塞在沟槽螺棱与螺杆螺棱的共同推力作用下正位移输送时,系统建压能力被显著提高,在固体输送段末端产生的沿螺杆轴向上的压力峰值有效保证了物料的稳定挤出。 相似文献
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动态成型注塑螺杆熔体输送能力的研究 总被引:1,自引:0,他引:1
根据动态注射成型时螺杆的工作特点,采用自行修正的Tanner本构方程研究了聚合物熔体在螺槽中的等温流动。同时,近似地给出了振动力场下注塑螺杆熔体输送能力的表达式,理论分析了振动参数对沿程压力降及动态成型熔体输送能力的影响。结果表明,振动力场使塑化过程中聚合物的粘度降低,流动阻力减小。沿螺槽方向的平均压力降减小,在保持成型条件不变的情况下,施加振动可以提高熔体输送能力。 相似文献
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在分析机筒衬套沟槽槽深、螺杆螺槽槽深和加工物料粒径关系的基础上,建立了沟槽机筒单螺杆挤出机3种常见的固体输送段产量粒径模型,该模型可用于研究机筒衬套沟槽槽深、螺杆螺槽槽深和颗粒物料粒径对固体输送机理的影响并定量计算沟槽机筒单螺杆挤出机固体输送段产量。此外,通过不同的机筒和螺杆组合及不同粒径的原料在自制的在线模拟试验机上对该模型进行了验证和试验分析。 相似文献
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螺旋沟槽单螺杆挤出机双螺棱推动理论模型的研究 总被引:2,自引:0,他引:2
潘龙;贾明印;薛平;金志明;唐广利 《中国塑料》2010,24(11):94-99
通过在单螺杆挤出机固体输送段机筒内壁开设螺旋沟槽,建立了将机筒与螺杆视为一个对物料协同作用的整体的新型物理模型——弧板模型;同时将嵌入机筒沟槽与螺杆螺槽中的物料视为固体塞,提出了新型"双螺棱推动理论",弥补了单螺杆挤出机不能实现正位移输送的传统理论缺陷;最后,通过理论分析确定了螺旋沟槽挤出机由摩擦拖曳输送向正位移输送转换的边界条件方程及正位移输送下沟槽结构参数的设计准则。 相似文献
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啮合同向双螺杆挤出机普通螺纹元件末端共混物的混合形态Ⅰ.物料三维流动路径的计算 总被引:3,自引:1,他引:2
用有限元方法对啮合同向双螺杆挤出机的螺纹元件流场进行了三维等温非牛顿模拟分析,根据流场分析所得到的速度场,通过编程计算得到了物料在啮合同向双螺杆挤出机螺纹元件中的三维流动路径。结果表明,由于存在着轴向回流,部分物料不能流出元件出口,而是从元件入口返流;物料在元件中的运动轨迹不尽相同,有的物料微元在整个流动过程中都围绕着2根螺杆以螺旋“∞”形向前运动,有的物料微元在流动过程中时而围绕1根螺杆连续旋转,时而围绕2根螺杆以螺旋“∞”形向前运动;在螺槽区,物料在螺槽的横截面内上下流动;回流物料微元数随着螺杆转速的增大、双螺杆挤出机产量的减小而增大。 相似文献
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In the single‐screw extruder, the vibration force field is applied to the solids conveying process by the axial vibration of the screw and the novel concept on the solids conveying process being strengthened with the vibration force field has been brought forward in this study. We establish the mathematical model that describes the solids conveying process with the vibration force field and obtain the approximative analytical solutions of the pressure and velocity of the solids conveying in the down‐channel. In the new theory, if the screw has no axial vibration the solids conveying pressure is the same as that of the Darnell and Mol theory, but the density and velocity of solids conveying along the screw channel is variable, which has modified the Darnell and Mol theory in which the density and velocity of the solids conveying along the screw channel was considered invariable. The results reveal that the axial vibration of the screw can increase the average pressure of solids conveying, decrease the channel length of the solids conveying section and increase the solids conveying angle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2998–3007, 2006 相似文献
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On the basis of the theory of relative motions, a novel nested screw extruder was invented in which one rotating outer screw acted as the barrel for an inner screw; the combination of the outer screw and outer barrel was the other extrusion system. It was realized that centrifugal force resulted in the difference between the forces acting on the solids by the screw and by the barrel, which further compacted the solid pellet or powder. These factors benefited the frictional drag of solids and the early melting. This was consistent with the fact that the solids conveying flow rate increased greatly when the barrel and screw rotated oppositely at the same time. Thus, centrifugal force and material compressibility were significant in the feeding zone. A mathematical model was developed to calculate the output, pressure, and velocity of the solids in the screw down‐channel with consideration of the centrifugal force and material compressibility. The predicted pressure distribution and output were better than those by previous models in fitting the experimental data. The simulations revealed that the maximum traction angle was close to 90° ? the helix angle for maximum output in contrast to the maximum traction angle of 90° predicted by the Darnell–Mol theory. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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This paper studies granular flow and compaction behavior of high‐density polyethylene by discrete particle modeling in order to gain greater understanding of the stress distribution within the solids‐conveying zone of a single‐screw extruder. The contact force–displacement model used in the simulations was first validated by simulating uniaxial compression in a batch compaction cell. Subsequently, the discrete particle approach was used to model in 3D the movement of particles within the solids‐inflow and solids‐conveying zone of a 32‐mm single‐screw extruder. Results of the simulations showed that axial pressure development did not increase in an exponential manner, as suggested by continuum models, largely due to the compressibility of the solids. The nature by which pressure developed was shown to be further complicated by the retarding frictional forces of the granular bed, indicating Archimedean transport phenomena close to the feed opening when the head pressure was low and inadequate stress transmission occurred along the screw. In the cross‐channel direction, the anisotropic stress field predicted found that the highest pressure in the screw channel was located at the screw root, while the lowest pressure corresponded to the retreating flight. The results were subsequently discussed in comparison to available continuum models. POLYM. ENG. SCI., 48:62–73, 2008. © 2007 Society of Plastics Engineers 相似文献
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A fully-predictive steady-state computer model has been developed for a single-screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt-conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature- and shear-rate-dependent viscosity equation is used to describe the melt-flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single-screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High- and low-density polyethylene resins were used. 相似文献
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Quan Wang 《Polymer-Plastics Technology and Engineering》2013,52(11):1055-1061
In the reciprocating extrusion, the vibration force field (VFF) is applied to the entire plasticating process by the axial vibration of screw and the novel concept on the polymer dynamic plasticating process being strengthened has been brought forward in the paper. The mathematical model is established that describes the plasticating process under the VFF and the approximative analytical solutions of the velocity distribution, pressure gradient in the screw channel and the plasticating capability are obtained. The theoretical results show that the axial vibration of screw can accelerate the blend capability of polymer and make melt temperature more uniform. With increase of the vibration intensity, the effect of blend and plasticating is enhanced further. The average pressure gradient drops down the channel under the VFF because of lower virtual viscosity of polymer melt and smaller flow resistance in the channel. The comparison between the theoretical analysis and the experimental results shows the plasticating capability of melt is improved with increase of vibration intensity. 相似文献
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An innovational vane extruder made polymeric materials endure an elongation stress that was much larger than the shearing stress in the extrusion process. The operating principle of the vane extruder was completely different than that of conventional screw extruders. As the first stage of polymer processing in the vane extruder, the process of solids conveying was composed of feeding, compacting, and discharging. Most of the energy was consumed in the compacting process of polymer particulate solids in this stage. A mathematical model was developed to analyze the power consumption in the process. The model showed that the power consumption was mainly influenced by the structural parameters of the vane extruder, including the rotor diameter, eccentricity, and axial width of the vane unit. The analysis indicated that more energy was used to generate pressure in the vane extruder than in a screw extruder. The theoretical model was verified by the experimental results. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
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The transport theory for the solids conveying zone in a single‐screw extruder was applied to calculate the pressure distributions along the screw channel for several bisphenol A polycarbonate resins based on the screw revolution speed and the flow rate. The pressure distributions and the flow rates of the resins were related to the structural and rheological properties. When polymers have the same chemical structure and number‐average molecular weight and the same mechanical properties, the polymer having a broader molecular weight distribution showed a lower glass transition temperature. For the polymer with broader MWD a relatively low pressure was developed along the screw channel, and an increased flow rate was observed. A relatively short melting length was also observed for this polymer and, accordingly, it was concluded that the polymer with a broader MWD has a better processability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2921–2929, 2002 相似文献