Modeling of Solid Conveying Pressure Throughput Behavior of Single Screw Smooth Barrel Extruders under Consideration of Backpressure and High Screw Speeds
Modeling of Solid Conveying Pressure Throughput Behavior of Single Screw Smooth Barrel Extruders under Consideration of Backpressure and High Screw Speeds
复制标题
考虑背压和高螺杆转速的单螺杆光滑机筒挤出机固体输送压力吞吐量行为建模
DOI：
--
复制
发表时间：
2018
影响因子：
1.3
通讯作者：
V. Schöppner
中科院分区：
文献类型：
--
作者：
J. Trippe;V. Schöppner
固体输送段的任务是收集进入的物料并将其输送到熔体控制段。因此，其上游界面是料斗，其下游界面是发生第一次熔化的部分。在料斗开口下方，螺旋旋转收集并向前输送材料。因此，假设颗粒之间的摩擦力高于螺杆和机筒上的传递力。出于该原因，用于描述单螺杆挤出机中的固体输送的公知模型假定螺杆通道总是完全填充，使得发生活塞流。然而，在高螺杆速度下，这些假设不再有效。为了分析和数学描述在螺杆速度高达2000 rpm时的固体输送行为，在先前的研究中已经执行了基于离散单元法的模拟。在此基础上，建立了一个描述固体输送行为的模型，该模型允许改变一般螺杆和料斗的几何参数，但忽略了抑制固体运动的背压。为此，本文提出了基于离散单元法的进一步研究，该方法能够考虑进料区的背压和压力积聚。令人惊讶的是，在高螺杆速度下，观察到螺杆通道中的低填充度，由于背压迫使颗粒堆积，这不满足总是完全填充通道的期望。在调查的基础上，开发了一个数学模型，该模型现在完全理解了固体输送部分发生的影响。随后进行的模拟实验研究进行了验证。因此，设计了一个测试台，使固体输送分析与可调背压。结果表明，与制定的模型，现在能够考虑的压力建立和填充度的固体输送区的计算有很好的一致性。
Abstract The task of the solid conveying section is to collect the entering material and transfer it to the melt dominated sections. Therefore, its upstream interface is the hopper and its downstream interface is the section in which the first melting occurs. Beneath the hopper opening, the screw rotation collects and conveys the material forward. It is hereby assumed that the friction forces among the particles are higher than the transferring forces on the screw and barrel. For that reason commonly known models for describing the solid conveying in single screw extruders assume that the screw channel is always completely filled so that a plug flow occurs. At high screw speeds, however, these assumptions are no longer valid. To analyze and mathematically describe the solid conveying behavior at screw speeds up to 2000 rpm, simulations based on the Discrete Element Method have been executed in previous investigations. Based on this, a model for describing the solid conveying behavior was developed which enables a variation of general screw and hopper geometry parameters but neglects the backpressure that inhibits the solid movement. For that reason, further investigations based on the Discrete Element Method are presented in this paper, which enable a consideration of the backpressure and pressure build-up in the feeding zone. Astonishingly, at high screw speeds a low filling degree in the screw channel was observed which did not fulfill the expectations of an always fully filled channel due to a backpressure forced particle backlog. Based on the investigations, a mathematical model has been developed which now fully comprehends the effects occurring in the solid conveying section. The conducted simulations were subsequently validated by experimental investigations. Therefore, a test bench was designed which enables solid conveying analysis with adjustable backpressures. The results indicate a good agreement with the formulated model which now enables the calculation of solid conveying zones with consideration of the pressure build-up and filling degrees.