Study Of The Design Priciple And Mixing Mechanism Of The Reciprocating Single Screw Pin-Barrel Extruder

In the resent years,because of the unique kneading characters,more and more reciprocating single screw pin-barrel extruder were used in the polymer mixing process.Based on the development of the WXJ-140 reciprocating single screw pin-barrel extruder,the design principle,dynamic simulation of the plasticating system and driving system,mixing mechanism,fluid flow and mix inside the screw elements,and the experimental measurement and modeling of the residence time distribution in the extruder were studied herein.The structures and functions of the reciprocating single screw pin-barrel extruder were analyzed using the systematic engineering design principle.In order to improve the design principle of this kind of the extruder,the dynamic simulation of the plasticating and driving systems was carried out,which was helpful to give a direct,comprehensive,real-time and dynamic observation of the extrusion process.Meanwhile,the mathematic model on the multiple motions of the pins mounted on the barrels and the flights of the screw elements was also founded.Furthermore,the application of the scale-up theories in the serialization development of the WXJ extruders was also studied.The flow and mixing characters of the common screw elements in the reciprocating single screw pin-barrel extruder were studied using a polyflow finite element software package.Base on the statistical treatment of the flow trajectories,the dynamic mixing process and the effects of the operating conditions,material viscosity and the pins on the mixing performances of the extruder was studied.At the same time,a novel mixing screw element named NKE with four flights was developed and compared with the traditional mixing element(KE element).After validating the feasibility of the digital image processing method in measuring the residence time distribution(RTD)of the plasticating extruder,a experimental study on the RTD in the reciprocating single screw pin-barrel extruder was done.For the sake of the control and forecast of the RTD,based on the assembly of the equipment and the component of the screw,two mathematical models on the RTD in the extruder were built by the chemical reaction engineering method and computing fluid dynamics method, respectively.At present,the technologies and markets of this kind of equipment are all controlled by a few of foreign manufacturers basically.Some domestic enterprises and institutes including Beijing University of chemical technology have developed small-and medium-sized reciprocating single screw pin-barrel extruder,but there is no enough dependable and systemic theory for the development of the lager-sized equipment.Generally speaking,all the preliminary investigations can provide not only the theoretical basis for application and serial development of this kind of equipment,but also a new scientific research stage for the improvement of the polymer materials science and technology of China.