Study On Solid Conveying Section In Helically Grooved Feed Single-Screw Extruder

The thesis was part of the research work of national natural science funds projects, a novel solid conveying theory (double flight driving theory) was proposed in the project, based on the theory, a new type of single-screw extruder with several helical grooves in the feeding sleeve was invented to achieve positive conveying. The materials between the barrel groove and the screw channel were pushed forward by the groove flight and the screw flight in solid conveying zone as a whole solid-plug. In this conveying theory, the friction between material and screw and the friction between material and barrel were both resistance for the conveying of material.The theoretical formulas of the double flight driving theory were quoted, the effecting parameters and the effecting trend were analyzed on the performance (including the throughput and the pressure of solid conveying section) of the novel extruder, and based on the original IKV extruder, the experimental platform of helically grooved feed single-screw extruder was built, two helical grooved feeding sleeves with different width and two screws with different pitch were designed, so six test systems were built combined with original IKV straight sleeve. The conveying ability and pressure building ability in solid conveying section had an important effect on the production and energy consumption of the extruder. Therefore, the study on properties of the solid conveying section was the key point in this paper. Accordingly, a pressure tester for solid conveying section was designed; both of the pressure and the output of the solid conveying section can be tested accurately by the self-designed pressure tester on line.Effects of the main structural parameters of feeding sleeve and screw, including the width of the sleeve and the pitch of the screw were tested by the self-designed pressure tester. The results show that:(1) The effects of groove width on the pressure are not obvious; however, the output increases with the groove getting wider. So it is helpful to widen the groove for output increasing.(2) The extruder shows high pressure building ability with big screw pitch; the output is decided by the screw pitch at the feed port, no difference with the screw pitch changing behind the feed port; therefore, it is good to enlarge the screw pitch, especially the screw pitch at the feed port.The particle size of material had an important effect on the pressure and throughput of solid conveying section, accordingly, four kinds of experimental material with different particle size were prepared by a twin-screw extruder, The results show that:the extruder shows high pressure building ability and high yield with small particle size, so it is helpful to decrease the particle size for output increasing. The effects of screw speed on the pressure are not obvious, and the yield increases linearly with the screw speed increasing, which proves that the extruder nearly achieves positive conveying.The comparisons in the pressure, output and energy consumption of solid conveying section between the novel extruder and IKV extruder were made. The results show that:the pressure building ability of helically grooved feed single-screw extruder is similar to IKV extruder, but it shows higher screw speed related output by 11% and lower specific energy consumption by 13% than IKV extruder, which is the superiority of the novel extruder.