PRESSURE-RELATED DRIVING FORCES IN THE FULLY FILLED NONINTERMESHING TWIN-SCREW EXTRUDER

Research in understanding the mechanisms behind driving forces in the fully filled nonintermeshing twin screw extruder concentrated on exper imental analysis of the relation between stagger, screw speed, and cro ss-channel flow due to measured pressure differential in the nip regio n. A new measure of the pressure driving force was also sought out, to correlate new data to previous findings from visual studies. The firs t part of the study was to obtain the values for the dynamic pressure on both sides of the nip region. Further refinements to the equipment used in previous studies allowed closer placement of the transducers i n the nip region. After the data were stored, analysis started by dete rmining the DELTAp values from the trace of the pressure differential. By plotting these values, we obtain a highly repeatable curve confirm ing that the greatest pressure flow occurs at small staggers. A simple 2-D model for pressure flow in the nip region was used to estimate th e effect of the cross-channel pressure differential. Values for the cr oss-channel pressure flow were calculated and compared with the drag f low and found to be significant. (C) 1993 John Wiley & Sons, Inc.