Simulation Of Extrusion Stability Of Melt Gear Pump ?28×28 And Experimental Validation

Gear pump was one of typical positive conveying equipment, which could be used to eliminate the macro fluctuation effectively in the extrusion process. However, a kind of micro fluctuation was also brought by gear pump simultaneously, due to the variation of the tooth space volume in the meshing process of two gears. A flow calculation model of gears with profile modification was established based on swept area method herein. Based on the model, the effect of modification coefficient on extrusion stability when the number of teeth was increased was analyzed for the situations for addendum modification, and positive angle modification and negative angle modification, using average flow rate and flow pulsation as evaluating indexes.A model with backflow port was developed to describe the extrusion stability of melt gear pump. Compared with conventional models, this model is able to calculate the fluctuation of output due to its capacity to analyze the pressure backflow caused by gear pump. Several factors on the application of this model were discussed, such as the number of simulation results in per meshing period of gears, number of re-meshing times on adaptive meshing technology and the post-processing of the output curves. The velocity and pressure profiles shows a deep insight on the working principle inside gear pump when pressure backflow was considered. The simulation results explained that reasons why the macro and micro fluctuations of output occurred. Both the rotation speed of gear wheel and variation of transient input rate dominate the fluctuation of output. Additionally, the geometry parameters also influence the extrusion stability of gear pump significantly.Compared rubber melt gear pump and plastic melt gear pump, a new rubber melt gear pump was designed based on the structural difference of these two types of gear pump. In order to guarantee the normal operation of the machine, safety interlock device of different security level was setting on temperature control system, pressure control and motor speed regulation on new rubber gear pump.