There is gear pump with not only the basic characteristics of flux and volume efficiency,torque and mechanical efficiency,power and total efficiency,but also the phenomenons of trapping,yawp,air pocket and so on. These characteristics and phenomenons have effect on the quality of gear pump,and it is difficult relatively to research them by theory. At present the research is limited to the phase of examination testing. Theoretic research of the characteristics and the phenomenons of polymer gear p...