Theoretical and Experimental Study of Whirl and Stability Phenomena in Internal Gear Motor/Pump

The stability of the internal gear motor/pump is mostly determined by the stability of the ring gear. In order to get insight into the stability of the motor/pump, the Sommerfeld theory and the micro-motion of the ring gear are used to define stable and unstable operating areas of the internal gear motor/pump. A test rig was designed and built. Experimental investigations were performed to validate the theoretical analytical results. The internal gear motor/pump worked in different regimes. The minimum film thickness, trajectories of the ring gear, as well as the whirl motion phenomena have been studied experimentally. Moreover, it is interesting that both forward and backward whirling motion of the ring gear have been observed experimentally. Based on the minimum film thickness, the trajectories, forward and backward whirling motion of the ring gear allow determining the stability and instability of the internal gear motor/pump corresponding to the rotating speed and the working pressure.