Influence of axial clearance on the performance characteristics of a turbopump

To evaluate the influence of axial clearance on the performance characteristics in turbopumps, numerical simulations of an entire flow passage were carried out. The simulations were validated by performance characteristic experiments. The progress of the reciprocating axial movement in the rotor between the front and back covers was disassembled into five fixed clearances groups. Hump characteristic occurs at the same flow rate under these clearances groups. The hydraulic loss of the inducer-impeller was clearly influenced by the clearances. In particular, the hydraulic loss of the impeller changes significantly at the low flow rate under the +/- 0.3 mm clearance. With the increase of the flow rate, the effect of the clearance change on the flow is weakened. An innovative entropy production analysis was also performed. The distribution of the high local entropy production rate at the impeller inlet under the 0 mm clearance and at the impeller outlet under the -0.15 mm and -0.3 mm clearances overlapped with the vortex caused by flow separation, and the counterpart at the back cover is concentrated around the clearance structures, thereby leading to high hydraulic loss.