A performance analysis method has been developed for twin-screw multiphase pumps. In addition to modeling the two-phase behavior of the internal flow for intake gas-void fractions (GVF) from zero to 100 percent, this method also fluid-dynamically models the leakage or slip through the internal clearances of the pump for the extreme range of liquid viscosity that these rotary positive displacement machines have traditionally been required to accommodate. The results of this theoretical approach compare closely with pump test data in that a) they produce the straight-line, laminar character of ingested volume flow rate against pump pressure rise that happens when pumping liquids of high viscosity at zero GVF, b) they reproduce the curved character of this relationship for the turbulent internal leakage flows that occur for low liquid viscosity, and c) they yield the unique feature of high-GVF flow in which the volumetric efficiency approaches 100 percent. This method is compared with others for this pump type and is found to more closely approximate actual single- and multiphase pump performance.
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