Cold flow testing and CFD analysis of screw pump for LOX pump of semi-cryogenic engine

The LOX (Liquid Oxygen) pump of a semi-cryogenic engine has an axially locked bearing cooled by LOX tapped from pump inlet. The required LOX flow rate through the bearing is ensured by a screw pump located just before the bearing. The screw pump assembly consists of helical grooves cut on the pump shaft and a bush sleeve. The baseline configuration of the screw pump has 6 helical starts and a plain bush. Test were carried out to study the effect of number of screws starts, helical grooves on the bush etc. on the pressure rise across the screw pump (4 configurations). CFD analysis was also carried out for the test setup and the results compared very well with the test data. A grid independence study for the CFD was done. CFD analysis was also carried out for 2 additional configurations with change in radial clearance between the screw and the bush.