Effects of the Recess Geometry on Flow Characteristics of Cryogenic Hybrid Journal Bearings for Rocket Turbopumps

Abstract

In the present study, a flow visualization experiment in the clearance between a clear floating-ring and a rotating journal was carried out in order to clarify the effects of the recess geometry on the flow characteristics. Five types of the floating-rings with different recess geometries, i.e., the plane rhombus, the plane circle, the revise circular Young Leaf Mark, the dome and the revise dome geometries, were operated at a rotational speed of up to 40,000 rpm using liquid nitrogen as the working fluid to observe the interaction between source flow from the recess and rotating flow induced by the journal rotation in the clearance. The cavitation cloud inside the clearance was induced by viscous frictional heating and the pressure drop. The influence of the sweepback angle (θs) of the recess leading edge on the flow characteristics was investigated by comparing flow coefficient (Cf) and the cavitation cloud area ratio (Ac) obtained from the visual image. Based on the experimental results, it may be confirmed that the effects of the recess geometry on the flow characteristics of the cryogenic hybrid journal bearings are mainly caused by the influence of the θs value on the flow condition.

Keywords

• journal bearing
• cryogenic turbopump
• flow visualization
• recess geometry
• recess sweepback angle
• cavitating flow
• liquid nitrogen