Two-phase windage and heat transfer in a rotating annular gap

Windage, average heat transfer coefficient, and pressure drop for air-oil mixtures within a rotating annular gap are examined. Windage represents the frictional power loss due to the shearing of a viscous fluid. An apparatus was constructed with a rotating inner cylinder and stationary outer cylinder to shape the flow field. Windage tests were conducted with controlled amounts of oil in the test article at selected temperature levels. Windage as a function of speed could then be determined from an unpowered spin down from 10000 rpm. Comprehensive post processing was performed to determine the effective quality of the fluid within the gap. Power multipliers are presented as the ratio of two-phase drum windage to air only windage. For the heat transfer tests a controllable two-phase mixture of air and oil is flowed through the test section. Film heaters are mounted on the stationary outer cylinder to simulate heated conditions. Temperature and flow measurements are taken in order to estimate the average heat transfer coefficient across the gap. A clear housing was fabricated to view flow characteristics and oil distribution during the spin-up and spin-down of the windage tests and the cross flow of the heat transfer and pressure drop tests.