Analysis of Two-Phase Supersonic Flow in Jet Pumps

A jet pump may be constructed from a pair of concentric tubes in which the center tube is shaped as a converging-diverging nozzle. Primary fluid is allowed to accelerate through the nozzle, thus creating a low-pressure region at the nozzle exit. Secondary fluid flowing in the peripheral region is drawn into the low-pressure region and is thus accelerated. In this study, the jet pump is employed as part of a space thermal-management system based on a cycle known as the Solar Integrated Thermal Management and Power (SITMAP). The latter is a combined vapor compression cycle and a Rankine cycle with the compression device being a jet pump instead of the regular compressor. The jet pump has several advantages for space applications as it involves no moving parts, a feature that results in decreasing the weight and vibration level while increasing the system reliability. The working fluid is cryogenic nitrogen, which is readily present onboard the spacecraft. This study presents a detailed component analysis of the jet pump allowing for two-phase supersonic flow. The model also accounts for Fabri choking either at the inlet or at an aerodynamic throat in the mixing chamber. The model also accounts for flow choking at the exit of the mixing chamber. The different choking situations limit the ability of the jet pump to entrain more secondary flow once the flow is choked at any location. In this study the various choking regimes will be identified and the entrainment ratios corresponding to the different choking scenarios will be calculated.