Measurement Of Pressure Profile Of Vortex Flashing Flows In Convergent-Divergent Nozzles

摘要

Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism which requires no change to the physical dimensions of the nozzle geometry. The control is achieved by adjustable nozzle inlet vortex. This novel control mechanism can potentially provide flow control with less sacrifice of nozzle efficiency, which is extremely important for ejector cooling cycle performance. It is also less vulnerable to clogging since the flow control is achieved without changing the flow area. However, the underlying mechanism behind the vortex control is still unclear. Measurement of the pressure profile of the vortex flashing flows in convergent-divergent nozzles under different conditions can provide more insights into the vortex nozzle flows and help to explain the vortex control mechanism. It also provides validation for modeling of vortex flashing flows. In this study, the experimental investigation of the pressure profile of the vortex flashing flows is presented. For initially subcooled conditions the pressure drop in the divergent part of the nozzle has been increased due to the vortex. This is mainly due to the more vapor generation in the divergent part caused by the applied vortex. Since the fluid is single-phase liquid in the convergent part of the nozzle, with elevated pressure at the throat and constant inlet conditions, the nozzle mass flow rate is therefore reduced. Vapor quality at different axial locations relative to the nozzle throat has been estimated with a proposed 1D model for initially subcooled conditions based on the measured pressure profile and mass flow rates. It has been shown that the applied vortex makes the outflow much closer to thermodynamic equilibrium than without vortex. By the introduction of inlet vortex, the isentropic efficiency of the nozzle has been improved from 29% to 55%.