nozzle, CFD, flashing flow, vortex, flow control
Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism by adjustable nozzle inlet vortex. It requires no change to the physical dimensions of the nozzle geometry. A nozzle with inlet vortex was called vortex nozzle (or swirl nozzle). Previous experiments on vortex nozzle with initially subcooled R134a showed that the nozzle becomes more restrictive as the strength of the inlet vortex increases. The maximum vortex control range has been observed to be 42% of maximum choked total mass flow rate through the nozzle. The control range of inlet pressures and mass flow rates that can be achieved by vortex control appears to be large enough to be suitable for numerous technical applications. This novel 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. In this study, 3D CFD simulation of vortex flashing flows in convergent-divergent nozzles has been conducted. The simulation results show increase of nozzle restrictiveness after the application of inlet vortex, which is the same as the experimental results. The vortex control mechanism has also been explained with the insight provided by CFD simulation.