Numerical study and experiments of cryogenic cavitating flows

The study is concerning the modeling and the experimental study of cavitating cryogenic flows. Historically, the application field of cryogenic fluids is the LNG (Liquefied Natural Gas) plants, in which the process of liquefy is based on a low temperature . Also in components of liquid rockets, mainly used to launch satellite systems, cavitating two-phase flows are present. In the rockets, the propellants (liquid hydrogen LH2 and liquid oxygen LOX) are supplied propellants to a combustion chamber with high pressure by a very fast turbopump, where cavitation occurs around the inducer, it induces disturbances that can result in substantial performance losses and/or in strong unsteady forces acting on the pump components. Cryogenic fluids, in fact, are characterized by larger compressibility if compared with fluids, such as water, at room temperature, by a small difference in density between vapor and liquid phases and by a small latent heat of vaporization. The aim of this paper is a numerical investigation of this phenomenon, using a multiphase formulation that accounts for the energy balance, variable thermodynamic properties of the fluid and nucleation transport equation. The lack of experimental data is an obstacle to the validation of cavitation models. So some experiments on the cavitation of cryogenic fluids have been done. In particular, a flow visualization and pressure measurements on two-phase nitrogen flow passing through a an orifice nozzle installed in a horizontal pipe were carried out to clarify the fundamental characteristics of the cavitating structures.