Modeling and simulation of cryogenic fluid injection and mixing dynamics under supercritical conditions

This research focuses on the modeling and simulation of cryogenic fluid injection and mixing processes under supercritical conditions. The objectives are: (1) to establish a unified theoretical framework that could accommodate full conservation laws, turbulence closure, and real-fluid thermodynamics and transport phenomena; (2) to systematically investigate the underlying physiochemical mechanism at near and supercritical conditions, and (3) to construct a quantitative basis for identifying and prioritizing the key design parameters and flow variables that exert strong influence on the injector behavior in different environments.; The theoretical formulation is based on the full conservation laws and includes real-fluid thermodynamics and transport phenomena over the entire temperature and pressure regimes of concern. Thermodynamic properties, such as enthalpy, internal energy, and heat capacity, are directly calculated from fundamental thermodynamics theories and a modified Soave-Redlich-Kwong (SRK) equation of state. Transport properties, such as viscosity and thermal conductivity, are estimated with an extended corresponding-state principle. Mass diffusivity is obtained by the Takahashi method calibrated for high-pressure conditions. Turbulence closure is achieved using a large-eddy-simulation (LES) technique, in which large energy-carrying structures are computed explicitly and effects of unresolved motions on the resolved scales are modeled. Modified Smagorinsky models extended to compressible flows is used to treat interaction with subfilter-scale. The resultant governing equations are calculated numerically using a preconditioned, density-based finite volume method along with a dual-time-stepping integration algorithm. All of the numerical relations, including the Jacobian matrices and eigenvalues, are derived from fundamental thermodynamics theories that can accommodate any equation of state. The resultant algorithm has been proven to be robust and efficient. Further numerical efficiency is achieved by utilizing a parallel computation scheme that involves the message-passing interface (MPI) library and multi-block treatment.; The theoretical model and numerical scheme were first validated against experimental data of cryogenic nitrogen fluid injection under supercritical conditions. Both two- and three-dimensional simulations were conducted. Reasonably good agreement was obtained in terms of the mean density distribution and the jet spreading angle, with a maximum deviation of 8%. The jet dynamics were largely dictated by the local thermodynamic state through its influence on the fluid thermophysical properties. When the fluid temperature transited across the inflection point on an isobaric density-temperature curve, the resultant rapid property variations might qualitatively modify the jet behavior compared with its counterpart at 1 atm. Increasing ambient pressure produced an earlier transition of the jet to the self-similar region in the simulations. (Abstract shortened by UMI.)...