Numerical study of cryogenic liquid nitrogen jets at supercritical pressures

Abstract

This paper discusses numerical modeling of the mixing and flow processes of cryogenic liquids that are encountered in liquid propellant rocket engines. In the present approach, turbulence is represented by an extended k–ɛ turbulence model. A conserved scalar approach together with a presumed probability density function approach is utilized to account for scalar fluctuation effects on the turbulent mixing processes of real fluids over transcritical and supercritical states. The two real-fluid equations of state (EOS) and dense-fluid correction schemes incorporated into our real-fluid code are validated for thermodynamic and transport properties over a wide range of pressures and temperatures. In this study, computations are made for four cryogen nitrogen jets at near-critical and supercritical pressures. Special emphasis is given to sensitivity analyses for two different equations of state. Based on our numerical results, the real fluid behaviors and precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results indicate that the present real-fluid model has the predicative capabilities to simulate the essential features of the cryogenic liquid nitrogen jets. The PR equation predicts the slightly better conformity with measured nitrogen density profiles, compared to the SRK equation. It is also found that increases in pseudo-boiling strength result in increases in the cold potential core length as well as decreases in the decay rate of the axial velocity.