Development of CFD Approaches for Modeling Advanced Concepts of Nuclear Thermal Propulsion Test Facilities

The current project is going to investigate, implement and begin validating the Computational Fluid Dynamics (CFD) options available for modeling multi-phase reactive flows in a fully coupled multi-physics framework to use in designing and supporting Nuclear Thermal Propulsion (NTP) Test ground test facilities. NTP is an advanced propulsion alternative to conventional chemical rockets with relatively high thrust and twice the efficiency of the Space Shuttle Main Engine. Ground testing facilities can validate thrust and efficiencies from testing if capturing and treating the nuclear exhaust satisfy current safety, health and environmental regulations. A fully-coupled, multi-physics, CFD analysis approach will be required to design such a NTP ground test facility system. The multi-physics approach will require simultaneous simulations of processes such as transient real-gas hydrogen flow through a supersonic diffuser, Liquid Oxygen/Gaseous Hydrogen (LO2/GH2) combustion at high speeds, and multi-phase condensation and evaporation of water sprays in a reacting flow environment. However, multiphase reactive CFD simulations are not simplistic or straightforward to obtain. In addition, fully coupling these flow simulations with transient thermal analysis of heat exchangers and thermal protection systems significantly increases the complexity. By developing this CFD analysis approach, a better understanding of requirements for NTP ground testing facilities can be better achieved. The project will be developing a CFD approach that can handle the additional complexities needed in a NTP testing facility when modeling the combustion processes in a transient environment for fluid flows that will extend from low subsonic to supersonic during a typical NTP ground test sequence. Complex combustion processes will eventually need to be modeled in conjunction with down-stream effluent cooling systems such as water sprays and heat exchangers. The simulation of water spray injection in a transient, time-accurate fashion will require implementation of robust numerical schemes which sufficiently capture the relevant physics of the water spray evaporation in the high-speed combusting flow. In addition, the simulation of heat exchanger cooling systems will require fully coupling these multi-phase combustion simulations with a transient thermal analysis in a multi-physics analysis framework. The successful demonstration of accurately and robustly coupling all these analysis into one simulation environment will be a new achievement for NASA. More »