Numerical Study of Single Flow Element in a Nuclear Thermal Thrust Chamber

Abstract

The objective of this study was to develop an efficient and accurate computational methodology to predict detailed thermo-fluid environments of a single flow element in a hypothetical solid-core nuclear thermal thrust chamber assembly. Several numerical and multi-physics thermo-fluid models, such as chemical reactions, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver used in this investigation. A secondary objective was to develop a porosity model for simulation of the whole solid-core nuclear thermal engine without resolving thousands of flow channels inside the solid core. Detailed numerical simulations of a single flow element with different power generation profiles were conducted to investigate the root cause of a phenomenon called mid-section corrosion that severely damaged the flow element assembly of early solid-core reactors. Under the assumptions employed in this effort and for the first time, the result demonstrated flow choking in the flow element. The possibility of flow choking in part of the flow element indicated a potential coolant mass flow imbalance, which could lead to a high local thermal gradient in coolant-starved flow elements and possibly the eventual mid-section corrosion.