Multiphysics Computational Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

Abstract

The objective of this effort is to develop an efficient and accurate computational fluid dynamics and heat transfer methodology to predict thermal, fluid, and hydrogen environments of a hypothetical solid-core nuclear thermal engine: the small engine. Several theoretical power profiles were imposed on the solid core to represent the effect of nuclear heating, and their effects on hydrogen conversion, heat transfer efficiency, and thrust performance were investigated and reported. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics and heat transfer platform, and formulations of flow and heat transfer through porous media were implemented to describe those ofthousands of flow channels inside the solid core. In addition, formulations of conjugate heat transfer were implemented in a previous study to describe the heat transfer between other supporting solid components and the working fluid. The computational domain covers the entire thrust chamber so that the heat transfer effects impact the thrust performance directly. The result shows that the computed core-exit gas temperature, specific impulse, and core pressure drop agree well with those of the small engine. Finite rate chemistry is found to be very important in predicting the proper energy balance, because naturally occurring hydrogen decomposition is endothermic. Locally strong hydrogen conversion associated with centralized power profile gives poor heat transfer efficiency and lower thrust performance. On the other hand, uniform hydrogen conversion associated with a more uniform radial power profile achieves higher heat transfer efficiency and higher thrust performance.