Numerical Simulation of Thermal-Hydrodynamic Transients in the Cooling Channels of a Nuclear Thermal Propulsion Engine

摘要

A mathematical model is developed to predict, numerically, the temperature and pressure transients inside the cooling channels of a NTP reactor. In the present study, only a single one of the cooling channels of the reactor core is simulated. The model adopted here assumes the flow of gaseous hydrogen in this cooling channel to be one-dimensional, unsteady, compressible, turbulent, and subsonic with temperature dependent physical and transport properties. The governing equations of the compressible flow in cooling channels are discretized using the second order accurate MacCormack finite difference scheme. Numerical experiments were then carried out to simulate the flow transients in a cooling channel of the reactor for a typical ROVER type NTR engine where the time dependent inlet mass flow rate to the cooling channels is given as an input. The time dependent heat generation and its distribution due to the nuclear reaction taking place in the fuel matrix surrounding the cooling channel are also prescribed as inputs. Time dependent temperature, pressure, density, and velocity distributions of the hydrogen gas inside the coolant channel are the outputs of the numerical simulations. It is concluded that the proposed one-dimensional mathematical model is capable of predicting the thermal-hydrodynamic transients expected inside the coolant channels of the NTR engine in response to the variations in the power generation in the nuclear core and/or variations in the inlet gas flow rate due to anomalies in the turbopumps.