A Hybrid Fine-Coarse Computational Mesh Simulation Tool for SpaceNuclear Systems

摘要

A hybrid fine and coarse mesh point computational model is developed for simulationrnand design analysis of very high temperature gas cooled nuclear reactors and Nuclear ThermalrnPropulsion (NTP) systems. The model is intended to simulate the entire system and its differentrncomponents as well as the thermal fluid dynamics of the real gas coolant/propellant flow in thernsystem. The coarse mesh simulation uses a 1-D model to account for pressure losses and heatrntransfer in the entire system. Very fine computational grids are used to predict flow, pressure, andrntemperature distributions in areas of the system with complex flow geometry. A three-dimensionalrnComputational Fluid Dynamics (CFD) model with capability to solve Navier-Stokes equations forrncompressible and turbulent flow is added to the 1-D simulation model for fine-mesh computationrnof flow, pressure, and temperature distributions in the system. The hybrid 1-D/3-D simulationrnmodel is used to calculate pressure losses and heat transfer in an advanced NTP system. Thernsystem considered in this paper is a full-topping expander cycle engine using hydrogen gas at veryrnhigh temperatures as a coolant/propellant. A new design of thrust chamber and nozzle is proposedrnand implemented in the NTP system. The simulated NTP system operates at lower thrust chamberrnpressures to allow for hydrogen dissociation at very high temperatures. The hydrogen dissociationrneven without accounting for the energy recovered after recombination in the expander part of thernnozzle results in fairly significant increase in the Ideal Specific Impulse (ISP).