Solid fuel combustion experiments in microgravity using a continuous fuel dispenser and related numerical simulations

Abstract

The conventional way of determining the flammability characteristics of a material involves a number of tedious single-sample tests to distinguish flammable from non-flammable conditions. A novel test device and fuel configuration has been developed that permits multiple successive tests for indefinite lengths of thin solid materials. In this device, a spreading flame can be established and held at a fixed location in front of optimized diagnostics while continuous variations of test parameters are made. This device is especially well-suited to conducting experiments in space (e.g. aboard the International Space Station) where the limited resources of stowage, volume, and crew time pose major constraints. A prototype version of this device was tested successfully in both a normal gravity laboratory and during low-gravity aircraft trials. As part of this ongoing study of material flammability behavior, a numerical model of concurrent-flow flame spread is used to simulate the flame. Two and three-dimensional steady-state forms of the compressible Navier-Stokes equations with chemical reactions and gas and solid radiation are solved. The model is used to assist in the design of the test apparatus and to interpret the results of microgravity experiments. This paper describes details of the fuel testing device and planned experiment diagnostics. A special fuel, developed to optimize use of the special testing device, is described. Some results of the numerical flame spread model are presented to explain the three-dimensional nature of flames spreading in concurrent flow and to show how the model is used as an experiment design tool.