A Burning Rate Emulator (BRE) for study of condensed fuel burning in microgravity

The Burning Rate Emulator (BRE) is a gas-fueled burner that emulates the burning of real condensed phase fuels. This is accomplished by matching four fundamental properties: heat of gasification, heat of combustion, surface vaporization temperature, and smoke point. Previous research has confirmed the BRE technique in normal gravity. The aim of the current study is to establish immediate sustained burning in a calm microgravity environment. This paper presents 49 BRE tests at NASA Glenn's 5.18-s Zero Gravity Research Facility for two burner diameters (25 mm and 50 mm) with methane, ethylene and nitrogen-diluted ethylene as fuels. The burner sizes and test parameters represent small laminar pool fires. The flames are nearly hemispherical within 5 s, with the flame height still increasing. The heat flux initially falls quickly and then becomes steadier. Steady-state theory correlates the end-of-drop experimental data, including the theoretical flame shape and fuel burning rate. The apparent lack of correlation of the burning rate for the larger burner is attributed to gas radiation. An approximate transient model is employed to evaluate the BRE burner in microgravity conditions. The analysis predicts that quasi-steady microgravity BRE flames will require much longer than 5 s.