COMBUSTION OF A SOLID FUEL TUBE WITH CONTAINED LIQUID OXIDIZER IN A HOT GAS ATMOSPHERE

Abstract

This work investigates the combustion behavior of a miniature configuration, which combines a solid fuel and a liquid oxidizer. A small diameter (about 1 mm) solid fuel tube is filled with a liquid oxidizer and embedded in a solid propellant strand. Two specific cases are studied experimentally: an aluminum tube filled with hydrogen peroxide and a polyethylene tube filled with nitric acid. During combustion, the regressing propellant surface exposes the aluminum/polyethylene tube, and provides the necessary thermal conditions for the establishment of a local miniature flamelet, resulting from oxidizer emerging from the inner core of the tube and fuel supplied by the tube wall. High speed video pictures reveal the details of the local diffusion flamelet expanding from the embedded tube. A qualitative miniature flamelet model is suggested, based on physical considerations and resembling, in the micro scale, solid oxidizer/solid fuel combustion. Thermochemical calculations show that an optimal combination of a polymeric fuel (e.g., HTPB), aluminum and a liquid oxidizer, can theoretically increase the heat of combustion by 10–20%, implying a potential enhancement of the specific impulse by about 6% to 12% over conventional solid propellants.

Keywords:

• modeling
• propellant combustion
• solid propellants