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DOI: 10.2514/1.B34488 This work presents a physical model of the combustion behavior of a liquid oxidizer droplet with adjacent solid fuel. It is the first modeling attempt related to a proposed new potential class of liquid-oxidizer-enhanced solid propellants, where liquid oxidizer units/capsules are embedded in a solid fuel/propellant, revealing a theoretical specific impulse increase of up to 12%. A one-dimensional mathematical model is formulated, which describes the main characteristics of the microscale flamelet formed by a volatile (typically polymeric) fuel component and an adjacent endothermically evaporating oxidizer droplet. The model predicts fuel and oxidizer surface temperatures, fluxes, and flame height as functions of operating pressure and droplet size. The transient nature of the combustion processisemphasized,revealingacombustioncycleattheindividualdropletscale,withpressure-dependentaverage burning rates typical to solid propellants.

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...