COMBUSTION OF SOLID PROPELLANT SANDWICHES: EFFECT OF BINDER OXYGENATION AND FINITE PECLET NUMBER

The combustion of AP/HTPB solid propellant sandwiches is investigated experimentally using ultraviolet (310±5 nm) chemiluminescent emission imaging and theoretically using Shvab-Zeldovich theory with finite Peclet number (Pe). Experimentally a thin binder lamina (50−300 μm) is sandwiched between two thick (∼ 1.5 mm) pressed AP layers, forming two AP/binder interfaces. Both pure and oxygenated binders (loaded with fine AP) are considered. Variations in Peclet number and stoichiometry are achieved through varying binder thickness and fine-AP loading. Both experimental and theoretical results show that fine-AP loading has a pronounced effect on the UV-active diffusion flame structure. For the same approximate binder thickness and Pe, adding fine-AP to the binder causes the observed flame intensity and height to decrease and the leading edge of the diffusion flame to shift from the AP region toward the AP/binder interface, in accordance with Shvab-Zeldovich mixing theory. Peclet number also affects diffusion flame structure in a predictable manner for both pure and oxygenated binders: increasing Pe increases the size and intensity of the UV-active diffusion flame.