Low Burning Rate Aluminized Propellants in Acceleration Fields

Abstract

To reduce slag formation and burning rate increases, the effects of radial acceleration (up to 20 g) and low pressure (2-7 MPa) on the combustion of low-burning rate aluminized propellants (87 formulations) were investigated. Experiments were performed to obtain agglomerate size distribution, slag formation, and burning rate data. Data sources included photographs under cross flow and acceleration conditions, scanning electron probe (Cl and Al) images, particle collection combustors, and rocket motors. The tendency to form slag increases as the agglomeration size at the burning surface increases. A lower burning rate increases acceleration effects. However, residue formation is more sensitive to formulation than is burning rate; for example, bimodal vs trimodal AP can cause significant changes in residue in the absence of burn rate changes; RDX produces larger agglomerates than HMX. Through understanding obtained from this research, reduction in agglomeration, slag formation, and burning rate augmentation are directly attributable to systematic changes in formulation ingredient levels and sizes.

Modeling of the Agglomeration Phenomena in Combustion of Aluminized Composite Solid Propellant

“…Calculations have been made for propellants of different compositions and original particle diameters. The basic trend reported by many studies [26][27][28][29][30][31], of increasing agglomerate diameter with increasing coarse AP particle size, was predicted in this work for various operating pressures, aluminum particle diameters, and propellant compositions, as seen in Figure 5.…”

Condensed combustion products of aluminized propellants. IV. Effect of the nature of nitramines on aluminum agglomeration and combustion efficiency

“…Another feature that distinguishes the propellant formulations in the present study from that in [21][22][23][24] is the large mass fraction (35%) of coarse nitramine (D 10 ≈ 490 µm for HMX and D 10 ≈ 380 µm for RDX). Therefore, one might expect that the combustion of E12 and R propellants would involve severe agglomeration, but its quantitative characteristics and their change due to the replacement of HMX by RDX cannot be predicted without experiments.…”

“…We note that in the literature there are data that RDX can cause more severe agglomeration than HMX (for example, for Al-HTPB-AP-nitramine propellants [21]). For E12 and R propellants, the agglomerate size is on the average larger than that for the nitraminebased propellants in [22][23][24], where D 43 = 190-510 µm.…”

“…For E12 and R propellants, the agglomerate size is on the average larger than that for the nitraminebased propellants in [22][23][24], where D 43 = 190-510 µm. However, in [21][22][23][24], the propellants contained the inert binder hydroxyl-terminated polybutadiene (HTPB), whereas the propellants used in the present study contained an energetic binder based on polybutadiene nitrile rubber plasticized with diethylene glycol dinitrate (DEGDN). It has been established [32] that the nature of the binder can have a significant effect on agglomeration.…”

Experimental investigation of agglomeration during combustion of aluminized solid propellants in an acceleration field

“…In a number of papers studying the burning rate under acceleration [1][2][3][4][5][6], the acceleration effect is associated to some extent with the behavior of condensed products in the surface layer and at the burning-propellant surface. It now seems to be generally accepted that normal compressive accelerations favor the retention of condensed products on the burning-propellant surface, which, in the limiting case, results in the formation of a liquid layer on this surface.…”