Laboratory scale method for preparation of mixture modeled composite fuels for hybrid propulsion

Thermal, Viscosimetric and Thermomechanical Combined Assessment of Mixture Modelled Composite Fuels for Hybrid Propulsion

“…In addition, its mass amounted to 89.29 g, thus allowing a 9.73 % theoretical porosity, also comparable to the 11.33 % figure for pure paraffin, both attained in a centrifugal casting process, without vacuum application, and thus significantly higher than the ones found in other studies [44,45]. This result seems coherent with the decrease in volumetric contraction stemming from centrifugal casting in pure paraffin, as compared to static casting data [19]. Nonetheless, Figure 7 (a) and (b) show that its dimensional regularity is noticeable, particularly across the port, as well as within the composite grain, as can be seen in Figure 7 (c), whose absence of major cracks and voids suggests that the attained porosity is related to minor bubbles of entrapped air, evenly distributed across the composite grain.…”

“…The resulting temperature gap of nearly 32 °C is considerably smaller than the one from pure organic components under the same experimental conditions (circa 41 °C), as can be seen by comparing Figure 2 (a) and (b). This suggests an acceptable LDPE-paraffin miscibility level allowed by the preparation protocol, in the same pattern previously observed for crystallization enthalpy [19]. The attained re-duction of the melting temperature gap, regardless of the solid oxidizer amount, would benefit the entrainment occurrence in a hybrid motor, given the appropriate oxidizer mass flux is provided.…”

“…It yielded a 3.55 cm length, a 6.51 cm and 2.69 cm external and internal diameters, respectively, as well as a volumetric contraction of 9.58 %, comparable to that of pure paraffin prepared under the same method, i. e. 9.90 % [19]. In addition, its mass amounted to 89.29 g, thus allowing a 9.73 % theoretical porosity, also comparable to the 11.33 % figure for pure paraffin, both attained in a centrifugal casting process, without vacuum application, and thus significantly higher than the ones found in other studies [44, 45].…”

“…The low-density polyethylene-macrocrystalline paraffin-ammonium nitrate composite fuel samples were produced ac-cording to a lab-scale protocol previously developed, based on two major steps, i. e., mixing and centrifugal casting [19], which can be outlined as follows: (1) raw materials weighing and mold assembly; (2) LDPE and paraffin pre-mixing in the mold, under 120 rpm, at ambient temperature; (3) mold immersion in a glycerin bath at 150 °C, melting and mixing at 50 rpm until the bath temperature returns to the initial setting; (4) stirring at 100 rpm, with the bath temperature at 150 °C, for 15-25 minutes; (5) slow addition of 297 < Φ < 590 μm NH 4 NO 3 , under 100 rpm stirring and with the bath temperature at 150 °C; (6) homogenization for 15 min at 100 rpm, bath temperature kept constant at 150 °C; (7) removal of the stirrer, followed by the upper stopper and lid assembly, horizontal centrifugal casting at 400 rpm for 120 min and subsequent demolding of the composite fuel grain. Figure 1 shows some of these steps, identified by the numbers defined above.…”

“…1, respectively. These formulations share the same B/A ratio, i. e., 1.1, which yielded excellent macroscopic homogeneity and structural integrity [19]. In addition, they range from ammonium nitrate absence (Nouv_2 V_00) to its maximum amount (Nouv_3 V_ 00), i. e., 20 wt%.…”