Table 2 –Silicon dioxide additive effect on metalless composition burning rate

SiO2 content (mass %)	, (mm/s)
0	0.6±0.2
2	0.6±0.1
10	0.6±0.1

Thermodynamic calculations of equilibrium composition of base fuel systems containing AN-EA-EB-Al combustion products were carried. Calculations were carried for fuel systems with fixed value of oxidizer excess factor α=0.545 and fixed EA content in a quantity of 26 mass %. The aluminum content was varied in range from 15 up to 30 mass % by means the change of AN/EB ratio.

Results of calculation show (table 3), that the aluminum content increase leads to growth of a specific impulse (I_sp), adiabatic temperature of burning (Т_ad), a mass fraction of all condensed phases (z), and also to increase in the content of incomplete oxidation components (H, OH, NO).

It is shown, that the introduction of metal from 15 up to 25 mass % increases a specific impulse on 7 s and simultaneously increases the content of condensed aluminum dioxide in combustion products from 2.8 up to 4.6 mole/kg. The last fact is important for considering in a problem of securing of condensed substances content reduction in combustion products in the nozzle exit section for reliable working capacity of the rocket engine. Introduction in a compound of investigated system over 25 mass % aluminum leads to decrease in a specific impulse. It is shown by calculations, that at a preset value α=0.545 technologically reproduced propellant systems correspond to the aluminum content in range from 15 up to 20 mass %.

Table 3 – Design values for mass-energetic fuel characteristics

Characteristic		Al content (mass %)
		15	20	22	25	27	30
Compound components:
EB AN EA Al		32 27 26 15	24 30 26 20	21 31 26 22	16 33 26 25	12.8 34.2 26 27	8 36 26 30
Тad, К		3257	3497	3580	3684	3738	3799
z		0.281	0.369	0.412	0.443	0.464	0.486
Isp, s		274.7	279.9	281.0	281.8	281.5	279.9
Decomposition product content in nozzle exit section (mole/kg)
H	0.018		0.143	0.276	0.630	0.993	1.695
O2	0.000		0.000	0.000	0.000	0.000	0.000
H2	11.835		12.177	12.344	12.572	12.683	12.701
OH	0.001		0.007	0.014	0.027	0.034	0.028
H2O	5.683		4.208	3.544	2.490	1.764	0.741
N2	9.106		8.934	8.861	8.749	8.673	8.553
NO	0.000		0.000	0.001	0.002	0.002	0.002
CO	10.137		8.783	8.164	7.175	6.483	5.397
CO2	1.137		0.559	0.402	0.223	0.135	0.045
Al2O3condenced	2.780		3.706	4.077	4.631	4.998	5.507

The analysis of experimental results shows that the most efficient burning rate control of the metallized propellants containing aluminum ASD-6 and "Alex" grades, based on chlorineless oxidizer, the energetic additive and energetic binder is possible by means of adding of silicon dioxide in amount of 2 mass % over 100 %. In compositions with an energetic binder is expediently to use the mixed metal fuel, especially by inletting additives that effect on the mechanism of initial aluminum combustion. It is shown, to ensure a high level burning rate of propellants, based on the mixed metal fuel, comparable with a burning rate level of propellant containing "Alex" as a metal fuel, the optimal ratio of ASD-6/"Alex" for composition № 1 is 40/60, and for composition № 2 is 50/50.

This work was carried out within the framework of realization of the Federal target program "The Scientific and scientific-pedagogical staff of innovative Russia" for 2009-2013 with a support of State contract П474 from 04.08.2009 “Developing and processing of the high-energy filled polymer compositions”.

References

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