Particle size, oxidizer

R.D. Gould, Combustion Instability of Solid Propellants Effect of Oxidizer Particle Size, Oxidizer/Fuel Ratio and Addition of Titanium Dioxide to Plastic Pro pell ants , Rept No RPE-TR-68/1, Westcott (Engl)... 

In this equation, Summerfield has shown that the parameter b1 should be very sensitive to the flame temperature of the propellant. At the same time, the factor b2 should be strongly dependent on oxidizer particle size. To check these predictions, Summerfield prepared four propellants using 120 and 16 oxidizer particles at 75 and 80% loadings. Correlation of the burning-rate data with Eq. (39) yields the values for the parameters given in Table I. The experimentally observed trends are consistent with predicted effects. 

Horton (H9, H10) has obtained additional acoustic-admittance data for a series of composite propellants. At a given frequency, decreasing the mean oxidizer particle size increases the acoustic admittance and thereby the tendency for instability. Horton also investigated the effects on the acoustic admittance of the incorporation of traces of copper chromite, a known catalyst, for the decomposition of ammonium perchlorate, lithium fluoride (a burning-rate depressant), and changes in binder these data are difficult to analyze because of experimental errors. 

Factor relating oxidizer particle size to gas pocket size rh/rfi,... 

Figure 14. Effect of oxidizer particle size on burning rate (equal parts PVC and dibutyl sebacate)...

The same coordinates that were found to correlate the effect of oxidizer particle size on burning rate also satisfactorily correlate the effect on burning rate of metal particle size when 10.3% of closely screened, spherical magnesium is added to standard Arcite. This is shown in Figure 19. At this level of metal added, burning rate is increased by magnesium particle size less than approximately 250/ but is decreased by larger particle size. 

This was followed by Taback s (94) study of the effect of copper chromite catalyst additives. In general, the results of these investigations fitted the Summerfield relation remarkably well over the range 1—100 atm. (Figures 3 and 6). Moreover, the effects of propellant composition and oxidizer particle size on the constants a and b, respectively, were consistent with qualitative predictions from the theory. Similar results have since been obtained by Yamazaki (101), Marxman (18), and the group at ONERA (8, 52, 64) in France (Figure 7). An alternative to the above equation has been proposed by Penner et al. (68)—i.e., (1/r)2 = (a/p)2 + (b/pm)2. A systematic survey (91) of all available data shows that when... 

Figure 17. Burning rate of 35% polysulfide + 65% NH,tClOh with varying mean oxidizer particle size...

Burning at subatmospheric pressure is accompanied by the evolution of white fumes which solidify upon contact with a cold surface. For the LP3 propellant, it is larger in quantity and increases considerably as soon as the ash starts forming. This smoke was found to contain 25% ammonium perchlorate and 55% ammonium chloride. A trap was installed to determine the amount of smoke evolved per unit mass of propellant as a function of pressure and oxidizer particle size, but the results were inconclusive. The weight of sublimate caught was approximately 20% of the original weight of the propellant. 

Pearson (66) found that hot solid surfaces drastically accelerate the ignition of these vapors. In line with our identification of the A/PA reaction zone as the major heat source, it is expected that both burning rate and extinction pressure depend on the total surface area of AP particles exposed to the A/PA reaction occurring in the pores of the ash. Thus, as observed experimentally, both burning rate and extinction pressure depend upon oxidizer particle size. However, this interpretation is obscured by the fact that combustion inefficiency, an important parameter, is also expected to be particle size dependent. [Total AP surface area exposed to A/PA reaction zone = A = na, where n = (number of AP particles exposed), (volume of each AP particle)"1 d 3, a = (exposed surface area of each AP particle) — dr. Therefore, A — d1.]... 

V. M. Gun ko, V. I. Zarko, R. Leboda, and E. Chibowski, Aqueous Suspensions of Fumed Oxides Particle Size Distribution and Zeta Potential, Adv. Colloid Interface Sci. 91(1), 1-112(2001). 

R. Ceschino, I. Fenoglio, M. Tomatis, D. Ghigo, B. Fubini, and G. Martra, Ultrafine versus fine iron oxide particles size effects on the surface reactivity towards model biological systems, Chem. Res. Toxicol, submitted for publication. 

Shang, C., and H. Tiessen. 1997. Organic matter lability In a tropical Oxisol evidence from shifting cultivation, chemical oxidation, particle size, density, and magnetic fractionations. Soil Science. 162 795-807. 

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