The Mechanism of Super-Rate Burning of Catalyzed Double Base Propellants

Abstract

of. the-Navy,-Washinricton,D.C.!1i)stuy isdirected -at-understanding-howv'o.rgai la -ats(4 the 1%level) -`alter the 'burn'ing-mechanisms of--double base proppllXants --to produce large (up to 300%) burning rate increases (super-rate burning) Sand domains of reduced burning rate pressure and temperature sensitivity-*I(plateau burning). Investigations wore carried out with nitrocelluose-. and trimethylolethane trinitrate (TMETN) double base propellants withSsystematic variations in additives (including -lead-powder, -lead-oxide,--lead salicylate, copper powder, copper ealicylate, finely divided carbon Fl'and oxainide),, particle size,.and degree of dispersion. Diagnostic experSiments (from 0.*1 to 100 atm) .examined burning -rate behavior, gasa-phase stutr, burning-surface structure, -temperature profiles interac ton zones, and global efet. -fhe micro -thermo couple experiments.-re~vealed that 1% lead salts have lest -than a 10% effect on surface temapera n ueadsraeha ees u produce significant increases (70 to 4'-1 1 j~100%) in the fizz zone temperature gradi~ents. Lead salts decompose andd1 T Sdircl affect the surface reaction layer (ru 20Vi thick at 20 atm). The -----------------------------------------lead salts' decomposition products react with the nitrate esters to proSduce an increased amount of solid carbon. 'The portion of decomposed organic molecules which appears at the surface in the form of carbon Srather than readily oxidizable dl ehydes reduce the effective fuel to Soxidizer ratio (aldehyde to NO 2 ) 1 (Ad,, thus,, shifts the equivalence ratio AFý toward, the stoichiometric 'value; thid.accelera~tes the reaction rates in ;ýr fizz zone and produces super rate burning. P' DD IoSS 473-___________ 50iRIS14f. Also, the authors thank Professor W. A. Sirignano for his review and comments concerning the gas phase reactions.The experimental work was accomplished with the capable support of the Technician Staff.In particular, Mr. C. R. Felsheim was responsible for the specialized processing of the propellants used in this study, Mr. E. R. Crosby participated in the photographic work, and Mr. J. H. Semler assisted in the experiments using the delicate micro-thermocouples. ABSTRACTThis study is directed at uwderstanding how organic lead salts used as catalysts a!;er the burning mechanisms of double base propellants (i.e., two nitrate esters interdiffused) to produce burning rate increases (known as super-. rate burning) and domains of reduced burning rate pressure sensitivity (known as plateau burning).Simultaneously, these same lead salts greatly reduce the temperature sensitivity of burning rate in the super-rate range. These effects are of great practical interest since they provide design flexibility and yield performance which is largely. constant over a prescribed range of operating I.ressures and initial temperatures.The experimental investigations were carried out with particulate nitrocellulose (PNC) and trimethylolethane-trinitrate (TMETN) double base propellants instead of with the more hazardous-t...

Erosive and strand burning of stick propellants. I - Measurements ofburning rates and thermal-wave structures

“…At pressures higher than 21.4 atm (300 psig), the flame is clearly visible and quite steady. This burning with steady luminous flame is called "steady flame mode"; it is also referred to by Kubota et al 12 as "flame burning. "…”

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