Burst Process of Spherical Aerial Shells
Y. Takishita, H. Shibamoto, T. Matsuzaki, K. Chida, F. Hosoya, and N. Kubota*
ABSTRACT: The burst process of spherical fireworks shells has been examined experimentally and presented as a simplified physical model. The pressure in a shell was measured with a straintype pressure transducer, which was inserted into the center of the shell. After the ignition of the bursting powder, pressure increased exponentially and the pressure also decreased exponentially, when the shell burst. The analysis of the pressure-versus-time curve indicated that the acting force on the stars in the shell was found to be dependent on various physical parameters: 1) the shape and material of the shell, 2) the characteristics of the bursting charge, and 3) the stars in the shell. The bursting process proposed in this study was confirmed by the observed ejection process of the stars in a Japanese-style, “warimono”* spherical shaped shell. *A spherical shaped shell containing stars and bursting charge that produces a chrysanthemum- flower shaped display in sky. [1]
Keywords: spherical aerial shell, burst process, pressure impulse, star acceleration
Ref: JPyro, Issue 10, 1999, pp1-6
(J10_1)
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Six Methods for Estimating the Formation Enthalpy of Organic Compounds
Will Meyerriecks
ABSTRACT: Finding published enthalpy of formation values for organic compounds is not always possible. Six methods are outlined for estimating this property, each utilizing different data that is generally readily available in one form or another. Additionally, a dozen different references for published thermodynamic data are provided.
Keywords: enthalpy of formation, heat of combustion, higher heating value, HHV, Benson group, flame temperature, free energy minimizatio
Ref: JPyro, Issue 10, 1999, pp7-16
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High-Nitrogen Fuels for Low-Smoke Pyrotechnics
David E. Chavez, Michael A. Hiskey and Darren L. Naud*
ABSTRACT: It has been demonstrated that the highnitrogen compound, 3,6-dihydrazino-s-tetrazine (DHT), can be utilized as a pyrotechnic fuel requiring small amounts of metal salts for coloring the flame. In addition, DHT pyrotechnic formulations using non-metallic oxidants, specifically ammonium perchlorate and ammonium nitrate, produce little smoke when burned. In light of this application of high-nitrogen compounds, we have determined that two other high-nitrogen fuels, bis-(1(2)H-tetrazol-5-yl)-amine monohydrate (BTAw), 5,5'-bis-1H-tetrazole (BT) and their salts are likely candidates for low-smoke pyrotechnic fuels. The various characteristics of these fuels have been examined in some detail; these include impact sensitivity with and without oxidant ammonium perchlorate, spectra of colored flames, and thermal analyses of their hydrates and salts.
Keywords: high nitrogen fuel, low smoke, pyrotechnics, bis-(1(2)H-tetrazol-5-yl)-amine,5,5'-bis-1H-tetrazole, 3,6-dihydrazino-s-tetrazine.
Ref: JPyro, Issue 10, 1999, pp17-36
(J10_17)
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Measurement of the Effectiveness of Various Mitigation Methods at Reducing the Projectile Hazards from Fragmenting Steel Firework Mortar Tubes
S. G. Myatt and M. R. Edwards ABSTRACT: Firework maroon shells were exploded inside mild steel spiral wound mortar tubes with various mitigation systems in place. It was found that the number of fragments was substantially reduced when the tube was prevented from expanding freely by sandbags or by burial of the tube in sand. For mitigation systems that allowed free expansion of the tube, the number of fragments was similar to that produced when no mitigation was employed. Mitigation systems should extend to the top of the tube to prevent fragments from hitting spectators or operators at displays.
Keywords: firework, mortar tube, safety, fragment, mitigation, steel, sandbag
Ref: JPyro, Issue 10, 1999, pp37-44
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Combustion of Ti/C Pyrolants
Michinori Takizuka, Toshio Onda, Takuo Kuwahara, and Naminosuke Kubota
ABSTRACT: The thermochemical characteristics of pyrolants composed of titanium (Ti) and carbon (C) were studied in order to develop high energy release materials used for igniters and fireworks. Since the Ti and C reaction occurs only at temperatures above 1200 K, polytetrafluoroethylene (PTFE) was mixed with the Ti/C pyrolants as an oxidizer. Various types of experiments were performed to gain information on the role of each ingredient. The results, measured by differential thermal analysis and thermal gravimetry, indicated that PTFE melts at about 605 K and reacts exothermically at about 830 K with Ti. The burning rate of the pyrolants increases as the mixing ratio of Ti and C approaches the stoichiometric ratio, (i.e., the burning rate increases as the adiabatic flame temperature increases within the range of the samples tested). Since the reaction starts from the surface of the Ti particles, the burning rate increases as the total surface area of the Ti particles increases.
Keywords: pyrolant, titanium, carbon, polytetrafluoroethylene, PTFE
Ref: JPyro, Issue 10, 1999, pp45-48
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