Willis A. Rosser

Thermal decomposition of ammonium perchlorate

Abstract The decomposition of ammonium perchlorate and ammonium perchlorate-copper chromite mixtures has been studied in the temperature range from 250°C to 325°C. The products of decomposition were identified and the yield of each was established. Good recovery of N and Cl was achieved. The effect of atmosphere composition on the rate of decomposition was studied. The reaction mechanism proposed for the uncatalysed decomposition involves the adsorbed dissociation products NH 3 and HClO 4 , self-protonation of HClO 4 to yield the intermediate ClO 3 + , and oxidation of NH 3 by ClO 3 + . The reaction mechanism proposed for the catalysed decomposition involves the formation of the free radicals NH 4 and ClO 4 , decomposition of the radicals to NH 3 and chlorine oxides, and subsequent oxidation of NH 3 .

The effect of metal salts on premixed hydrocarbon—air flames☆

Abstract A study has been made of the inhibition of premixed flames by finely divided metal salts, some of which were found to be effective inhibitors of hydrocarbon combustion. The mechanism of inhibition by powders probably involves this succession of steps: (a) heating of the powder particles by the hot flame gases, (b) evaporation of the powder particles, (c) decomposition or reaction of the evaporated material to provide metal atoms, and (d) inhibition of the combustion process by the metal atoms.

Heat-release kinetics of ammonium perchlorate in the presence of catalysts and fuel

The rate of heat release of ammonium perchlorate-fuel and ammonium perchlorate-catalyst mixtures under adiabatic conditions was studied as a function of temperature. In the presence of catalysts, the autocatalytic feature associated with nucleation of pure ammonium perchlorate disappears and the adiabatic reaction kinetics follow Arrhenius-type behaviour. Studies made with ammonium perchlorate-fuel show that measurable heat release occurs at temperatures below the phase transition temperature of ammonium perchlorate and that the rate of heat generation per mass of material is greater than that of pure ammonium perchlorate. The rate of exothermic decomposition of pure ammonium perchlorate is unaffected by an increase in pressure. This observation suggests that the heat release is controlled by homogeneous or heterogeneous reactions in the condensed phase.

COMBUSTION OF FUEL DROPLETS

Droplets in the size range commonly encountered in spray combustors (50 to 200 /x) were produced in dilute sprays with a narrow size-distribution by means of an electrostatic atomizer. They were allowed to fall through a flat premixed methane-oxygen-nitrogen flame. As the droplets entered the flame, they ignited and subsequently burned in the hot gases resulting from the combustion of methane. The composition and temperature of these gases were controlled by adjusting the composition of the preflame gaseous mixture. The point of droplet ignition and the droplet lifetime under various experimental conditions were measured by optical methods. Such measurements were made with a variety of fuels. In the presence of sufficient oxygen to sustain combustion, it was found that ignition occurred in less than about 0.1 msec. However, the burning lifetime of the droplets varied from 2 to 20 msec depending on the initial droplet diameter and the gaseous environment. In the absence of sufficient oxygen for complete combustion, both evaporation of the droplet and thermal cracking of the fuel vapor were noted. The experimental data can be interpreted in terms of a model in which the rate of conductive heat transfer to the droplet controls its burning rate under specified conditions of oxidizer and fuel composition.

The quenching of premixed flames by volatile inhibitors

Quenching of premixed fuel-oxidizer flames by volatile additives was studied; the change in quenching diameter with inhibitor concentration was used to measure inhibitor effectiveness. The fuel-oxidizer combinations studied comprised methane-air, methane-nitrogen dioxide, methane-nitrogen dioxide-air and methane-nitric oxide. The experimental results indicate that the nature of the oxidizer is the most important oxidizer seem to be susceptible to chemical inhibition.

A study of decomposition burning.

The decomposition burning of liquid hydrazines in the form of small spheres is reported. Some aniline and water were contained in the hydrazine. A theoretical decomposition model is proposed and examined. It shows that the mass burning rate is proportional to the radius only for very low reaction rates or in the evaporative limit. For high reaction rates the mass burning rate is proportional to the square of the radius.

Adiabatic decomposition of ammonium perchlorate

An adiabatic method for studying exothermic solid reactions has been developed. Adiabatic conditions can be maintained in samples of a few grams weight for rates of temperature rise from 2–150 deg./min. The adiabatic decomposition of NH4ClO4 has been studied in the temperature range from 240–325°C.

Thermal stability of a reactive spherical shell

Abstract The conditions required for the spontaneous ignition of a volatile fuel drop suddenly exposed to a hot oxidizing environment have been investigated theoretically using a simplified model of the physical situation. Analysis of the model, a reactive spherical shell with unequal boundary temperatures, defined the conditions consistent with thermal stability of the shell. Two types of reaction rate were used, one with a simple Arrhenius form, and a second explicitly involving radial distance as well as a temperature dependence in Arrhenius form.