Prilled/granulated ammonium nitrate is commonly used as a fertilizer and a basic ingredient of industrial explosives, especially of ANFO. One of the most important factors that affect the explosive properties of ANFO is the porosity of the prills/granules. This paper describes an attempt to manufacture ammonium nitrate prills of determined porosity in order to investigate its influence on the ANFO detonation velocity. A method of manufacturing porous ammonium nitrate prills with a high-level of oil absorption (up to 20% by volume) was developed. The relations between porosity and granulometric distribution of ammonium nitrate prills versus the detonation velocity of ANFO were examined. It has been proved that the detonation velocity of ANFO increases significantly with higher porosity and smaller size of ammonium nitrate prills/granules. The influence of ANFO oxygen balance (researched by changing the content of fuel oil in the mixture) on detonation velocity has been determined for two kinds of ammonium nitrate prills–one with a low and another one with a high level of porosity.

Influence of Ammonium Nitrate Prills' Properties on Detonation Velocity of ANFO

Passage en revue des mecanismes qui affectent la sensibilite a la temperature: les mecanismes directs traites dans les modeles analytiques, les aspects non ideaux du processus de combustion, la derive des mecanismes de controle

Mechanisms and models of solid-propellant burn rate temperature sensitivity - A review

The development of new propellant binder systems requires the thermodynamic calculation of physico-chemical data as well as the adaption of the mechanical properties in order to achieve a reliable innerballistic profile of the resulting propellant. Therefore, this study focuses on the mechanical properties of a binder system comprising GAP, NC as well as the energetic plasticizer DNDA and the curing agent Desmodur N100. By applying statistical methods, the mechanical properties of the binder can be predicted as a function of its composition. A macroscopic analysis of the interrelations between the E-modulus, the ultimate tensile strength as well as the elongation at break and the specific deformation energy lead to the creation of failure master curves, which can be used as a rule of thumb criterion for the formulation of propellant binders.

Optimization of Propellant Binders – Part Two: Macroscopic Investgation of the Mechanical Properties of Polymers

The temperature sensitivity of the burning rate of double-base propellants was studied to determine the parameters which control the temperature sensitivity mechanism. The temperature sensitivity of high and low energy propellants was examined in the temperature range between −30°C and +70°C. Experimental results indicated that the temperature sensitivity decreases as the energy contained in the unit mass of propellant increases. The burning surface temperature and the temperature in the fizz zone increased when the initial propellant temperature increased at a constant pressure. Thus, when the reaction rate in the fizz zone increased, the heat feedback from the gas phase to the burning surface increased. Consequently, the burning rate increased with increase in the initial propellant temperature. The heat released at the burnign surface remains relatively unchanged when the initial propellant temperature is increased. The temperature sensitivity of the burning rate is determined by the two parameters: “temperature sensitivity of the gas phase” and “temperature sensitivity of the condensed phase.” The temperature sensitivity of the gas phase can be decreased by decreasing the activation energy of the fizz zone reaction and/or by increasing the temperature in the fizz zone. The temperature sensitivity of the condensed phase can be decreased by increasing the burning surface temperature. These characteristics were confirmed by temperature sensitivity measurements of high and low energy propellants.

Analysis of the temperature sensitivity of double-base propellants

A Promising Fuel for Variable Thrust Motor: HTPB Propellant with High Pressure Exponent

The object of this paper is to obtain expressions for the burning rate pressure exponent and the temperature sensitivity of AP-based and HMX-based CMDB propellants in terms of the respective physical constants on the basis of a recently developed model of combustion for CMDB propellants and to examine the effects, if any, on these two parameters, of the changes in propellant composition, AP particle size and pressure. Computer programs were developed for this purpose and the results obtained for typical sets of input data presented in the paper. While the results of the calculation indicate a markedly strong dependence of the pressure exponent and the temperature sensitivity on pressure and composition for both AP-based and HMX-based CMDB propellants, the parameters are characterized by far lesser dependence on AP particle size for the AP-based propellant.

On the Burning Rate Characteristics of CMDB Propellants

The present paper describes a method for determining the equilibrium composition of the combustion products and the performance of propellants by using the Free Energy Minimization Technique. This minimization is sought to be carried out by a direct random search technique and systematic reduction of the size of the search region. The problem was programmed on the IBM 360/ Model 44 Computer in FORTRAN IV and rhe results for a typical metallized propellant are shown in the paper.

Propellant Evaluations by Free Energy Minimization through Random Search

The object of this paper is to present a method for determining, for a typical metallized solid propellant system, the optimum combination of the reactants so as to arrive at a composition which can yield the maximum specific impulse. A direct approach of this kind for optimization of propellants does not appear to have been attempted so far. The optimization is sought to be carried out by expressing the theoretical specific impulse of the propellant under frozen flow conditions as a function of the different variables involved and maximizing the same, subject to the usual linear and non-linear constraints of mass balance, mass action, pressure balance, energy conservation and entropy conservation. The gradient projection technique due to Rosen has been adopted for carrying out this optimization. The method was programmed on the IBM 360/Model 44 Computer in FORTRAN IV language and the results of the computations for a typical metallized solid propellant system are presented in the paper. The investigations reveal that the gradient projection technique can be a useful computational device for determining the optimum composition and the corresponding performance parameters of propellant systems containing a large number of reactants and products with or without condensed phases.

Performance Optimization of Metallized Solid Propellants

One of the principal parameters associated with a solid propellant is its linear burning rate. Many attempts have been made in the past to determine theoretically the burning rates of solid propellants by the use of appropriate combustion models. The object of the present paper is to propose a simplified theory of burning rate suitable for composite solid propellants. While the paper follows basically the scheme suggested for this purpose by Beckstead, Derr and Price using multiple flamelets, certain simplifying assumptions have been introduced with a view to make the model easier to operate. An attempt is also made in the paper to extend it to the case of aluminized solid propellants as well on the basis of a specific hypothesis regarding the role of aluminium. The relevant transcendental equations of combustion were solved on a digital computer. The burning rates and related characteristics were evaluated by this technique for two specific ammonium perchlorate-based solid propellants, one aluminized and the other non-aluminized, and the results obtained agree reasonably with the reported experimental trends.

Burning Rate Evaluation of Composite Solid Propellants. A simplified approach

The object of the present paper is to carry out a parametric study which takes into consideration the variations of the detonation characteristics such as CJ pressure, CJ temperature, velocity of detonation (VOD), and gas volume of CHNO-based condensed explosive systems in connection with the changes in input parameters like loading density and heat of formation of the explosive in question. Meaningful equations which describe adequately the interrelationships between the parameters were derived for a typical CHNO-type explosive. The study is likely to be of considerable help in determining the variations in the magnitudes of the detonation parameters corresponding to a given change in the relevant input characteristics. The results of such studies should also be important in estimating the uncertainty of a parameter, like VOD, arising from the uncertainty in the heat of formation of the explosive which is often determined experimentally and whose values is often of questionable validity. The principal features that emerge from the investigations in this paper are: (1) while CJ pressure and VOD tend to increase sizably with the loading density of the explosive, CJ temperature and CJ volume decrease with an increase in the loading density; and (2) all the four parameters, viz., CJ pressure, CJ temperature, VOD, and CJ volume increase, however, being of a marginal nature, barring the CJ temperature whose variations with the heat of formation are not insignificant.

V. Swaminathan

Papers

On the Burning Rate Characteristics of CMDB Propellants

Propellant Evaluations by Free Energy Minimization through Random Search

Performance Optimization of Metallized Solid Propellants

Burning Rate Evaluation of Composite Solid Propellants. A simplified approach

On the Detonation Characteristics of CHNO‐Type Condensed Explosives. A parameter study