Catalytic effects of nano additives on decomposition and combustion of RDX-, HMX-, and AP-based energetic compositions

A = E(l T^ admittance function, Eq. (1) sensitivity of gas phase to pressure changes specific heats of solid and gas activation energy for surface reaction E = ES/RTS enthalpy latent heat for surface reaction; Hp > 0 for exothermic s_urface reaction H = Hp/cT average mass flux fluctuation of mass flux at the surface index in the linear burning rate law, r = ap index in the surface pyrolysis law, Eq. (25) average heat release (per unit volume) in solid heat release in gas phase fluctuations of heat transfer at the average position of the surface, x = 0 fluctuations of heat release at the burning surface linear burning rate universal gas constant initial temperature of propellant, x -*• — co temperature of burning surface flame temperature average chamber temperature, x -*+ °° surface displacement, velocity functions defined in Eqs. (22) and (27) functions defined in Eqs. (22) and (27) stands for p'/p Eqs. (17-20) thermal conductivities of solid and gas stands for (ms'/m)r density of solid propellant and gas phase average density in chamber normalized temperature or a time lag dimensionless frequency parameters for the solid and gas phases; Eqs. (18) and following Eq. (34) real angular frequency mean value fluctuating value evaluated at the solid-gas interface evaluated on the gas (+) or solid ( — ) side evaluated on the gas or solid side of the mean position of the burning surface evaluated at the flame, or just downstream of the flame real part imaginary part

/pdf/a-review-of-calculations-for-unsteady-burning-of-a-solid-3nva2o5hxr.pdf

A review of calculations for unsteady burning of a solid propellant.

An experimental investigation of the regression-rate characteristics of hydroxyl-terminated polybutadiene (HTPB) solid fuel burning with oxygen was conducted using a windowed, slab-geometry hybrid rocket motor. A real-time, x-ray radiography system was used to obtain instantaneous solid-fuel regression rate data at many axial locations. Fuel temperature measurements were made using an array of 25- πm e ne-wire embedded thermocouples. The regression rates displayed a strong dependence on axial location near the motor head-end. At lower mass e ux levels, thermal radiation was found to signie cantly ine uence the regression rates. The regression rates werealso affected by theadditionofactivated aluminum powder.A 20%by weightaddition of activated aluminum to HTPB increased the fuel mass e ux by 70% over that of pure HTPB. Correlations were developed to relate the regression rate to operating conditions and port geometry for both pure HTPB and for HTPB loaded with certain fractions of activated aluminum. Thermocouple measurements indicated that the fuel surface temperatures for pureHTPBwerebetween930 and1190 K.TheHTPBactivationenergywasestimatedat11.5 kcal/mole,suggesting that the overall regression process is governed by physical desorption of high-molecular weight fragments from the fuel surface.

Regression Rate Behavior of Hybrid Rocket Solid Fuels

This volume brings together international scientists in the field of solid rocket propulsion. Thirty-nine papers present in-depth coverage on a wide range of topics including: advanced materials and non-traditional formulations; the chemical aspects of organic and inorganic components in relation to decomposition mechanisms, kinetics, combustion and modelling; safety issues, hazards and explosive characteristics; and experimental and computational interior ballistics research, including chemical information and the physics of the complex flow field.

Solid propellant chemistry, combustion, and motor interior ballistics

Thermal decomposition of energetic materials 3. A high-rate, in situ, FTIR study of the thermolysis of RDX and HMX with pressure and heating rate as variables☆

This paper presents a model for the purpose of estimating the fraction of aluminum powder that will form agglomerates at the surface of deflagrating composite propellants. The basic idea is that the fraction agglomerated depends upon the amount of aluminum that melts within effective binder pocket volumes framed by oxidizer particles. The effective pocket depends upon the ability of ammonium perchlorate modals to encapsulate the aluminum and provide a local temperature sufficient to ignite the aluminum. Model results are discussed in the light of data showing effects of propellant formulation variables and pressure.

A pocket model for aluminum agglomeration in composite propellants

: The objective of this program was to investigate and define the effects of inert binder properties on composite solid propellant burning rate. Experimental pyrolysis data were obtained for many binders of practical interest over a wide range of heating rates and pressures, in several environmental gases, with and without 10-percent ammonium perchlorate (AP) contained in the sample, and in some cases with catalysts. These data were used to extract kinetics constants from Arrhenius plots, and heat of decomposition. In addition, motion pictures were taken of the pyrolyzing surface and gas samples were extracted for analysis. Pyrolysis kinetics varied between binders, but were found to be independent of pressure, the presence of AP, and the presence of burn rate catalysts; however, a chlorine gas environment had a material effect upon the results. All of the binders exhibited molten, boiling surfaces mingled with char, to varying degrees; the amount of char increased with AP present, and in chlorine. Relevant data were input to the Derr-Beckstead-Price combustion model in order to associate binder properties with known binder effects on burning rate. Although the effects were predictable, they stemmed from properties other than pyrolysis kinetics; however, the binder data as applied to the model revealed possible deficiencies in the model, which are discussed. It appears that the approach of combustion tailoring by binder modification would have to involve the gas phase combustion processes rather than surface pyrolysis. Therefore, future work concerning the role of binder should be directed toward the gas phase.

/pdf/role-of-binders-in-solid-propellant-combustion-165jbx73v6.pdf

Role of Binders in Solid Propellant Combustion

This paper presents several improvements in the Beckstead-Derr-Price model of steady-state burning of AP composite solid propellants. The Price-Boggs-Derr model of AP monopropellant burning is incorporated to represent the AP. A separate energy equation is written for the binder to permit a different surface temperature from the AP. The discussion includes an analysis of the sharing of primary diffusion flame energy and a correction in treating the binder regression rate. A method for assembling component contributions to calculate the burning rates of multimodal propellants is also presented. Results are shown in the form of representativ e burning rate curves, comparisons with data, and calculated internal details of interest. Ideas for future work are discussed in an Appendix.

An improved model for the combustion of AP composite propellants

Steady-state combustion modeling of composite solid propellants is discussed with emphasis on the Beckstead-Derr-Price (BDP) model The BDP model and some revisions are considered with respect to the analysis of monomodal ammonium perchlorate/inert binder propellants: topics examined include continuity relations, surface area relations, characteristic surface dimension, flame heights, and energy balance Application of the BDP model to more complicated propellants containing multiple active ingredients is described These propellants include multimodal, mixed oxidizer, active binder, aluminized, catalyzed, and nitramine propellants Example cases of modeling (with comparison to experimental data) are presented, and strengths and weaknesses of current modeling approaches are evaluated

Review of Composite Propellant Burn Rate Modeling

The Cohen and Strand model for ammonium perchlorate (AP) composite propellants is applied as boundary conditions, one for AP and one for binder, in solving the heat conduction equation in each to compute linear and nonlinear combustion response properties for each and for the aggregate propellant. Iterations couple AP and binder through the quasi-steady flame processes. Illustrative results for linear response functions (pressure coupled and velocity coupled) are presented for a monomodal AP propellant showing effects of varying AP size, pressure, and crossflow speed. Examples of nonlinear responses to arbitrary waveforms are also shown. The model predicts a very large response at high pressures with coarse AP due to AP monopropellant combustion, underpredicts peak response amplitude for low pressures due to a possible change in mechanism, and shows a stabilizing effect of the diffusion flame. A quantitative comparison with response function data is limited to one well-characterized research formulation. Mechanistic implications are discussed, including recommendations for future modeling work.

Norman S. Cohen

Papers

A pocket model for aluminum agglomeration in composite propellants

Role of Binders in Solid Propellant Combustion

An improved model for the combustion of AP composite propellants

Review of Composite Propellant Burn Rate Modeling

Combustion response of ammonium perchlorate composite propellants