A two-phase mixture theory for the deflagration-to-detonation transition (ddt) in reactive granular materials

A Multiphase Godunov Method for Compressible Multifluid and Multiphase Flows

Advances in science and technology of modern energetic materials: an overview.

Metal-based reactive nanomaterials

Metal combustion has received renewed interest largely as a result of the ability to produce and characterize metallic nanoparticles. Much of the highly desirable traits of nanosized metal powders in combustion systems have been attributed to their high specific surface area (high reactivity) and potential ability to store energy in surfaces. In addition, nanosized powders are known to display increased catalytic activity, superparamagnetic behavior, superplasticity, lower melting temperatures, lower sintering temperatures, and higher theoretical densities compared to micron and larger sized materials. The lower melting temperatures can result in lower ignition temperatures of metals. The combustion rates of materials with nanopowders have been observed to increase significantly over similar materials with micron sized particles. A lower limit in size of nanoenergetic metallic powders in some cases may result from the presence of their passivating oxide coating. Consequently, coatings, self-assembled monolayers (SAMs), and the development of composite materials that limit the volume of non-energetic material in the powders have been under development in recent years. After a brief review of the classifications of metal combustion based on thermodynamic considerations and the different types of combustion regimes of metal particles (diffusion vs. kinetic control), an overview of the combustion of aluminum nanoparticles, their applications, and their synthesis and assembly is presented.

Metal particle combustion and nanotechnology

The paper describes a quasi-one-dimensional model of combustion of sandwich heterogeneous solid rocket propellant designed to predict the burnup rate of individual components (oxidizer and binder) and the average mass rate of combustion of the entire propellant. This model includes the heat- and mass-transfer and kinetic-gasdynamic processes in the gas phase above the surface of burning solid propellant, as well as the heat-transfer processes in solid material. Included in the calculations are the thermochemical properties of ammonium perchlorate (AP, oxidizer) and of polybutadiene rubber (PBR, fuel). The thermochemical processes are included in the kinetic scheme of two overall chemical reactions involving five effective chemical components. Systematic calculations are performed of the process of solid fuel combustion with different mass ratios of oxidizer to fuel. It is demonstrated that the employed kinetic model of thermochemical processes provides an adequate description of the available experimental data on the rate of combustion of AP- and PBR-based solid propellants.

Quasi-One-Dimensional Model of Combustion of Sandwich Heterogeneous Solid Propellant

: Laser Propulsion is the production of high specific impulse rocket thrust using a high power laser as a remote energy source Specific impulses in excess of 1000 seconds are achievable because propellant temperatures are very high and low molecular weight gases can be used This report focuses on the energy conversion mechanisms of laser-sustained plasmas in flowing argon The status of AFOSR sponsored experiments to determine thermal efficiency and global absorption is detailed An improved testing facility has allowed plasma operating conditions never before possible The results indicate that nearly all of the input laser power can be absorbed by a plasma Plasmas at elevated gas pressure have been tested, and preliminary results presented Optimal operating conditions have yet to be determined for the available laser powers and gas pressures Further experimentation at very high argon gas velocities ( 20 m/s) must be performed in order to completely characterize plasma behavior Keywords: Beamed energy propulsion, Laser plasma formation

Energy Conversion Measurements in Laser-Sustained Argon Plasmas for Application to Rocket Propulsion.

An experimental investigation of the combustion times for micro-sized Aluminum particles in conditions interesting to solid rocket motor (SRM) conditions, pressures 4-20 atm, temperatures near 2650 K, and oxidizer compositions 15-70% for oxygen, carbon dioxide, and water vapor oxidizers are presented. C ombustion in these conditions is in the transition regime between the diffusion limit which would be predicted for larger particles, and the kinetic limit, which would be predicted for nano particles. Burn times were calculated based upon emission from AlO, an aluminum combustion intermediate for all three oxidizers. These burn times are in contrast t o those that could otherwise be predicted by the Beckstead correlation in the diffusion limit ed regime. A heterogeneous shock tube was used to create the combustion conditions for in jected particles. The burn time of particles in the transition regime were shown to ha ve a stronger dependence upon composition mole fraction and pressure, but not str ong temperature dependence. A correlation is presented which should aid modelers in predicting burn times with particles down to a few micrometers.

Herman Krier

Papers

Quasi-One-Dimensional Model of Combustion of Sandwich Heterogeneous Solid Propellant

Energy Conversion Measurements in Laser-Sustained Argon Plasmas for Application to Rocket Propulsion.

Combustion of Aluminum Particles in the Transition Regime Between the Diffusion and Kinetic Limits

Application of internal Langmuir diagnostics to arcjets

An analysis of the chemically reacting boundary layer during hybrid combustion