We have compared the combustion of the monopropellant nitromethane with that of nitromethane containing colloidal particles of functionalized graphene sheets or metal hydroxides. The linear steady-state burning rates of the monopropellant and colloidal suspensions were determined at room temperature, under a range of pressures (3.35−14.4 MPa) using argon as a pressurizing fluid. The ignition temperatures were lowered and burning rates increased for the colloidal suspensions compared to those of the liquid monopropellant alone, with the graphene sheet suspension having significantly greater burning rates (i.e., greater than 175%). The relative change in burning rate from neat nitromethane increased with increasing concentrations of fuel additives and decreased with increasing pressure until at high pressures no enhancement was found.

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Functionalized Graphene Sheet Colloids for Enhanced Fuel/Propellant Combustion

We have compared the combustion of the monopropellant nitromethane with that of nitromethane containing colloidal particles of functionalized graphene sheets or metal hydroxides. The linear steady-state burning rates of the monopropellant and colloidal suspensions were determined at room temperature, under a range of pressures (3.3514.4 MPa) using argon as a pressurizing fluid. The ignition temperatures were lowered and burning rates increased for the colloidal suspensions compared to those of the liquid monopropellant alone, with the graphene sheet suspension having significantly greater burning rates (i.e., greater than 175%). The relative change in burning rate from neat nitromethane increased with increasing concentrations of fuel additives and decreased with increasing pressure until at high pressures no enhancement was found.

Functionalized Graphene Sheet Colloids for Enhanced Fuel/Propellant

Combustion and heat transfer characteristics of nanofluid fuel droplets: A short review

The automatic building of quantum mechanical/molecular mechanical models (QM/MM) of rhodopsins has been recently proposed. This is a prototype of an approach that will be expanded to make possible the systematic computational investigation of biological photoreceptors. QM/MM models represent useful tools for biophysical studies and for protein engineering, but have the disadvantage of being time-consuming to construct, error prone and, also, of not being consistently constructed by researchers operating in different laboratories. These basic issues impair the possibility to comparatively study hundreds of photoreceptors of the same family, as typically required in biological or biotechnological studies. Thus, in order to carry out systematic studies of photoreceptors or, more generally, light-responsive proteins, some of the authors have recently developed the Automatic Rhodopsin Modeling (ARM) protocol for the fast generation of combined QM/MM models of photoreceptors formed by a single protein incorporating in its cavity a single chromophore. In this chapter, we review the results of such research effort by revising the building protocol and benchmark studies and by discussing selected applications.

Challenges and advances in computational chemistry and physics

Interest in developing an oxidizer matrix for reaction with nano-aluminum for energy-intensive applications involving explosives and propellants have led to the development of an aerosol-based sol−...

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Aero-Sol-Gel Synthesis of Nanoporous Iron-Oxide Particles: A Potential Oxidizer for Nanoenergetic Materials

Summary In combustion research, nitromethane is an important nitro-compounded liquid propellant offering high performance. Additionally it can be used as a model substance for understanding mechanisms of combustion of solid propellants. The objectives of investigations were the burning behaviour and the flame spectrum in the UV=VIS spectral range because of the appearance of strong radical emissions also present in flames of other energetic materials. The evaluation is based on a detailed chemical kinetics and a linear combustion model including a reduced mechanism.

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Modelling Nitromethane Combustion

Electro-thermal-chemical (ETC) initiation and combustion offers the possibility to increase the performance of guns substantially as new propellant formulations and high loading densities (HLD) can be safely ignited and burnt in an augmented way. This paper reports investigations of burning phenomena in the low pressure region for JA2 and the effects of plasma interaction on ignition and study its in ̄uence on the burning rate. The comparison of transparent and opaque versions of the propellant is of special interest. Electrically produced plasma can strongly in ̄uence the ignition and combustion of solid propellants. Predominantly, plasma arcs in ̄uence strongly the burning of propellants by its radiation. The high intensity of the radiation initiates burning with short time delays in the ms-range and high conversion during exposure also in the case of a stable burning. Radiation can penetrate into the propellant interior and partially fragment at absorbing structures which could be arti®cially introduced or be inherently present as in the case of a JA2 propellant. Simpli®ed approaches based on the heat ̄ow equation and radiation absorption can explain these effects at least on a qualitative scale. Dynamic effects are understood by more sophisticated models.

Plasma Ignition and Combustion

Burn Rate Models for Gun Propellants

Influence of the Metal Particle Size on the Ignition of Energetic Materials

Thermite type reactions are usually used when high quantities of heat should safely be produced with low gas release. Stoichiometric samples of aluminium, magnesium and titanium particles in μm-scale were mixed with iron(III) oxide and filled into small test tubes maintaining a constant bulk density. The metals were chosen regarding their heat release, melting and boiling point, the latter also important for the metal oxides. The samples were burnt in a window bomb pressurised from 0.1 to 13 MPa with nitrogen. The reaction was observed using a colour high-speed camera equipped with a macro object lens and different fast scanning emission spectrometers in UV/Vis and NIR to determine burning velocity, emitting species and reaction temperatures. The residues were analysed using scanning electron microscopy (SEM) including energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). The samples burnt in a reproducible way at a linear regression rate. A strong influence of pressure on the burning velocity and reaction zone temperatures was observed. The burning velocity varied by a factor of 3 forming a maximum at a certain pressure that is characteristic to the type of metal. In correlation, temperatures varied by several hundred Kelvin. Results were discussed regarding the decomposition, melting and boiling behaviour also including thermodynamic equilibrium calculations resulting in a qualitative two-step model of interacting and reacting droplets.

Stefan Kelzenberg

Papers

Modelling Nitromethane Combustion

Plasma Ignition and Combustion

Burn Rate Models for Gun Propellants

Influence of the Metal Particle Size on the Ignition of Energetic Materials

Thermite Type Reactions of Different Metals with Iron‐Oxide and the Influence of Pressure