Begell House
International Journal of Energetic Materials and Chemical Propulsion
International Journal of Energetic Materials and Chemical Propulsion
2150-766X
6
5
2007
SIZE EFFECT OF ALUMINUM NANO-PARTICLES ON HTPB/AP PROPELLANT COMBUSTION
For a few years, nano-aluminum was supposed to bring about better combustion and ballistic properties to propellants. The actual published results seem a little disappointing. For the purpose of evaluating the properties of such particles, experiments were conducted to complete existing information from literature review.
A specific nano-aluminum powder has been selected because of its well-adapted chemical properties. A HTPB/AP/Al propellant has been processed by traditional techniques and tests were performed to ensure the good dispersion of the nano-Al.
By means of quenching and particle collection, it is observed that agglomeration phenomena takes place at the propellant combustion surface, limiting the initially expected effect of nano-aluminum. Interpretation of the particles' size and X-ray identification analyses are compared to the agglomeration prediction model (typically called 'pocket model') to verify whether this approach can be used in the nanometric domain or not. ONERA application of the Cohen-Beckstead's pocket model leads to a better agreement between experimental and predicted agglomeration globules. It appears that a few remaining overestimated cases, not foreseen by the model, can be attributed to rapid combustion of the finest Al particles.
Visualization experiments show the evolution of the combustion zone of the composite propellant versus the aluminum particles' sizes. As expected, the first visualization results outline the aluminum combustion zone coming closer to the propellant combustion surface. This distance is correlated with the aluminum particle diameter.
The Al combustion model proposed by Widener-Beckstead provided a good validation on a wide micrometric size range and in various experimental conditions. New combustion time measurements, extracted from ONERA visualization tests of very fine, yet visible, particles, allow validation of the model down to the particle size limit of 3−5 μm.
Jean-Francois
Trubert
ONERA, 29 avenue de la Division Leclerc, 91322 Châtillon cedex, France
Dominique
Lambert
ONERA, 29 avenue de la Division Leclerc, 91322 Châtillon cedex, France
Olivier
Orlandi
SNPE Matériaux Energétiques, Centre de Recherches du Bouchet, 91710 Vert-le-Petit, France
529-550
COMBUSTION BEHAVIOR AND FLAME STRUCTURE OF NITROMETHANE
Better knowledge of nitromethane (CH3NO2) flame structure and combustion behavior is desirable for a number of possible propulsion applications, both earth-based and extraterrestrial. When considered for rocket applications, nitromethane monopropellant is more energetic and less toxic than some current storable monopropellants such as hydrazine, though shock sensitivity questions still remain. In this investigation, the combustion behavior of nitromethane was studied using a variety of experimental and theoretical techniques over a broad range of pressures from 2.5 to 170 MPa. Its burning rates at different pressures were measured in quartz tubes and at a free surface, and found to fall into 3 regimes. At low pressures (4 to 6 MPa), temperature profile measurements using fine-wire thermocouples showed a thick thermal wave in the liquid subsurface, extremely thin flame zone, and final flame temperature of near 2,100 K, significantly less than the equilibrium value of 2,460 K. A model was formulated that included both gas-phase and condensed-phase processes. Using the detailed reaction mechanism for nitromethane developed by Yetter and Rabitz coupled with the CHEMKIN code, flame structure was calculated and compared to observations and measured values. Significant differences were found; however, with the modification of kinetic parameters in two elementary reactions, the measured temperature trace was duplicated.
Eric
Boyer
The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Kenneth K.
Kuo
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
551-573
ELECTROLYTIC-INDUCED DECOMPOSITION AND IGNITION OF HAN-BASED LIQUID MONOPROPELLANTS
Experimental results are reported on the ignition characteristics of XM46 liquid propellant at room conditions using electrolysis. The ignition system employed a titanium microfin electrode module, which is comprised of 8 parallel fins evenly spaced with separation distance of 1-mm. Each fin has a dimension of 9 × 19 × 0.25 mm generating a surface area of approximately 350 mm2. Input voltage to the electrodes ranged from 7 to 26 VDC and electrode surface area ranged from 1050 to 4200 mm2. Experiments were performed in a liquid strand burner in which the propellant ignited, combusted, and propagated downward. The propellant initially bubbled at the surface of the electrodes and then ignited to establish a self-propagating thermal wave. The observed linear burning rates were consistent with extrapolated values of published rates at higher pressures. At one atmosphere, a highly luminous gas-phase flame positioned above the surface of the propellant was not observed. A higher input voltage facilitated the gasification of XM46 while minimizing the total energy required. The time delay to peak power (reactivity) decayed exponentially from 160 seconds to 2-3 seconds with an increase in the input voltage from 7 to 12 VDC. Beyond 12 VDC, the time delay dependency became less significant and appeared to remain constant. Peak power increased from 30 to 550 W when the input voltage was increased from 7 to 15 VDC. The power density decreased with increasing surface area indicating that the power was not linearly dependent on electrode surface area. The propellant liquid temperature reached a nearly steady-state temperature of 115°C, which agrees with the temperature or pure HAN during thermal decomposition.
Grant A.
Risha
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, Altoona College, Division of Business and Engineering, Altoona, PA, USA
Richard A.
Yetter
Department of Mechanical and Nuclear Engineering, Pennsylvania State University University Park, PA, USA
Vigor
Yang
Department of Mechanical Engineering The Pennsylvania State University University Park, PA 16802, USA; School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
575-588
SUPPRESSION OF DUST-AIR MIXTURES EXPLOSIONS BY MEANS OF WATER SPRAY
The aim of the presented work was the development and testing of the code enabling numerical simulation of the dust explosion suppression process. The obtained results were compared with those received from the experiments. Corn starch was used as the explosive dust and water as the suppressing material. A good agreement was found between the results obtained from numerical simulations and from the experiment.
P.
Oleszczak
Warsaw University of Technology, Warsaw
Rudolf
Klemens
Institute of Heat Engineering, Warsaw University of Technology, Poland
589-607
NEW NUMERICAL APPROACHES TO MULTIPHASE FLOWS MODELING
We present new numerical approaches for solving systems of partial differential equations associated with mathematical models for multiphase flows. We are concerned with the construction of modern numerical methods for solving the equations for hyperbolic models in conservative or non-conservative form. Here, we apply new approximate Riemann solvers for two-phase flow, whereby, a closed-form non-iterative solution can be obtained,1 and a new approach for general hyperbolic systems called EVILIN.2 In order to produce upwind numerical methods, the local approximate Riemann solution provides the necessary information to compute numerical fluxes that can be used in the finite volume approach or the Discontinuous Galerkin approach.
We utilize these approximate Riemann solvers locally to produce upwind numerical methods in the finite volume framework suitably modified to deal with systems in non-conservative form. Non-oscillatory schemes of second-order accuracy are then designed following the TVD approach. In addition, we construct second-order numerical schemes for multiphase flows following the recently proposed ADER3 approach, which also permits the handling of source terms to a high order of accuracy.
We perform a comprehensive and systematic assessment of the numerical methods constructed using reference numerical solutions and exact solutions that we have obtained for special cases.
C. E.
Castro
Laboratory of Applied Mathematics, Faculty of Engineering, University of Trento, Trento
E. F.
Toro
Laboratory of Applied Mathematics, Faculty of Engineering, University of Trento, Trento
609-627
METHOD OF CHARACTERISTICS SIMULATION OF INTERIOR BALLISTIC PROCESSES OF M1020 IGNITION CARTRIDGEIN A 120-mm MORTAR SYSTEM
The objective of this study was to simulate the flame spreading and combustion processes in the ignition cartridge of a 120-mm mortar propulsion system under realistic firing conditions for performance improvements. In this work, theoretical modeling, numerical technique, and results of numerical simulation of the interior ballistic processes in the M1020 ignition cartridge of a 120-mm mortar system are presented. Modeling and simulation of the combustion processes in the granular propellant bed loaded with M48 ball propellants involves the solution of six coupled quasi-linear inhomogeneous hyperbolic partial differential equations (PDEs). These equations were formulated by applying the principles of conservation of mass, momentum and energy for condensed phase and gas phase in the granular propellant bed. In order to solve these equations for quantities of interest (i.e. pressure, propellant surface temperature, gas temperature, porosity, gas velocity, and propellant particle velocity), they were first converted to a system of ordinary differential equations (ODEs) using the method of characteristics (MOC). The MOC approach was selected because it introduces minimum numerical errors in converting the original system of PDEs into an equivalent system of ODEs. Calculated pressure-time traces showed axial pressure wave phenomena and compared closely with the measured pressure-time traces. The reason for the presence of pressure waves was found to be the non-uniform discharge of mass and energy of the combustion products from the vent holes of the flash tube.
Peter J.
Ferrara
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University University Park, PA 16802
Jeffrey D.
Moore
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University University Park, PA 16802
629-650
MODELING AND SIMULATION OF NANO-ALUMINUM SYNTHESIS IN A PLASMA REACTOR
The synthesis of aluminum (an energetic material) nanoparticles in a plasma reactor is simulated. The effects of flow-field mixing on nanoparticle growth are investigated via direct numerical simulation. The flow consists of high temperature argon/aluminum jet impinges on a low-temperature argon jet. To analyze the influence of fluid dynamic mixing on nanoparticle growth, the momentum ratio of the two jets is varied. The flow-field is obtained by solving the compressible Navier-Stokes equations while the evolution of the particle field is obtained by using a nodal approach to represent the aerosol general dynamic equation. The results indicate that increasing the momentum of the cooler jet increases dilution of the aluminum jet and increases flow-through time of nanoparticles (the time required by particles to travel the length of the domain).
Nelson
Settumba
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN
Sean C.
Garrick
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN
651-663