Mathematical Model and Numerical Investigation of Combustion Front Propagation Velocity in an Aerosol of an Aluminum Nanopowder Suspension in Kerosene

2021 ◽  
Author(s):  
A. Yu. Krainov ◽  
V. A. Poryazov ◽  
K. M. Moiseeva ◽  
D. A. Krainov
Keyword(s):  
Mathematical Model ◽  
Numerical Investigation ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Front Propagation ◽  
Aluminum Nanopowder ◽  
Front Propagation Velocity

Investigation of propagation modes and temperature/velocity variation on unstable combustion synthesis

2002 ◽  
Vol 17 (12) ◽  
pp. 3213-3221 ◽  
Author(s):  
H. P. Li
Keyword(s):  
Activation Energy ◽  
Combustion Synthesis ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Combustion Reaction ◽  
Velocity Variation ◽  
Material Synthesis ◽  
Unstable Combustion

Combustion synthesis/micropyretic synthesis is a technique in which material synthesis is accomplished by the propagation of a combustion front across the sample. In some cases, the combustion front may propagate in an unstable mode where the propagation velocity and combustion temperature of the combustion front are altered periodically. In this study, the processing conditions leading to unstable combustion reaction were first studied theoretically. The boundary temperatures separating stable and unstable reactions were then determined. The numerical analysis showed that the combustion temperature and the propagation velocity changed periodically during unstable combustion. As the combustion reaction became unstable, the average propagation velocity and the oscillatory frequency of front propagation decreased. The products of unstable combustion synthesis possessed the banded structures, implying the occurrence of the unstable oscillatory propagation, as demonstrated experimentally. In this study, high activation energy combustion (Ti + 2B reaction) and low activation energy combustion (Ni + Al reaction) were both chosen to illustrate the effect of unstable combustion. It is the first time the experimental and numerical results were combined to investigate the temperature and propagation velocity variations during unstable combustion.

Preparation of (Mo,Nb)Si2 Ternary Alloys by Self−Propagating High−Temperature Synthesis

2011 ◽  
Vol 266 ◽  
pp. 219-222
Author(s):  
Pei Zhong Feng ◽  
Shuai Zhang ◽  
Xiao Hong Wang ◽  
Wei Sheng Liu ◽  
Jie Wu
Keyword(s):  
High Temperature ◽  
Flame Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Ternary Alloys ◽  
Combustion Mode ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Front Propagation Velocity

An experimental study on the preparation of (Mo,Nb)Si2 ternary alloys was conducted by self-propagating high-temperature synthesis method from elemental powder compacts of different stoichiometries. And the combustion mode, combustion temperature, flame-front propagation velocity and product structure were discussed. The results show that (Mo,Nb)Si2 ternary alloys are characterized by an unsteady state combustion mode with a spiral−trajectory reaction front from top to bottom. The combustion temperature and flame−front propagation velocity decrease with the addition of coarse niobium powder. The combustion temperature and flame-front propagation velocity of MoSi2 are 1629K and 3.13mm/s respectively. However, those of (Mo0.8Nb0.2)Si2 alloy are 1460K and 1.97mm/s. The solid solubility of niobium in MoSi2 is less than 2.5at.%, and the combustion synthesis produce still remains Cllb single-phase structure in (Mo1-x,Nbx)Si2(x<0.075) sample. The C40-type structure appears in (Mo0.925,Nb0.075)Si2 compact and the intensity of diffraction peaks of C40-type phase gradually reinforces with the increase of niobium content. Combustion synthesis is an effective technology for producing (Mo,Nb)Si2 ternary alloys.

MATHEMATICAL MODELING OF FLAME PROPAGATION IN THE AEROSUSPENSION OF NANOSIZED ALUMINUM POWDER

2020 ◽  
Author(s):  
A. Yu. Krainov ◽  
◽  
V. A. Poryazov ◽  
K. M. Moiseeva ◽  
◽  
...  
Keyword(s):  
Combustion Front ◽  
Propagation Velocity ◽  
Mass Concentration ◽  
Initial Temperature ◽  
Large Diameter ◽  
Front Propagation ◽  
System Of Equations ◽  
Conservation Equations ◽  
Gas Dispersion ◽  
Al Powder

This paper provides a mathematical model of combustion of a nanodispersed aluminum-air suspension (NAAS). The main feature of the model is the local approach for oxidant diffusion which implies the diffusion of oxidizer through alumina layer on the particle surface and its reaction with aluminum. The oxidation rate of aluminum particles and the rate of heat release for the whole assembly of particles are determined from the solution of local combustion problems for each Al nanoparticle. The parameters of the NAAS are determined from the solution of the system of equations which include the energy conservation equations for gas and particles and the mass conservation equations for the components of the gas-dispersion mixture. The developed model does not require setting the ignition temperature of Al nanoparticles. The system of equations is solved numerically. The problem of combustion front propagation is solved with the following formulation: NAAS is placed in a tube of large diameter and length with a closed left end and open right end. The initial mass concentration of Al powder in the air is uniform and less than the stoichiometric value. Since a high-temperature ignition source on the left end of the tube ignites the NAAS, a combustion wave occurs and starts propagating along the tube. In the present study, the dependences of the combustion-front propagation velocity on the Al mass concentration and initial temperature of the NAAS have been determined. With increasing the initial temperature and mass concentration of Al powder, the propagation velocity of the combustion front increases.

scholarly journals Binary frontal polymerization: Velocity dependence on initial composition

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
John A. Pojman ◽  
Jerry Griffith ◽  
H. Archie Nichols
Keyword(s):  
Propagation Velocity ◽  
Binary Systems ◽  
Reaction Rate ◽  
Front Propagation ◽  
Analytical Description ◽  
Frontal Polymerization ◽  
Velocity Dependence ◽  
Initial Composition ◽  
Arrhenius Dependence ◽  
Front Propagation Velocity

Abstract Frontal polymerization is a mode of polymerization in which a localized zone of reaction propagates through the coupling of thermal diffusion and the Arrhenius dependence of the reaction rate. The dependence of the front propagation velocity on the initial composition has been determined in initially miscible binary systems of a free-radically cured diacrylate and an amine- or cationically cured epoxy resin. A minimum of the velocity as a function of the monomer mole fraction is observed if the two polymerizations occur independently. Excellent agreement with an analytical description was found with the diacrylate and an amine-cured epoxy but not for a diacrylate and a cationically cured one because of the effect of HCl impurities on the peroxide.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

2021 ◽  
pp. 1-13
Author(s):  
Melek Deniz Paker ◽  
Murat Cinar
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Combustion Front ◽  
Fractured Reservoirs ◽  
Front Propagation ◽  
High Permeability ◽  
Vertical Orientation ◽  
In Situ Combustion ◽  
Horizontal Orientation

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (/SC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of /SC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied /SC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several /SC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to airflow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil AP/ gravity was higher. Based on the experimental results a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

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