Spin gas combustion in a narrow slot

Combustion in a gap between two thin circular plates with point injection of the gas in the center is experimentally examined. The existence of several combustion regimes is demonstrated. Unstable pulsed combustion is observed in the case of high flow rates. As the flow rate decreases, a transition to spin combustion occurs under certain conditions. If the distance between the plates is sufficiently small, the so-called excess-enthalpy flame can be realized in an expanding gas flow. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 23–26, May–June, 2006.     

Unsteady combustion processes in a channel with gas stream swirling and its termination

Results of numerical simulation of the flow and combustion of a pre-mixed gas mixture in a cylindrical channel at sudden swirliing of the flow and its sudden termination are considered. The calculations conducted show that the flow swirling allows flame localization in a given volume of the combustion chamber and is an effective method for combustion control. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 4, pp. 33–40, July–August 1999.     

Characteristics of the boundary layer with hydrogen combustion with variations of thermal conditions on a permeable wall

The paper describes a numerical study of the influence of thermal and boundary conditions on the structure of laminar and turbulent diffusion flames in the cases with hydrogen injection through a porous surface and with hydrogen combustion in an air flow. Two types of boundary conditions are compared: with a given constant temperature T _w = const over the length of the porous surface for arbitrary intensities of fuel injection and with a constant temperature T′ = const of the fuel injected through the porous wall. The first case occurs during combustion of a liquid fuel whose burning surface temperature remains unchanged. Injection of gaseous fuel usually leads to the second case with T′ = const. Despite significant differences in velocity and temperature profiles, the skin friction coefficients in the laminar flow are close to each other in these two regimes. In the turbulent regime, the effect of the thermal boundary conditions on friction and heat transfer is more pronounced. Moreover, the heat flux to the wall as a function of fuel-injection intensity is characterized by a clearly expressed maximum. A principal difference of the effect of combustion on friction and heat transfer in the laminar and turbulent flow regimes is demonstrated. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 3–11, May–June, 2009.     

Investigation of the structure of a diffusion hydrogen plume in a supersonic high-enthalpy air jet

The results of investigation of the plume structure in the case of diffusion combustion of hydrogen in a cocurrent supersonic high-enthalpy off-design air jet are presented. Based on the registration of radiation within the wavelength range of 260–350 nm across and along the flame, a three-dimensional tomographic reconstruction of the plume was obtained, which confirmed the interrelation between the gas-dynamic structure and combustion intensity. A possibility of existence of combustion regimes with periodically repeated cycles of complete extinction and subsequent ignition of hydrogen in accordance with the barrel-shaped structure of the off-design jet is established experimentally. The existence of local peripheral regions of combustion is noted, which can indicate the presence of vortex structures. In the three-dimensional representation (obtained under the assumption of axial symmetry of radiation), these vortex structures have the form of annular zones. In a real flow, helical structures are possibly formed at the plume periphery. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 5, pp. 3–5, September–October 1999.     

Operation of a gas generator controlled by supplying a gaseous oxidizer

The possibility of arranging a gas generator with the heat-release process being controlled by supplying a gaseous oxidizer is experimentally checked. Gaseous hydrogen, liquid gasoline, and solid hexamethylene tetramine (solidified alcohol) is used as a fuel. The gas generator with a proposed configuration is demonstrated to ensure stable operation during combustion of various fuels; the pressure in the gas-generator combustion chamber does not exceed the pressure of oxidizer supply and clearly correlates with variations of the oxidizer mass flow. Quasi-steady calculations allow determining all parameters of the process, including those that are not measured in the experiment. In particular, the temperature of combustion products is found to be 600–1900 K, and the gas generator forms a high-temperature mixture containing a non-reacted fuel (the air-to-fuel ratio is α = 0.55–2.30). __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 18–25, November–December, 2008.     

Effect of heat transfer on the distributions of OH and CH radicals in the boundary layer with ethanol combustion

The reasons for formation of superequilibrium concentrations of radicals are studied by means of joint consideration of experimental data on the distributions of CH and OH molecules formed during diffusion combustion of ethanol and data on heat transfer in the chemical reaction region. The air flow velocity near the stagnation point in experiments with combustion is 0.7 m/sec, and the flow velocity along a flat plate is 10 m/sec (the turbulence levels are 1 and 18%). Mutual locations of specific features in the distributions of the heat-release rate and temperature are analyzed and compared with the distributions of OH and CH radicals. For all turbulence levels and flow velocities considered, the maximum concentration of radicals is reached on the boundaries of the heat-release region, whose locations are determined by molecular transport mechanisms. It is demonstrated that this conclusion is applicable to experimental data on diffusion combustion of a submerged hydrogen jet in air. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 3–11, November–December, 2008.     

Combustion of thermite systems with orthogonal orientation of the overload and combustion-velocity vectors

The mechanism of combustion of the Fe₂O₃+Cr₂O₃+Al+C system in a field of centrifugal forces with orthogonal orientation of the overload and combustion-velocity vectors is studied. It is shown that a centrifugal force has a pronounced effect on the combustion mechanism and velocity. It is found that the flow of gaseous combustion products strongly influences the dependence of the combustion velocity on the magnitude of overload. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 1, pp. 57–60, January–February, 1998     

Efficiency of hydrogen combustion in a high-temperature supersonic air flow for different methods of injection

The efficiency of hydrogen burnup in a supersonic air flow is studied for different methods of fuel injection. The combustion rate and combustion efficiency were determined by detecting the emission intensity of the OH radical over the length of the flare. The distinctive features and heat release characteristics of each of the delivery methods are established, so that a desired heat release behavior can be obtained by choosing suitable injectors. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 2, pp. 3–8, Mach–April 1999.     

Effect of the external electric field on the combustion of a suspension of aluminum particles in air

On the basis of experimental studies, it is shown that the rate of turbulent combustion of ASD-1 aluminum in air increases by a factor of 1.2–1.3 and the geometric parameters of the flame change under the action of a 0.9 kV electric field. These effects are explained. The positive result is obtained under the conditions of a developed turbulent flow and can serve as a basis for practical recommendations on the intensification and control of ignition and combustion processes under laboratory conditions (a laminar flow) and in power installations. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 6, pp. 23–28, November–December 1998     

Propagation of spherical gas filtration combustion waves in inert porous media

The behavior of spherical combustion waves of gases in inert porous media is described in terms of one- and two-temperature models. Parametric dependences are obtained for the wave velocity and acceleration and for the temperature of the gas and porous medium in the wave. It is shown that in a diverging spherical gas flow, combustion waves initiated at different radii of the sphere converge to the standing wave coordinater ^*, and in a converging flow, on the other hand, they diverge from it. The experimentally observed propagation behavior of spherical combustion waves is well described by the proposed models. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 60–66, January–February 1999     

Special features of the combustion process in a channel with a supersonic velocity at the entrance

Results of combustion studies in channels are presented. These researches deal with anomalous phenomena in steady turbulent flows: unsteady heat transfer, two-layer flow, oscillations of a gas column of different intensity and frequency. Under certain conditions, these phenomena lead to substantial redistributions of enthalphy and stagnation pressure at the exit of the combustion chamber, which significantly affects the integral characteristics of the combustor. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 4, pp. 24–32, July–August 1999.     

Numerical study of combustion in a cylindrical porous burner

Hybrid combustion waves in a two-section apparatus with cylindrical symmetry were studied using a two-temperature mathematical model. A program was written and a large series of numerical calculations was performed using an algorithm developed earlier. For one-and two-section apparatuses with various flow rates, characteristics of the process such as the position of the steady-state point, the maximum gas temperature, the gas velocity at the steady-state point, the width of the combustion zone, etc., were determined. It is shown that, in the two-section apparatus, there is a stabilization of the position of the combustion front near the interface. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 17–21, May–June, 2008.     

Specific features of combustion in a variable-section narrow channel with a periodically changing gas flow

Results of numerical and theoretical research of flame behavior in a periodically changing gas flow during combustion in a variable-section narrow channel are presented. The influence of the mean mass flow of the gas and amplitude and frequency of periodic oscillations of the flow on the mean position and temperature of the flame front is studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 16–24, September–October, 2008.     

Fireball during combustion of hydrocarbon fuel releases. I. Structure and lift dynamics

The formation, combustion, and thermal interaction of the fireballs which develop upon ignition of a cloud of hydrocarbon fuel near the Earth’s surface are simulated numerically. The axisymmetric nonstationary flow is described by a system of Favre averaged conservation equations invoking a (k−ε)-turbulence model, a model for turbulent combustion, and a global-kinetic scheme for formation and burnup of soot particles. The optical properties of the mixture of combustion products and soot are modeled by a weighted sum of gray gases. The radiation field is calculated using a combination of a volume emission approximation and a diffusion approximation. Calculations are done for fireballs formed during vertical releases of gaseous propane masses of 1 g to 10³ kg with ignition near the release point. The internal structure of a fireball is analyzed in detail at various stages of its evolution. The lift dynamics of a fireball is illustrated for release velocities corresponding to Froude numbers (defined as the square of the ratio of the linear outflow velocity to the characteristic velocity owing to buoyancy forces) ranging from 5–250. The temperature, concentrations, and reaction rates in the fireball are determined as functions of time. It is shown that for these ranges of fuel mass and release velocity, the dimensionless parameters introduced here can be used for scaling the results and using the calculated dependences obtained here in a unified fashion. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 7–19, May–June 1999.     

Influence of geometric and regime parameters on flame stabilization of a swirl burner

The influence of geometric and regime parameters of a swirl burner with a central body and a diffuser on flow characteristics and flame stabilization in the combustion of a premixed gas mixture was investigated using Reynolds equations and thek-ε model of turbulence. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 5, pp. 21–26, September–October 1999.     

Critical conditions of the combustion of compressed titanium specimen

Critical combustion conditions were investigated for compressed titanium specimens concerning the specimen density and the oxygen concentration in a O₂−Ar mixture. It was shown that there is a minimum specimen density at which combustion characteristics undergo a significant change. The completeness of combustion monotonically decreases with increase in density. Possible causes of the observed phenomena are considered. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 3, pp. 50–55, May–June 1998.     

Competing chemical transformations in the combustion wave in the Fe2O3-Cr2O3-Al mixture

Laws of combustion of a thermit-type mixture Fe₂O₃-2Al-γCr₂O₃ are considered. The limits of liquid-phase combustion and separation of the oxide and metal phases in the final products are determined. Chromium oxide is demonstrated to weakly compete with iron oxide in the oxidation-reduction reaction with aluminum and to participate mainly in oxide-phase formation. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 89–91, May–June, 2006.     

Similarity between high-temperature destruction of rubber-like thermal protective materials in gas flows and erosion combustion of powders

The mechanism of high-temperature destruction of a typical rubber-like thermal protective material in a gas flow is studied experimentally. It is shown that the high-temperature destruction of thermal protective materials in gas flows and erosion combustion of powders is similar. A new hypothesis on the mechanism of erosion combustion of powders is proposed. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 1, pp. 65–69, January–February, 1998.     

Effect of Initial Turbulence on Ignition, Combustion, and Flame Stabilization in a Gas-Suspension Flow

The influence of initial turbulence of an air flow with suspended aluminum particles and the aluminum-particle size on ignition, combustion, and flame stabilization in a combustor with sudden expansion is considered. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 39–48, January–February, 2006.