Numerical investigation of the process of interrupting the detonation wave propagation in monofuel gas suspensions using an inert particle layer

A numerical investigation was performed of the process of interrupting the propagation of a heterogenous detonation wave in a reacting dispersed mixture by means of a layer of inert particles located inside an atomized monofuel cloud. It was found that depending on the parameters of the monofuel and the inert particle suspension, regimes are possible of both interrupted, as well as of a continuous detonation wave propagation. An attempt was made to explain the mechanism of combustion wave suppression with an inert particle layer. An energy criterion is proposed for estimating the possibility of suppressing the detonation waves by means of an interrupter consisting of a suspension of inert particles.Tyumen'. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 90–98, March–April, 1993.     

Mathematical simulation of heterogeneous detonation of coal dust in oxygen with allowance for the ignition stage

A consistent physicomathematical model that describes ignition and detonation combustion of a gas suspension of coal-dust particles is developed. The model is based on the concepts of the two-velocity two-temperature continuum of mechanics of heterogeneous media with allowance for reduced reactions of pyrolysis, combustion of volatiles, and combustion of the coke residue. The model is verified with the use of available experimental data on the dependence of the detonation velocity on the initial concentration of the discrete phase and the dependence of the ignition delay on the Mach number of the incident shock wave. An analysis of ignition of the gas suspension of bituminous coal in shock waves shows that the stage of ignition proceeds under conditions of both temperature and velocity nonequilibrium. The influence of particle heating due to stagnation temperature on devolatilization dynamics and ignition delay is established. Examples of computed flow structures behind shock and detonation waves with allowance for the ignition stage are presented.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 89–99, January–February, 2005.     

Detonation of Secondary Explosives in a Vacuum Suspension

The existence of self–sustaining detonation in an evacuated suspension of the particles of a secondary explosive is shown experimentally. The experiments with HMX were performed in a vertical shock tube of diameter 0.07 m and length 7 m in the range of volume–average particle concentrations 0.32—0.9 kg/m³. It is shown that the vacuum–detonation velocity does not almost depend on the volume–average concentration of particles and it is (1750±50) m/sec and that the pressure profile of a vacuum–detonation wave is smooth. The data on the electric conductivity of vacuum–detonation products and the length of the reaction zone are given.     

Limits of detonation propagation in a suspension of propellant particles in vacuum in a tube

The problem of stationary detonation in vacuum with monopropellant particles propagating in a tube is formulated and analyzed numerically. It is shown that friction and heat removal onto the tube walls affect the structure of a disperse wave. The dependences of the detonation velocity on the tube diameter, the size of the propellant particles, and on their mass concentration have been determined, and the limits of detonation propagation have been found.Lavrent'ev Institute of Hydrodynamics, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 76–84, March–April, 1994.     

Possibility of detonation wave propagation in the Chapman-Jouguet regime in inhomogeneous media

We consider detonation wave propagation in an inhomogeneous fuel gas mixture at rest, whose initial state is characterized by values of pressure and density that are in the general case, functions of the spatial and time coordinates. The distance form the plane, axis or center of symmetry can be used as the spatial coordinate. The sources of mass, pulse, and energy are assumed to be present behind the detonation front. The appropriate necessary conditions for the detonation wave to propagate in the Chapman-Jouguet regime are determined. The relations obtained are analyzed for some inhomogeneous media: media with variable density, media with heat release varying with distance, and media with burnout sources behind the detonation front.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 98–109, March–April, 1993.     

Mathematical Simulation of Detonation Processes in a Coal-Particle Suspension

A physicomathematical model is developed, which describes propagation of detonation waves in a suspension of coal-dust particles in air or oxygen within the framework of the concepts of one-velocity, two-temperature continuum mechanics. The model is verified by available experimental data on the dependence of the detonation velocity on the particle concentration, on ignition delays behind shock waves, and on characteristic times of pyrolysis and combustion processes. Stationary detonation structures are analyzed. Formation and stable propagation of stationary detonation waves are demonstrated by means of numerical simulation of shock-wave initiation. Key words: shock waves, detonation, gas suspension, coal-dust particles, mathematical simulation.     

Exit of a Heterogeneous Detonation Wave into a Channel with Linear Expansion. II. Critical Propagation Condition

Propagation of a detonation wave in monodisperse suspensions of reacting particles (based on the model of the suspension of aluminum particles in oxygen) in channels with linear expansion is studied within the framework of mechanics of heterogeneous reacting media. Reduced kinetics is described with allowance for the transitional (from diffusion to kinetic) regime of combustion of micron-sized and submicron-sized spherical aluminum particles. The effects of the channel width, particle diameter, and expansion angle on propagation conditions and detonation regimes are determined. The critical channel width is found to be a nonmonotonic function of the expansion angle, which is associated with qualitatively different wave patterns behind an oblique step. Flow charts are constructed, and the results are compared with solutions of problems of heterogeneous detonation wave propagation in channels with a backward-facing step and with sudden expansion.     

Dependence of the Shape of a Detonation Wave Front on the Detonation Wave Velocity upon Detonation of a Cylindrical Charge

The transition of a system of partial differential equations which describe the stationary flow behind the shock–wave front of a detonation complex upon detonation of a cylindrical charge to a system of ordinary differential equations is performed by means of the series expansion in terms of the radial variable. The necessary equations for determination of the derivatives of solutions with respect to the parameters and the initial conditions for them are formulated. Imposing the condition of continuous extendibility of the solutions leads to equations that allow one to determine the shape of a shock–wave front as a function of wave velocity.     

Detonation in a relaxing gas and relaxational instability

Conclusions It is well known that the one-dimensional structure of DW is encountered relatively rarely in practice. As a rule, detonation waves have a three-dimensional pulsating structure (triple configurations [10, 24]). There is no question that the one-dimensional model of detonation studied here cannot and does not pretend to describe the nature and structure of three-dimensional pulsations caused by the thermal or relaxational instability of the wave front. In the case of a pulsating detonation the proposed model, like the classical theory (limit of small ), refers to time-averaged gasdynamic quantities and to the selection rule for the velocity of detonation. In addition, the one-dimensional model can be used (see the section concerning the relaxational instability) as a starting point for the analysis of the instability of DW.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 22, No. 5, pp. 75–86, September–October, 1986.     

Radio wave method for study of physical phenomena and chemical conversions in heterogeneous explosives under shock wave action

A method is described for determination of shock wave parameters (wave and mass velocity) in heterogeneous explosives. The example of exciting explosion in an octogene composition by weak shock waves is used to demonstrate the possibility of reliable measurement of the velocity of the initiating shock wave, the depth at which detonation develops, and the extent of the predetonation zone, as well as the character of the change in shock wave velocity upon propagation through the specimen.Chelyabinsk. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 107–109, November–December, 1991.     

Estimating the burning rate of an explosive gas mixture at elevated pressures and temperatures

The flame speed has been estimated from the flow behind a shock wave from recordings of the expansion in the flame focus arising between the shock wave and the combustion front in states transitional between combustion and detonation. The result is close to the difference between the speeds of the shock wave and the mass gas flow in it and greatly exceeds the calculated velocity for a normal flame, which shows that the combustion behind the shock wave is turbulent.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 4, pp. 44–48, July–August, 1992.     

Detonation of a Column of a Chemically Active Bubbly Medium in a Liquid

The problem of a detonation wave propagating in a cylindrical column of a chemically active bubbly medium screened by a liquid from the tube walls is formulated and numerically solved within the framework of the Iordanskii–Kogarko two-phase model with allowance for energy dissipation due to acoustic radiation of bubbles. The wave structure of the reaction zone and the detonation velocity of the bubbly medium column are calculated. It is found that the self-sustaining wave can propagate with a velocity greater than the velocity of one-dimensional bubble detonation by a factor of 1.5–2.5.     

Nonshock initiation of detonation in vacuum with unitary-fuel particles

The nonshock initiation of detonation in vacuum with unitary-fuel particles is considered. The dynamics of reaction-zone formation of a nonsteady detonation wave with disperse structure is discussed. The approach to steady Chapman—Jouquet detonation is considered. The critical initiation energies of a plane detonation wave with variation in length of the initiation section and the energy density supplied are calculated, and may be used in experimental investigations.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 4, pp. 136–142, July–August, 1992.     

Unconfined charge detonation of monofuel particles in vacuum

The problem of the detonation of an unconfined cylindrical charge of monofuel particles in vacuum is formulated and solved numerically. The steady-state detonation regime is obtained. The structure of a two-dimensional reaction zone and the mechanism of detonation-wave propagation in an unconfined charge of monofuel particles in vacuum are discussed.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 3, pp. 86–94, May–June, 1996.     

Model of bubble detonation

A model of detonation in a two-phase heterogeneous mixture consisting of bubbles of chemically reacting gas in a chemically inert liquid is proposed. The model takes account of the compressibility and viscosity of the liquid, the presence of an induction period of the chemical reaction, and shift of the chemical equilibrium. The initiation of the wave and its approach to steady conditions are calculated. The calculation results agree with experiment. It is shown for the first time that wave propagation at supersonic (relative to the frozen sound velocity) velocity is possible with large initial pressures in the mixture. The structure of the wave in sub- and supersonic conditions is significantly different. In the first case, there is smooth pressure variation in the compression wave; in the second, there is a pressure discontinuity at the leading shock front of the wave.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 4, pp. 129–136, July–August, 1992.     

Detonation wave structure in a vacuum with unitary fuel particles

The structure of steady state detonation in a vacuum with unitary fuel particles is studied. It is shown that the detonation structure lacks a shock wave frozen in the gas, and that the detonation wave zone consists of a contact discontinuity with jump in gas temperature and continuous pressure, a compression relaxation wave with contact discontinuity in the ignition plane and adjacent combustion zone. Parameters of the two-phase flow in the reaction zone are calculated.Novosibirsk. Translated from Fizika goreniya i Vzryva, Vol. 27, No. 6, pp. 109–115, November–December, 1991.     

Inductive method of registration of shock-wave parameters in condensed media

We discuss a method of measurement of particle velocity behind a shock-wave front in a condensed dielectric medium. The method is based on recording of the electromotive force(emf) that is induced in a current-carrying coil when the shock wave deforms it. A toroidal probe coil was used to reduce electrical noise. A current of 500 A was supplied to the coil by means of aperiodic discharge of a capacitor. The recordedemf amplitude is proportional to the measured particle velocity and equals 20 V for a velocity of1 km/sec. The influence of some phenomena accompanying shock-wave propagation along the coil on the accuracy of the particle-velocity measurements was estimated.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 3, pp. 134–139, May–June, 1996.     

Existence of stationary self-maintained combustion of porous and channel propellants

It is shown theoretically that in channel and porous propellants there exists a stationary self-maintained regime of propagation of a convective flame front. The existence of a spherical structure of the combustion zone results in the appearance of a qualitatively new propagation regime — subsonic relative to the condensed phase and supersonic relative to the gas phase ahead of the front. The final states of the reaction products lie on the branch of the detonation adiabat corresponding to weak detonation. It is shown that in a propellant with constant average density and thermal conductivity the velocity of the wave is variable and can be regulated by adjusting the size of the individual channels.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 4, pp. 18–24, July–August, 1991.     

Detonation of liquid explosive mixtures in powdered media

The propagation of detonation in liquid explosive mixtures (LEM) (nitrobenzene solutions in tetranitromethane) in inert and active powdered media of normal loose packing has been experimentally studied. It is shown that for small distances the general wave process is determined only by the propagation of detonation in LEM through narrow channels formed by separate particles of the powdered material independently of its acoustic stiffness. As the distance increases, in heterogeneous explosive mixtures with HMX a comparatively low-velocity wave smoothly changes to stationary detonation of the composition as a whole.All-Russian Research Institute of Experimental Physics, Arzamas-16 607200. Translated from Fizika Gorenia i Vzryva, Vol. 31, No. 2, pp. 156–160, March–April, 1995.     

Mechanism of low-speed detonation wave propagation in gas-drop mixtures

Results are offered from an experimental study of propagation of a low-speed detonation wave through a chain of liquid hydrocarbon drops in a pure oxygen atmosphere. Detonation was initiated by a planar shock wave at Mach numbers M=2.0–3.5. The detonation wave structure is reflected by the x, t-diagrams obtained. The propagation of the flame front was found to be pulsating in character, and reasons were established for this phenomenon. It is shown that the microspray in the drop wake does not self-ignite, but is ignited by combustion products from the preceding drop.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 149–154, May–June, 1993.