LINE OF INVESTIGATIONS AT THE HEAT AND MASS
S. A. Zhdanok, O. G. Penyazkov,
and N. A. Fomin
The history of development of works on physical gasdynamics and high-temperature thermal physics that were initiated by the outstanding scientist, Corresponding Member of the USSR Academy of Sciences, Academician of the BSSR Academy of Sciences, Lenin Prize Winner Rem Ivanovich Soloukhin at the A. V. Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus is described. Particular emphasis is placed on investigations into physicochemical kinetics under nonequilibrium conditions, combustion, detonation, and the gasdynamics of explosions and reactive systems; these investigations have been carried out at the Institute during the last three decades. Also, R. I. Soloukhin’s works at the Siberian Branch of the USSR Academy
of Sciences, where the foundations of this scientific line of investigations were laid, are briefly described.
110 YEARS OF EXPERIMENTS ON SHOCK TUBES
N. A. Fomin UDC 633.6.071.8
A brief account of the history of development of shock tubes throughout the world, the USSR, and Belarus is given. The principle of operation of a shock tube and some results for high-temperature gasdynamics obtained on shock tubes in the past years are shown. In these studies, the role of Rem Ivanovich Soloukhin is noted as a pioneer of experiments on shock tubes at the G. M. Krzhizhanovskii Institute of Power Engineering (1953–1958), the Siberian Branch of the Academy of Sciences of the USSR (from 1959), and in Belarus (from 1976). Keywords: shock tube, shock wave, experiment, optical diagnostics, gasdynamic lasers, plasma, high-temperature
gasdynamics, nanoparticle generation, detonation, laser spectrograph.
PANORAMIC DIAGNOSTICS OF SURFACE TEMPERATURES
AND HEAT FLUXES IN AN AERODYNAMIC EXPERIMENT
G. M. Zharkova and V. N. Kovrizhina UDC 532.783
The principles of visualization and measurement of surface temperatures and heat fluxes by the method of liquid-
crystal tomography in an aerophysical experiment are described. The properties of polymeric liquid-crystal, heat-sensitive coatings and application of them in subsonic and hypersonic facilities for investigating the structure of a near-wall flow and aerodynamic heating are considered.
Keywords: liquid crystals, cholesteric liquid crystals, polymeric liquid-crystal, heat-sensitive coatings, liquidcrystal tomography.
EXPLOSION GENERATION OF MICROATOMIZED
LIQUID-DROP AEROSOLS AND THEIR EVOLUTION
B. I. Vorozhtsov, O. B. Kudryashova, A. N. Ishmatov,
I. R. Akhmadeev, and G. V. Sakovich
The formation of a microatomized aerosol was investigated with the use of a model of an explosion atomizer based on a hydrodynamic shock tube with atomization through a clearance (nozzle). It is shown that the cavitation of the liquid subjected to atomization plays a great role in the production of a microatomized liquiddrop aerosol. A mathematical model describing the genesis of an aerosol cloud is proposed. The time of propagation of a compression wave in the liquid subjected to atomization and the time of its outflow from the atomizer were estimated, the size distribution of the aerosol particles was constructed, and the dependence of this distribution on the coagulation, evaporation, and precipitation of the aerosol particles was determined. A technique for undisturbed measurement of the genesis of an aerosol is described. Results of an experimental investigation of the dispersion parameters of an aerosol and the processes of formation and propagation of an aerosol cloud produced as a result of the explosion atomization of a liquid are presented.
Keywords: aerosol, atomization, coagulation, evaporation, precipitation, cavitation, explosion.
COMPRESSION IGNITION OF HYDROGEN-CONTAINING
MIXTURES IN SHOCK TUBES
S. P. Medvedev, B. E. Gelfand,
S. V. Khomik, and G. L. Agafonov
The state of the art of the problem of discrepancy between the values measured in shock tubes and calculated for the delay of ignition of hydrogen-containing systems has been analyzed. It is shown that in the low-temperature region the off-design appearance of reaction sites leads to the propagation of a flame in a mixture heated by a reflected shock wave. The parameter of the time of mixture combustion in a deflagration regime has been introduced and the use of it together with the calculated delay in self-ignition for delimitation and classification of thermal and gas-dynamic phenomena on compression ignition of hydrogen-containing mixtures
in shock tubes has been suggested.
Keywords: hydrogen-containing mixture, delay in self-ignition, combustion regime.
DIFFRACTION OF WAVES IN COMBUSTIBLE MIXTURES
A. A. Vasil’ev and V. A. Vasil’ev UDC 534.222.2+536.46+661.215.1
The results of investigations of combustion and detonation wave diffraction, including the nonstationary regimes
of combustion–detonation transition, are presented. A wide variety of transient regimes upon diffraction have been revealed. On the basis of diffraction investigations, a criterion of detonation excitation is proposed and formulas for estimating the critical energy of initiation of plane, cylindrical, and spherical waves have been obtained. The calculated values are in good agreement with the experiment.
Keywords: combustion, detonation, combustion–detonation transition, critical diffraction diameter, diffraction reinitiation criterion.
FORMATION OF A DETONATION WAVE IN THE PROCESS OF CHEMICAL CONDENSATION
OF CARBON NANOPARTICLES
A. V. Emel’yanov, A. V. Eremin,
and V. E. Fortov
A new physical phenomenon — the formation of a detonation wave as a result of the condensation of substances
— was investigated in detail. A detonation wave was formed under the action of the energy released
in a process of chemical condensation of carbon nanoparticles behind a shock wave in the mixture initially containing 10–30% of the carbon suboxide C3O2 or acetylene C2H2 in argon. The propagation of the shock wave in this mixture led to the rapid thermal disintegration of its initial molecules and the subsequent formation of a condensed carbon with a significant energy release. The increase in the temperature and in the pressure of the reacting mixture leads to a strengthening of the shock wave and to its transformation into a detonation wave. The main kinetic characteristics of the reaction of thermal disintegration of the indicated molecules and their subsequent chemical condensation as well as the interrelation of these characteristics with the heat-release processes forming the detonation wave were determined.
Keywords: detonation wave, chemical condensation of carbon nanoparticles, shock and detonation waves, thermal
deisintegration of molecules.
MATHEMATICAL MODELING OF INSTABILITIES
IN THE INTERACTION OF WAVE PROCESSES
WITH THE CONTACT DISCONTINUITIES BETWEEN
GASES OF DIFFERENT DENSITIES
A. V. Fedorov, V. M. Fomin,
and G. A. Ruev
Works performed in the field of mathematical modeling of the process of mixing of gases of different densities on the interface between them under the action of transmitted and reflected shock waves and compression and rarefaction waves are reviewed. A mathematical model of two-velocity, two-temperature gases, which has been derived from the basic principles, is proposed for this modeling. A number of examples on the interaction of the above wave processes with the interfaces in helium–xenon and helium–argon mixtures are given; the appearing Richtmyer–Meshkov instability and the distinctive features of the wave dynamics of flow of a mixture are described. The performed comparison of the time dependence of the mixing-zone breadth and other dependences
has shown that the description of the phenomenon within the framework of the proposed approach
Keywords: mixing of gases of different densities, laser thermonuclear fusion, contact discontinuity, shock waves, compression waves.
DIAGNOSTICS OF CONVECTIVE PROCESSES
IN THE BOUNDARY LAYER OF A LIQUID
BY THE LASER-REFRACTOGRAPHY METHOD
I. L. Raskovskaya, B. S. Rinkevichyus,
and A. V. Tolkachev
A mew method of nondisturbing remote diagnostics, i.e., laser refractography, has been used for experimental investigation of convective microflows. The theoretical foundations of the method and the principles of construction of a measuring system have been presented. The dynamics of the temperature distribution in the boundary layer at a cooled or heated sphere in water in the presence of free convection has been diagnosed quantitatively. The results of the experiment have been compared to the results of computer simulation based
on the FLUENT software package. The advantages of using laser refractography for diagnostics of substantially
nonstationary processes have been demonstrated.
Keywords: laser refractography, structured laser emission, diffraction optical elements, convective flows.
INFLUENCE OF THE METHODS OF ENERGY ACTION
ON DEFLAGRATION-TO-DETONATION TRANSITION
V. V. Golub, D. I. Baklanov,
V. V. Volodin, and S. V. Golovastov UDC 534.222.2+536.46+661.215.1
The results of experimental gas-detonation investigations carried out in the past decade at the Department of
Physical Gasdynamics of the Joint Institute of High Temperatures of the Russian Academy of Sciences (JIHT
RAS) in connection with the problems of creation of a pulse detonation engine have been presented. Consideration
has been given to the influence of the shape of injectors on the formation of detonation in a gas flow
with separate feed of the fuel and the oxidant, the influence of acoustic action on the ignition region, reduction
in the predetonation length in the flow of a mixture capable of detonation, and improvement in the efficiency
of electric-discharge initiation of detonation by the self-magnetic and induced external magnetic field.
Keywords: detonation, mixing, injectors, acoustics, flow, magnetic field, electric discharge.
EXCITATION AND QUENCHING OF DETONATION IN GASES
V. A. Levin, I. S. Manuilovich,
and V. V. Markov
The results of investigations on the problems of initiation, propagation, and stabilization of detonation waves and flowing combustible gaseous mixtures are presented. To describe the flows, we used ideal perfect gas equations and two models of the detonation wave: the classical infinitely thin model and a model in which behind the shock wave chemical reactions described by the single-stage kinetics for propane– and methane–air combustible mixtures proceed. Investigations were carried out by both analytical and numerical methods based on the S. K. Godunov scheme on stationary and movable computational meshes with explicit resolution of the bow shock and the surfaces separating gases with different properties.
Keywords: detonation, combustion, initiation, optimization, stabilization, channel, structure of the detonation wave, numerical simulation.
THERMALLY THIN SYSTEM FOR INVESTIGATING
SURFACE DIFFUSION FLAMES
V. S. Babkin and A. A. Korzhavin UDC 536.46
A thermally thin layered system representing a liquid fuel on a metal substrate was investigated. The characteristic parameters of such a system are the thickness of the fuel layer and the thickness of the substrate, equal to 3–12 and 10–100 μm respectively. Hydrocarbons were used as a fuel. It has been established that in this system a number of stationary and nonstationary combustion regimes with conductive and convective mechanisms of chemical-reaction transfer and non-one-dimensional combustion waves with an unusual structure
and an "excess of energy" can take place.
Keywords: flame, combustion, thermally thin system, excess of energy.
IN GASES IN TUBES WITH CAVITIES
N. N. Smirnov, V. F. Nikitin,
and Yu. G. Phylippov
UDC 634.222.2 + 662.7
The existence of a supersonic second combustion mode — detonation — discovered by Mallard and Le
Chatelier and by Berthélot and Vieille in 1881 posed the question of mechanisms for transition from one
mode to the other. In the period 1959–1969, experiments by Salamandra, Soloukhin, Oppenheim, and their
coworkers provided insights into this complex phenomenon. Since then, among all the phenomena related to
combustion processes, deflagration-to-detonation transition is, undoubtedly, the most intriguing one. Deflagration-
to-detonation transition (DDT) in gases is connected with gas and vapor explosion safety issues. Knowing
mechanisms of detonation onset control is of major importance for creating effective mitigation measures addressing
two major goals: to prevent DDT in the case of mixture ignition, or to arrest the detonation wave
in the case where it has been initiated. A new impetus to the increase in interest in deflagration-to-detonation
transition processes was given by the recent development of pulse detonation devices.
The probable application of these principles to creation of a new generation of engines put the problem of
effectiveness of pulse detonating devices at the top of current research needs. The effectiveness of the pulse
detonation cycle turned out to be the key factor characterizing the Pulse Detonation Engine (PDE), whose operation
modes were shown to be closely related to periodical onset and degeneration of a detonation wave.
Those unsteady-state regimes should be self-sustained to guarantee a reliable operation of devices using the
detonation mode of burning fuels as a constitutive part of their working cycle. Thus deflagration-to-detonation
transition processes are of major importance for the issue. Minimizing the predetonation length and ensuring
stability of the onset of detonation enable one to increase the effectiveness of a PDE. The DDT turned out to
be the key factor characterizing the PDE operating cycle. Thus, the problem of DDT control in gaseous fuel–
air mixtures became very acute.
This paper contains results of theoretical and experimental investigations of DDT processes in combustible
gaseous mixtures. In particular, the paper investigates the effect of cavities incorporated in detonation tubes
at the onset of detonation in gases. Extensive numerical modeling and simulations allowed studying the features
of deflagration-to-detonation transition in gases in tubes incorporating cavities of a wider cross section.
The presence of cavities substantially affects the combustion modes being established in the device and their
dependence on the governing parameters of the problem. The influence of geometrical characteristics of the
confinement and flow turbulization on the onset of detonation and the influence of temperature and fuel concentration
in the unburned mixture are discussed. It was demonstrated both experimentally and theoretically
that the presence of cavities of wider cross section in the ignition part of the tube promotes DDT and shortens
the predetonation length. At the same time, cavities incorporated along the whole length or in the far-end
section inhibit detonation and bring about the onset of low-velocity galloping detonation or galloping combustion
modes. The presence of cavities in the ignition section turns an increase in the initial mixture temperature
into a DDT-promoting factor instead of a DDT-inhibiting factor.