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The combustion dynamics for hydrogen–air mixtures with a hydrogen content of 15 and 20 vol % in tubes with an annular cross section and central and annular ignition was studied experimentally. In studying annular ignition, the width of the ring gap was varied. The dynamics and structure of the flame front were determined by shadow imaging and high-speed video recording. The optimal value of the size of the ring gap, which provides the maximum velocity of the flame front at the initial stage of propagation, was established. The slowing of the flame before transition to a quasi-plane front was also obtained. The results can be used in developing advanced power plants using both combustion and detonation of hydrogen–air mixtures. [ABSTRACT FROM AUTHOR]

In this paper, we consider the scatter of the laminar flame front velocities caused both by an error in the composition of the combustible mixture and by artificial initial disturbances. It is shown how the configuration of the initial perturbations of an initially flat front of a laminar flame in a gas mixture with the constant composition affects the velocity spread of expanding spherical flames. The effect of the error in the composition of the combustible mixture on the parameters that determine the flame front velocity was analyzed from the literature data on the spread of the flame propagation velocity. These parameters were recalculated for the possible variation in the mixture composition obtained based on the data on the accuracy of the equipment used in the experiments. [ABSTRACT FROM AUTHOR]

The electrical characteristics of a dielectric barrier discharge (DBD) symmetrical actuator at low pressures gave been investigated. A power source–actuator–DBD system has been analyzed. The plot of the feed voltage frequency at which a voltage resonance is observed at the outer electrodes of an actuator with a given configuration against air pressure has been constructed. The DBD density, as well as the capacitance and Q factor of the system, as a function of pressure in a pressure chamber, has been determined. It has been found that, as the pressure drops, the fraction of the DBD energy spent on generating a synthetic jet grows. [ABSTRACT FROM AUTHOR]

The authors study the normal reflection of weak shock waves from several types of dispersion materials: steel wool, foam rubber with different porosities, and their combinations. The Mach number of the incident shock waves was equal to 1.15. The authors obtain the dependences of the amplitude and the impulse of the reflected shock waves on the following parameters of the studied material: thickness, porosity, and the presence of the open pores. They show that the porous materials used in the experiments noticeably attenuate the reflected shock wave (more than 50%) and smooth its front. [ABSTRACT FROM AUTHOR]

Discusses the thermal correction of the inlet diffuser of a hypersonic scramjet engine. Comparison of two methods of maintaining constant the Mach number of flow before the first oblique shock; Description of the calculation procedure; Parameters of gas at the outlet of the region of energy contribution; Finding that the average value of static pressure in the diffuser was approximately three times higher in the case of mechanical correction of the diffuser.

The molecular properties of diluted solutions of Pepper's lignin from the stems of Serratula coronata L. saw-wort in dimethylformamide are studied by capillary viscometry and sedimentation-diffusion analysis. The MMs of fractions and the hydrodynamic radii of macromolecules are determined, and the scaling dependences are analyzed within the framework of the Mark–Kuhn–Houwink equation. It is shown that lignin from the stems of Serratula coronata L. saw-wort differs noticeably in the complex of physicochemical properties from linear polymers and other lignins of different botanical origin and corresponds to hyperbranched polymers. [ABSTRACT FROM AUTHOR]

The work is devoted to experimental and numerical study of flame interaction with acoustic waves in closed and semiclosed pipes filled with preliminarily mixed gaseous mixtures. We analyze the influence of eigenfield (generated by the flame itself) and external acoustic field on the flame dynamics. We show that acoustic field affects the combustion process at all stages. The effect increases with any increase in the energy of initiation of combustion. At later stages of flame development, acoustic waves can initiate the transition to detonation or prevent it. Thus, it is possible to control the combustion modes using external acoustic field. [ABSTRACT FROM AUTHOR]

Examines the effect of magnetic field on the detonation initiation by spark discharge in hydrogen-air mixture. Intensity of shock wave arising in the detonation combustion chamber; Effect of magnetic field on the plasma region formed by the electric discharge; Influence of magnetic induction on the velocity of primary shock wave.

Proposes a method of experimental and numerical analyses of perturbations from a rocket engine nozzle into a bounded space. Shadow photograph of shock-wave egress; Load distribution.