S. V. Golovastov

Inhibition of Spontaneous Decomposition of Acetylene by Hydrocarbon and Hydrogen

An experimental study is made of the process of inhibition of exothermal spontaneous decomposition of acetylene by diluting it with a household gas (propane/butane) and hydrogen, which serve as fuel themselves. A mixture of acetylene with inhibitor, located in a cylindrical shock tube, is heated by a reflected shock wave. The shock waves are provided by detonation waves that are initiated in a stoichiometric acetylene-oxygen mixture. The detonation waves change to shock waves in the acetylene-inhibitor mixture. Minimal limits of bulk concentration of inhibitors are obtained, at which no spontaneous decomposition of acetylene occurs.

Influence of an Acoustic Field on Flame Development and Transition to Detonation

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.

Parametric investigation of the propagation of detonation in narrow channels filled with a propane-butane-oxygen mixture

In this article, the propagation of the detonation of a propane-butane mixture with oxygen is investigated in a channel of constant cross section with a diameter smaller than the critical one for detonation propagation. The ignition of the mixture is performed in a precombustion chamber. The entering of the flame front into the narrow channel causes the development of detonation in the channel. In this work the profiles of the pressure at the entry into the channel and the average velocities of propagation of the flame front for different sections of the channel are presented. The values of the velocity correspond to the values of the Chapman-Jouguet velocity. In this work various scenarios of the propagation of detonation depending on the size of the precombustion chamber have been investigated.

An experimental study of the diffusion-controlled self-ignition of hydrogen in a channel

The pulsed outflow of hydrogen into channels of circular and rectangular cross sections with a surface area of 20 mm2 was experimentally studied. It was revealed that the shock wave formed during the outflow of a pulsed jet is the reason why it ignites at the contact surface. The range of initial pressures of hydrogen at which it ignites was determined and the dependence of the distance from the diaphragm at which a flame arises at the contact surface on the pressure in the shock wave front for circular and rectangular cross section channels was obtained.

Formation of an overdriven detonation wave in the flow of methane–oxygen mixtures in a variable cross section channel

The formation of an overdriven detonation wave in methane-oxygen mixtures in an axially symmetrical channel with a variable cross section was experimentally investigated. The ignition of gas mixture was carried out using the spark gap, located at the closed end of the channel. To create the overcompressed shock detonation wave, the decay of the stationary detonation wave was performed at the transition to the channel of a larger cross section. The created complex of shock wave and flame front, moving behind it, propagated in a channel with conical narrowing. The formation of the overdriven detonation wave, with parameters exceeding the parameters of Chapman–Jouguet stationary detonation by a few times, was registered at the outlet of conical narrowing. The rates and pressures on the front of the detonation wave were determined, depending on the mixture composition. The sizes of detonation cells, diagrams of compression waves propagation, flame front, and detonation wave in a combustion chamber, depending on the mixture composition, were presented.

PRECHAMBER INITIATION OF GASEOUS DETONATION IN A CHANNEL

ABSTRACT Deflagration-to-detonation transition in propane-butane-oxygen mixtures, in an open channel with a circular cross section with a diameter of 3 mm, was investigated experimentally. Detonation initiation was carried out by burning the mixture in the prechamber connected to the channel. To measure the velocity of a flame front, photodiodes installed along the axis of the channel were used. To determine the boundary conditions at the entrance to the channel, a piezoelectric pressure transducer was used. The influence of the dimensions of the prechamber and equivalence ratio on the pressure profile, and evolution of the flame front along the axis of the channel are presented. Effect of the prechamber detonation initiation in the channel has been analyzed. It was shown that the dynamics of the flame front and shock waves in the channel can occur in different scenarios depending on the geometry of the prechamber and equivalence ratio. The pre-detonation distances were determined.

Propagation of detonation wave in hydrogen–air mixture in channels with sound-absorbing surfaces

The possibility of using sound-absorbing surfaces for attenuating the intensity of detonation waves propagating in hydrogen–air mixtures has been experimentally studied in a cylindrical detonation tube open at one end, with an explosive initiated by spark discharge at the closed end. Sound-absorbing elements were made of an acoustic-grade foamed rubber with density of 0.035 g/cm3 containing open pores with an average diameter of 0.5 mm. The degree of attenuation of the detonation wave front velocity was determined as dependent on the volume fraction of hydrogen in the gas mixture.

Attenuation of a hydrogen-air detonation by acoustic absorbing covering

Using of sound-absorbing surfaces to weaken and decay of a detonation wave in hydrogen-air mixtures was investigated experimentally. Experiments were carried out in a cylindrical detonation tube open at one end. Initiation of the explosive mixture was carried out by a spark discharge, which is located at the closed end of the detonation tube. Acoustical sound absorbing foam element of a specific weight of 0.035 g/cm3 with open pores of 0.5 mm was used. The degree of attenuation of the intensity of the detonation wave front was determined.

Prechamber initiation of detonation in gaseous mixtures

A process of deflagration-to-detonation transition in propane-butane-oxygen and acetylene-oxygen mixtures, in an open channel with a circular cross section with a diameter of 3 mm, was investigated experimentally. Detonation initiation was carried out by burning the mixture in the prechamber connected to the channel. The prechamber was considered as an extended source for the initiation of the detonation of a finite volume. To measure the velocity of a flame front, photodiodes, installed along the axis of the channel, were used. To determine the boundary conditions at the entrance to the channel, a piezoelectric pressure transducer was used. The influence of the dimensions of the prechamber, equivalence ratio and fuel on the pressure profile, and evolution of the flame front along the axis of the channel are presented. It was shown that, the dynamics of the flame front and shock waves in the channel can occur in different scenarios depending on the geometry of the prechamber and equivalence ratio. Two limit effects of the prechamber detonation initiation in the channel have been analyzed. The pre-detonation distances and the minimal energy of direct initiation of the detonation were determined.

Diffusion-controlled autoignition of hydrogen outflowing into an air-filled channel

The results of a numerical study of the pulsed outflow of hydrogen into an air-filled channel are presented. The adjustable parameters were the initial pressure of hydrogen in the reservoir and the distance from the diaphragm to the ignition point. The pressure, temperature, and water vapor mass fraction profiles along the channel wall at various moments of time were calculated. The autoignition parameters were calculated with account of turbulence, boundary layer formation, heat transfer, and diaphragm opening time. It was demonstrated that the boundary layer effect promotes hydrogen autoignition. The dependence of the distance from the diaphragm to the autoignition point was calculated as a function of the pressure in the reservoir with hydrogen. The simulation results were found to be in close agreement with the available experimental data.