V. S. Babkin

Velocity and temperature fields in the combustion of rotating gas in a closed vessel

Nonsteady flame propagation in a closed vessel generates a complex velocity and temperature distribution in the fresh gas and its combustion products. In rotating the flow of the gas, additional forces such as inertial and Coriolis appear, leading to significant rearrangement of the flow and, in particular, to the appearance of an angular velocity distribution over the vessel radius. This paper attempts to elucidate mathematically the thermodynamic and gas dynamic features of this rotational flow in a closed vessel. The model is tested against experimental data for a methane-air mixture.

Superadiabatic temperature phenomenon in the combustion processes due to a competition between chemical reactions

The existence of a new type of superadiabatic temperature phenomenon in flames and during autoignition due to a competition between chemical reactions is inferred from literature data and the results of mathematical modeling of chemical kinetics and numerical experiments. The mechanisms, conditions for the occurrence, and nature of the phenomenon are discussed. It is noted that this phenomenon may have promising academic and practical applications.

Numerical study of the combustion chemistry of fuel-rich mixtures of formaldehyde and air

The combustion chemistry of formaldehyde in fuel-rich flames has been studied by numerical modeling and sensitivity analysis. It has been shown that the wide flammability limits of CH2O/air mixtures are due to features of the combustion chemistry of formaldehyde at high equivalence ratios rather than to the superadiabatic temperature effect. In this case, the thermal decomposition reaction of hydrogen peroxide H2O2 plays a key role in the conventional branching reactions.

Classification of Similarity Criteria in Combustion Theory and the Problem of Autoignition of a Combustible Mixture by Compression

The dynamic problems of the theory of combustion and explosion are classified from the point of view of competition of the characteristic times of bulk chemical reaction, frontal combustion, heat transfer, gas flow from the vessel, compression (motion of the piston), and heating (cooling) rate. We consider dynamic similarity criteria such as the ratio of the characteristic times in problems of classical thermal explosion, dynamic thermal explosion, flammability limits, combustion in communicating vessels, competition of frontal and volumetric combustion, autoignition by adiabatic compression, competition of frontal combustion and piston motion, as well as compound similarity criteria (such as functions of simple dynamic similarity criteria). The problem of autoignition of a mixture by compression is considered, and a method for obtaining an analytical solution of the problem and an algorithm for the approximate solution based on a special differential criterion are proposed.

Numerical investigation of the distribution of oxygen atoms in syngas combustion products

The distribution of air oxygen atoms in the oxidation products of rich mixtures of syngas with air in flame and the under autoignition conditions at constant volume has been investigated by numerical simulation using the tracer method. It has been found that in rich mixtures, the oxidation of hydrogen and carbon oxide has a stepwise nature, which is clearly visible in the profiles of the rates of production of H2O and CO2. The observed stepwise nature inevitably results in the heat-release rate occurring in steps. The reaction pathways and the role of the oxygen atom of the CO molecule in the heat release in these flames has been investigated.

Numerical study of laminar rich hydrogen–air flames with added ethanol

The propagation of fuel-rich hydrogen–air flames with added ethanol has been studied using numerical methods. It has been shown that the inhibition by ethanol is less effective compared to propane and propylene. The addition of ethanol leads to the effect of superequilibrium temperatures, but it takes place only at ethanol concentrations above a certain value. At the flammability limit of fuel-rich mixtures of hydrogen, ethanol, and air, determined by the Le Chatelier rule, the estimated maximum flame temperature is constant. The exception is mixtures with a small addition of ethanol.

Validation of a kinetic scheme for numerical investigation of hydrogen–methanol–air flames

Normal burning velocities in methanol–air mixtures and in the same mixtures with added 4.5 and 7.2% hydrogen as a second fuel were measured over a wide range of equivalence ratio and for initial conditions of 0.16 MPa and 354 K. It has been shown that the mechanism previously proposed for the combustion of mixtures of CO, CH2O and CH3OH with air is applicable to multicomponent mixtures containing hydrogen and methanol.