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This review deals with the formation of solid carbon (in particular, soot) under various conditions of methane conversion: pyrolysis, diffusion flame combustion, steam reforming, conversion in supercritical water and high-pressure water-oxygen fluid. Particular attention is paid to the consideration of the conditions of carbon formation at high pressure; the goal is to identify the parameter regions with a lack of experimental information or its insufficient presentation, but where carbon formation is very likely. When designing the equipment with continuous operation, it is necessary to know the corresponding parametric boundaries of the areas of solid carbon formation in order to avoid emergency situations and/or to reduce depreciation costs.

Within the framework of lubrication theory, numerical studies of thin film movement along the surface of a wing with the NACA0012 airfoil were carried out. The film is created by incoming drops of water and drifted by the external air flow. A model problem of one-dimensional film motion in the presence of a retarding longitudinal stress caused by disjoining pressure is considered. A cubic equation was obtained to determine the film thickness. If the contact angle exceeds a certain critical value, then the solution of this equation loses its physical meaning at some distance from the front critical point (the film thickness becomes negative). This means that the one-dimensional flow assumption is no longer satisfied. The maximum coordinate for existence a one-dimensional solution can be approximately considered as the beginning for the film disintegration into rivulets. Theoretical results are compared with the available experimental data.

The object of this study is a straight rivulet flowing over an inclined plate whose surface is covered with regular nonlinear waves. Such waves can be modeled in full three-dimensional statement, but it is also possible to use a simplified quasi-two-dimensional approach with self-similar shape of rivulet cross-section. In this study we directly compare the results of two- and three-dimensional approaches, where the shape of the wave rivulet surface is reconstructed experimentally using the laser-induced fluorescence technique. It is shown that the three-dimensional model reproduces well the wave surface of a rivulet, including such three-dimensional peculiarities as the wave front curvature and minor perturbations of its rear slope. Though the two-dimensional model is unable to reproduce such peculiarities, it describes well the parameters and shape of a wave in the central longitudinal cross-section of the rivulet.

Results of an experimental study of the evolution of a vortex flow formed under the action of a submillimeter arc discharge moving in a constant magnetic field in a supersonic air flow near a flat surface are presented. Owing to the high reproducibility of the discharge parameters and precise synchronization of the equipment, it is possible to study the flow structure in much detail by the methods of particle image velocimetry and Schlieren visualization. It is found that the spaced and time characteristics of the generated vortex structures can be effectively controlled by changing the direction of the electromagnetic force arising during the discharge.

The Direct Simulation Monte Carlo (DSMC) method is widely used to solve problems of rarefied gas dynamics. The choice of the model of particle collisions with each other in implementation of the DSMC algorithm significantly affects the accuracy of simulations and the complexity of computations. One of the most popular particle collision models is the Variable Soft Sphere (VSS) model. In the present study, we simulate a flow arising when a heated wire is placed into a quiescent gas atmosphere (helium or argon). It is shown that the use of the VSS model with parameters based on viscosity and diffusion can lead to errors in estimating the heat flux from the wire to the ambient gas.

Various issues of implementation and application of the AUSMPW+ solver for computing inviscid flows at the control volume face in the HyCFS code on a structured grid are discussed. It is shown that the use of AUSMPW+ allows the carbuncle formation in the flow around a cylinder to be successfully prevented. Simulations of flows with boundary layer separation by using the AUSMPW+ solver leads to results that coincide with those obtained by the HLLC solver. The pressure and heat transfer coefficients for a cone-flare model predicted by HyCFS coincide with the experimental data of LENS-XX with the same accuracy as the results of other researchers computed by independent numerical codes.

The results of multi-criteria analysis obtained on the basis of experimental data in the process of studying the main properties and characteristics of thermal conversion of alternative liquid fuels are presented. Kerosene was used as the basic hydrocarbon component. Bioadditives are represented by vegetable oils (rapeseed oil, tall oil, camelina oil, and waste culinary oil) and methyl esters of fatty acids obtained during the processing of these oils. The combustion characteristics of fuel compositions were experimentally determined: ignition delay times, threshold temperatures of combustion initiation, burnout duration, and concentrations of the main gas emissions. Promising fuel compositions are identified taking into account the main energy and environmental indicators. The possibilities of using compositions with methyl esters of fatty acids to reduce specific anthropogenic emissions in the composition of combustion products are substantiated.

Physics-Informed Neural Networks (PINNs) represent an innovative method for solving a wide range of problems in mathematics, physics, and engineering. PINNs combine the neural networks concepts and physical equations aimed to modeling and analysis of various physical processes. In particular, PINNs can be applied to solve differential equations, including the one-dimensional convection equation. The research shows that the standard implementation of PINNs efficiently solves a one-dimensional convection equation at relatively small convection velocity values, but diverges for higher values of this parameter. This paper provides an overview of existing approaches for solving the one-dimensional convection equation using PINNs and demonstrates improvement for model performance through different methods. The results of comparison indicate the superiority of the approach based on dynamically adjusting collocation points according to the residual at the current training step (as compared to other approaches).

A generalized two-stage model of chemical kinetics of detonation combustion of a binary stoichiometric mixture of methane with hydrogen and air is proposed. It allows calculating the heat release of the chemical reaction, the molar mass, the internal energy and the adiabatic index of the mixture without calculating its detailed chemical composition, which significantly simplifies kinetic calculations and reduces their volume compared to detailed kinetics. The model is physically substantiated and does not contain adjustable parameters. For the mixture under consideration, a numerical two-dimensional calculation of the multifront structure of the detonation wave was made with a variation in the ratio between the combustibles. Chemical transformations were described using the proposed kinetic model. The calculated size of the detonation cell, as well as the qualitative structure of the detonation wave (the presence of regions of unburned gas in the reaction zone and the irregularity of the cellular structure caused by the formation of both primary and secondary transverse waves) are in good agreement with the experiment.

In order to study the combustion stabilization mechanisms, the gas parameters near the flame leading edge behind the rib and behind the step in the boundary layer with ethanol evaporation and combustion were compared. It was shown that at an air flow velocity of ≈11 m/s, an attached flame is formed behind the step, and the ethanol evaporation intensity is lower than behind the rib with a detached flame. At the flame leading edge behind the barriers, a zone is localized where the maximum heat release is located at the mixture ignition temperature, and the static and dynamic pressures are equal. It was shown that under conditions of gas motion with combustion and separation behind the rib, the maximum contribution of turbulent momentum transfer reaches ≈30 ÷ 40% of the averaged convective, and the share of molecular transfer is 2 ÷ 3%.