Verification and validation of the model of the reduced kinetics of hybrid detonation in hydrogen-air mixtures with fine aluminum particles was carried out. The formula of integral heat release is obtained depending on the fuel excess coefficient for poor hydrogenair mixtures. The results are consistent with experimental data on the detonation rate. The constants of the aluminum combustion reactions are determined, which ensure the coordination of the detonation rate in air suspensions of aluminum particles. The processes of gas detonation in hydrogen-air mixtures and hybrid detonation with aluminum particles are numerically modeled. The dependencies of the hybrid detonation rate on the particle concentration are consistent with the known data. The comparison with experiments on cellular gas and hybrid detonation patterns is carried out: the degree of regularity, the size of the cells, the slope of the trajectories of triple points.

A physical and mathematical model of hybrid detonation in a hydrogen–oxygen–argon mixture with additives of microdispersed aluminum particles is presented. Hydrogen and aluminum combustion is described within the framework of the reduced kinetics. Formation of suboxides and solid aluminum oxide particles are taken into account in an aluminum combustion reaction. Numerical simulation of two-dimensional flows in a 10-cm wide plane channel is applied to study the formation and propagation of cellular detonation in a 0.72H2 + O2 + 2.58Ar mixture at an initial pressure of 0.26 atm with additions of aluminum particles 3.5 and 5 μ m in size. Properties of regularization and reduction of cell size are obtained. It is revealed that front velocity, as well as peak pressures and temperatures in the hybrid mixture increase in comparison with gas detonation. Double-front regimes that exist for a limited time are obtained. Merging of the fronts is followed by detonation acceleration and a transition to a fine-cell structure. The relationship between cell size and average detonation velocity is similar to the overcompressed gas detonation equation.

A simple mathematical model of hybrid detonation in oxygen-hydrogen-argon mixtures with suspended aluminum particles is suggested. The model is based on the approaches of the mechanics of multiphase media and equations of reduced chemical kinetics to describe gaseous and heterogeneous reactions. Production of alumina in the form of nanoparticles is considered. The problem of initiation and propagation of cellular detonation in a planar channel is analyzed. The results of calculations show that addition of small amount of combustible particles leads to increase in the detonation velocity and transformation of the cellular structure.

A physical and mathematical model of hybrid detonation of a mixture of hydrogen — oxygen — argon — aluminum particles is presented. Using this model, the influence of aluminum particles on the process of detonation propagation in a channel with expansion was studied. To speed up the results, the numerical model was extended using the Open MP libraries. As a result, it was found that the mode of propagation of hybrid detonation is affected by both the loading and the size of the particles. In general, the hybrid mixture is more resistant to changes in the geometry of the area to be filled.

The processes of attenuation and suppression of detonation in gas suspensions of aluminum particles by extended clouds of inert particles are studied on the basis of numerical simulations of two-dimensional flows. The normalized detonation velocity is found as a function of the concentration of inert particles. The conditions of detonation failure are determined for non-stoichiometric mixtures with oxygen and for the case with concentration gradients across the channel. It is demonstrated that a one-dimensional approach has certain limitations in determining the detonation failure criteria because transverse waves of cellular detonation favor its re-initiation. Sufficient conditions of detonation suppression for 1- μ m particles are determined.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Sergey Lavruk, Tatiana Khmel; Investigation of detonation propagation in inhomogeneous suspensions in a channel with expansion. AIP Conference Proceedings 16 February 2023; 2504 (1): 020005. https://doi.org/10.1063/5.0132707 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The processes of formation and propagation of hybrid detonation plane waves in hydrogenoxygen-argon mixtures with aluminum particles ranging in size from 3:5m to 13m with various loadings are numerically simulated. A physical and mathematical model of the reduced kinetics of hydrogen and aluminum combustion is used, taking into account the formation of solid oxide and gaseous suboxides. A stabilizing effect of aluminum particles on the flow, an increase in the detonation velocity and peak pressures and temperatures has been established. At the intermediate stage, temporary two-front configurations are formed. As the fronts propagate they merge the structures are transformed into singlefront ones. The established Chapman-Jouguet structures and their differences from gaseous detonation structures are analyzed.

Results of numerical simulation of two-dimensional flows of cellular detonation in plane channels in gas suspensions of submicron aluminum particles (0.6 and 0.3  $$\mu$$ m) in oxygen are presented. Mixtures with uniform and nonuniform concentrations are considered. A previously developed model of reduced kinetics verified on the basis of the detonation velocity dependence on the particle concentration and extended to mixtures with nonuniform concentrations is used. The size and character of detonation cells are found as functions of the particle size and concentration. Problems of detonation propagation in channels with transverse concentration gradients and intermittent distributions of concentration are considered.

Изучение гибридных детонационных структур связано с увеличением удельного импульса детонационных двигателей, а также с точки зрения взрыва и пожаробезопасности. Основная задача состоит в том, чтобы исследовать свойства ячеистой гибридной детонации. Целью данного исследования является разработка физической и математической модели гибридной детонации в смесях кислород–водород–аргон с добавлением алюминиевых частиц.

Under study are the regimes of detonation propagation in channels with linear expansion filled with monodisperse mixtures of oxygen and ultrafine aluminum particles of various loading; the methods of numerical simulations are used. The detonation combustion of submicron aluminum particles is described within the semi-empirical model of reduced kinetics with due regard to the transition from the diffusion-limited regime of combustion to the kinetic one. Waves of both planar and developed cellular detonation are considered as initial conditions. The characteristics of the main flow regimes are obtained and described: the subcritical (detonation failure), critical (detonation failure in some part of the channel) and supercritical (continuous detonation propagation). The maps of flow regimes in suspensions of 200-nm – 400-nm particles are presented in the plane of parameters: the channel width, expansion angle. The obtained critical conditions are similar to those observed in the gas detonation. The critical channel width linearly depends on the expansion angle up to a first critical value (35°–38°). Behind the second critical value (50°), the channel width is independent on the expansion angle. Between these values, there is an interval of nonmonotonicity similar to the detonation of micro-sized suspensions of aluminum particles. The effect of particle loading on the critical conditions in poor mixtures appears in the form of a sharp increase in the critical channel width, if the mass concentration falls below 0.25.

A review of investigations dealing with mathematical and numerical modeling of shock wave and detonation processes in gas suspensions of fine-grained inert or reacting particles is presented. The basic models of mechanics of continuous media that describe dilute and dense gas suspensions are mentioned and analyzed. Models with internal pressure in the particle phase, including those with the description of particle collision dynamics within the framework of molecular-kinetic approaches, are identified. Problems of interphase interaction and equations of state are discussed. Various issues of the qualitative analysis of the characteristic properties of models and theoretical analysis of shock wave structures (conditions on shock waves, classification of shock waves and combined discontinuities) are outlined. Numerical algorithms most widely used for simulations of shock wave processes are mentioned. Some results of numerical studies of the processes of detonation initiation and propagation, interaction of shock waves with clouds and layers of particles, and dispersion of the layers are noted.

A physical and mathematical model of the reduced kinetics is presented describing heterogeneous detonation in suspensions non-uniform in particle concentration. The model is based on the heterogeneous media approaches, semi-empirical laws of ignition and combustion, and data on the dependence of the detonation velocity on particle concentration. Formation of suboxides and incomplete combustion of aluminum are taken into account integrally. The dependence of the heat release of chemical reactions and the fraction of unburnt particles on the initial composition is determined from the solution of the stationary problem of the structure of the detonation wave. In the calculations of unsteady detonation flows, it is supposed to solve an additional equation for the spatial distribution of initial concentrations. The problems of initiation and development of cellular detonation in flat channels in suspensions of micron-sized aluminum particles are studied. Dependences of the cell size on particle concentration in uniform suspensions are determined. The flow patterns of cellular structures, the forms of the leading front, and the propagation velocities in channels with longitudinal or transversal gradients of particle concentration are analyzed.

Methods of mathematical and numerical modeling of two-dimensional flows are used to study the modes of heterogeneous detonation in gas suspensions of aluminum particles with non-uniform distribution of the particle concentration over the width of the flat channel. In the model of the reduced kinetics of detonation combustion of aluminum particles in oxygen and air, the dependence of the integral heat release on the particle loading is determined in accordance with the known data on the detonation velocity. Concentration limits of detonation for homogeneous mixtures are determined. Two-layer systems and systems with a transverse concentration gradient are considered when the mixture in a layer or in a part of a region is outside the concentration limits. The flow patterns are presented and the scenarios of propagation and detonation breakdown are described.