D. O. Glushkov

Numerical simulation of solid-phase ignition of metallized condensed matter by a particle heated to a high temperature

Numerical simulation of the ignition of a composite propellant by a single “hot” particle of metal is carried out in the framework of the solid-phase model of ignition. The dependences of the ignition lag time for a metallized condensed matter on the initial temperature of a local energy source are determined. Close agreement of the obtained theoretical results with the known experimental data is found.

Low-temperature ignition of coal particles in an airflow

A numerical study of the low-temperature (less than 500 K) ignition of a single coal particle within the framework of a model taking into account the interrelated processes of heat transfer in the particle and the surrounding gaseous medium, thermal decomposition of the coal, diffusion of decomposition products (volatiles) and their oxidation, heating of the coke residue (carbon), and heterogeneous ignition is carried out. The integral characteristic (delay time) of the low-temperature gas-phase ignition of the products of the thermal decomposition of 50- to 500-μm coal particles are determined. The minimum temperature of the air medium at which the ignition of the volatiles occurs and the lowest surface temperature of the particle at which its heterogeneous ignition after the burnout of the volatiles occurs are evaluated.

Mathematical simulation of the ignition of coal particles in airflow

A numerical study of interrelated heat and mass transfer processes with consideration for the thermal reaction of the organic matter of fuel on the gas-phase ignition of coal particles with sizes from 50 to 500 μm in airflow was performed. Minimum air temperatures at which the ignition of volatile substances occurs in an oxidizing atmosphere were determined. The calculated values are lower than the level of maximum permissible temperatures in the individual sections of systems for the preparation of pulverized coal at coal-burning power plants.

Solid-phase ignition of a composite propellant by a hot particle under free-convection heat sink into the environment

A mathematical model of the solid-phase ignition of a structurally inhomogeneous metallized composite propellant by an incandescent small particle in the form of a cylindrical disk with allowance for free-convection heat sink into the environment is developed. A numerical study of the ignition delay time, the main integral characteristics of the process, is performed. The calculation results are compared to experimental data on the ignition of model propellant compositions based on ammonium perchlorate, butyl rubber, and ASD-4 aluminum powder.

Stability of composite solid propellant ignition by a local source of limited energy capacity

A numerical simulation of solid-phase ignition of a composite propellant by a single small disk-shaped metal particle heated to a high temperature is performed. In the “heat flux amplitude-ignition delay ” coordinates, an region of stable initiation of combustion of a typical composite solid propellant under local heating by a source of limited energy capacity is selected. The limiting amplitudes of heat fluxes during ignition of the condensed substance under conductive and radiative heating are compared.

Differences in the ignition characteristics of coal–water slurries and composite liquid fuel

The processes of the inert heating, ignition, and combustion of the drops of typical coal–water slurries and promising composite liquid fuel were experimentally studied with the use of high-speed (to 105 frame/s) video recording facilities. The particles of brown and black coals with of sizes 80–100 μm were used as the basic components of the coal–water slurries and composite liquid fuel. Spent automobile oil (from an internal combustion engine) was also added to the composite liquid fuel (relative mass concentration, 0–15%). The characteristic stages of the processes of the inert heating and evaporating of liquid components and the ignition and combustion of coal–water slurries and composite liquid fuel (the initial radii of drops varied from 0.5 to 2 mm) were established. The ignition delay and complete combustion times of the drops of fuel compositions were determined under changes of the temperature of an oxidizing agent (air) in a range from 600 to 900 K at fluid velocities from 0.5 to 5 m/s. Representative temperatures at the centers of coal–water slurry and composite liquid fuel drops were measured at all of the established stages of the combustion initiation process. The necessary and sufficient conditions for the steady ignition of the drops of the test fuel compositions were recognized.

Numerical study of ignition of a metallized condensed substance by a source embedded into the subsurface layer

A numerical simulation of the ignition of structurally heterogeneous condensed material by a small single particle heated to high temperature, a typical limited heat content source of is performed within the framework of a solid-phase ignition model. The effect of the depth of embedment of the heated particle into the subsurface layer of the metallized material on the integral characteristics of the ignition is examined.

Ignition of a coal particle on a heated surface

With the use of high-speed (to 6 × 105 frames per second) video recording facilities, the following three physicochemical transformation regimes were recognized on the induction heating of the single particles (4–6 mm in size) of D coal on a steel plate (at a temperature of no higher than 1000 K): thermal decomposition without ignition, smoldering, and ignition. The limiting (minimum) values of heat source temperatures necessary and sufficient for the initiation of combustion of coal particles were established.The effect of particle sizes on the integral characteristics of the test process was found. The particle-size dependence of the time of heating of a natural solid fuel particle to the intense development of an exothermic reaction was obtained. It was found that the characteristic times of the initiation of the ignition and smoldering regimes were no longer than 10 and 20 s, respectively, with variations in coal particle size.

Ignition of polymeric material with single hot metallic and nonmetallic particles under diffusive-convective heat and mass transfer in an oxidizing medium

A mathematical model of the gas-phase ignition of a typical polymeric material by a single hot particle of parallelepiped shape with consideration for the associated physicochemical processes (conductive heat transfer and thermal degradation in the condensed phase, diffusive-convective heat and mass transfer and oxidation in the gas phase) is developed. Based on numerical simulations, the dependence of the delay time of the ignition of the polymer, the main integrated characteristic of the process, on the initial temperature of the source of the limited energy capacity are determined. A number of modes of ignition differing in the location the leading oxidation reaction in the gas phase are identified.

Simulation of the process of coal dust ignition in the presence of metal particles

A mathematical model was developed for the gas-phase ignition of a layer of the dust of typical 2B brown coal by a metal particle heated to high temperatures (above 1100 K) under ideal thermal contact conditions. This model took into account the heating and thermal decomposition of ground coal upon the cooling of a local source, the yield of volatile components, and the formation, heating, and ignition of the gas mixture. The effect of heat source parameters (shape and dimensions) on the fundamental process characteristic—the delay time of ignition—was found. A relationship of the ignition zone position near a hot particle with the heating intensity of a gas mixture of volatile substances and an oxidizing agent was revealed. The results of numerical studies are consistent with well-known experimental data on the conditions and characteristics of ground coal burning on local heating by sources of limited energy capacity.