P. A. Strizhak

The motion of a manifold of finely dispersed liquid droplets in the counterflow of high-temperature gases

The motion of a manifold of liquid droplets in the counterflow of high-temperature (above 1000 K) gases has been experimentally studied for variable initial size (0.01–0.05 mm) and velocity (0.1–0.5 m/s) of droplets and the gas flow velocity (0.1–2 m/s). The properties of gas-vapor-droplet mixtures were monitored by optical diagnostic techniques. Conditions under which the trajectories and velocities of droplets moving in a high-temperature gas counterflow exhibit significant changes are determined.

Evaporation of two liquid droplets moving sequentially through high-temperature combustion products

We have performed an experimental study of the evaporation intensity for droplets in atomized-liquid flow moving through a flame of fixed height. Integral characteristics of the atomized-liquid evaporation process were evaluated. Evaporation of two water droplets moving sequentially one after the other through high-temperature combustion products is analyzed. A comparison of obtained data with available theoretical predictions is given.

Simulation of the ignition of liquid fuel with a local source of heating under conditions of fuel burnout

The processes of heat and mass transfer with phase transitions and chemical reactions in the ignition of liquid fuel by a local source of heating, a hot metal particle, under conditions of fuel burnout are studied. The influence of liquid fuel burnout on the ignition characteristics is analyzed, and the results of investigation of the extent of influence of this factor for solid and liquid condensed materials under conditions of local heating are compared.

Organic coal-water fuel: Problems and advances (Review)

The study results of ignition of organic coal-water fuel (OCWF) compositions were considered. The main problems associated with investigation of these processes were identified. Historical perspectives of the development of coal-water composite fuel technologies in Russia and worldwide are presented. The advantages of the OCWF use as a power-plant fuel in comparison with the common coal-water fuels (CWF) were emphasized. The factors (component ratio, grinding degree of solid (coal) component, limiting temperature of oxidizer, properties of liquid and solid components, procedure and time of suspension preparation, etc.) affecting inertia and stability of the ignition processes of suspensions based on the products of coaland oil processing (coals of various types and metamorphism degree, filter cakes, waste motor, transformer, and turbine oils, water-oil emulsions, fuel-oil, etc.) were analyzed. The promising directions for the development of modern notions on the OCWF ignition processes were determined. The main reasons limiting active application of the OCWF in power generation were identified. Characteristics of ignition and combustion of coal-water and organic coal-water slurry fuels were compared. The effect of water in the composite coal fuels on the energy characteristics of their ignition and combustion, as well as ecological features of these processes, were elucidated. The current problems associated with pulverization of composite coal fuels in power plants, as well as the effect of characteristics of the pulverization process on the combustion parameters of fuel, were considered. The problems hindering the development of models of ignition and combustion of OCWF were analyzed. It was established that the main one was the lack of reliable experimental data on the processes of heating, evaporation, ignition, and combustion of OCWF droplets. It was concluded that the use of high-speed video recording systems and low-inertia sensors of temperature and gas concentration could help in providing the lacking experimental information.

Environmental indicators of the combustion of prospective coal water slurry containing petrochemicals

Negative environmental impact of coal combustion has been known to humankind for a fairly long time. Sulfur and nitrogen oxides are considered the most dangerous anthropogenic emissions. A possible solution to this problem is replacing coal dust combustion with that of coal water slurry containing petrochemicals (CWSP). Coal processing wastes and used combustible liquids (oils, sludge, resins) are promising in terms of their economic and energy yield characteristics. However, no research has yet been conducted on the environmental indicators of fuels based on CWSP. The present work contains the findings of the research of CO, CO2, NOx, SOx emissions from the combustion of coals and CWSPs produced from coal processing waste (filter cakes). It is demonstrated for the first time that the concentrations of dangerous emissions from the combustion of CWSPs (carbon oxide and dioxide), even when combustible heavy liquid fractions are added, are not worse than those of coal. As for the concentration of sulfur and nitrogen oxides, it is significantly lower for CWSPs combustion as compared to coals. The presented research findings illustrate the prospects of the wide use of CWSPs as a fuel that is cheap and beneficial, in terms of both energy output and ecology, as compared to coal.

Influence of the initial parameters of spray water on its motion through a counter flow of high-temperature gases

The motion of spray water through a counter flow of high-temperature gases is experimentally studied on a macroscopic level using optical techniques for diagnostics of two-phase liquid-gas and vapor-liquid flows. It is found that the initial temperature, concentration of typical impurities, and dispersity of water influence the component composition of the forming gas-vapor-droplet mixture. The integral characteristics of evaporation of solitary droplets with initial sizes (conditional characteristic radii) of 3–5 mm and a spray water flow with droplets less than 0.5 mm across through a high-temperature gaseous medium are compared.

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.

Influence of solid inclusions in liquid drops moving through a high-temperature gaseous medium on their evaporation

The influence of solid inclusions (nonmetallic particles from several tens of micrometers to several hundred micrometers in size) in liquid drops moving through hot gases on the integral characteristics of their evaporation is studied experimentally with optical techniques for diagnosing two-phase gas-liquid and vapor-liquid flows. It is found that when liquid drops less than 1 mm in size move through a hot gas flow, solid inclusions intensify the liquid evaporation.

Numerical Investigation of Water Droplets Shape Influence on Mathematical Modeling Results of Its Evaporation in Motion through a High-Temperature Gas

The numerical investigation of influence of a single water droplet shape on the mathematical modeling results of its evaporation in motion through high-temperature gases (combustion products of a typical condensed substance) has been executed. Values of evaporation time, motion velocity, and distance passed by various droplet shapes (cylinder, sphere, hemisphere, cone, and ellipsoid) in a high-temperature gases medium were analyzed. Conditions have been defined when a droplet surface configuration affects the integrated characteristics of its evaporation, besides temperature and combustion products concentration in a droplet trace, insignificantly. Experimental investigations for the verification of theoretical results have been carried out with using of optical diagnostic methods for two-phase gas-vapor-liquid flows.

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.