G. V. Kuznetsov

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.

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 ignition of particles of a coal–water fuel

The problem of particle ignition of coal–water fuel has been solved. The simultaneous processes of water vaporization and thermal decomposition of the solid fuel are taken into account. The conditions and characteristics of particle ignition of coal–water fuel under typical furnace conditions were determined by numerical simulation. The obtained values of the ignition delay time are in good agreement with published experimental data.

Evaporation of liquid droplets from a surface of anodized aluminum

The results of study of evaporation of water droplets and NaCl salt solution from a solid substrate made of anodized aluminum are presented in this paper. The experiment provides the parameters describing the droplet profile: contact spot diameter, contact angle, and droplet height. The specific rate of evaporation was calculated from the experimental data. The water droplets or brine droplets with concentration up to 9.1 % demonstrate evaporation with the pinning mode for the contact line. When the salt concentration in the brine is taken up to 16.7 %, the droplet spreading mode was observed. Two stages of droplet evaporation are distinguished as a function of phase transition rate.

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.

The influence of heat transfer conditions on the parameters characterizing the ignition of coal-water fuel particles

The future of thermal power engineering both in Russia and abroad will depend in many respects on the use of coal as main fuel for generating heat and electricity. In this connection, matters concerned with development and introduction of new environmentally friendly and energy efficient coal firing technologies are becoming of much importance. Firing coal in the form of coal-water fuel is one of the most promising solutions. However, despite a rather long history of its development (more than 40 years), this technology has not found wide use as yet, which in all likelihood is due to lack of full mathematical and physicochemical models describing the processes that take place when a coal-water fuel particle undergoes thermal treatment and ignition. The article presents the results obtained from numerical solution of the coal-water fuel particle ignition problem taking into account simultaneously occurring main thermal treatment processes (thermal conductivity, water evaporation, filtration heat and mass transfer, thermal decomposition of the fuel organic part, and thermochemical interaction between water vapor and coke carbon). The ignition problem is solved using the finite difference method. For calculating the evaporation process taking into account nonequilibrium nature of the parameters at the interface boundary of the initial “coal-water fuel—dry coal” system, the method of capturing the phase transition front at the difference mesh node was used. The results obtained from numerical modeling were used for determining the conditions and parameters characterizing the ignition of coal-water fuel particles under the conditions typically existing in the furnace space of boiler units. The extent to which radiant heat transfer influences the ignition delay time is determined. It is shown that radiant heat transfer plays a determining role in the thermal preparation of fuel for ignition.

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.