R. S. Volkov

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.

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.

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.

Experimental determination of times, amplitudes, and lengths of cycles of water droplet deformation in air

The regularities of deformation of water droplets moving in air at the moderate Weber numbers (We < 7) are experimentally investigated with the use of high-speed cross-correlation recording equipment at frame delays of less than 100 ns. Deformation cycles with characteristic times, amplitude, lengths, and droplet forms are established. The effect of the droplet velocity on the main characteristics of the deformation cycles is determined.

Investigation of Regularities of Heat and Mass Transfer and Phase Transitions during Water Droplets Motion through High-Temperature Gases

The macroscopic regularities of heat and mass transfer and phase transitions during water droplets motion through high-temperature (more than 1000 K) gases have been investigated numerically and experimentally. Water droplet evaporation rates have been established. Gas and water vapors concentrations and also temperature values of gas-vapor mixture in small neighborhood and water droplet trace have been singled out. Possible mechanisms of droplet coagulation in high-temperature gas area have been determined. Experiments have been carried out with the optical methods of two-phase gas-vapor-droplet mixtures diagnostics (“Particle Image Velocimetry” and “Interferometric Particle Imaging”) usage to assess the adequateness of developed heat and mass transfer models and the results of numerical investigations. The good agreement of numerical and experimental investigation results due to integral characteristics of water droplet evaporation has been received.

Weber numbers at various stages of water projectile transformation during free fall in air

The process of breakage of water projectiles (spherical “balls” with initial volumes ranging within 0.05–40.5 L) during free fall in air from a height of 3 m has been studied by means of high-speed (up to 105 fps) video recording. Four stages of projectile transformation are distinguished that precede the formation of a cloud of droplets. It is established that the transitions from one stage to another proceed within shorter fall times for greater initial volumes of water. Weber numbers at these stages are determined.

Statistical analysis of consequences of collisions between two water droplets upon their motion in a high-temperature gas flow

Consequences of collisions between two water droplets upon their motion in high-temperature (about 1100 K) gases are analyzed statistically. The initial radii and motion velocities of the droplets varied within 0.1–0.25 mm and 0.5–5 m/s, respectively. The velocity of the counterflowing gas was 1.5 m/s. Using panoramic methods and tools of high-speed and cross-correlation video recording, conditions corresponding to different consequences (coagulation, decomposition, or breakup) of collisions between droplets are determined.

Deformation of liquid drops moving in a gas medium

Deformation of drops (with initial characteristic sizes of 3–6 mm) of widely used liquids (water, kerosene, and ethyl alcohol) moving in air with moderate velocities (up to 5 m/s) is investigated experimentally using a high-speed (105 frames per second) video camera. The characteristic “deformation cycles” for drops are established. The duration, length, and amplitude of variation of the drop sizes in each cycle are determined. It is shown how the initial size and velocity of drops affect these characteristics. The experimental results are processed using the similarity criteria (Weber and Reynolds numbers) adopted for investigating the motion of liquid drops. The features of the processes under investigation are outlined; it is shown that the conditions and characteristics of deformation of drops are determined not only by the effect of viscous, inertial, and surface tension forces.

Evaporation of a water drop with a solid opaque inclusion moving through a high-temperature gaseous medium

The process of evaporation of an inhomogeneous (containing a graphite particle) water drop moving through a high-temperature (about 1100 K) gas medium has been experimentally studied using highspeed (no less than 105 fps) video recording tools, the PIV scanning optical method, and Tema Automotive software. The influences of the ratio of water and inclusion masses, shape of inclusion (by the example of cylindrical disk, cube, and parallelepiped), and its surface area on the integral characteristics of liquid evaporation when heterogeneous drops are passed through a channel (length 1 m, inner diameter 0.2 m) with high-temperature gases are established.

Features of water droplet deformation during motion in a gaseous medium under conditions of moderate and high temperatures

Using cross-correlation video recording facilities, the features of deformation of water droplets with characteristic dimensions of 3–6 mm are studied experimentally during their motion in a high temperature (about 1100 K) gaseous medium (in combustion products) with velocities of up to 5 m/s. In addition, experiments for water droplets moving with identical initial velocities and dimensions in air at moderate (about 300 K) air temperatures are carried out. Typical shapes of droplets and cyclical character of their variation during motion in the considered gaseous media are established. The numerical values of the main characteristics of the isolated “deformation cycles” (amplitude, times, and durations) are determined, and their susceptibility to high temperatures of the gaseous medium, droplet dimensions, and droplet motion velocities is revealed.