Techniques of PIV in stratified two-phase headers

Influence of the initial parameters of liquid droplets on their evaporation process in a region of high-temperature gas

“…According to [20,21], for such values of We, conditions for droplet breakup do not arise. The volume concentration of droplets in the high-temperature gas medium was specified in a fairly narrow range of 0.0010-0.0012 (see [15]) as a result of limited applicability of optical methods of tracer imaging (particle image velocimetry (PIV) [22][23][24][25][26][27] and interferometric particle imaging (IPI) [28,29]) used in processing the results of experiments.…”

“…The experiments were conducted at velocities of motion of kerosene combustion products in the channel 13 less than 0.5 m/s (laminar flow of gases) under natural convection. To estimate the velocities of gases, particles of titanium dioxide nanopowder (approximately 5000 particles) were blown into the channel, which provided the minimum number of tracers in the computation domains of video records [22][23][24][25][26][27][28][29]. We recorded the tracer velocity fields, their distributions along the radius of the channel, and calculated the corresponding gas flow velocities.…”

“…The velocity of liquid droplets was determined from the displacements of tracers in them using the PIV method [22][23][24][25][26][27]. Experiments have shown that small relative displacements of tracers in a droplet have a negligible effect on its velocity [15].…”

“…Subsequent image processing was performed to calculate the particle displacement in the time interval between flashes of the light source and construct tracer velocity fields. A cross-correlation algorithm based on the fast Fourier transform technique was used which took into account the conditions of satisfaction of the correlation theorem [22][23][24][25][26][27]. Note that the droplet velocities U m are the velocities averaged over time between laser flashes according to [22][23][24][25][26][27].…”

“…For each domain, the correlation function was calculated [22][23][24][25][26][27]. The maximum of the correlation function corresponded to the most probable shift of particles in the recording region.…”