Table of contents

The paper reports on the study of flow structure of a reacting propane-air jet, issued from contraction nozzle and impinged on flat metallic surface, by using the particle image velocimetry technique. Flows with different nozzle-to-surface distance H/d were studied. The Reynolds number Re was in the range of 500÷5500, equivalence ratio Φ was varied from 0.8 to 1.4. Velocity field was measured for a conical premixed flame for Re = 1500 and Φ = 0.9. A region with flow recirculation was detected between the flame cone and the impingement surface for the case of H/d = 4. This flow feature may result in a reduced local heat transfer.

Two-phase bubble flows have been used in many technological and energy processes as processing oil, chemical and nuclear reactors. This explains large interest to experimental and numerical studies of such flows last several decades. Exploiting of optical diagnostics for analysis of the bubble flows allows researchers obtaining of instantaneous velocity fields and gaseous phase distribution with the high spatial resolution non-intrusively. Behavior of light rays exhibits an intricate manner when they cross interphase boundaries of gaseous bubbles hence the identification of the bubbles images is a complicated problem. This work presents a method of bubbles images identification based on a modern technology of deep learning called convolutional neural networks (CNN). Neural networks are able to determine overlapping, blurred, and non-spherical bubble images. They can increase accuracy of the bubble image recognition, reduce the number of outliers, lower data processing time, and significantly decrease the number of settings for the identification in comparison with standard recognition methods developed before. In addition, usage of GPUs speeds up the learning process of CNN owning to the modern adaptive subgradient optimization techniques.

The present paper reports on analysis of flow structure and turbulent transport in swirling flames. The particle image velocimetry and spontaneous Raman scattering techniques were used for the measurements of 2D velocity and density distributions. The focus was placed on comparison between low- and high-swirl flows. A pronounced bubble-type vortex breakdown with strong flow precession took place in the latter case.

The method for experimental determination of energy efficiency in the multichannel heat exchanger was tested. The visualization of a temperatures field has been performed to determine the thermal structure of gas flows with the use of fast-response fine- meshed wire. Thermograms of the temperature fields of the multi-channels assembly at the outlet were registered by thermal imaging camera. Results show that the 2D method provides a sufficient time resolution for the temperature field for the steady-state gas flow regime, heat generation, and nonsteady regime. The 2D method allows us to determine the gas stream parameters at the channel outlet in real time, which are necessary for determining the efficiency of the heat exchanger. Qualitative and quantitative characters of temperature changes in the thermograms are consistent with modern physical understanding of the gas flow in channels.

Experimental and numerical study of the steady-state cyclonic vortex from isolated heat source in a rotating fluid layer is described. The structure of laboratory cyclonic vortex is similar to the typical structure of tropical cyclones from observational data and numerical modelling including secondary flows in the boundary layer. Differential characteristics of the flow were studied by numerical simulation using CFD software FlowVision. It was found that helicity in a described system has non-zero value. Physical interpretation of helicity distribution is provided.

Mixed formulations of ultrafine PETN+soda and RDX+soda have low detonation velocity and small critical diameters, which makes them attractive for application to new technological processes, such as welding explosion [1]. The above properties of these formulations are due to the use of nanopowders of PETN and RDX along with a phlegmatizing agent of sodium bicarbonate. The detonation parameters of these mixtures were studied using synchrotron radiation from the VEPP-3 accelerator (Budker Institute of Nuclear Physics). Techniques we developed were applied to the measurement of density distribution in the detonation front and the width of the reaction zone, as well as volume distribution of pressure, density and spread velocities in detonation of cylindrical charges.