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In this work, a numerical study of the combustion of pulverized coal in a gas flame is carried out on the basis of the proposed mathematical model of combustion processes, using a nonstationary method for modeling turbulence, complex heat transfer and a reduced mechanism for chemical kinetics. The calculation results show acceptable agreement with the experimental data on the main characteristics of the flame, make it possible to qualitatively correctly determine the structure of the dust and gas flow and derive such parameters as the gas composition, the temperature of particles and gas, the degree of carbon burnout, etc.

A superhydrophobic phenomenon during fluids flow through microchannel due to the presence of the textures on the walls of the channels was considered. A numerical study of fluids flow and mixing in the microchannel at different Reynolds numbers and average roughness sizes has been carried out. The shift in the critical Reynolds number of the transition from the vortex symmetric flow regime to the vortex asymmetric (engulfment) regime towards lower values in the T-shaped microchannels with textured walls was found. The substantially unsteady structures in the straight microchannels with textured walls at Reynolds numbers of about 1000 were obtained.

A spatial mathematical model of the evaporation system using film flows has been developed. A numerical study of several modes of film flow in an evaporation cell at a heater temperature below the boiling point has been carried out. The characteristics of the film flow and the features of the coupled heat and mass transfer processes in the gas-film-metal substrate system have been studied. Good agreement between the calculation and the experiment on the main parameters of the wave motion of the film and the heat transfer characteristics has been obtained.

A mathematical model of heat and mass transfer processes in the combustion chamber of diesel generator sets with valve-inductor generators has been developed. The main characteristics of a diesel generator have been analysed within a wide range of operating modes.

The paper presents the results of an experimental study of oil displacement by distilled water and an aqueous suspension of aluminum oxide nanoparticles. The correlation of extracted oil volume on the flow rate of the displacing fluid is obtained, and the pressure drop during the pumping of the displacing fluid through the rock sample is measured. It has been revealed that the suspension of nanoparticles can significantly improve the extraction of oil from sandstone.

The calculated study of the flow regimes of two-phase oil and water mixture in straight microchannels simulating a pore or crack in the rock formation was carried out. It was shown as a result of the literature survey that all modern, industrially developed methods of the oil recovery from the oil reservoirs is considered as unsatisfactory in all oil-producing countries. The average value of the final oil recovery is varied from 25% to 45%, so, it is easy to count, that residual or unrecoverable oil reserves in the subsoil reach an average of 55-75% of their initial values. Also, it was found, that the use of micro and nanotechnologies in a broad sense is one of the possible and promising ways to solve these problems. A numerical method called «Volume of Fluid» (VOF) was used to simulate the two-phase flows of oil and displacing agents in the considered microchannels. It was proposed to use the dimensionless number, called Regime number, to describe the different flow regimes of oil/water mixture and transitions between these regimes. The plug flow, the slug flow, the parallel flow and the emulsion flow regimes were observed.

This paper presents the results of laboratory tests and numerical simulation of polymer drilling fluids. The influence of the rotation speed on the values of the pressure ratio and cutting transport is studied. The influence of rheological parameters on the efficiency of cuttings transport is investigated.

It was experimentally investigated the nanofluids evaporation rate in this study. The nanofluids were prepared using the distilled water and different nanoparticles. The nanoparticles of aluminium oxide, silicium and zirconium dioxides, as well as the nanodiamonds were used. The average diameters of the particles were as follows: SiO2 – 25 nm, ZrO2 – 105 nm, Al2O3 particles – 43 nm and nanodiamonds – 5 nm. The Simultaneous Thermal Analyzer STA 449 C Jupiter (NETZSCH) was used to carried out the study of the evaporation rates of fluids. The dependence of the evaporation rate on the material of the nanoparticles was investigated. It was found in that study that the evaporation rate significantly depends on the nanoparticles material. Moreover, based on the obtained results it was shown, that the evaporation rate of nanofluids monotonically increases with an increase of nanoparticles volume concentration.

The study of suspensions with aluminum nanoparticles was carried out. Ethylene glycol was used as the base fluid. The mass concentration of Al nanoparticles varied from 2.5 to 20%. The viscosity coefficient of the suspension at different shear rates was measured. The dependence of the viscosity on the concentration of Al nanoparticles in ethylene glycol was obtained. The attenuation of the suspensions was measured. The dependence of the sound speed in suspension on the nanoparticle concentration was obtained. The acoustic parameters of the suspension, such as adiabatic compressibility, acoustic impedance, intermolecular free length, viscous relaxation time, are calculated.

The evaporation of the nanofluids based on Al2O3 nanoparticles and different fluids was experimentally investigated. The distilled water and isopropyl alcohol were used as base fluids. The average diameter of Al2O3 particles was 100 nm. The investigations of fluids evaporation rates were carried out using the Simultaneous Thermal Analyzer STA 449 C Jupiter (NETZSCH). The investigation of the evaporation rate dependence on the carrier media was carried out. It was found that the average relative evaporation rate of fluids increased, and the time of complete evaporation accordingly decreased with an increase in the volume concentration of nanoparticles. In addition, the absolute value of the evaporation rate was found to significantly depend on the type of base fluid. However, the relative value of the evaporation rate for different base fluids remains approximately the same.

This paper reports on the investigation of screw rotors with different geometric parameters by numerical simulation. The study was performed for the free flow around a fully submerged system. The effect of the inner shaft diameter, the rotor screw pitch and running frequency on the energy characteristics, as well as the torque on a shaft and generated power are shown. Following up upon the conducted research of the screw rotor the geometric parameters and operating modes, which allow achieving maximum effectiveness at the same initial parameters, were determined.

This paper reports on the investigation of combustion features of synthesis gas/air and methane/air flames in a model gas turbine combustor with swirling flow via numerical simulation. This combustor developed for experimental investigation of flow, heat transfer and combustion. For synthesis gas combustion ratio of hydrogen and carbon monoxide was 1:1. The equivalence ratio Φ in both cases was 1.5. The combustor contains systems for water- and air-cooling that provides reasonable temperature value of combustor walls in operating mode. The methane/air flame has the lifted V-shape and synthesis gas/air flame has the columnar tubular flame. In practical, the V-shape flames are more often used. To provide more practical combustion regimes for synthesis gas/air mixture it is necessary to increase the fuel-oxidant mixing efficiency in the premixer of the combustor.

The influence of different volume concentrations and average diameters of Al2O3 nanoparticles on the contact angle of wetting between nanofluids and different substrates was experimentally investigated. The concentrations of aluminium oxide nanoparticles were varied from 0.0625 vol.% to 1 vol.%. The average diameters of aluminium oxide nanoparticles were varied from 43 nm to 150 nm. Andesite, diabase, gabbro-diabase and metabasalt were chosen as the substrates. The dependences of the value of the contact angle of wetting between nanofluids and different substrates were obtained as a result of the experiments. It was shown, that the contact angle of wetting nonlinearly depended on the nanoparticles volume concentration. In addition, it was found that the wetting angle also depends on the substrate material, on which the drop lies. It was also obtained that the contact angle of wetting between different substrates and nanofluids with average and huge nanoparticles (> 75 nm) increased 1.25-1.5 times even at the smallest concentration (0.0625 vol.%) and then achieved the plateau. In contrast, the contact angle of wetting between different substrates and nanofluids with small nanoparticles (< 50 nm) reached maximum at a concentration of 0.0625 vol.% and after that slowly decreased to the values lower than those for the pure water.

Numerical simulation of the oil displacement process from a porous medium by nanofluid was carried out. To describe this process a flow model of two immiscible fluids taking into account the surface tension forces and the wetting angle was used. The simulation results of the penetration of fluid with nanoparticles into a porous medium are obtained using the example of the oil displacement. The nanoparticles addition to the displacing fluid affects the process of oil displacement from porous medium significantly. SiO2 particles with a size of 5 nm were used as nanoparticles. The concentration of nanoparticles ranged from 0 to 1 wt.%. The main reason for the increase in ORF (oil recovery factor) during oil displacement by nanofluid is the improvement of rock wetting.

In this work, the process of diesel fuel combustion in a laboratory sample of an original evaporation-type burner with superheated steam supply to the reaction zone was investigated by numerical simulation. Fuel burning in such a burner occurs in a steam jet flowing through the nozzle. In the framework of research, a mathematical model was developed, the influence of various models of turbulence, approaches to simulation of combustion, and response schemes were investigated.

The paper presents test results of the method for numerical simulation of liquid fuel spraying based on the Eulerian-Lagrangian model. This model describes the fluid flow inside the injector and directly behind it using the Euler-VOF method, while the dispersed medium (droplets) formed at a certain distance from the injector is described using the Lagrange approach. When using the VOF (volume of fluid method), the dynamical adjustment of the calculation grid at the phase interface is applied. Turbulence is modeled by the large eddy simulation (LES) method. The research results were compared with the data of direct numerical simulation (DNS) [1]. The calculation results based on the Eulerian-Lagrangian model show an acceptable agreement with the data of direct numerical simulation in terms of the main characteristics of the spraying. Thus, the structure of the two-phase flow, the parameters, and shape of the drops, as well as the speed and direction of their movement are determined qualitatively correctly.

This research is focused on the dependence of viscosity of water-based drilling fluid modified by nanoparticles on temperature. Silicon oxide of 10 nm size was used as nanoparticles. The nanosuspensions were prepared for nanoparticle concentrations from 0.25 to 3 wt%. An aqueous solution of bentonite with a mass fraction of 5 % was used as a base drilling fluid. Rheological studies were conducted at varying temperatures (25, 40, 55 and 80 °C). The dependences of the effective viscosity of these suspensions on the concentration of nanoparticles and temperature have been obtained.

Flow patterns and mixing efficiency of fluids with different inlet flow rate pulsation frequencies in T-shaped micromixer were numerically investigated at Reynolds numbers Re = 100 and Re = 180. The flow rate pulsations were set sinusoidal with different frequencies of 0; 1; 10 and 50 Hz. The relative mixing efficiency means the mixing efficiency of active mixer regarding the mixing efficiency of an identical passive mixer without pulsations at the input; it was considered as the main value. The dependences of such value on the pulsation frequencies were obtained. It was found that active micromixers are much more efficient than the passive ones. Herewith, in the engulfment regime, the mixing efficiency increases twofold regarding the passive mixer, and in the region, before the onset of the engulfment regime, the mixing efficiency increases by about 170 times. In addition, it was found that the increase in mixing efficiency is almost independent of the frequency of pulsations.

An experimental study on the effect of silica nanoparticles addition on the viscosity of water-based mud at different temperatures was carried out. The mass concentration of clay was 5%, and the nanoparticles concentration varied from 0.5wt% to 3wt%. The nanoparticle size was 10 nm. Viscosity coefficient measurements were carried out in a wide temperature range.

The laminar forced convection in a recuperative heat exchanger operating with nanofluids with MgO nanoparticles was investigated experimentally. In the experiments, nanoparticle concentration varied in the range from 2.5 to 12 wt. %. The nanoparticle size equalled 50 nm. The viscosity and thermal conductivity coefficients of the nanosuspensions were experimentally determined. The dependence of the average heat transfer coefficient and pressure drop on the Reynolds number for nanofluids was obtained.

The work is devoted to experimental and computational modeling of the flow around water droplets behind an incident shock wave and its effect on deformation and decay. The structure of the flow near and in the wake of the drop, the evolution of the shape and breakup delay were investigated in the range of shock wave Mach numbers Ms=1.109–1.34 and Weber numbers We=200–2200. Comparison of calculations with experiments allowed constructing a phenomenological picture of the behavior of a drop in shock wave as a response to a rapidly changing flow field at an early stage of interaction.

This paper reports on the investigation of combustion features of turbulent swirling methane/air and synthesis gas/air flames via using modern CFD-approaches. For methane/air mixture the equivalence ratio Φ was 0.7 which is near to the lean blow off limit. Two regimes with 1:1 and 1:2 ratios of hydrogen and carbon monoxide in the fuel mixture have been considered for synthesis gas combustion. For validation of numerical models, the reliable experimental data has been used. It is found that LES approach demonstrates good agreement with the experimental data. Comparison between methane/air and synthesis gas/air flames demonstrates that in the latter case the size of recirculation zone and the flame temperature are decreasing. But, addition of carbon monoxide in synthesis gas/air mixture leads to flame temperature rise.

The dependence of thermal conductivity of suspension on the concentration of single-walled carbon nanotubes was investigated. Mass concentration of nanotubes ranged from 0.05 to 0.5%. Sodium dodecyl sulfate was used as a surfactant. The enhancement of 34.8% were achieved for thermal conductivity coefficient of suspensions at 0.5wt.% of CNT.

The paper deals with the numerical simulation of the flow in the Francis-99 hydraulic turbine at three different problem formulations, namely, the application of the method of rotating coordinate system, sliding mesh model, and consideration of a compressible fluid. The pulsations intensity and pressure pulsation spectra obtained by numerical simulation and experimentally are compared. It is shown that the simulation of a problem considering compressible fluid, and that conducted by the sliding mesh method gives significantly greater pressure amplitudes. It is also shown that the precessing vortex core is a source of pressure waves in the entire turbine flow path.

The paper presents a verification of calculation modeling methods of atomizing of a gas and gas-liquid stream from a pneumatic nozzle based on the experimental data obtained in the IT SB RAS. Turbulent supersonic flow of compressible gas is considered here. Mathematical model includes description of gas phase motion based on the RANS (Reynolds Averaged Navier-Stokes) and URANS (Unsteady RANS) approach using two-parameter turbulence model k-ω SST and Reynolds Stress Model (RSM). The Lagrange method was used to model flow of water droplets. Dispersed phase is solved by tracking a large number of droplets through calculated flow field. Dispersed phase can exchange momentum, mass, and energy with fluid phase. Comparative analysis showed an acceptable qualitative and quantitative agreement between calculation and experiment, both for subsonic and supersonic flow.

The results of experimental studies of the microsuspensions filtration with silicon oxide nanoparticles additions through a porous medium with different permeability are presented. The particle concentration in fluids ranged from 0.25 to 4 wt.%. The microparticle size was 1.2 μm. The nanoparticle size was 5 nm. The nanoparticle concentration was 2 wt.%. Dependences of the filtration losses of microsuspensions on the microparticle concentration and the permeability of a porous medium were established.

The paper presents numerical simulation of the flow in hydraulic turbine based on the experimental data of the II Francis-99 workshop. The calculation domain includes the wicket gate, runner and draft tube with rotating reference frame for the runner zone. Different turbulence models such as k-ω SST, ζ-f and RSM were considered. The calculations were performed by means of in-house CFD code SigmaFlow. The numerical simulation for part load, high load and best efficiency operation points were performed.

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at startup regimes. Numerical technique for calculating of low frequency pressure pulsations in a water turbine is based on the use of DES (k-ω Shear Stress Transport) turbulence model and the approach of "frozen rotor". The structure of the flow behind the runner of turbine was analysed. Shows the effect of flow structure on the frequency and intensity of non-stationary processes in the flow path. Two version of the inlet boundary conditions were considered. The first one corresponded measured time dependence of the discharge. Comparison of the calculation results with the experimental data shows the considerable delay of the discharge in this calculation. Second version corresponded linear approximation of time dependence of the discharge. This calculation shows good agreement with experimental results.

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at three regimes, using two eddy-viscosity- (EVM) and a Reynolds stress (RSM) RANS models (realizable k-, k-ω SST, LRR) and detached-eddy-simulations (DES), as well as large-eddy simulations (LES). Comparison of calculation results with the experimental data was carried out. Unlike the linear EVMs, the RSM, DES, and LES reproduced well the mean velocity components, and pressure pulsations in the diffusor draft tube. Despite relatively coarse meshes and insufficient resolution of the near-wall region, LES, DES also reproduced well the intrinsic flow unsteadiness and the dominant flow structures and the associated pressure pulsations in the draft tube.

The paper presents the results of experimental study of turbulent forced convection of water-based nanofluid with ZrO2 nanoparticles. Volumetric concentration of the nanoparticles in the experiments was equal to 4%. The average particle size was 105nm. The study was carried out for a smooth round tube and round tube with knurling ring. The effect of additives of ZrO2 nanoparticles on the average heat transfer coefficient and the pressure drop in the channel was investigated. Has been shown that the intensification of heat transfer by using nanofluid weakly dependent on the shape of the channel, and determined only by the properties nanofluid.

Several popular turbulent combustion models have been tested in a computational study of three experimentally well-documented non-swirling and swirling jet flames. Different combinations of turbulence, combustion and reaction mechanisms models were considered. It is shown that the eddy- dissipation concept (EDC) and the probability-density function (PDF) of flamelet combustion models with detailed kinetics mechanisms provide the best results for all flames examined. For some cases, a combination of RANS turbulence models and less costly combustion approaches (Hybrid or EDC with 4 reactions) also gives acceptable results.

The paper presents the results of systematic measurements of the thermal conductivity coefficient of nanofluids at room temperature. It is shown that the thermal conductivity of all considered nanofluids depend on concentration, nanopartical size, as well as the base fluid properties. It was revealed that thermal conductivity coefficient of nanofluids increases with increasing concentration and size of nanoparticles.

The paper presents the numerical simulation method of three-dimensional turbulent flows in the hydraulic turbine. This technique was verified by means of experimental data obtained on a water model of the Francis turbines. An aerodynamic stand, which is a miniature copy of the real hydraulic turbine, was designed. A series of experiments have been carried out on this stand and the corresponding calculations were performed. The dependence of the velocity and pressure pulsations profiles for different operation regimes are presented.

The paper presents numerical simulation of flow in Francis-99 water turbine under three operation modes: part load, best efficiency point and high load. Calculations were performed by means of Reynolds stress model and detached eddy simulation based on k-omega SST model. The paper focuses on the flows in the draft tube. The calculated mean velocity components in the draft tube are in close agreement with experimental results. Calculated r.m.s velocity components agree with experimental pulsations qualitatively.