Publishing House SB RAS:

Publishing House SB RAS:

Address of the Publishing House SB RAS:
Morskoy pr. 2, 630090 Novosibirsk, Russia

Advanced Search

Thermophysics and Aeromechanics

2019 year, number 4

Suppression of transonic buffet with plasma vortex generators

A.A. Sidorenko1, A.D. Budovsky1, P.A. Polivanov1, O.I. Vishnyakov1, V.G. Sudakov2, V.N. Ishchenko3
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Zhukovskii Central Aerohydrodynamic Institute, Zhukovskii, Russia
3Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, Russia
Keywords: трансзвуковой бафтинг, электрический разряд, управление течением, transonic buffet, electric discharge, flow control

Abstract >>
In the present paper, we report on the results of an experimental study of the possibility to control the transonic buffet on a rectangular wing using plasma vortex generators. The influence of the developed device on the flow consists in creating a longitudinal vortex in the boundary layer as a result of asymmetric energy supply at the surface of a small vertical wedge. The experiments were performed using a wing model with a supercritical airfoil in the range of free-stream Mach numbers 0.73 to 0.78 and Reynolds numbers Re = (2.64-2.8)x106. The experimental data obtained using the method of high-speed schlieren visualization and pressure distribution measurements in the wake of the model show that the technique allows one to control both the average flow characteristics and the characteristics of shock-wave oscillations.

Numerical simulation of a multicomponent mixing layer with solid particles

A.P. Makasheva, A.Zh. Naimanova
nstitute of Mathematics and Mathematical Modeling MES RK, Almaty, Kazakhstan
Keywords: двухфазный поток, твердые частицы, многокомпонентный газ, уравнения Навье-Стокса, эйлерово-лагранжев метод, two-phase flow, solid particles, multicomponent gas, Navier-Stokes equations, Euler-Lagrange method

Abstract >>
The work is devoted to the numerical simulation of a supersonic plane mixing layer of multicomponent gases in the presence of injection of particles at the interface of flows. An algorithm for solving the system of Navier-Stokes equations for the gas phase and the system of ordinary differential equations for solid particles based on the Eulerian-Lagrangian representation is proposed. It is assumed that the turbulent flow is quasi-two-dimensional and the solution of the an original system is produced by the 2D-DNS approach without using additional closure models of turbulence. A detailed study of the influence of the gas phase on the particles distribution and their capture with coherent structures is performed with the variance of Mach numbers and particles injection locations The enhancing influence of the centrifugal force on the dispersion of particles is obtained with increase in the input Mach number. A quasi-equilibrium state with a gas flow of small particles is established.

The influence of the period switching frequency on the heat exchange of a regenerative air heater

Yu.A. Kirsanov1, D.V. Makarushkin1, A.Yu. Kirsanov2
1Institute of Energy and Advanced Technologies, Kazan Scientific Center RAS, Kazan, Russia
2Kazan National Research Technical University n.a. A.N. Tupolev, Kazan, Russia
Keywords: лабораторный стенд, регенеративный воздухоподогреватель, нестационарные процессы, измерения, температура, теплоотдача, критериальное уравнение, laboratory stand, regenerative air heater, unsteady process, measurement, temperature, heat exchange, criterial equation

Abstract >>
A laboratory stand with a regenerative air heater, an automated system for control and measurement of air flow parameters and a nozzle designed to study the heat transfer of a package of parallel plates under non-stationary conditions for different periods are described. The technique of measuring the transient temperature of cold and hot coolant flows taking into account the inertia of thermocouples and the method of measuring the heat transfer coefficient of plates are presented. The time variations of the Nusselt number and the heat power transmitted by the nozzle for individual periods are shown. Values of the average Nusselt number for the period obtained in experiments with the packages of plates of different materials and thicknesses are generalized by a criterial equation convenient for engineering calculations of regenerative air heaters with sheet packing of various types.

Experimental investigation of heat transfer in the separation zone behind a backward-facing step in presence of tabs

A.Yu. Dyachenko1, V.L. Zhdanov2, Ya.I. Smulskii1, V.I. Terekhov1
1Kutateladzer Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Lykov Institute of Heat and Mass Transfer NASB, Minsk, Belarus
Keywords: турбулентный поток, отрывное течение, табы, обратный уступ, теплообмен, turbulent flow, separation flow, tabs, backward-facing step, heat transfer

Abstract >>
The paper presents the experimental data on distribution of static pressure and heat transfer in a separation zone behind a backward-facing step equipped with vortex generators. The size and gaps between generators (tabs) of rectangular shape were varied in experiments. Experimental results were compared with two limiting cases: a smooth step (no tabs), and a step with a solid fin. The strongest influence on flow and heat transfer from the set of installed tabs was observed within the recirculation zone just behind the step base. The tabs allocated at the step edge resulted in the displacement of the Nusselt number maximum to the step base that caused the enhancement of a local and average heat transfer.

Heat transfer in turbulent separation region of pulsating flow behind a backward-facing step

I.A. Davletshin1,2, A.K. Aslaev1, N.I. Mikheev1, A.A. Paereliy1
1Institute of Power Engineering and Advanced Technologies RAS, Kazan, Russia
2Kazan National Research Technical University n.a. A.N. Tupolev, Kazan, Russia
Keywords: обратный уступ, отрыв потока, пульсации потока, число Струхаля, интенсификация теплоотдачи, backward-facing step, flow separation, flow pulsations, Strouhal number, heat transfer enhancement

Abstract >>
Heat transfer in a pulsating air flow was studied experimentally in the separation region behind a backward-facing step. The data on distributions of heat transfer coefficient have been obtained. At the distance of more than ten step heights away from the step edge, the heat transfer coefficient in pulsating flow deviated by no more than ±10 % from the steady flow values. Towards the step, heat transfer became more intensive relative to the steady regimes. Immediately beyond the separation edge, flow pulsations led to local twofold enhancement of heat transfer and even higher. In general, heat transfer augmentation in the separation region behind the step reached a maximum (70 %) at the Strouhal number Sh ~ 1.

Experimental and numerical study of forced convection heat transfer from array of fins with various cross perforations

H. Saadat1, M.M. Tavakol1, M. Yaghoubi2,3
1Islamic Azad University Shiraz Branch, Shiraz, Iran
2Shiraz University, Shiraz, Iran
3Academy of Sciences, Tehran, Iran
Keywords: перфорированные ребра, конвекционный теплообмен, эффективность, турбулентный поток, вычислительная гидродинамика, perforated fins, convection heat transfer, effectiveness, turbulent flow, CFD

Abstract >>
In this paper, heat transfer characteristics of new types of perforated fins with cross perforations are investigated using experimental measurement and numerical simulations. Conjugate equations of turbulent flow and conduction heat transfer are solved around fins and within fins using a finite volume code. Solution includes two types of circular and square perforations and Reynolds numbers from 2×104 to 4×104 based on the fin length. From the results of numerical simulation, structures of flow field and heat transfer for each configuration are illustrated and discussed. For validation, comparison is made with solid fin as well as perforated fins and reasonable trend for heat transfer is observed. For further analysis, a series of measurements is carried out for a model of perforated fins with one streamwise opening and one cross opening. It is shown that among different perforation configurations, a fin with 1 longitudinal perforation and 3 vertical perforations shows the best heat transfer performance. In addition, it is found that the circular perforation is preferred in comparison with square perforation considering both heat transfer performance and pressure drop.

Heat transfer of a tube bundle in a pulsating flow

V.M. Molochnikov, A.N. Mikheev, A.K. Aslaev, O.A. Dushina, A.A. Paereliy
Institute of Power Engineering and Advanced Technologies FRC RAS, Kazan, Russia
Keywords: пучок цилиндров, вынужденные пульсации скорости потока, теплоотдача, визуализация, SIV-измерения, профили статистических характеристик, механизм интенсификации теплоотдачи, cylinder bundle, forced pulsations of flow velocity, heat transfer, visualization, SIV measurements, profiles of steady-state characteristics, mechanism of heat transfer enhancement

Abstract >>
In the present paper, we report on the results of an experimental study of the transfer of heat and flow structure in the inter-tube space of in-line and staggered tube (cylinder) bundles in a pulsating external flow. For two values of the relative pitch in the bundles, the average heat transfer of a cylinder, and the distributions of the components of flow velocity and rms pulsations of that velocity in the inter-tube space, were measured. It is found that the change in the heat transfer of a bundle cylinder under forced flow unsteadiness correlates well with the level of the energy of velocity pulsations in the cylinder wake. The possibility of enhancement of heat transfer in a cylinder bundle using forced flow oscillations is demonstrated.

Prediction of thermal conductivity of liquid and vapor refrigerants for pure and their binary, ternary mixtures using artificial neural network

N. Ghalem1, S. Hanini2, M.W. Naceur1, M. Laidi2, A. Amrane3
1University of Blida, Blida, Algeria
2University of MГ©dГ©a, MГ©dГ©a, Algeria
3University of Rennes, National Higher School of Chemistry, Rennes, France
Keywords: хладагент, чистая система, смеси, теплопроводность, искусственная нейронная сеть, прогнозная модель, refrigerant, pure system, mixtures, thermal conductivity, artificial neural network, predictive model

Abstract >>
The determination of thermophysical properties of hydrofluorocarbons (HFCS) is very important, especially the thermal conductivity. The present work investigated the potential of an artificial neural network (ANN) model to correlate the thermal conductivity of (HFCS) at (169.87-533.02) K, (0.047-68.201) MPa, and (0.0089-0.1984) W/(m·K) temperature, pressure, and thermal conductivity ranges, respectively, of 11 systems from 3 different categories including five pure systems (R32, R125, R134a, R152a, R143a), four binary mixtures systems (R32 + R125, R32 + R134a, R125 + R134a, R125 + R143a), and two ternary mixtures systems (R32 + R125 + R134a, R125 + R134a + R143a). Each one received 1817, 794 and 616 data points, respectively. The application of this model for these 3227 data points of liquid and vapor at several temperatures and pressures allowed to train, validate and test the model. This study showed that ANN models represent a good alternative to estimate the thermal conductivity of different refrigerant systems with a good accuracy. The squared correlation coefficients of thermal conductivity predicted by ANN were R 2 = 0.998 with an acceptable level of accuracy of RMSE = 0.0035 and AAD = 0.002 %. The results of applying the trained neural network model to the test data indicate that the method has a highly significant prediction capability.

Density and thermal expansion of samarium in a wide temperature range

Yu.M. Kozlovskii, S.V. Stankus
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: термический коэффициент линейного расширения, плотность, самарий, высокие и низкие температуры, непрерывный фазовый переход, полиморфное превращение, критический индекс, точка Нееля, linear thermal expansion coefficient, density, samarium, high and low temperatures, continuous phase transition, polymorphic transformation, critical index, NГ©el point

Abstract >>
The results of a dilatometric study of the linear thermal expansion coefficient (LTEC) of polycrystalline samarium in the temperature range of 110-1050 K are presented. Temperature dependences have been obtained and reference tables of recommended values of thermal properties for the 110-1900 K interval of its solid and liquid states have been calculated. The nature of the LTEC change in the regions of phase transformations of the first and second kinds has been established. The critical indices of the linear thermal expansion coefficient at the Néel point have been determined.

Investigation of the melt movement along the fuel pin surface during accidents

E.V. Usov1, I.A. Klimonov1, S.I. Lezhnin2,1, P.D. Lobanov2,1
1Nuclear Safety Institute of the Russian Academy of Sciences, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: ТВЭЛ, авария, расплав, пленка, fuel pin, accident, melt, film

Abstract >>
Methods for calculating the motion of a melt along the fuel element surface under the conditions of an accident are presented. The calculation was carried out using semianalytic methods for the shear stress and gravity-driven films. The results of calculations of the motion of a melt under various initial conditions are presented. Particular attention is paid to the influence of surface tension forces on the interface between the melt and a solid surface.

Propane burning in argon, carbon dioxide, and water vapor at increased pressure

O.N. Fedyaeva, D.O. Artamonov, M.Ya. Sokol, A.A. Vostrikov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: пропан, самовоспламенение, цепно-тепловой взрыв, диоксид углерода, водяной пар, propane, self-ignition, chain-thermal explosion, carbon dioxide, water vapor

Abstract >>
The paper presents investigation results on propane combustion in argon, carbon dioxide, and water vapor under the conditions of O2 deficiency and high reagent density when they are uniformly heated up to 620 K. Based on time dependences of reaction mixture temperature, the self-ignition temperature of propane was determined. It has been established that the oxidation of propane in an Ar and Н2О medium proceeds according to the mechanism of chain-thermal explosion. The results of mass spectrometric analysis showed that oxidation in a CO2 medium is characterized by the lowest degree of propane conversion. It was also found that at a low density of water vapor, the oxidation of propane is accompanied by a high yield of H2. The mechanisms of CO2 and H2O molecule participation in the oxidation of propane are discussed in the paper.

Thrust production from in-water gas charge combustion near a flat wall

V.S. Teslenko, A.P. Drozhzhin, R.N. Medvedev
Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia
Keywords: водный движитель, генерация тяги, сжигание газа, удельная тяга, средняя тяга, water mover, thrust generation, gas combustion, specific thrust, average thrust

Abstract >>
The paper presents experimental results on study of production of force pulses and bubble pulsation near a flat thrust-producing wall with the diameter of 100 mm designed for combustion of stoichiometric propane-oxygen gas mixture. In combustion of the same gas charges for production of thrust, the design of combustion at a flat wall has qualitative and quantitative benefits vs. case of combustion in a cylindrical duct. The force amplitude becomes higher due to the larger contact area between the bubble and thrust wall. The period of bubble pulsation is shorter for this case as compared to bubbles generated in a cylindrical duct; the pulsation period is described by the Rayleigh-Willis law. The shorter bubble pulsation period ensures better conditions for increase in the average thrust generated in pulse-in-cycle mode of combustion of gas charges in water medium.

The speed of sound in vapor phase refrigerant R-134a (57.24 wt. %) - R-227ea (42.76 wt. %)

S.G. Komarov, S.V. Stankus
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: смесевой хладагент, скорость звука, пар, температура, давление, ультразвуковой интерферометр, mixed refrigerant, speed of sound, vapor, temperature, pressure, ultrasonic interferometer

Abstract >>
The speed of sound of the gaseous mixed refrigerant R-134a (57.24 wt.%) - R-227ea (42.76 wt. %) was investigated by the method of ultrasonic interferometer in the temperature range from 293 to 373 K and at pressures from 0.08 to 0.97 MPa. The measurement errors of temperature, pressure, and speed of sound were ±20 mK, ±4 kPa, and ±(0.20-0.35) %, respectively. Approximation dependences of the speed of sound on five isotherms have been obtained, and the experimental data have been compared with calculations using the REFPROP program.

Features of vapor bubbles evolution at liquid boiling at subatmospheric pressures

V.S. Serdyukov1,2, I.P. Malakhov1,2, A.S. Surtaev1,2
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: кипение, субатмосферные давления, динамика парообразования, сухие пятна, высокоскоростная визуализация, ИК-термография, boiling, sub-atmospheric pressure, vapor bubbles evolution, dry spots, high-speed visualization, IR-thermography

Abstract >>
The article presents the results of an experimental study of the dynamics of vaporization at water boiling at subatmospheric pressures up to 8.8 kPa. The usage of a transparent heater, high-speed video and IR thermography allowed analyzing the effect of pressure on the dynamics of vapor bubbles, the evolution of dry spots as well as the surface superheating corresponding to the onset of boiling. It is shown that the pressure reduction at a given heat flux density leads to a significant increase in the Jacob number at the activation of the nucleation site and the growth rate of vapor bubbles. It has been found that the curve of dry spots growth rate has a nonlinear dependence on the pressure in the range of 8.8-103 kPa. The minimum value of the growth rate of dry spots is observed at a pressure of 42 kPa.

75th Anniversary of Viktor I. Terekhov

Abstract >>
August 5, 2019 was the 75th anniversary of the Honoured Scientist of the Russian Federation, Doctor of Technical Sciences, Professor Viktor I. Terekhov.