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Thermophysics and Aeromechanics

2020 year, number 5

Investigation of the influence of a local change in surface temperature on the laminar boundary layer stability in a hypersonic nozzle

S.O. Morozov1,2, A.N. Shiplyuk1,3
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: hypersonic nozzle, boundary layer, linear stability theory, laminar-turbulent transition, Goertler vortices, local heating

Abstract >>
The influence of a local change in surface temperature of a contoured nozzle corresponding to the Mach number M = 6 on the boundary layer stability and laminar-turbulent transition is numerically studied. The profiles of the laminar boundary layer are obtained by solving the Navier-Stokes equations with the use of the Ansys Fluid software system. N-factors of the growth rates of the Goertler vortices and also disturbances of the first and second Mack modes are calculated in the approximation of the linear stability theory. It is demonstrated that local heating ensures lower growth rates of the amplitudes of the Goertler vortices and the first Mack mode as compared to the base case; the more intense the heating, the more expressed this effect. The growth rate of the amplitude of the second-mode disturbances decreases during local heating of the nozzle to a temperature close to the stagnation temperature and increases at higher temperatures of local heating. It is found that local cooling leads to an increase in the growth rates of the amplitudes of the Goertler vortices and second Mack mode. The amplitude of the first Mack mode in the cooling region is smaller than that in the base case; however, further downstream, it is much greater than that in the base case. It is found that the surface of contoured nozzles should be heated in the region of the maximum growth rates of the amplitudes of the Goertler vortices; the higher the temperature, the more pronounced the expected effect. However, the maximum possible temperature is determined by the growth of the second Mack mode. The optimal option is to use the temperature of local heating of the surface at which the growth rate of the amplitude of the second mode is smaller than that of the Goertler vortices.

Mode decomposition of disturbances in a supersonic flow

I.S. Tsyryulnikov, Yu.V. Gromyko, T.V. Poplavskaya
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: supersonic flow, disturbances, noise, acoustics, receptivity, numerical simulation, aerodynamic experiment, mode decomposition of disturbances

Abstract >>
Controlled disturbances are inserted into the wind tunnel flow, and probing measurements of the fields of the amplitudes of pressure and phase velocity oscillations of these disturbances are performed. Based on the relations for inviscid interaction of long-wave vortex, entropy, and acoustic disturbances with the shock wave on a wedge and numerical simulations, the coefficients of conversion of various modes to pressure oscillations on the model surface are determined for the test conditions of a supersonic flow in the T-327B blowdown wind tunnel located at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences. The method of mode decomposition for controlled disturbances with the use of disturbance conversion coefficients is implemented in the case of a flat plate model with a sharp leading edge aligned at different angles of attack and sideslip in the flow.

Evolution of a stall vortex over an external dihedral corner in a supersonic flow

A.I. Maksimov, I.N. Kavun
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: corner configuration, experiment, calculation, flow visualization, attached vortex, vortex core, streamline, density isolines, skin friction coefficient

Abstract >>
The work is devoted to the study of a vortex system formed in a flow past a streamwise-aligned external dihedral corner due to the drop of pressure between the corner faces. A detailed comparison of experimental and calculated data on the visualization of the flow and on the distribution of pressure over the model surface obtained at Mach number М = 2.27 in the range of angles of attack α = 0-20° is reported.

Numerical study of a round jet impinging on an axisymmetric grooved surface: effect of the groove size

A. Derdouri1, Z. Nemouchi1, A. Benhacine1, K. Abed-Meraim2, A. Sakout2
1Universite Freres Mentouri, Constantine 1, Algeria
2Universite de La Rochelle, La Rochelle, France
Keywords: axisymmetric impinging jet, corrugated surface, square grooves, SST k-П‰ turbulence model, Nusselt number

Abstract >>
The effects of the groove size on the dynamical and thermal behavior in a round jet impinging on an axisymmetric corrugated surface are investigated numerically. The geometry is similar to that considered by Sagot et al. (2010, Int. J. Therm. Sci., 49, 1026-1030) in their experimental study. Three side lengths of the square grooves are tested, one eighth, one quarter and three eighths of the jet diameter. A comparison is made with the flat plate case. The nozzle-to-plate distance is 2D, the Reynolds number is Re = 23000 and the ratio of the plate-radius to nozzle-diameter is R/D = 6. The SST k-ω model is employed to take account of turbulence effects. An attempt is made to understand thoroughly how key parameters such as mean velocity, turbulent kinetic energy and temperature fields can influence the heat transfer performance. The local normal-to-wall temperature gradient and thus the local heat flux through the fluid/wall interface are strongly dependent on these parameters. This justifies our interest in analyzing the distributions of such determining factors in the wall jet and, particularly, in the recirculating zones inside the cavities. Their imprints on the friction coefficient and the local and averaged values of the Nusselt number are highlighted.

Modeling the effect of body oscillations at the highenthalpy flow around a spherically blunted coneon conjugated heat and mass transfer

K.N. Efimov, V.A. Ovchinnikov, A.S. Yakimov
Tomsk State University, Tomsk, Russia
Keywords: conjugated heat and mass transfer, oscillations, angle of attack, supersonic flow

Abstract >>
Mathematical modeling is offered for describing the effect of variable incidence between the body axis and the high enthalpy air flow on conjugated heat and mass transfer in a heat shield material while thermochemical decomposition of the shield. Results of numerical simulation were obtained for spatial supersonic flow near a body with pitch variations. The effect of body oscillation with the rates 0-100 deg/s on heat and mass performance was studied.

Numerical study of thermal wall protection from a hot air by the evaporation of a binary liquid film

I. Bouchelkia1, M. Feddaoui2, Y. K. Benkahla1, A. Charef2, N. Labsi1
1University of Science and Technology Houari Boumediene, Algiers, Algeria
2Ibn Zohr University, Agadir, Morocco
Keywords: wall protection, liquid film evaporation, heat and mass transfer, binary mixture, vertical channel

Abstract >>
In this paper, a numerical study is performed to investigate the influence of adding glycol or alcohol to water on the thermal protection of a channel wall from hot air by evaporating this binary liquid film. The coupled governing equations in both phases with the boundary and interfacial conditions are solved using a finite difference numerical scheme. The effectiveness of adding a fraction of glycol or ethanol to water for the thermal wall protection is analysed. The influence of the film composition, the liquid mass flow, the velocity and the gas flow temperature at the inlet, on the intensity of heat and mass transfer is discussed. The results indicate that with a lower inlet liquid flow, the mixture ethanol-water presents the best solution for the thermal wall protection compared to ethylene glycol-water mixture. However, for higher inlet liquid flow rate, the two mixtures have the same trends for a water amount higher than 60%. The presence of ethylene glycol in the mixture reduces the heat transfer by latent mode. Consequently, the decrease of the wall temperature is mainly due to the sensible heat flux. The ethylene glycol-water mixture offers the best wall protection from the hot air stream. Accordingly, the most important factor for the wall protection is the thickness of the film that acts as an insulator. The pure water presents a better thermal protection but a very bad conservation of the liquid film. Furthermore, the heat transfer by sensible heat exchange contributes efficiently in wall protection than heat transfer by latent mode.

Correlation between the dynamic velocity and average heat transfer coefficient in transversely streamlined in-line and staggered tube bundles

V.I. Rachkov, V.N. Fedoseev, M.I. Pisarevskiy, M.I. Pisarevskaya
National Research Nuclear University В«MEPhI», Moscow, Russia
Keywords: heat transfer coefficient, in-line tube bundles, staggered tube bundles, dynamic velocity, dissipation energy

Abstract >>
On the basis of the analysis of a large array of experimental data on average heat transfer and hydraulic resistance, calculations of the dynamic velocity on the wall in deep rows of in-line and staggered tube bundles transversely streamlined by the turbulent flow of the coolant are performed. In addition, energy consumption is calculated based on experimental data on the hydraulic resistance of rod assemblies. The obtained results serve to determine the coefficient of proportionality between the dynamic velocity and the energy consumption for pumping the coolant. The proposed calculation formulas for the proportionality coefficient allow computing the average heat transfer coefficient in transversely streamlined in-line and staggered tube bundles in a wide range of rod packing spacings and Reynolds numbers, using the universal dependence of heat transfer on dynamic velocity.

Studying coolant hydrodynamics in the area of a guide channel of fuel assembly with intensifier grids

S.M. Dmitriev, A.A. Dobrov, D.V. Doronkov, D.S. Doronkova, A.N. Pronin, E.V. Rubtsova, A.V. Ryazanov, D.N. Solntsev, A.E. Khrobostov
Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Nizhny Novgorod, Russia
Keywords: nuclear reactor, core, fuel assembly, intensifier grid, guide channel, coolant hydrodynamics

Abstract >>
The article presents the results of studies of the coolant flow in fuel assemblies behind the intensifier grids of FA-Square reactors of the PWR type. The aim of this work is to evaluate the effectiveness of using various designs of the intensifier grid for the flow mixing. To achieve this goal, a number of experimental studies are carried out on an aerodynamic stand with scale models of fragments of fuel assemblies with intensifier grids of various designs. Adjacent cells of the guide channel, the design feature of which is different spatial orientation of turbulators installed on the intensifier grids, are selected as a representative area of research. The general flow pattern is represented by vector fields of tangential velocities, as well as by graphical dependences of the distribution of transverse velocities in the gaps between the rods of the research area. To evaluate the efficiency of using various intensifier grids’ designs for the coolant flow mixing, the parameters of intracellular vortex formation and intercellular mixing are analyzed. Analysis of the spatial distribution of tangential flow velocities allows studying and detailing the coolant flow pattern behind the mixing grids with various designs of deflectors. The accumulated database on the coolant flow in the FA-KVADRAT is the basis for engineering justification of the PWR reactor core designs. The results of experimental studies are used to verify CFD codes of both foreign and domestic development, as well as programs for detailed cell-based calculation of active zones in order to reduce conservatism in justifying thermal reliability.

Improving adiabatic film-cooling effectiveness spanwise and lateral directions by combining BDSR and anti-vortex designs

Mustapha Grine1, Khadidja Boualem2, Ahmed Zineddine Dellil1, Abbes Azzi2
1University Oran 2 Mohamed Ben Ahmed, Oran, Algeria
2University of Science and Technology Mohamed Boudiaf, Oran, Algeria
Keywords: film cooling, Barchan dune, sister, CRV, anti-CRV

Abstract >>
In the present study, a numerical investigation was conducted to enhance the film cooling efficiency by using anti-vortex designs. Four configurations are considered in this paper, which are the configuration with the streamwise cylindrical injection, the case with an upstream Barchan dune shape ramp (BDSR), the case with sister holes and the configuration that combine the Barchan dune shape with sister holes. The effects of a blowing ration (M = 0.5, 0.85, 1.0 and 1.5) on the film cooling effectiveness are considered. The validation shows good agreement and almost all flow structures are well reproduced by the RANS computation. Results show that the Barchan dune shapes with sister holes have an influence on thermal and flow structures, this configuration substantially augments the film cooling efficiency.

Effect of echeloned supply of a swirling air flow on particle layer formation in a vortex chamber

N.A. Dvornikov, V.V. Lukashov, R.Kh. Abdrakhmanov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: vortex chamber, centrifugal fluidized bed, particle entrainment from the chamber

Abstract >>
The conclusions about the nature of bed fluidization and the rate of polyfractional material entrainment in the cylindrical vortex chamber with the air supply through the lower and upper end swirlers were drawn, based on visual observation of the fluidized bed, determination of entrainment of the bed dispersed material by weighing the material after a given time of vortex chamber operation, and also by means of numerical simulation of dynamics of the fluidized bed of particles.

Bubble diameters variation along the gas-liquid flow in a flat channel at various inclination angles

A.E. Gorelikova1,2, V.V. Randin1,2, A.V. Chinak1
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: flat channel, gas-liquid flow, bubbles, bubble diameters, histograms

Abstract >>
The results of an experimental study of a bubble diameters variation with a distance from the gas injection point in an upward bubbly flow in an inclined flat channel are presented. The measurements were carried out for a superficial liquid velocity of 0.51 m/s (Re = 12400) and various volumetric gas flow rate ratios. It is shown that at low values of volumetric gas flow rate ratio ( β < 2 %) there is almost no bubble coalescence; therefore, the channel inclination angle and distance from the point of gas injection into the liquid flow do not affect the average diameter of gas bubbles.

Combined cycle plants with complete capturing of carbon dioxide for clean power projects

V.V. Datsenko, Yu.A. Zeigarnik, E.O. Kalashnikova, A.A. Kosoy, A.S. Kosoy, M.V. Sinkevich
Joint Institute for High Temperatures RAS, Moscow, Russia
Keywords: power plant, combined cycle plant without compressor, thermal efficiency, capturing of СО in liquid state, combined production of power and heat

Abstract >>
The energy security of Russia is at threat due to recent trends of dependency of national power industry on imported technologies, equipment, spare parts and materials. The next challenge is a tendency of more strict environmental standards and restrictions for power generation equipment. The paper considers one option to meet those challenges - using technologies based on compressorless combined cycle plant with complete capturing of СО2 in liquid state (developed by JIHT in cooperation with NPO Almaz). This technology offers efficient production of heat and power from hydrocarbon fuel with a minimal environmental impact. This plant can be incorporated into a power-engineering complex with chemical products outcome. According to the developed scheme, the hydrocarbon fuel is burnt in a mixture of oxygen, provided by an air-separation setup (or another source), steam and carbon dioxide. The components are compressed in the liquid phase. The heat from exhaust gas is recuperated in a developed heat recovery system. The steam condensation takes place, and the heat of condensation is utilized for district water heating in water utility grids and for capturing of СО2 in liquid phase. Through varying of proportions between Н2О and СО2 inputs, the proportions in generation of electric power and heat can be varied in a wide range. Our estimates demonstrate that this new plant has a thermal efficiency higher than for the best CCGT plants and close to the efficiency for the best worldwide analogs.

Subcooled water boiling on a microheater under conditions of pulsed heat release

A.S. Surtaev1,2, V.S. Serdyukov1,2, I.P. Malakhov1,2, M.V. Timoshevskiy1,2, A.S. Safarov1,3
1Novosibirsk State University, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
3Melentiev Energy Systems Institute SB RAS, Irkutsk, Russia
Keywords: pulsed heating, boiling, subcooled liquid, bubble evolution, high-speed visualization, microheater

Abstract >>
The paper deals with the experimental study of the process of subcooled liquid boiling on a transparent microheater with pulsed heat release. Dependences of the maximum bubble diameter, rates of their growth and times of boiling incipience on the heat flux density and degree of liquid subcooling in the ranges of 11-32 MW/m2 and 50 - 75 K, respectively, were obtained. The nucleation temperature was calculated for the studied regimes using the COMSOL Multiphysics software.

Refractory HfC-HfN ceramics tested in a plasma flow

A.P. Zavyalov1, D.V. Sergachev2, I.P. Gulyaev2, O.O. Shichalin1,3, E.K. Papynov1,3
1Far Eastern Federal University, Vladivostok, Russia
2Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
3Institute of Chemistry FEB RAS, Vladivostok, Russia
Keywords: refractory ceramic, spark plasma reaction-based sintering, hafnium carbide, hafnium nitride, system hafnium carbide-hafnium nitride

Abstract >>
The paper presents a study in stability of ceramics of hafnium carbide-nitride subjected to impact of a nitrogen plasma jet in air atmosphere. The best thermal resistance was demonstrated for ceramics with N/C » 0.698, which is determined by the maximum of surface temperature and minimum mass loss in the series of HfC- HfN solid solutions.

80th Anniversary of Vyacheslav N. Yarygin

Abstract >>
On September 21, 2020, Doctor of Technical Sciences, Professor Vyacheslav N. Yarygin was 80 years of age.