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Thermophysics and Aeromechanics

2017 year, number 4

A review on the effects of different parameters on contact heat transfer

H. Abdollahi1, S. Shahraki1, and  M. Motahari-Nezhad2
1University of Zabol, Zabol, Iran
2Iran University of Science and Technology, Tehran, Iran
Keywords: contact heat transfer, thermal contact conductance, experimental setup, numerical solution
Pages: 499512

Abstract >>
In this paper, a complete literature review for thermal contact between fixed and periodic contacting surfaces and also thermal contact between exhaust valve and its seat in internal combustion engines is presented. Furthermore, the effects of some parameters such as contact pressure, contact frequency, the contacting surfaces topography and roughness, curvature radius of surfaces, loadingunloading cycles, gas gap conductance and properties, interface interstitial material properties, surfaces coatings and surfaces temperature on thermal contact conductance are investigated according to the papers presented in this field. The reviewed papers and studies included theoretical/analytical/experimental and numerical studies on thermal contact conductance. In studying the thermal contact between exhaust valve and its seat, most of the experimental studies include two axial rods as the exhaust valve, and seat and the one ends of both rods are considered at constant and different temperatures. In the experimental methods, the temperatures of multi-points on rods are measured in different conditions, and thermal contact conductance is estimated using them.

DOI: 10.1134/S0869864317040011

Simple fundamental equation of state for liquid, gas, and fluid of argon, nitrogen, and carbon dioxide

A.B. Kaplun and A.B. Meshalkin

Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

Keywords: fundamental equation, compressibility factor, temperature, pressure, density, enthalpy, heat capacity, sound velocity
Pages: 513522
Abstract >>
A new fundamental low-parametric equation of state in the form of reduced Helmholtz function for describing thermodynamic properties of normal substances was obtained using the methods and approaches developed earlier by the authors. It allows us to describe the thermal properties of gas, liquid, and fluid in the range from the density in ideal-gas state to the density at a triple point (except the critical region) with sufficiently high accuracy close to the ac-curacy of experiment. The caloric properties and sound velocity of argon, nitrogen, and carbon dioxide are calculated without involving any caloric data, except the ideal gas enthalpy. The obtained values of isochoric heat capacity, sound velocity, and other thermodynamic properties are in good agreement with experimental (reliable tabular) data.

DOI: 10.1134/S0869864317040023

Semi-empirical model for intense evaporation

Yu.B. Zudin

National Research Centre Kurchatov Institute, Moscow, Russia

Keywords: semi-empirical model, intense evaporation, linear kinetic theory, extrapolation drops for parameters, vapor parameters, gas-dynamic region
Pages: 523536
Abstract >>
A semi-empirical model based on the linear kinetic theory was developed for intense evaporation. The extrapolated drops for pressure and temperature at the condensed phase surface were calculated through summing of linear and squared terms. The analytical dependencies were obtained for gas parameters in gas-dynamic zone as functions of Mach number, condensation coefficient, and the number of degrees of freedom for molecules of ideal gas. The calculations from semi-empirical model are in agreement with results from known analytical and numerical studies.

DOI: 10.1134/S0869864317040035

Dynamics of explosive boiling and third heat transfer crisis at subcooling on a vertical surface

B.P. Avksentyuk1 and  V.V. Ovchinnikov2

1Vinnytsa Institute of Trade and Economics of Kyiv National University of Trade and Economics, Vinnitsa, Ukraine

2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

Keywords: boiling, subcooling, evaporation front, heat transfer crisis
Pages: 537544
Abstract >>
Results of experimental studies on dynamics of explosive boiling and third heat transfer crisis under the conditions of liquid subcooling are presented for the vertical arrangement of the heat-transfer surface. Acetone was used in experiments at the pressure in the working volume from 20 to 46 kPa and subcooling from 0 to 20 K. The studied processes were recorded. Data on the velocity of evaporation front propagation at liquid subcooling were obtained. These data are compared with the results of calculations according to the models available in the literature. The effect of liquid subcooling on the regions of regime parameters corresponding to explosive boiling and third heat transfer crisis is studied.

DOI: 10.1134/S0869864317040047

Loss of efficiency in a coaxial arrangement of a pair of wind rotors

V.L. Okulov1, 2, I.V. Naumov1, M.A. Tsoy1, and  R.F. Mikkelsen2

1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

2Denmark Technical University, Lyngby, Denmark

Keywords: wind farm, rotor wake, interaction between turbines and wakes, power loss of wind turbines
Pages: 545551
Abstract >>
The efficiency of a pair of wind turbines is experimentally investigated for the case when the model of the second rotor is coaxially located in the wake of the first one. This configuration implies the maximum level of losses in wind farms, as in the rotor wakes, the deceleration of the freestream is maximum. As a result of strain gauge measurements, the dependences of dimensionless power characteristics of both rotors on the distances between them were determined for different modes at different tip speed ratios. The obtained results are of interest for further development of aerodynamics of wind turbines, for optimizing the work of existing wind farms and reducing their power losses due to interactions with wakes of other wind turbines during design and calculation.

DOI: 10.1134/S0869864317040059

The surface roughness effect on the performance of supersonic ejectors

D.V. Brezgin1, K.E. Aronson1, F. Mazzelli2, and A. Milazzo2

1Ural Federal University named after the First President of Russia  B.N. Eltsin: Ural Power Engineering Institute, Ekaterinburg, Russia

2University of Florence, Florence, Italy

Keywords: supersonic ejector, entrainment ratio, CFD, wall log-law, sand-grain roughness
Pages: 553561
Abstract >>
The paper presents the numerical simulation results of the surface roughness influence on gas-dynamic processes inside flow parts of a supersonic ejector. These simulations are performed using two commercial CFD solvers (Star-CCM+ and Fluent). The results are compared to each other and verified by a full-scale experiment in terms of global flow parameters (the entrainment ratio: the ratio between secondary to primary mass flow rate - ER hereafter) and local flow parameters distribution (the static pressure distribution along the mixing chamber and diffuser walls). A detailed comparative study of the employed methods and approaches in both CFD packages is carried out in order to estimate the roughness effect on the logarithmic law velocity distribution inside the boundary layer. Influence of the surface roughness is compared with the influence of the backpressure (static pressure at the ejector outlet). It has been found out that increasing either the ejector backpressure or the surface roughness height, the shock position displaces upstream. Moreover, the numerical simulation results of an ejector with rough walls in the both CFD solvers are well quantitatively agreed with each other in terms of the mean ER and well qualitatively agree in terms of the local flow parameters distribution. It is found out that in the case of exceeding the critical roughness height for the given boundary conditions and ejectors geometry, the ejector switches to the off-design mode and its performance decreases considerably.

DOI: 10.1134/S0869864317040060

Operating safety of a hot-shot wind tunnel with combined test gas heating in stabiliza-tion mode

V.V. Shumskii  and  M.I. Yaroslavtsev

Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia

Keywords: hot-shot wind tunnel, settling chamber, test gas, stabilization of parameters, pressure multiplier, controlled diaphragm, driver air
Pages: 563568
Abstract >>
In the present paper, we analyze emergency situations typical of short-duration wind tunnels with electric-arc or combined test-gas heating in the presence of stabilization and diaphragm-rupturing systems, which occur in the case of no discharge initiation in the settling chamber, with the capacitor battery having remained charged during the start of wind-tunnel systems. For avoiding such emergency situations, some additional changes based on using feedback elements are introduced into the wind-tunnel design: the piston of the fast-response valve is made hollow for increasing the volume of the shutoff cavity and for making the release of pressure from this cavity unnecessary; the high-pressure channel, which connects the piston and the piston rod with the settling-chamber cavity, is filled with a liquid and is closed from the side of the settling chamber with a piston; the device for controlled diaphragm breakdown is provided with an external electric circuit intended to control the diaphragm-rupturing process. Those modifications allow subsequent functioning of the wind-tunnel systems only in the presence of heat-supply-induced pressure growth in the settling chamber of the wind tunnel.

DOI: 10.1134/S0869864317040072

Heat transfer from a cylinder in pulsating cross-flow

V.M. Molochnikov1,2, N.I. Mikheev1,2, A.N. Mikheev1, and A.A. Paereliy1

1Kazan Scientific Center RAS, Kazan, Russia

2Kazan National Research Technical University named after A.N.Tupolev, Kazan, Russia

Keywords: heat transfer, cylinder in cross-flow, forced flow pulsations, dimensionless number, empirical correlation, correction factor
Pages: 569575
Abstract >>
The paper presents results on heat transfer from a cylinder in pulsating flow. The results are local heat transfer distributions that match four different flow modes identified previously by the authors. A new kind of dimensionless number was introduced for pulsating flows: this is a ratio of flow acceleration during unsteady movement to the centrifugal acceleration due to streamlines bending over the cylinder. The experimental data were generalized as a dependency of the average heat transfer on the new dimensionless criterion. The generalization offered a correction factor to a traditional relation for heat transfer between a cylinder and air flow past the cylinder; this correction takes into account the effect of parameters of forced flow pulsations on the average heat transfer.

DOI: 10.1134/S0869864317040084

Heat transfer at a laminar free convection and separated flow past a rib in a vertical channel with isothermal walls

V.I. Terekhov1,2, A.L. Ekaid3, and  K.F. Yassin2,4

1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

2Novosibirsk State Technical University, Novosibirsk, Russia

3University of Technology, Baghdad, Iraq

4Northern Technical University, Kirkuk, Iraq

Keywords: laminar free convection, heat transfer, flow separation
Pages: 577581
Abstract >>
The results of numerical computations of a free laminar convection and heat transfer between two parallel isothermal plates in the presence of a single rib on the channel surface are presented. The investigations have been conducted for a channel with the aspect ratio AR = L/w = 10, where L is the channel height, and w is the distance between the plates. An infinitely thin adiabatic rib was located on one of the channel walls in the middle of its height. The relative rib height l/w was varied in the range 0¸0.8. The wall temperature was higher than the ambient temperature, and the Rayleigh number was varied in the range Ra = 102¸105. The main attention has been paid to the study of the influence of the rib height and the Rayleigh number on local and integral heat transfer and the Reynolds number in the channel (the convective thrust). A fundamental difference in the heat transfer over the channel height has been shown on the ribbed wall and on a smooth surface. The computational results have been compared with the case of a symmetric distribution of the ribs on the both walls with the integral height equal to a single rib.

DOI: 10.1134/S0869864317040096

In-water gas combustion for thrust production

V.S. Teslenko, A.P. Drozhzhin, and  R.N. Medvedev

Lavrentiev Institute of Hydrodynamics SB RAS, Novosibirsk, Russia

Keywords: pulse combustion of gas in water, force pulses, thrust, specific thrust, hydrojet propulsion
Pages: 583591
Abstract >>

The paper presents the results of experimental study for hydrodynamic processes occurring during combustion of a stoichiometric mixture propane-oxygen in combustion chambers with different configurations and submerged into water. The pulses of force acting upon a thrust wall were measured for different geometries: cylindrical, conic, hemi-spherical, including the case of gas combustion near a flat thrust wall. After a single charge of stoichiometric mixture propane-oxygen is burnt near the thrust wall, the process of cyclic generation of force pulses develops. The first pulse is generated due to pressure growth during gas combustion, and the following pulses are the result of hydrodynamic pulsations of the gaseous cavity. Experiments demonstrated that efficient generation of thrust occurs if all bubble pulsations are used during combustion of a single gas combustion. In the series of experiments, the specific impulse on the thrust wall was in the range 104-105 s (105-106 m/s) with account for positive and negative components of impulse.

DOI: 10.1134/S0869864317040102

Heat and mass transfer at gas-phase ignition of grinded coal layer by several metal particles heated to a high temperature

D.O. Glushkov*, G.V. Kuznetsov, and  P.A. Strizhak

National Research Tomsk Polytechnic University, Tomsk, Russia

Keywords: grinded coal, hot particle, heat transfer, volatiles, diffusion, gas-phase ignition
Pages: 593604
Abstract >>
Characteristics of gas-phase ignition of grinded brown coal (brand 2B, Shive-Ovoos deposit in Mongolia) layer by single and several metal particles heated to a high temperature (above 1000 K) have been investigated numerically. The developed mathematical model of the process takes into account the heating and thermal decomposition of coal at the expense of the heat supplied from local heat sources, release of volatiles, formation and heating of gas mixture and its ignition. The conditions of the joint effect of several hot particles on the main characteristic of the process ignition delay time are determined. The relation of the ignition zone position in the vicinity of local heat sources and the intensity of combustible gas mixture warming has been elucidated. It has been found that when the distance between neighboring particles exceeds 1.5 hot particle size, an analysis of characteristics and regularities of coal ignition by several local heat sources can be carried out within the framework of the model of single metal particle / grinded coal / air. Besides, it has been shown with the use of this model that the increase in the hot particle height leads, along with the ignition delay time reduction, to a reduction of the source initial temperatures required for solid fuel ignition. At an imperfect thermal contact at the interface hot particle / grinded coal due to the natural porosity of the solid fuel structure, the intensity of ignition reduces due to a less significant effect of radiation in the area of pores on the heat transfer conditions compared to heat transfer by conduction in the near-surface coal layer without regard to its heterogeneous structure.

DOI: 10.1134/S0869864317040114

Simulation of the organic-waste processing in plasma with allowance for kinetics of thermochemical transformations

V.E. Messerle1,2 and A.B. Ustimenko3,4*

1Institute of Combustion Problems, Almaty, Kazakhstan

2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

3NTO Plasmotekhnika Ltd., Almaty, Kazakhstan

4Research Institute of Experimental and Theoretical Physics, Almaty, Kazakhstan

Keywords: organic waste, plasma processing, fuel gas, kinetic modeling, calculation
Pages: 605614
Abstract >>
Kinetic calculations of the plasma processing/utilization process of organic waste in air and steam ambient were carried out. It is shown that, during the time of waste residence in the plasma reactor, 0.7 and 1.2 s, at the exit from the reactor there forms a high-calorific fuel gas with a combustion heat of 3540 and 5070 kcal/kg, respectively. In this process, 1 kg of waste yields 1.16 kg of fuel gas at air gasification of waste and 0.87 kg of pure synthesis gas at steam gasification. The energy efficiency of the waste gasification process, defined by the ratio between the calorific value of the resultant fuel gas and the initial calorific value of the waste amounts to 91 % in air plasma and 98 % in steam plasma. A comparison between the results of kinetic and thermodynamic calculations has revealed their good agreement.

DOI: 10.1134/S0869864317040126

Thermodynamic analysis of gasification of renewable carbonaceous materials of natural and artificial origin in plasma electric furnace

V.A. Faleev1, E.B. Butakov1, and S.I. Radko2

1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

2Novosibirsk State Technical University, Novosibirsk, Russia

Keywords: organic waste, gasification, heat content, gas composition, power inputs
Pages: 615620
Abstract >>
Thermodynamic analysis of plasma gasification of various renewable carbon-bearing materials was carried out using various oxygen-containing oxidants (oxygen, air, water). The possibility of obtaining calorific synthesis gas suitable for the needs of heat power engineering was confirmed.

DOI: 10.1134/S0869864317040138

Synthesis of TiOx-based ceramics by plasma spraying

A.Kh. Abduev1*, A.K. Akhmedov1, A.Sh. Asvarov1,2, K.Sh. Rabadanov2, R.M. Emirov3, S.P. Vashchenko4, I.P. Gulyaev4, V.I. Kuzmin4**, and  D.V. Sergachev4

1Amirkhanov Institute of Physics, Dagestan Scientific Center RAS, Makhachkala, Russia

2Dagestan Scientific Center RAS, Analytical Center for Collective Use, Makhachkala, Russia

3Dagestan State University, Makhachkala, Russia

4Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia

Keywords: titanium oxide, rutile, plasma spraying, microstructure
Pages: 621627
Abstract >>
Structure of ceramics obtained by the plasma spray deposition of spherical TiO2 powders has been investigated. An electron microscopy study of the surfaces and cross sections of particles in the initial powder and of the deposited ceramic coatings was performed. X-ray diffraction and Raman scattering data proved that the coatings were mainly structured as rutile. In addition, Raman and X-ray diffraction data have revealed an amorphous phase, an anatase phase, and non-stoichiometric phases Ti8O15, Ti10O19, Ti7O13, etc. being present in the coatings. The observed suppression of (011) and (111) XRD peaks and an increased intensity of (110) peak are indicative of a predominant orientation of grains in the synthesized ceramics. Mechanisms of formation of the complex coating structure are discussed.

DOI: 10.1134/S086986431704014X

Impact of frontal-porous-insert temperature on the cylinder drag in supersonic flow

S.G. Mironov, T.V. Poplavskaya, and S.V. Kirilovskiy

Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia

Novosibirsk State University, Novosibirsk, Russia

Keywords: supersonic flow around a body, gas-permeable cellular-porous materials, impact of temperature, numerical simulation
Pages: 629632
Abstract >>
In the present paper, we report on experimental and simulated data on the impact of cellular-porous-material heating on the wave drag of a cylinder with a frontal gas-permeable porous insert streamlined by a supersonic flow ( = 4.85, Re1∞ = 3.3×106 m-1). Weighing data obtained in the supersonic wind tunnel are compared with data simulated using a discrete model of the cellular-porous material. An increase of the wave drag with a growth of porous-insert temperature and its decrease occurring upon decreasing the temperature are demonstrated.

DOI: 10.1134/S0869864317040151

The methodological features of studying energy efficiency of a combined mini-TPP on the basis of a gas-piston unit and a steam turbine

P.A. Shchinnikov and  N.V. Marasanov*

Novosibirsk State Technical University, Novosibirsk, Russia

Keywords: Rankine cycle, Otto cycle, efficiency, mini-TPP, energy flow
Pages: 633636
Abstract >>
The technology of electricity production by a mini-thermal power plant, operating on combined cycles of Otto and Rankine, is considered. The main aspects of the investigation methodology are outlined. It is shown that the design and layout parameters of all the major energy elements of the developed technology allow implementing it in a block and modular version; and the efficiency of electricity supply for the proposed technology will be at least 50 %.

DOI: 10.1134/S0869864317040163

70th Anniversary of Amir A. Gubaidullin

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia
Pages: 637 638

Abstract >>
4 August, 2007 is the 70th Anniversary of the well known scientist, Doctor of the Physical and Mathematical Sciences, Professor Amir A. Gubaidullin.

DOI: 10.1134/S0869864317040175