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Thermophysics and Aeromechanics

2020 year, number 6

Simulation study for injection of two-phase fuel mixture into a cylindrical afterburner with asymmetric air inlet

A.V. Voronetskii1, K.Yu. Aref’ev1,2,3, M.A. Abramov1,2,3
1Bauman Moscow State Technical University, Moscow, Russia
2Baranov Central Institute of Aviation Motors, Moscow, Russia
3Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
Keywords: mathematical simulation, condensed phase, power plant, afterburner, gasification products, fuel injection

Abstract >>
A method is developed for secondary data processing of the results of simulation of two-phase flow in an afterburner with a complex geometry. This method offers a prediction for mixing process efficiency (quality estimate) and combustion efficiency in an afterburner of a power plant. The opportunities of this method were demonstrated at the example of simulation of mixing the two-phase fuel with air in the afterburner of a model power plant with gas generation outlay. The paper presents a mathematical model for studied processes and the simulation results. The fuel was the gasification products (GP) of a high-energy composition (a mixture of gaseous and condensed phases). An algorithm was applied for processing the mathematical simulation results: the output is the evaluation of mixing between GP condensed phase and air flow. The parametric study offers the dependencies for size distributions of GP particles in the afterburner cross sections. The limiting values for GP combustion efficiency in the afterburner were evaluated from analysis of GP flow (gas and condensed phases) mixing with air flow. Simulation gives the data on the influence of injection configuration and GP condensed phase dispersion profile on the mixing efficiency in the afterburner. The results of study can be useful in recommendations for gaining on the cycle efficiency in novel propulsion plants.

Numerical simulation of the dynamics of a non-stationary liquid jet

P.K. Senachin1,2, I.I. Kiryushin3, A.V. Samarin1, A.P. Senachin1, S.A. Ulrich3
1Polzunov Altai State Technical University, Barnaul, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
3, Barnaul, Russia
Keywords: diesel, injector, non-stationary liquid jet, mathematical model, numerical simulation

Abstract >>
A simple mathematical model of the dynamics of a non-stationary liquid jet (NSLJ) is presented to describe the injection of diesel fuel in a diesel engine, supplied under pressure to the combustion chamber. The proposed model describes the dynamics of the NSLJ as a motion of the center of mass of a material point of variable mass based on the laws of Newton's mechanics. In this case, the mass of the material point is made up of the mass of liquid fuel and air involved in the motion, taking into account the uneven distribution of fuel and air along the length of the NSLJ. Numerical modeling using new experimental data shows a satisfactory agreement between the theoretical and experimental results on the dynamics of the NSLJ development. The model allows optimizing the dynamics of NSLJ and mixing processes for specific sizes of the diesel combustion chamber on the basis of numerical modeling.

Experimental study of shear stress during liquid flow in the model of fuel assembly

N.A. Pribaturin1,2, P.D. Lobanov3, V.V. Randin3, O.N. Kashinsky3, M.A. Vorobyev3, S.M. Volkov3
1Nuclear Safety Institute of RAS, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS
3Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: experiment, fuel assembly, fuel element, friction

Abstract >>
The original experimental data on axial distributions of the shear stress on the surface of a rod - a fuel element simulator - during fluid flow through a model of fuel assembly (FA) are presented depending on the rod diameter (9, 10, 15 mm), relative distance between the rods (1.2, 1.3, 1.4, 1.45), and number of rods (7 and 37) for the laminar, transient, and turbulent liquid flows in fuel assemblies.

Study of regimes for methane - carbon dioxide replacement in natural gas hydrates by liquid carbon dioxide injection into a porous stratum

M.K. Khasanov1, M.V. Stolpovsky1,2, I.K. Gimaltdinov2
1Sterlitamak Branch BashSU, Sterlitamak, Russia
2Ufa State Petroleum Technological University, Ufa, Russia
Keywords: filtration, gas hydrate, replacement

Abstract >>
A developed mathematical model offers a study of methane-carbon dioxide replacement in gas hydrate through injection of liquid carbon dioxide into a porous stratum with final sizes. Depending on the parameters of injected carbon dioxide flow and depending on the stratum boundary conditions, the process of formation of the gas hydrate comprising carbon dioxide can occur through methane replacement in the gas hydrate or through the formation of zones with free methane and water. The critical diagrams are presented that map the conditions for both regimes.

Features of convective sublimation in gas mixtures

E.M. Bochkareva, V.V. Lukashov, N.B. Miskiv
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: sublimation, heat and mass transfer, organometallic compounds

Abstract >>
The paper presents experimental data on convective heat and mass transfer during sublimation of a single spherical particle of a mixture of organometallic compounds Zr(dpm)4 /Y(dpm)3 in a high-temperature flow of an inert gas (He, Ar). The influence of the carrier gas velocity and composition on the characteristics of the mass transfer processes is considered. Data on dynamics of changes in the size and temperature of a sample during sublimation are obtained.

On diffusion of single-walled carbon nanotubes

V.Ya. Rudyak1,2, D.S. Tretiakov3
1Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, Russia
2Novosibirsk State University
3Novosibirsk State University, Novosibirsk, Russia
Keywords: dynamic light scattering, diffusion, nanofluid, single-walled carbon nanotubes

Abstract >>
The study is aimed at investigating the diffusion of single-walled nanotubes in liquids with the weight concentration of nanotubes varied from 0.00001 to 0.01%. Water solutions of sodium dodecylbenzene sulfate and polyvinylpyrrolidone, which are usually used as surfactants, are applied here as a carrier liquid. Their concentration is either equal to the concentration of nanotubes or twice greater. Depending on the concentration, the diffusion coefficient of nanotubes is found to change from 1.02×10-11 QUOTE to 0.7×10-12 QUOTE m2/s. Based on the data on the diffusion coefficient, the effective hydrodynamic size of nanotubes and their length are retrieved. The efficiency of nanotube separation by means of centrifugation and the changes in their characteristics during long-term storage are discussed.

Formation of local separation zones on the wings with a rigid and varioform wavy surface

I.D. Zverkov1,2, A.V. Kryukov1,2
1Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
2Novosibirsk State Technical University
Keywords: low Reynolds numbers, flow around a wing with a wavy surface, boundary layer, separation bubble, laminar-turbulent transition, oil-film visualization, waviness criterion

Abstract >>
In the present paper, a method for choosing the parameters of a wing-surface waviness intended for use on small aircraft is introduced. We propose choosing the waviness geometry based on the parameters of the boundary layer for the given regime of the flow around the classical wing installed at zero angle of attack, a = 0°. We propose to check the result of the choice of the waviness parameters by the change of the flow structure in the boundary layer of the wing. For the properly chosen waviness, the continuous separation zone characteristic of the classical wing should transform into local separation zones. To substantiate and verify the proposed method, we investigate the flow around two wing models, one model being a wavy wing with a rigid surface and the other, a wavy wing with a varioform surface characterized by variable hump height. The study was carried out at wing-chord-based Reynolds numbers Re ranging from 0.35×105 to 1.4×105 at a = 0°. Using oil-film visualization, a transition of local separation zones into a continuous separation zone on the rigid-surface wing model with a decrease of Reynolds number implemented by decreasing the flow velocity was revealed. By measuring the velocity profile in the boundary layer on the varioform wing, the transformation of the continuous separation zone into local separation zones yet at a constant velocity with a change in waviness height has been also demonstrated. It is experimentally shown that the formation of local separation zones is observed provided that the waviness height f is one order of magnitude greater than the displacement thickness s 1 in the boundary-layer pre-separation region, and the waviness coefficient K w is greater than unity. A distinct formation of local separation zones is revealed by oil-film visualization at K w = 2.8.

Preliminary numerical study of three-temperature model investigation of hypersonic oxygen flow under rotational nonequilibrium

Y. Ghezali1, R. Haoui1, A. Chpoun2
1University of Sciences and Technology Houari Boumediene, Algiers, Algeria
2University of Evry Paris-Saclay, Evry, France
Keywords: hypersonic, nonequilibrium, shock wave, rotation, vibration, oxygen flow

Abstract >>
The effect of rotational nonequilibrium on the macroscopic parameters of the flow behind a normal shock wave in oxygen gas flow has been examined. The electron thermal equilibrium was taken into account where the electron temperature was equal to the vibrational temperature according to Park’s assumption. Therefore, only the effect of rotational nonequilibrium on the translational and vibrational temperature was analyzed. Rotational and vibrational relaxation time for the O2-O2 and O2-O collisions proposed recently by Andrienko and Boyd are used. Also, the O2 dissociation rates proposed by Kim and Park are used. The results obtained with the three-temperature model well reproduce the data obtained in shock tube for the shock velocity of 4.44 km/s.

Evaporation front propagation over a non-isothermal surface

V.E. Zhukov, E.Yu. Slesareva
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: self-sustaining evaporation front, evaporation front, change in phase, hydrodynamic stability, metastable fluid

Abstract >>
The experiments are performed on R21 freon at a reduced pressure of 0.04 under conditions of natural convection. The propagation velocity of a self-sustaining evaporation front over a heat transfer surface is measured in the presence of a substantial temperature gradient along the heat transfer surface. The stabilization of the front propagation velocity is shown in accordance with the isotherm propagation velocity. The experiments show that when the evaporation front propagates over a heat-transfer surface with a significant temperature gradient, the stabilization of the front velocity occurs on a scale of the order of the capillary constant.

80thAnniversary of Academician Vasiliy M. Fomin

Abstract >>
On November 5, 2020, Vasiliy M. Fomin, the Full member of the Russian Academy of Sciences and noted researcher, working on mathematical simulation of the problems of continuum mechanics and mechanical engineering, became 80 years of age.