Simulation study for injection of two-phase fuel mixture into a cylindrical afterburner with asymmetric air inletVoronetskii, A. V.; Aref’ev, K. Yu.; Abramov, M. A.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060013
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 jetSenachin, P. K.; Kiryushin, I. I.; Samarin, A. V.; Senachin, A. P.; Ulrich, S. A.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060025
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 assemblyPribaturin, N. A.; Lobanov, P. D.; Randin, V. V.; Kashinsky, O. N.; Vorobyev, M. A.; Volkov, S. M.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060037
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.
On diffusion of single-walled carbon nanotubesRudyak, V. Ya.; Tretiakov, D. S.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060062
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 to 0.7·10−12 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 surfaceZverkov, I. D.; Kryukov, A. V.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060074
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, α = 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 1.4105 at α = 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 σl in the boundary-layer pre-separation region, and the waviness coefficient Kw is greater than unity. A distinct formation of local separation zones is revealed by oil-film visualization at Kw = 2.8.
Evaporation front propagation over a non-isothermal surfaceZhukov, V. E.; Slesareva, E. Yu.
2021 Thermophysics and Aeromechanics
doi: 10.1134/S0869864320060098
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.