In the article we consider nanostructure consisting of endless carbon nanowires. This structure serves as a filter for methane and helium molecules. A carbon nanowire is approximated by a continuum model in the calculation. The interaction energy of a gas molecule and a nanowire is described with the Lennard-Jones potential. The formula for the interaction potential between carbon cylinder nanowire and a test molecule is obtained. Helium He and methane CH4 molecules interaction with nanostructure, the basic element of which is an endless carbon cylinder nanowire, is studied. The pore size favorable for helium molecules penetration and methane molecules nonpenetration into the carbon layer have been defined through calculation.
The influence of the interaxial distance of the gears on the performance of an eccentric-cycloid engagement is studied by computer simulation. With wide variation in the interaxial distance, there is little shift in the contact point of the profiles, which remains at the front of the cycloid curves describing the tooth shape. This greatly simplifies gear manufacture for such engagements, since the surface area to be finished is considerably reduced.
A fundamentally new design of planetary gear with intermediate rolling bodies is proposed. This gear permits self-braking and is characterized by high efficiency in forward motion. Results for the efficiency of this gear in forward and inverse motion are obtained by computer simulation and calculation. In certain conditions, the gear is characterized by guaranteed self-braking. In that case, all the attractive properties of transmissions with intermediate rolling bodies are retained: small mass and size, high-strength, and high contact ratio of the coupling.
A mathematical model of a reduction gear with the cycloid eccentric gearing has been developed. Such gearing possesses advanced power characteristics and makes it possible to obtain high reduction ratios in a single phase. A computer program has been developed which illustrate einematieally cooperative motion of ideal geometrical figures. This program can be used to obtain numerical characteristics necessary for the design purposes.
The comparison of two theoretical approaches for the numerical investigation of turbulent gas–solid flows with heat transfer in a pipe are presented in this paper. The first approach is based on Eulerian–Eulerian modelling of investigated phenomena, the second one is formulated within the framework of the Eulerian–Lagrangian approach. The verification of numerical models under consideration. Their testing against available experimental data show good prognostic properties of the elaborated theoretical tool for research activities to study new physical fundamentals of turbulent gas-suspended particles flows in pipes and channels.
A mathematical model of nonisothermal turbulent flow of a gas suspension in a pipe is formulated on the basis of the mixed Euler–Lagrange representation. The testing of the model revealed good agreement of the calculation results with experimental data and with the data obtained using the continuum model developed by us previously. The use of two essentially different (continuum and mixed) approaches to the simulation of dusty flows leads to nearly identical results for the fields of averaged velocities and temperatures and for characteristics such as the coefficient of accommodation of the tangential component of the velocity and the intensity of the particle collisions with the wall surface.
The continual model developed by us is used to investigate the effect of the force of gravity on a nonisothermal turbulent flow of a gas suspension in a vertical pipe for upward and downward motion. The reasons behind the intensification of heat transfer in the case of a downward locally nonequilibrium motion of gas suspension are found.
A mathematical model for describing the turbulent flow of a gas suspension in a tube has been formulated within the framework of the combined Euler–Lagrange approach. Results of calculations by this model are in good agreement with theoretical data obtained using the continuous model developed by the authors [Teplofizika Aéromekhanika, No. 1, 5?–71 (1999)]. The importance of detailed modeling of the turbulent structure of the carrying medium in the near‐wall zone has been shown based on a comparative analysis of computational and experimental data.
Computer calculations of two-dimensional gas–particle flow through a separator which consists of four rows of U-beam elements show that particles coarser than 100 μm are fully separated in the first two rows, particles with dimensions 30–80 μm have better separation in the 3rd and 4th rows, but with less total efficiency. The design of U-beam separators influences the pressure drop more than the separation efficiency. The pressure drop increases with an increase of particle concentration in the flow. Visual observation using a liquid model confirms the general results of the calculations and shows the swirl in the cavities of the U-beam elements (primarily in the first two rows).
Investigations of the operation of channel-type separators, including hydraulic and mathematical modeling, as applied to boilers with a circulating fluidized bed were carried out.
A mathematical model and a computing technique are proposed for the motion, heat transfer, and combustion in the initial region of a pulverized-coal jet injected through a burner into the furnace volume. In the simulation, the dispersed phase is divided into two kinds of particles: particles that enter the region being studied from the portion of the furnace volume that is external with respect to the selected zone and the burner-jet particles. The continual approach and the assumption of equilibrium with respect to the gas phase are used to describe the motion of particles of the first kind and the Lagrangian approach taking into account the dynamic and thermal lag of particles is used to simulate the processes in the medium of particles of the second kind. The model also describes the evolution of volatile substances and burnup of the coke residue. The results obtained using this numerical model make it possible to analyze in detail the combustion of a pulverized coal-air jet in the area near the burner. The degree of detail achieved allows one to make effective decisions for organization of an optimal jet aerodynamics to reduce nitric-oxide formation.
