The problem of the membrane separation of a helium–methane mixture containing 0.1 wt % He, which imitates the composition of a helium-rich natural gas field, has been numerically analyzed. The helium and methane flux distribution along the length of a flat-sheet membrane module have been calculated. The distribution of the average mass concentration of helium in the channels is presented. The gas pumping expenditures have been estimated. The optimal working parameters of the gas mixture have been determined. Heating the mixture above 400 K does not enhance the helium–methane separation efficiency.

The flow in the vortex chamber with centrifugal fluidized bed of solid particles was studied experimentally and simulated numerically. The chambers of different configurations were considered, and this allowed us to change the ratio of centrifugal and gravity forces. To estimate the hydraulic losses in the vortex chamber, a simple model was suggested.

Based on experiments on flame extinction in air flow over a horizontal porous plate with uniform injection of H2/N2 and H2/He fuel mixtures, we found that the blow-off condition for a laminar boundary layer can be uniquely defined by two parameters: the nondimensional fuel-mixture blowing rate and the hydrogen mass fraction. It turns out that the injection corresponding to extinction is inversely proportional to the hydrogen concentration, J¯w∗∼1/YH21. The measured velocity, temperature and concentrations of O2, H2O and N2 showed that approaching the blow-off conditions shifts the flame front ever closer to the wall whereas the velocity profiles remain almost unaffected. The numerical solutions of the field equations and reaction kinetics supported the experimental findings and provided details on the flow properties that are inaccessible to measurements. The simulations showed that burning begins only at the location where the concentration of fuel reaches a threshold value corresponding to the lean flammability limit. Finally, a simple analytical model based on the Shvab-Zel'dovich arguments is shown to mimic qualitatively well the experimental J¯w∗-YH21 extinction correlation.

Results of an experimental study of a laminar boundary layer with combustion of a hydrogen-nitrogen fuel mixture uniformly injected through a porous wall into an air flow are presented. Data characterizing the ignition conditions are obtained. Based on the recorded temperature distributions, streamwise changes in the location and temperature of the flame front are analyzed as functions of the free-stream velocity (1–4 m/s), injection intensity, and fuel composition. It is demonstrated that heat transfer can be adequately described by a “standard” dependence for the boundary layer with boundary conditions of the second kind.

The aim of present research was to obtain data on the conditions of flame blowout in a laminar boundary layer with uniform injection of H2/N2 or H2/He fuel mixture through a horizontal porous plate into the air stream. This shows that the conditions of ignition and extinction of the flame in the boundary layer can be described by two quantities: dimensionless parameter and concentration of hydrogen in the fuel mixture. It turns out that the injection, corresponding to extinction, is inversely proportional to concentration of hydrogen.

In the present paper, we consider the variation of heat and mass diffusion fluxes on a permeable plate with blowing of a foreign gas into the boundary layer, the fluxes being considered as functions of the permeability parameter, varied through variation of blowing intensity, free-stream velocity, or longitudinal coordinate. It is shown that at a fixed distance from the leading edge of the plate one can, varying the value of blowing intensity while preserving the uniformity of the blowing over the plate length, obtain a non-monotonic variation of the wall heat and mass diffusion fluxes. In contrast to the heat and mass diffusion fluxes, the shear stress always monotonically decreases with increasing the blowing intensity. Similar to the shear stress, on increase of permeability parameter achieved through changing either the free-stream velocity or the longitudinal coordinate the heat flux and the mass diffusion flux both show a monotonic reduction. Using the integral relations of boundary-layer theory, we have derived simple analytical expressions allowing determination of the maximum values of the heat and mass diffusion fluxes in laminar and turbulent flow regimes. The obtained analytical relations were verified by performed numerical simulations.

Consideration is given to swirling gas-dispersed flows in the cylindrical combustion chamber with a lateral swirler, in the conical combustion chamber with a nonflow bed of a dispersed material, and in the cylindrical combustion chamber with lower end injection of the gas through a slot swirler.

The features of swirling flows in a cyclone chamber of diameter ∼0.4 m have been investigated experimentally for various configurations of inlet nozzles and sizes of the outlet hole. The existence of general laws of swirling flows independent of the inlet and outlet geometry of the chamber, as well as of the air blow velocity has been established. Equations for calculating the main characteristics of the swirling flow in the above chamber have been obtained and their comparison with the dependences established for chambers with other geometric parameters has been made.

An experimental and numerical study of a laminar boundary layer with combustion has been carried out at hydrogen and nitrogen fuel mixture blow through a porous plate. At that main flow velocity ranged from 2 to 4 m/sec and the mass fraction of hydrogen in the fuel from 1 to 11%. The lower limit of stable combustion depending on the blow intensity and hydrogen content in the fuel mixture was obtained experimentally. Data on the temperature distribution in the boundary layer have been obtained and analyzed. The simulation results show that in this range of parameters combustion occurs in the kinetic mode.

A flow near the blind end in vortex chambers with angles of flow entry into the chamber of 0 and 45 degrees relative to the tangential direction at different flow rates is investigated. The averaged values of the tangential and radial components of the velocity vector have been measured, as well as the values of their pulsations over the height of the end boundary layer with the aid of a two-component Doppler laser anemometer.

Results of numerical simulations of methane combustion in a laminar boundary layer on a porous plate with an impermeable initial section are presented. The analysis of results is based on comparisons of data with and without combustion, and also for different initial section lengths including the zero length. The flow history is demonstrated to exert a significant effect on heat transfer and friction in the boundary layer with injection without combustion, whereas the influence of the flow history in the case with combustion is smaller. The phenomenon experiencing the least effect of the flow history is heat transfer.

In the present paper, we analyze, both numerically and analytically, the influence a favourable pressure gradient has on the characteristics of dynamic boundary layer. It is shown that at a certain value of the pressure gradient asymptotic conditions can be reached in laminar boundary layer, with the skin-friction coefficient value being independent of the Reynolds number, like in the case of asymptotic suction of boundary layer through the porous wall. Some analogy between the two types of flow can be traced: in both cases, namely, at porous suction and in the boundary layer of an accelerated flow, a cross flow is generated, directed from the outer edge of the boundary layer toward the wall. For the conditions of the two types, an approximate analytical solution to the boundary-layer equations has been obtained. It is shown that in problems with first- and second-kind boundary conditions the favourable pressure gradient exerts an influence on the heat-transfer characteristics.

Numerical modeling of Prandtl equations was undertaken in order to investigate into the effect of mainstream acceleration on characteristics of dynamic and thermal boundary layers. Unlike in dynamic boundary layer, nondimensional characteristics of thermal boundary layer proved to be rather conservative to the action of the favorable pressure gradient. It was found that, unlike the skin-friction coefficient and the momentum-thickness Reynolds number, the Stanton number and the energy-thickness Reynolds number both exhibit no saturation with increasing the Kays acceleration parameter. Also, an analysis of the violation of Reynolds analogy by the stream acceleration is given.

The paper describes a numerical study of the influence of thermal and boundary conditions on the structure of laminar and turbulent diffusion flames in the cases with hydrogen injection through a porous surface and with hydrogen combustion in an air flow. Two types of boundary conditions are compared: with a given constant temperature T w = const over the length of the porous surface for arbitrary intensities of fuel injection and with a constant temperature T′ = const of the fuel injected through the porous wall. The first case occurs during combustion of a liquid fuel whose burning surface temperature remains unchanged. Injection of gaseous fuel usually leads to the second case with T′ = const. Despite significant differences in velocity and temperature profiles, the skin friction coefficients in the laminar flow are close to each other in these two regimes. In the turbulent regime, the effect of the thermal boundary conditions on friction and heat transfer is more pronounced. Moreover, the heat flux to the wall as a function of fuel-injection intensity is characterized by a clearly expressed maximum. A principal difference of the effect of combustion on friction and heat transfer in the laminar and turbulent flow regimes is demonstrated.

A numerical study was performed to examine how thermal and diffusion boundary conditions affect the structure of laminar diffusion flame in air flow with porous blowing and combustion of hydrogen. Boundary conditions of two types were compared, with lengthwise-constant porous-wall temperature (TW=const throughout the whole range of blowing ratios), and with lengthwise-constant temperature of the fuel supplied into the main flow (T′=const). With a liquid fuel having constant evaporating-surface temperature, we deal with boundary conditions of the first type. With a gas fuel, as a rule, we encounter the regime with T′=const. It is shown that, in spite of the significant difference in velocity and temperature profiles, in both cases the surface friction coefficients have close values. Also, it is found that the wall heat flux exhibits a maximum if considered as a function of fuel supply intensity. Nonetheless, the function of relative heat transfer monotonically decreases with blowing intensity, much like it does in non-reactive flow.

This paper deals with adiabatic evaporation of various liquids into an air-steam mixture and pure superheated steam. The focus is made on the inversion temperature, which means that the rate of liquid evaporation into an air-steam mixture (superheated steam) becomes equal to the rate of evaporation into dry air. A simple analytical solution for finding of inversion temperature was derived, and the required conditions of existence of the given phenomenon are found. The influence of parameters of the main flow (vapor quantity, pressure, and flow regime) on the value of inversion temperature is analysed. It is shown that consideration of the influence of injection flow on relative function of heat transfer for inversion temperature definition of ethanol, acetone, and benzene is necessary. A comparison with numerical modelling was made to estimate the analytical solution accuracy.

Chemical processes proceeding during incomplete oxidation of heavy hydrocarbons in multiphase nonideal systems are modeled. A program is developed for calculating the composition of products of incomplete oxidation of hydrocarbons with the use of equilibrium and kinetic models with allowance for imperfection of the gas phase and solutions. The yield of the product was calculated by the equilibrium and kinetic models to optimize the yield of hydrogen during incomplete oxidation of eicosane (C 20 H 42 ) in the presence of water in the supercritical domain of state of the system. The data calculated by the kinetic model are compared with experimental data.

It has been established experimentally that in helium injection through a permeable wall into an air flow of the same temperature the heating of the wall up to about 8 degrees C is observed. On the other hand, in the outer part of the boundary layer the flow is cooled. Such a structure of the thermal boundary layer is caused by redistribution of heat in the boundary layer due to the diffusion thermoeffect (Dufour effect). The magnitude of the thermal effect on the wall is preserved in transition from a laminar to a turbulent mode of flow.

This paper deals with adiabatic evaporation of water into an air–steam mixture and pure superheated steam. The focus is made on the inversion temperature, which means that the rate of liquid evaporation into superheated steam becomes equal to the rate of evaporation into dry air. A simple analytical solution for the inversion temperature was derived. The analytical and numerical methods were applied for analysis of different factors (vapor quantity, flow rate, flow regime) on the value of inversion temperature.