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The study presents the results of numerical studies of mixing, ignition, and combustion of a jet of cold hydrogen along the bottom wall of the channel parallel to the supersonic free stream (M = 2) of an inert gas / vitiated air. The calculations were carried out using the commercial package ANSYS CFD Fluent based on the solution of unsteady Favre-averaged Navier-Stokes equations, supplemented by the k-ω SST turbulence model, models of turbulence-chemistry interaction (TCI), and several kinetic schemes of hydrogen combustion. Two detailed kinetics, including 16 and 37 reactions, are considered. The work used two models of turbulence-chemistry interaction: the vortex dissipation model (EDM) and its extended version eddy dissipation concept (EDC). This work aims to select the calculation method, the kinetic mechanism, and the TCI model, which provide good agreement with the experimental data. It is shown that, in the case of a non-reactive flow, the computational algorithm makes it possible to accurately predict the mixing parameters of a hydrogen jet and an external inert gas flow. For a reacting flow, the Kelvin-Helmholtz instability, which develops at the boundary of the combustion layer with the external flow, significantly affects the flow characteristics. [ABSTRACT FROM AUTHOR]

In this work, the problem of axisymmetric gas flows through porous object with heterogeneous combustion sources under natural convection is considered. Heterogeneous combustion is a combustion which occurs when fuel and oxidizer are in different phases. The numerical approach based on combination of explicit and implicit finite-difference schemes is suggested for investigating these processes. It is shown that the location of ignition zone effects on process of propagating the combustion waves. For the axisymmetric case, as well as for the plane case, under natural convection vortex gas flows are observed near the combustion zone. This vortex flows effect on flow of oxidizer into the reaction zone. As in the plane case, the solid combustible component burns out completely, but the direction of the combustion wave propagation in the axisymmetric case can differ from the plane case. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of the thermal modes of a supersonic combustion chamber at Mach numbers at the channel inlet 3-4, operating on hydrogen. Model is made in the form of a rectangular channel with a combined flame holder with a backward-facing step and wedge-shaped injectors. The experiments were carried out in the mode of a connected pipeline under conditions close to flight ones. It was found that the maximum level of heat flux is reached in the region where the ignition of the mixture is initiated, and this value is achieved during the non-stationary ignition of the combustion chamber. The position of this region shifts upstream with a decrease in the Mach number, which depends on the change in the position of the separation region of shock waves interaction with the boundary layer. With an increase in the Mach number to 4, intense combustion does not occur due to the displacement of this region downstream into the diverging channel and is accompanied by a significant increase in the flow rate. The data obtained show that when developing systems for thermal protection of the combustion chamber, it is necessary to take into account the uneven distribution of heat fluxes along the combustor length in order to prevent local destruction of the walls and possible saving of the coolant resource. [ABSTRACT FROM AUTHOR]

The paper presents the results of the assessment of the applicability of structured laser illumination in combination with Rayleigh scattering or spontaneous Raman scattering methods for evaluating the local density and temperature distribution in a premixed methane flame. The examples presented in this paper show that the use of structured laser illumination makes it possible to obtain a signal free of background and reflected light by registering the scattering signal only at one S-polarization of the laser. The best quality of image reconstruction was obtained using a grating with a line spacing of 0.5 mm. Gratings with a larger step gave a strong blurring and loss in spatial resolution, a grating with a smaller line spacing during reconstruction led to the formation of secondary structures with lines. [ABSTRACT FROM AUTHOR]

The flow structure and statistical features of a turbulent stable stratified boundary layer are studied by using the RANS (Reynolds averaged Navier-Stokes) model of turbulence, which takes into account the influence of internal waves. The possibility of the RANS model of turbulence description of intermittent turbulence both near the surface and above the surface in the vicinity of the low-level jet flow formed above the boundary layer is analyzed. The role of turbulent diffusion (third-order statistical moments) in intermittent turbulence generation and energetics is discussed. An analysis of the energetics based on the balance equations of kinetic and potential turbulence energies shows, in particular, that the weak mixing (Rig >1) is quite capable on transferring momentum. [ABSTRACT FROM AUTHOR]

This paper was focused on studying of turbulent mixing in a model gas-turbine combustor by using planar laser-induced fluorescence. The case of model fuel injection through the pilot jet with Re = 30 000 was considered. Acetone was used as a fluorescent tracer. Data processing methods including correction of sensor sensitivity, background signal correction and correction of non-uniformity of the laser sheet were described. The instantaneous and averaged concentration fields and the concentration pulsations were demonstrated. [ABSTRACT FROM AUTHOR]

Processes in thermal energy storages (TES) based on granular phase change materials with gaseous heat transfer fluid are considered. The effect of side walls shape on charging and discharging performance of the TES with circular and rectangular cross-section is investigated. For this purpose, using the novel numerical model, the charging and discharging processes in TES with straight, narrowing and expanding side walls are compared. It is shown that preference of the TES shape in general case depends on used preferability criteria, but TES with non-straight walls are preferable in rare cases and TES with straight walls are the most preferable. [ABSTRACT FROM AUTHOR]

Numerical simulation of self-induced pitch oscillations of a segmental-conical body at Mach number M = 2.0 is performed using the mathematical model of the pitching moment, which includes an ordinary linear differential equation of the first order. The parameters of the mathematical model were determined from the condition of the best agreement between the calculated and experimental transient processes pitch angle in time. Numerical modeling of self-induced oscillations was also carried out using the time-lag hypothesis and concepts of aerodynamic derivatives. It is shown that the proposed mathematical model is not only satisfactory describes the experimental transient process like the other two, but also explains the known experimental effects. [ABSTRACT FROM AUTHOR]

Basing on the solution of the Navier-Stokes equations and using the k-ω SST turbulence model, a numerical simulation of the supersonic flow in an air intake with an internal channel of a rectangular cross section was performed for the case when the shock wave generated by the inlet cowl interacted with the turbulent boundary layer on the inner surfaces of the channel. The three-dimensional configuration consisted of a convergent entrance section and a throat of a constant cross-sectional area is considered. Flow parameters at the entrance of the air intake were set taking into account the boundary layer developing on a pre-compression surface of an aircraft in front of the inlet. Two variants of the internal channel geometry were considered: firstly, when the lower surface of the channel was plane and, secondly, when this surface was arranged with longitudinal ribs. Numerical simulation of the three-dimensional flow was performed at the free-stream Mach number M = 4. [ABSTRACT FROM AUTHOR]

In the present study, to describe particulate matter transport processes in the air around the bluff body that simulates building, computational fluid dynamics methods (CFD) were used. The paper considers the Euler-Lagrange approach for modeling a multiphase "air-solid particles" flow, in which the gas phase is modeled using the 3D unsteady Reynolds-Averaged Navier-Stokes equations, and the dispersed phase is modeled using the DPM method. The model configuration is considered to describe the PM10 particles' injection into the air crossflow in an obstacle's vicinity. Based on the numerical simulation results, the gas flow structure and particle transport parameters for two different configurations were investigated. It is shown that the chosen numerical model makes it possible to give a detailed qualitative description of the unsteady particle plume transport and to provide additional data for the experiment. [ABSTRACT FROM AUTHOR]