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This paper presents the results of an experimental study of the characteristics of a swirling flow with the formation of vortex structures in a radial burner under isothermal and reacting conditions for various flow swirling parameters. For isothermal conditions, the distributions of average and fluctuating velocity fields, including those tied to the phase of a precessing vortex, are obtained, the pressure fluctuations induced by the precessing vortex are analyzed, and the contribution of the precessing vortex structure to the overall level of turbulence is determined. The studies are carried out using modern contactless experimental methods of flow diagnostics, such as optical imaging and particle image velocimetry (PIV). An acoustic field generated by the vortex core precession (VCP) is recorded using four measuring microphones with pressure taps. The contribution of the VCP to the overall level of turbulence is revealed using the method of proper orthogonal decomposition (POD), also applied to analyze the velocity distributions obtained by the PIV method. The experiments show that, in the isothermal case, the VCP that occurs after the twist parameter overcomes a value S = 0.6 is a single-helix vortex structure, whose contribution to the overall level of kinetic turbulence energy is up to 27 %. For reacting conditions, the flame is visualized at different flow swirls and the frequency characteristics of the VCP occurring in the flow at S ≥ 0.6 are measured. It is shown that the dependence of the dimensionless frequency of the VCP as a function of the flow swrl S has the same nonmonotonic character both in the case of combustion and in the isothermal case.

This paper presents the results of a study of the ignition of nine brands of coal from the Kuznetsk Basin by laser pulses (120 μs and 1064 nm). Depending on the laser pulse energy density, three types of processes can be distinguished in the general process of coal ignition, and they differ in threshold, temporal, and spectral-kinetic characteristics. The first type is associated with flame ignition on the surface of coal particles, and the second and third types are related to the initiation of various thermochemical reactions within particles. The laser pulse energy density defines the intensity and duration of the flame glow, as well as the flame column height.

The detonation characteristics of an aluminized EMX with a density of ≈0.5 g/cm³ and with a mass content of aluminum up to 20 % were determined. The addition of aluminum leads to an increase in detonation velocity and detonation pressure in comparison with the parameters of the pure EMX. Replacing aluminum with ground glass leads to a decrease in both detonation velocity and pressure. The increased detonation characteristics of the aluminized EMX can be due to the partial reaction of aluminum before the Chapman-Jouguet plane. The brightness temperature of detonation products of the aluminized EMX was measured. It is shown that it decreases with the addition of aluminum to the EMX. This result demonstrates the complex effect of aluminum addition on the detonation characteristics of the EMX.

The article describes a technical approach to justification of pitwall parameters based on an integrated geomechanical research of pitwall rock mass using cores from specially drilled earth bores. The sizes of structural blocks, the rock mass quality index and structural weakness coefficient are determined. The strength characteristics of rocks and their physical properties are studied on a laboratory scale. Estimates of pitwall stability using different methods show a good agreement. The optimal pitwall parameters are recommended.

The experimental and theoretical studies show that plane deformation of granular medium induces formation of clusters with sizes of the order of 10-15 diameters of particles. The process of biaxial compression is examined. It is found that deformation has four basic modes conformable with different shapes of clusters. The modes feature a very complex alternation behavior. The process of deformation possesses memory with the Hurst exponent of 0.84. The limit loads in different modes can differ by 2 or 3 times. In problems on deformation of granular media, the calculation of mechanical condition of domains less than 80-100 diameters of particles in size should use not the continuum models but the discrete element method.

The article describes a new method proposed for the mine geometry-based prediction of location and vertical amplitude of faults within the boundaries of an extraction panel using the data on survey network coordinates. A survey network is split into cells-convex quadrilaterals with their vertexes representing the survey grid points. For each quadrilateral, the geometric uncertainties of the coal seam hypsometry are estimated as closure errors and are eliminated in the course of the survey grid adjustment by means of correction of heights. The method consists in calculation and analysis of corrections for the measured absolute heights of the coal seam points arranged in mine roadways, the introduction of which eliminates the interpretation uncertainty of geological data. The corrections are only assumed to be the weights of the measurement and interpolation errors in the neighborhood of specific measurement points. A fault is predicted when there is a jump between the values of the correction for the neighbor measurement points.

To enhance the scientific nature and the reliability of physical modeling of tailings dams, the present developments and main achievements are discussed from four perspectives: dam break, downstream evolution, stability evaluation and protection tests. The experiment materials, methods of measurement and instruments used are summarized. The problems and shortcomings of physical model tests are investigated in terms of the difference between a physical model and a prototype, nature of the experiment, methods of measurement, etc. Emerging technologies such as artificial intelligence and 3D printing to improve safety of tailings dams are discussed. The scope of the review embraces environmental impact of tailings dams in case of accidents.

The article describes the studies into the geological conditions and geotechnologies of coal mining in brachysyncline-type fields. It is found that such coalfields have some specifics which governs the choice of the open pit mining technologies to be efficient. The authors propose an approach to justification of a sequence of mining and to selection of geotechnologies for coalfields in brachysynclinal folds.

In mid-May 2014, heavy rainfall caused unprecedented floods in Serbia. Kolubara Mining Basin, the greatest coal producer in the Electric Power Industry of Serbia, has suffered enormous material damage. Coal production at four open-pit mines was suspended and the operation of four thermal power plants was threatened. The consequences of the uncontrollable water, physically visible on open-pit coal mines, were felt in all system sectors. Intersectorial analysis was used to view and diagnose the situation of the system’s production sectors. The paper gives the summaries of uncontrollable water, mining and energy system structure, the implementation of the intersectorial model in the analysis, comments on the analysis results, evaluation, and a conclusion from the aspect of efficiency and reliability of application in solving practical problems.

The author proposes a determination procedure for calibration factors for current frequency converter of a tunnel fan motor with regard to air flow rate control time at each train density. The ranges of three quality criteria of ventilation control in subways are determined. The ventilation energy consumption at a subway station is analyzed as function of an opening angle of air governor flaps in the ventilation connection at the station, and the economic runs are selected for the flap air governor. The change in the air flow rate at a station versus the flap air governor setting angle serves the basis to create the automatic air control algorithm for a shallow subway with ventilation due to the piston effect in the absence of tunnel fans. The algorithm allows maintenance of the required air renewal at subway stations in rush hours.