The paper presents an experimental and computational study of various regimes of firing coal-water fuel in a low-power hot-water boiler that enable both dry and liquid slag removal. The experimental...

We report on the experimental study of a precessing vortex core (PVC) in an air model of a Francis turbine. The focus is placed on the modal decomposition of the PVC that occurs in the draft tube of the model turbine for a range of operation conditions. The turbulent flow fluctuations in the draft tube are assessed using stereo particle image velocimetry (PIV) measurements. Proper orthogonal decomposition (POD) is applied to the antisymmetric and symmetric components of the velocity fields to distinguish the dynamics of the azimuthal instabilities. The pressure pulsations induced by the PVC are measured by four pressure sensors mounted on the wall of the hydro turbine draft tube. Spatial Fourier decomposition is applied to the signals of the pressure sensors to identify the contributions of azimuthal modes, $m=1$ and $m=2$, to the total pressure fluctuations. The analysis based on velocity and pressure data shows similar results regarding the identification of the PVC. The contribution of the $m=2$ mode to the overall turbulent kinetic energy is significant for the part load regimes, where the flow rates are twice as low as at the best efficiency point (BEP). It is also shown that this mode is not the higher harmonic of the PVC, suggesting that it is driven by a different instability. Finally, we show a linear fit of the saturation amplitudes of the $m=1$ and $m=2$ oscillations to determine the critical bifurcation points of these modes. This yields critical swirl numbers of $S_{cr}=0.47$ and $0.61$, respectively. The fact that the PVC dynamics in hydro turbines are driven by two individual instabilities is relevant for the development of tailored active flow control of the PVC.

A review is given for the state of the art and future development of the geothermal power engineering. Different diagrams of GeoPP are shown for different levels of geofluid temperature. A special focus is made on challenges for petrothermal power production. The huge amount of heat from petrothermal resources can be harnessed through creating geothermal circulation systems within the dry rocks. Estimates for system lifetime and heat production capacity of circulation systems are given for different flow rates of coolant.

A series of experimental investigations is performed for determining the thermal and environmental characteristics of burning heavy fuel oil of the M-100 type sprayed by a jet of superheated steam in a laboratory prototype of a new burner. A scheme of liquid fuel burning preventing choking of narrow fuel channels of injectors is proposed; this scheme ensures effective burning of high-viscosity fuels and wastes. The process of stable burning of heavy fuel oil in a low-power (7 kW) burner with low concentrations of toxic emissions and high combustion efficiency is realized.

Currently, thermal power plants operating on hydrocarbon fuels (gas, fuel oil, peat, shale, etc.) are one of the main sources of electricity. An effective and promising method for suppressing harmful emissions (NO_x, carbon oxides, soot) from the combustion of fossil fuels is the injection of steam into the combustion chamber. The influence of various mathematical submodels was studied on the accuracy of the numerical simulation of the process of n-heptane combustion in a laboratory burner with steam additive to the reaction zone as a promising chemical engineering method for the disposal of substandard liquid fuels and combustible waste with the production of thermal energy. The problem was solved in a three-dimensional stationary formulation. Systematic verification of these submodels, and a comparison of the results of the calculation with the experimental data obtained were carried out. The comparison with the experimental data was carried out for gas components and temperature distribution at the burner outlet; high agreement of the results was achieved. Optimal submodels of the methodology for calculating the process of fuel combustion in a jet of steam were determined. The best agreement with the experiment data was obtained using the EDC model in combination with a mechanism consisting of 60 components and 305 elementary reactions. More correct simulation results were obtained using the RSM turbulence model and the DO radiation model.