Numerical simulation of fuel staged swirl combustion in the invert furnace of boiler on advanced ultra-supercritical steam parameters

The paper considers the schemes of Kuznetsky lean coal combustion for the M-shaped boiler. With such a boiler profile, it is possible to significantly reduce the length of main steamlines, which is especially important for the advanced ultra-supercritical parameters of the superheated steam. The furnace in this boiler unit is performed downward (invert). In this work, the aerodynamics of 6 combustion schemes was simulated by means of computational fluid dynamics. All considered schemes were designed on the basis of direct-flow burners and nozzles. For the most aerodynamically reasonable scheme the thermal processes in the boiler furnace firing Kuznetsky lean coal have been simulated by means of computational hydrodynamics. The simulation results showed a high efficiency of fuel burnout: loss due to unburned combustible equaled 0.1%, carbon-in-ash loss equaled 0.8%. Carbon monoxide concentration at the furnace outlet in conversion to excess air equal α = 1.4 amounted 226 mg/m3, the nitrogen oxides concentration in the flue gases (in conversion to normal conditions) equaled 424 mg/m3. It is appropriate to use the results obtained in this research in the development of new solid fuels combustion schemes.

VERIFICATION OF ELECTRICALLY CONDUCTIVE FLUID FLOW CALCULATION IN CIRCULAR PIPES

Magnetohydrodynamics (MHD) treats the phenomena that arise in fluid dynamicsfrom the interaction of an electrically conducting fluid with the electromagnetic field. Thedevelopment of computational hydrodynamics has significantly improved the accuracy ofcalculations on mathematical models, but it is still difficult to choose the optimal turbulence models,mesh quality, model parameters to solve a particular problem. The aim of the work is to verify thecalculation of the conducting fluid flow in circular pipes and to determine the optimal error of theturbulence model calculation and the parameters of its use. The study was conducted on the basis ofa comparison of experimental studies by the PIV-method of velocimetry with the results of numericalcalculations. The liquid is considered viscous, incompressible, and electrically conducting. Controlnonlinear momentum equations are solved numerically using the method of control volumes.Comparison of velocity profiles showed that almost all models show a fairly good match with theresults of the experiment. Analysis of the sum of squares residuals of calculation points fromexperimental shows that the BSL Reynolds Stress turbulence model is the best for the flow withoutthe influence of the magnetic field, and the k-ɛ model is the best in the presence of a magnetic field.The SST k-ω model has quite enough results regardless of the Hartmann number. The number ofmesh elements has little effect on the ac-curacy of the pressure drop calculation. For simplegeometries it is enough to use meshes with the number of elements that does not exceed the 500000elements. According to all criteria, it is rational to choose the k-ɛ turbulence model for furthercalculations. This model has some shortcomings in the calculation of wall layers, but allows to obtainhigh-quality and adequate results for the flow of conducting fluid with a limit on the mesh elementsnumber.

Thrusters Physical Model Formalization With Regard to Situational and Identification Factors of Motion Modes

Within the framework of the research of diagnos-tics and prediction of technical state of ship power plants (SPP) of combined propulsion complexes (CPC) depend-ences of correcting factors influencing components of thrusts and moments, proportional dimensions of model and real thrusts (THRs), tied to the original geometry were obtained. This was done by formalizing the physical model of the azimuth thruster with the means of identifying the degradation effects on the flow lines of the propellers by methods of computational hydrodynamics. The technique of improving the structure of the mathematical models of the SPP CPC according to experimental studies by measur-ing the input and output parametric coordinates of the THRs CPC of a vessel operating in the dynamic positioning mode is announced.

Investigation of Coolant Local Hydrodynamics in the Mixed Core of the VVER Reactor

The article presents the results of experimental studies of the local hydrodynamics of the coolant flow in the mixed core of the VVER reactor, consisting of the TVSA-T and TVSA-T mod.2 fuel assemblies. Modeling of the flow of the coolant flow in the fuel rod bundle was carried out on an aerodynamic test stand. The research was carried out on a model of a fragment of a mixed core of a VVER reactor consisting of one TVSA-T segment and two segments of the TVSA-T.mod2. The flow pressure fields were measured with a five-channel pneumometric probe. The flow pressure field was converted to the direction and value of the coolant velocity vector according to the dependencies obtained during calibration. To obtain a detailed data of the flow, a characteristic cross-section area of the model was selected, including the space cross flow between fuel assemblies and four rows of fuel rods of each of the TVSA fuel assemblies. In the framework of this study the analysis of the spatial distribution of the projections of the velocity of the coolant flow was fulfilled that has made it possible to pinpoint regularities that are intrinsic to the coolant flowing around spacing, mixing and combined spacing grates of the TVSA. Also, the values of the transverse flow of the coolant caused by the flow along hydraulically nonidentical grates were determined and their localization in the longitudinal and cross sections of the experimental model was revealed. Besides, the effect of accumulation of hydrodynamic flow disturbances in the longitudinal and cross sections of the model caused by the staggered arrangement of hydraulically non-identical grates was determined. The results of the study of the coolant cross flow between fuel assemblies interaction, i.e. between the adjacent TVSA-T and TVSA-T mod.2 fuel assemblies were adopted for practical use in the JSC of “Afrikantov OKB Mechanical Engineering” for assessing the heat engineering reliability of VVER reactor cores; also, they were included in the database for verification of computational hydrodynamics programs (CFD codes) and for detailed cell-based calculation of the reactor core.

A panel method for both marine propulsion and renewable energy

A computational hydrodynamics method was formulated and implemented as a tool from screw propeller propulsion to renewable energy performance prediction, design and optimization of horizontal axis turbines. As an example for tidal energy generation, a comparative analysis between screw propellers and horizontal axis turbines was presented, in terms of geometry and motion parameters, inflow velocity analysis and the implementation methodologies. Comparison and analysis are given for a marine propeller model and a horizontal axis turbine model that have experimental measurements available in literature. Analysis and comparison are presented in terms of thrust coefficients, shaft torque/power coefficients, blade surface pressure distributions, and downstream velocity profiles. The effect of number of blades from 2 to 5, of a tidal turbine on hydrodynamic efficiency is also obtained and presented. The key implementation techniques and methodologies are provided in detail for this panel method as a prediction tool for horizontal axis turbines. While the method has been proven to be accurate and robust for many propellers tested in the past, this numerical tool was also validated and presented for both tidal and wind turbines.