Numerical investigation of flow structure and pressure pulsation in the Francis-99 turbine during startup

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at startup regimes. Numerical technique for calculating of low frequency pressure pulsations in a water turbine is based on the use of DES (k-ω Shear Stress Transport) turbulence model and the approach of "frozen rotor". The structure of the flow behind the runner of turbine was analysed. Shows the effect of flow structure on the frequency and intensity of non-stationary processes in the flow path. Two version of the inlet boundary conditions were considered. The first one corresponded measured time dependence of the discharge. Comparison of the calculation results with the experimental data shows the considerable delay of the discharge in this calculation. Second version corresponded linear approximation of time dependence of the discharge. This calculation shows good agreement with experimental results

Numerical investigation of flow structure and pressure pulsation in the Francis-99 turbine during startup

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at startup regimes. Numerical technique for calculating of low frequency pressure pulsations in a water turbine is based on the use of DES (k-ω Shear Stress Transport) turbulence model and the approach of "frozen rotor". The structure of the flow behind the runner of turbine was analysed. Shows the effect of flow structure on the frequency and intensity of non-stationary processes in the flow path. Two version of the inlet boundary conditions were considered. The first one corresponded measured time dependence of the discharge. Comparison of the calculation results with the experimental data shows the considerable delay of the discharge in this calculation. Second version corresponded linear approximation of time dependence of the discharge. This calculation shows good agreement with experimental results

Francis-99 turbine numerical flow simulation of steady state operation using RANS and RANS/LES turbulence model

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at three regimes, using two eddy-viscosity- (EVM) and a Reynolds stress (RSM) RANS models (realizable k-epsilon, k-ω SST, LRR) and detached-eddy-simulations (DES), as well as large-eddy simulations (LES). Comparison of calculation results with the experimental data was carried out. Unlike the linear EVMs, the RSM, DES, and LES reproduced well the mean velocity components, and pressure pulsations in the diffusor draft tube. Despite relatively coarse meshes and insufficient resolution of the near-wall region, LES, DES also reproduced well the intrinsic flow unsteadiness and the dominant flow structures and the associated pressure pulsations in the draft tube

The regularities of rock mass stressed state formation in the upper part of the Earth crust

It was determined that in the upper part of Earth crust up to 500-600 m depth the rock mass stressed state in some areas may correspond to the A. Geim, A.D. Dinnik, N. Hast hypotheses, as well the hypotheses developed in UB RAS and is mean interchanged for 11 year cycle of solar terrestrial relations. During this cycle 2-3 years rock mass consolidation is observed, and progress on displacement is absent or very small; then rock mass compession decreases for 3-4 years and is accompanied by an array of fault events, after that rock mass consolidation is again observed for 1-2 years. Further, both rock mass and earth’s crust compression increases for 4-5 years accompanied by thrust phenomena. The analysis of stresses values in the elements of mining systems shows that by 2020-2030 years the access to minerals in these workings at over 500 m depth will be difficult

Francis-99 turbine numerical flow simulation of steady state operation using RANS and RANS/LES turbulence model

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at three regimes, using two eddy-viscosity- (EVM) and a Reynolds stress (RSM) RANS models (realizable k-epsilon, k-ω SST, LRR) and detached-eddy-simulations (DES), as well as large-eddy simulations (LES). Comparison of calculation results with the experimental data was carried out. Unlike the linear EVMs, the RSM, DES, and LES reproduced well the mean velocity components, and pressure pulsations in the diffusor draft tube. Despite relatively coarse meshes and insufficient resolution of the near-wall region, LES, DES also reproduced well the intrinsic flow unsteadiness and the dominant flow structures and the associated pressure pulsations in the draft tube

Numerical Study of Devolatilization Models on the Combustion Process of Pulverized Fuel Flow Swirling

Приведены результаты расчётных исследований влияния моделей выхода летучих веществ на процессы воспламенения и горения пылеугольного топлива при закрутке потока на огневом стенде мощностью 2.4 МВт. Рассмотрено несколько моделей выхода летучих веществ: в одностадийном и двухстадийном приближении, а также модели, основанной на структурных особенностях строения угольного вещества. Для численного моделирования турбулентного течения несжимаемой жидкости использовались уравнения Рейнольдса с учетом межфазного взаимодействия. Для замыкания уравнения Рейнольдса применена двухпараметрическая стандартная k–ε-модель турбулентности. Для решения уравнения переноса теплового излучения взято P1-приближение метода сферических гармоник. Для описания оптических свойств газов была использована модель суммы серых газов. Для описания процессов движения угольных частиц обратились к методу Лагранжа. Сравнительный анализ результатов математического моделирования с экспериментальными данными показал, что при выборе правильных значений эффективных кинетических констант, а также параметров, характеризующих структуру угольного вещества, модели выхода летучих веществ согласуются между собой и с экспериментальными данными по распределению температур и составу газов в топочной камереThe results of computational studies of the effect devolatilization models in the processes of ignition and combustion of pulverized coal in the swirling flow at the shooting bench with capacity 2.4 MW. Consider a few devolatilization models in a one and a two-stage approach, as well as models based on the structural features of the structure of the coal substance. For the numerical simulation of turbulent flow of an incompressible fluid used Reynolds equation based on the interfacial interactions. To close the Reynolds equations used a standard two-parameter model of turbulence k–ε. To solve the equation of heat radiation used P1 approximation of the method of spherical harmonics. To describe the optical properties of the gas model was used the sum of gray gases. To describe the processes of the movement of coal particles used the method of Lagrange. Burning char based on diffusion – kinetic approach. Comparative analysis of the results of mathematical modeling with experimental data showed that when choosing the correct values of the effective kinetic constants and parameters characterizing the structure of the carbon material, a model release volatiles are consistent with each other and with the experimental data on the distribution of temperature and composition of gases in the combustion chambe