Dmitry Platonov

Numerical modeling of flow in the Francis-99 turbine with Reynolds stress model and detached eddy simulation method

The paper presents numerical simulation of flow in Francis-99 water turbine under three operation modes: part load, best efficiency point and high load. Calculations were performed by means of Reynolds stress model and detached eddy simulation based on k-omega SST model. The paper focuses on the flows in the draft tube. The calculated mean velocity components in the draft tube are in close agreement with experimental results. Calculated r.m.s velocity components agree with experimental pulsations qualitatively.

Application of Hybrid Methods to Calculations of Vortex Precession in Swirling Flows

Application of DES method for swirling flows was considered. Swirling flow in a diffuser and vortex breakdown past an abrupt expansion were considered to test the application of detached eddy simulation method for swirling flows. Calculations of unsteady flows in draft tube of Kaplan turbine Holleforsen and in draft tube of high head Francis turbine were provided to investigate vortex rope precession in hydro turbine.

Investigation of free discharge through the hydro units of high head Francis turbine

Free discharge through the units is applied in the course of construction of hydro power plant or in case of excessive water inflow during floods or emergency situation. Free discharges throw the hydro units at 80 m head and more are unknown. Possibility of high velocity swirling flow discharged through the whole hydro unit consisting of penstock, turbine (with Francis runner and distributor or without them) and draft tube is being analyzed in the present paper. Investigation method is based on mathematical simulation of unsteady flow through the hydro unit under the following conditions: with the free running or locked runner and with removed runner. Physical researches of the swirling flow behavior in the model bent penstocks and model turbine water passages have been performed. Based on the results of calculations and model tests the following extensive data have been obtained: pressure fluctuation in the whole hydro unit, fluctuation of hydrodynamic forces acting on guide vanes, torque fluctuation on the runner and discharge fluctuation. Thus, based on this data preferable designs of free discharge are proposed.

Numerical and experimental study of low-frequency pressure pulsations in hydraulic units with Francis turbine

The paper presents the numerical simulation method of three-dimensional turbulent flows in the hydraulic turbine. This technique was verified by means of experimental data obtained on a water model of the Francis turbines. An aerodynamic stand, which is a miniature copy of the real hydraulic turbine, was designed. A series of experiments have been carried out on this stand and the corresponding calculations were performed. The dependence of the velocity and pressure pulsations profiles for different operation regimes are presented.

Experimental study of pressure pulsations in the flow duct of a medium-size model hydroelectric generator with Francis turbine

In the present study, we report on the results of an experimental study of pressure pulsations in the flow duct of a medium-scale hydrodynamic bench with Francis turbine. In various regimes, integral and pulsation characteristics of the turbine were measured. With the help of high-speed filming, the structure of the flow behind the turbine runner was analyzed, and the influence of this structure on the intensity and frequency of pressure pulsations in the flow duct was demonstrated.

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-, 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.