Analysis Of High Narrow Turbine Draft Tube Interior Flow Based On Numerical Simulation

There are some safety problems, for examples, turbine vibration, piping system hydraulic resonance and blade crack. Many reasons lead to these safety problems. One of them is draft tube cavity vortex rope which appears at the condition that Francis turbines under part-load conditions. For Francis turbine at home and abroad in the condition that under partial load tail pipe pressure pulsation research has become more and more widely. At present through numerical calculation has good simulation model test observed in cavity vortex rope, forecast pressure pulsation of the tested value of the characteristics and also have certain degree of agreement; the conduit of vortex with produce in understanding of the mechanism of more clear.Based on the parameters of prototype draft tube in Ertan Hydro Station, this research established a geometric and physical mode for full flowing passage of the draft tube.3D numerical simulation and analysis of interior flow characteristics through the high narrow turbine draft tube were conducted on the basis of3D Navier-Stokes equations.Paper’s specific content of the work completed is shown as follows:1.According to actual hydraulic parameters of Ertan Hydro Station, the physical model is established for hydraulic turbine draft tube;2.Research on the use of ICEMCFD software on the method for mesh generation of draft tube, and also research on the use of FLUENT software on model selection of draft tube, parameters, solving a series of software applications, such as calculation of the key steps;3.The numerical simulation was conducted by standard k-ε turbulence model under different conditions. Post-processing the convergence of the results, this paper gain various regional distribution of the velocity, static pressure distribution, total pressure distribution, to analyse the fluid flow characteristics, state and static and total pressure numerical changes;4.Based on the steady turbulent flow simulation, the unsteady numerical simulation was conducted by RNG k-ε turbulence model, the calculation results were closer to the actual distribution of the flow filed;5.At the same time, adopting gas-liquid phase of mixed homogeneous hypothesis and transport equation which based on components of cavitation model, through solving the3-D unsteady Reynolds averaged Navier-Stokes equation with a transport-equation-based cavitation model of pseudo-homogeneous flow theory, and considering the non-condensable gas phase influence, the hydraulic calculation of the conduit internal spiral cavitation flow field.