Study On Flow Pattern Of Runner And Draft Tube Of Francis Turbine Based On Full Channel

In today’s process of development of hydropower, installed capacity of hydro units in general increases, and as one of the core device of the hydroelectric turbine, the internal flow condition is complex and varied, such as interblade of the Runner internal turbulence in the leaves caused by interblade vortex; draft tube vortex flow by turning the flow of water deviated from the normal position of the tail in the tail pipe and the formation and which is one of the important causes of hydraulic vibration unit, therefore, the flow characteristics of hydraulic control unit to improve its internal performance has an important value. Current understanding of the domestic and foreign turbine inner flow field mainly by the method of field data collection, model experiments, numerical simulation, among which field data collection and modeling experimental conditions are more restricted, and in the numerical simulation technology, we can use the computer analyze and display the flow field in the phenomenon, which can achieve the effect of prediction of flow field in a short period of time, thus saving manpower, material and closing times. Therefore, through the establishment of full passage of hydraulic turbine model to simulate the flow field analysis of the characteristics of its rotor and tail pipe inside; vortex formation and evolution processes put forward on how to eliminate and reduce hydraulic vibration is important.Consider the influence when deviate from design conditions, due to the viscous and non-uniform which can cause big affects. Through establishment the model of full runner Francis turbine, select two flow operating point in its characteristic curve deviates from the design flow field calculation in CFX, and analysis of the differences in the two flow conditions of the turbine inside the flow characteristics and vortex evolution; At the same time, before and after increasing the diversion grid were unsteady simulation under two different conditions.To study the difference between before and after the installation of tail pipe tail pipe diversion grid inside the pressure pulsation flow characteristics and vortex zone. Thus explain the justified of installation of tail pipe diversion grid and whether a certain sense.Numerical calculations show that:Since the velocity vector difference when water entering the wheel in the two types of traffic flow conditions. Resulting the different of distribution of channel vortex and flow field in the runner.The same water flowing through the rotor into the tail pipe will produce different amounts and different speed loop deviates from the normal direction of flow characteristics and will end within the water vortex tail pipe with a different impact. In addition, by comparing the tail pipe is installed before and after the diversion grid the flow characteristics inside the tail pipe can explain to some extent the tail pipe diversion grid on the eccentric motion guide runner outlet flow and reduce tail water vortex can play a positive acts. As numerical simulation of vortex distribution map and diagram displays the pressure pulsation phenomenon tail pipe fence installed around the eccentric motion instructions tail water diversion grid vortex has a certain influence, which can serve to reduce pressure pulsation action, so as to achieve the effect of reducing vibration.