Numerical Analysis And Flow Characteristics Of Impingement Turbine In Whole Basin

With the rapid development of Chinese society and the continuous improvemen t of production level of all industries,electric energy is indispensable and important for everyone,power enterprises and even the country.In recent years,the national power production and development has entered a white-hot stage,in which hydroelectric power generation is an important source of power production,and its development momentum and technology have gradually matured.In China,hydroelectric power generation gradually develops from low head to high head and from low flow to high flow.Among them,the turbine undertakes the role of main energy conversion and converts the kinetic energy of water flow into the mechanical energy of the runner.Among the hydraulic resources with many different conditions,each turbine should deal with different head and working conditions respectively.Among all kinds of turbine types,Pelton turbine is suitable for operation under high head conditions and it is easy to install and perform well in low and high flow rates with low maintenance cost.Compared with foreign countries,the research level of Pelton turbine in China is still at the stage of experience accumulati on.In addition,the internal flow of Pelton turbine belongs to unsteady three-dimensional two-phase flow and its complex flow characteristics also cause many difficulties in the research.There are classical elbow flow and bifurcated flow in the distributi on ring pipe of Pelton turbine.The secondary flow accompanied by these two flows exi sts in the distribution ring pipe and nozzle and continuously interf eres with the advance of the mainstream,thus affecting the pressure and speed of free jet downstream.It is the main energy loss point in the water supply mechanism of Pelton turbine.Therefore,it is very important to study the flow characteristics of dis tribution ring pipe,nozzle and jet of Pelton turbine.In view of this,the internal flow characteristic s of a four-nozzle pelton turbine are numerically simulated in this paper.The specif ic research contents are as follows:1.Study the energy loss mechanism of internal water supply mechanism of four-nozzle pelton turbine and find out the cause of internal loss of four-nozzle pelton turbine.2.The development characteristics of secondary flow in water supply mechanism of four-nozzle pelton turbine are explored by studying the flow characteri stics of secondary flow produced in operation.3.Through the numerical simulation of the whole watershed of four-nozzle pelton turbine,combining the characteristics of gas-liquid two-phase flow,the overall working process of free jet is analyzed and the flow characteristics of jet and runner in working state are explored.The results show that the energy loss of the water supply mechanism in the four-nozzle pelton turbine is concentrated on the distribution ring pipe and the nozzle,in which the energy loss of the nozzle accounts for the main part.The energy loss in the distribution ring pipe mainly concentrates on the corner wall of each branch nozzle and the secondary flow generated by the elbow closure.The energy loss of the nozzle is mainly concentrated in the evolving secondary flow from the water distribution ring pipe into the nozzle.The jet impingement on the runner bucket makes the bucket not fully transform the energy with the jet and it is one of the main energy loss points during the work process.