| In Nowadays,with the continuous consumption of fossil energy and the increasingly serious problem of environmental pollution,hydro power resources as a kind of clean energy has been vigorously developed in various countries.At present,the technology of development and utilization of middle head hydro power resources has become more and more perfect,but also with less and less exploitable resources,the focus of hydropower construction has begun to shift to the western region with high head hydro power resources which is difficult to develop,and the Pelton turbine with unique advantages began to receive widespread attention.However,compared with other types of turbines,the research on Pelton turbine is still relatively backward,which has just gradually started to involve in the complex dynamic process with the interference between different jets and between jets and buckets during the interaction of jet and bucket.Few researches have considered the mixing of sediment particles in the flow medium in the actual operation of the turbine Therefore,on the basis of completing the unsteady calculation of gas-liquid two-phase in the whole basin of the Pelton turbine,solid particles are added into the flow field to simulate the real situation of sediment in the water during the actual operation of the turbine.The specific contents and conclusions of this paper are as follows:1.Combined with the model test,under the condition that the needle opening is 18 mm,i.e.fixed flow,the unsteady calculation of gas-liquid two-phase in the whole basin with three different rotating speeds of the runner is completed.The results of numerical simulation are compared with the results of model test.The comparison result shows that the numerical simulation method can predict the external characteristics of gas-liquid two-phase flow of Pelton turbine accurately,and the reliability of numerical simulation method is verified.Through the analysis of the process of the interaction between the jet and a single bucket,it is found that the rotating speed of the runner will directly affect the process with interaction between the jet and a single bucket,and will also affect the discharge process of the waste water and then indirectly affect the jet expansion,making the single bucket present different output characteristics.And then the total output of the runner and the efficiency of the turbine will be different.2.On the basis of two-phase calculation,solid particles are added into the flow field to realize the simulation of sediment flow.Through the numerical simulation under different particle diameters and concentrations,the distribution rule of sediment particles in the flow field of the water supply mechanism of the Pelton turbine and its influence on the flow characteristics of the water supply mechanism are analyzed.It is found that the distribution of sediment particles in the water supply mechanism is mainly affected by its own centrifugal inertia force and the vortex structure in the field.At the same time,the addition of sediment particles will change the shape and distribution of vortex structure in the original flow field and cause the generation of new vortex structure.and then cause the increase of energy loss.Particles with different diameters have different distribution characteristics due to their difference influence on the flow pattern and their own inertia.The energy loss of some bifurcated pipes in the water distribution pipe is greatly affected by the particle diameter and concentration,but the loss in the nozzle is less affected by the particle diameter and concentration.3.Further analyze the impact of sediment particles on the flow characteristics in Pelton turbine runner area.Through the comparison and analysis of the interaction process between the jet and the bucket under the condition of clear water and sediment laden water,it is found that after adding sediment particles,the expansion process of the jet after impacting on the bucket and the discharge process after it becomes waste water are affected: The shape of the water film formed by the jet changes,and the particles are concentrated in the working face of the bucket,resulting in the uneven distribution of water in the water film.Thus,the effective effect of water on the bucket is greatly reduced,reducing the energy conversion efficiency between the jet and the bucket,and then the average output of a single bucket and the total output of the runner are reduced,the efficiency of the turbine is also reduced.Compared with the particle diameter,its concentration can more affect the output of the bucket and runner,and then affect the overall efficiency of the turbine. |
PDF Full Text Request