| This paper mainly studies the change of hydraulic characteristics of the inlet section of the box inlet passage to the section of the horn.The box-type inlet runner is a common form of inlet runner.The size of the runner is mainly determined by geometric parameters such as inlet width,rear wall distance,suspended height and submerged depth.Reasonable flow channel structure design is not only conducive to improving the operating efficiency of the pump device,but also conducive to reducing engineering construction investment.Commercial software CFX was used to carry out three-dimensional steady and three-dimensional unsteady numerical simulation calculation for the box-type inlet channel pump device,and the water flow from the inlet of the outlet channel to the horn section and its hydraulic characteristics were accurately simulated.The main conclusions are as follows:(1)Through the determination of the optimal operating point,it is determined that when the impeller speed is 1250 r/min and the flow rate is 300 L/s.the pump efficiency reaches the highest value of nearly 82%.(2)Three-dimensional steady and three-dimensional unsteady numerical simulation of the box-type intake pump device were carried out respectively.By comparing the streamline distribution,pressure distribution and velocity distribution on the typical section,and calculating the hydraulic loss of the intake channel,the velocity uniformity on the typical section and the external characteristics of the pump device.It can be concluded that the hydraulic characteristic parameters of the box inlet passage are basically unchanged with time.Because of the influence of impeller rotation,the flow characteristic parameters of the horn section change little with time.(3)By using single factor analysis method,the geometric parameters of box channel width.suspension height,back wall distance and submergence depth are controlled,and the only variables are guaranteed.Under the three flow rates of 0.8QBEP,1.0Q1BEP and 1.2QBEP,the constant values are calculated many times,and the appropriate geometric dimensions are explored.The width of box inlet channel is controlled above 2.3 Di:the suspension height of bell tube can be reduced to(0.6-0.8)DL,and the optimum height is 0.7 DL;considering the construction investment,it is suggested that the back wall distance should be controlled within(0.9-1.1)DL and the optimum height should be 1.0 DL;considering the safe operation of pump device,it is suggested that the submergence depth should be controlled above 1.0DL.(4)In this chapter,the three-dimensional unsteady numerical simulation of the box-type intake pump device is carried out under the optimal operating conditions.The key research area is the inlet section and outlet section of the trumpet section.Twelve pressure fluctuation monitoring points and velocity fluctuation monitoring points are arranged in the circumferential direction and diameter direction of the section respectively,and the fluctuation distribution law of water flow through the monitoring points is analyzed.On the exit and import sections of the horn section,the main frequency of the fluctuation of each monitoring point is 4 times of the frequency conversion,that is,the blade frequency is the main frequency.From the inlet section to the outlet section,the pressure fluctuation amplitude decreases and the velocity fluctuation amplitude increases.The monitoring points of the inlet section of the horn section are affected by the inflow of the inlet passage,and are more affected by the blade rotation than the outlet section.The amplitudes of pressure and velocity fluctuations are larger. |
PDF Full Text Request