1. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. College of Energy and Electric Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 3. College of Agricultural Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 4. Air Force Hospital of Eastern Theater Command, Nanjing, Jiangsu 210001, China
Abstract：In order to study the change of external characteristic parameters and flow pattern during the acceleration start-up of large tubular pumping units, a three-dimensional model of bulb tubular pumping units was built, UDF in Fluent software was used to control the start-up process of the gates, and dynamic grid technology of laying method was used to control the generation and elimination of grid at the gates. Setting S-A model as turbulence model, the transient numerical simulation of the whole flow channel for the start-up process of bulb tubular pump unit was carried out. The calculation results show that when the fast gate of tubular pump unit starts at 10 times the rated speed, the speed and flow rate of the unit will reach the rated speed and flow rate faster, and the instantaneous maximum back-flow rate will increase by 30% compared with that of the non-accelerated start-up. When the tubular pump unit is in the backward flow state, the pressure on the impeller blade passage near the hub pre-sents a gradually increasing distribution law from the impeller inlet side to the outlet side. When the unit is in the critical state of zero flow rate, the chaotic flow leads to further aggravation of pressure concentration and flow separation phenomenon, and the negative pressure area at the inlet edge of impeller is wi-dened and deepened.
