Influences Of Axial-flow Pump Impeller And Pumping Station Intake Design On The Flow Pattern At The Inlet Of The Impeller Chamber

A large pumping station with low head has characteristics of low head, large discharge and long operation time. Therefore, it is extremely important to increase the reliability and efficiency of the pump system.The flow pattern at the inlet of the impeller chamber has greatly influence on the safe, stable and efficient operation of the pump. Because the factors of influence on the flow pattern at the inlet of the impeller chamber of axial-flow pump are complex, there are many different understandings of pre-swirl flow at the inlet of the impeller chamber at home and abroad. With a broad perspective, the problem of the pre-swirl flow at the inlet of the impeller chamber was studied comparatively in depth from two aspects: impeller of axial-flow pump and pump intake design.The significance of the studies in this paper are that as follows:clarifying the various vague understandings on the pre-swirl flow at the inlet of the impeller chamber of axial-flow pump in the past, pointing out the importance of pumping station intake design for the flow pattern at the inlet of the impeller chamber, providing the basis for design theory and method of pumping station intake design.The idiographic contents include several aspects as follows:(1) The problem of the pre-swirl flow at the inlet of the impeller chamber of axial-flow pump was studied by the methods of both3D turbulent flow numerical simulation and model test;(2) The problem of the pre-swirl flow at the inlet of the impeller chamber of the vertical axial-flow pump system was studied by the methods of both3D turbulent flow numerical simulation and model test;(3) The influence of pumping station intake design on the pre-swirl flow at the inlet of the impeller chamber of axial-flow pump was analyzed;(4)Characteristic of the American National Standard for Pump Intake Design was analyzed in terms of the influence of intake flow pattern on flow pattern at the inlet of the impeller chamber, and the model test for a project layout of pumping station and sluice which referred to this standard was presented; The main conclusions that are obtained via the studies on the problem of the pre-swirl flow at the the inlet of the impeller chamber are as follows:(1) The influence of the axial-flow pump impeller on the flow pattern at the inlet of the impeller chamber1, When the axial-flow pump works on the normal operating condtions, the direction of flow at the inlet of the impeller chamber is axial, the pre-swirl flow does not exist.2, When the axial-flow pump works on the small flow rate operating condition, the flow at the outer ring of the inlet of the impeller chamber is pre-swirl with the same direction of impeller rotating, the flow at the inner ring flow into the inlet of the impeller chamber axially, while the flow at the middle ring swing comparatively obviously. It was perliminary analyzed the second backflow in axial-flow pump bring about the backflow at the local region before the impeller chamber. From the perspective of the external characteristic the small flow rate operating condition is located at saddle area of curve-fitting of pump performance.3, During the start-up process of axial-flow pump, the flow in front of the inlet of the impeller chamber is in a state of small flow rate flow which is transient and unstable.(Ⅱ) The influence of pumping station intake design on the flow pattern at the inlet of the impeller chamber1, Whether the pre-swirl flow exist at the inlet of the impeller chamber or not is mainly effected by the intake flow pattern, the intake design has obviously influence on the flow pattern at the inlet of the impeller chamber, more attention should be paid to studying the intake design unified from the perspective of the system in the future.2, From the perspective of the influence of intake flow pattern on flow pattern at the inlet of the impeller chamber, the characteristics of American National Standard for Pump Intake Design were summarized as follows:(1) The conception of the swirl angle was introduced which can quantitative express the intensity of the flow pre-swirl at the inlet of the impeller chamber;(2) The device swirl meter was introduced to measure the swirl angle;(3) The swirl angle was emphasized as the main indicator to test pumping station intake design; (4) In the hydrualic model test of checking up the pumping station intake design, the water supply pump was used to simulation the flow rate, and the swirl meter was used to instead of the model pump;3, The improved scheme, which could further improve the intake flow pattern, was presented and it was suggested to be used to the project;4, At the present, the model test regulation for the intake design of pumping station has not been promulgated in our country, it is suggested to strengthen the research on the American National Standard for Pump Intake Design, and be ready to formulate the corresponding test regulation at a proper time.