The Analyse And Research On Flow Stability And Structural Strength Coupling Of Large Diffuser Entrifugal Pump

A large diffuser centrifugal pump,which is several hundred times larger than conventional centrifugal pumps,possesses high flow rate and power characteristics.Because it directly affects the operating cost of pump stations,the efficiency requirements for these pumps far exceed the standard efficiency of centrifugal pumps with variable speed in China.Additionally,the flow excitation characteristics of diffuser centrifugal pumps are complex,resulting in high-energy pressure pulsation and transient hydraulic excitation caused by frequent shutdowns and state changes.These factors directly affect the flow stability and operational reliability of the unit.Due to the challenges in design and manufacturing,The core technology is controlled by several well-known foreign companies,such as Andritz and Ebara.Against this background,this article conducts in-depth research on the flow stability and structural strength of pumps by integrating product development with engineering applications.This dissertation focuses on a model pump of the large diffuser centrifugal pump.Through extensive literature research,the following main work has achieved innovative research results:1.Proposed a method for calculating the transient process of the prototype unit based on the water column separation model.This method obtained hydraulic performance parameters,pipeline pressure,and changes in pressure regulation chamber water level under steady-state conditions and hydraulic interference conditions.The flow-solid coupling method was used to statically model the main force components.By analyzing theoretical strength,equivalent stress,and deformation,the hydraulic characteristic parameters of the unit were integrated,the strength reliability of key components was solved,and the impact of multiple weld repairs on strength and the influence of the impeller’s heat-affected zone organization and mechanical properties were analyzed.2.Proposed a non-steady flow structure and pressure pulsation excitation numerical calculation method based on the RANS model inside the model pump.This method determined the main excitation source,the main excitation frequency,and the spatio-temporal distribution of pressure pulsation in the typical region of the pump under different working conditions.It also clarified the dynamic and static interference excitation effect.3.Used the Ω-vortex recognition method to describe the evolution of the impeller wake vortex,the interference stator blade,and the development process in the flow passage in detail.The vortex flow diagnosis method(BVF)was used to analyze the flow structure on the surface of the guide vanes and identify areas of poor flow in the pump.Additionally,based on the entropy production theory,the energy dissipation coefficient was introduced to evaluate flow dissipation phenomena in the pump.This provided intuitive information on energy loss inside the pump,revealing the law of flow energy dissipation.The aforementioned results were applied to the model pump test bench at the North China Institute of Water Conservancy and Hydroelectric Power of the South-to-North Water Transfer Project in Tianjin.Theoretical and methodological validations were conducted through energy performance tests,cavitation performance tests,and full feature tests including negative flow rate and turbine operating conditions.