Study On Internal Flow Numerical Analysis And Optimization Method For Vertical-shaft Centrifugal Pump With Space Guide Vane

Vertical long-shaft pump, one type of centrifugal pump with space guide vane,with the advantage of simple piping, compact structure, wide optional range of capacity and head, and strong adaptability to water quality, finds widespread application in irrigation, metallurgical mining, power supply, municipal administration, etc. Although it was introduced to China and got applied quite early, recent years saw the comparative delay in its development, as inefficiency and poor stability still exist comparing with foreign advanced products. Additionally, the National Twelfth Five-year Plan also clarifies request to develop new energy-efficient, advanced environment friendly equipment and product. In this sense, it is urgent and significant to conduct performance optimization for current long-shaft pump products.This paper starts from performance analysis of the original model of CPLC vertical long-shaft pump and presents the performance optimization study based on hydraulic loss ratio of flow components and the inner flow field. To match the impeller and space guide vane, and optimize key geometric parameters inside, performance matching equation and area ratio coefficient equation are established by theoretical deduction. The author then selects key factors associated with pump performance and adopts orthogonal combination design to get the optimal combination scheme for prototype testing to finalize a new hydraulic model with better performance.This paper also investigates the influence of vane cutting in impeller inlet and outlet on external characteristic parameters and inner flow field employing a method combining numerical simulation and experimental verification. By cutting the blade to modify the inlet, the situation of sharp drop of pump head in large flow can be improved. As centrifugal impeller and space guide vanes are used as flow components in long-shaft pump, this special structure may lead to large error when cutting the impeller following the traditional impeller-cutting law. To address this problem, numerical simulation is conducted to do the parallel cutting and bevel cutting, the result of which can modify the cutting index of external characteristic parameters. In this way, another equation is proposed, which is expected to be more applicable to impeller cutting in long-shaft pump.To explore the pressure fluctuation phenomenon resulted from impeller-guide vane rotor-stator interaction between vertical long-shaft pump impeller and space guide vane, original model of vertical long-shaft pump is selected as the study object and unsteady flow information of each monitoring point in the flow field are obtained by transient numerical computation. The time-domain pressure fluctuation information is then transformed into frequency-domain information by FFT(fast Fourier transform) to conduct an analysis based on the spectrum in terms of pressure fluctuation type, source, intensity and propagation rules. Meanwhile, the author further analyzes the formation mechanism and propagation rules of pressure fluctuation in rotor-stator interaction area according to the transient computation results.In conclusion, this paper provides further evidence and methods for hydraulic performance optimization of long-shaft pump with space guide vane, performance study of impeller cutting, as well as pressure fluctuation generated in rotor-stator interaction area. Moreover, it also has its own reference value for further studies on other types of fluid machinery.