Study On Optimization Of LUV Pump’s Casing Dimension Based On Numerical Simulation

LUV pumps, the main series products of KSB AG Pump and Valve Corporation,are mainly used as boiler circulation pumps. In industrial fields, the primaryrequirements for boiler circulation pumps are high safety and low costs. Thus, studyingthe methods to reduce costs, like optimizing the dimension of LUV pump casing, is thedemand from industrial fields.This study was developed by numerical simulation methods. Firstly, computationalfluid dynamics (CFD) technology was used to study the hydraulic performances ofLUV pumps with different internal casing diameters. An optimized internal casingdiameter was determined then. Hydraulic stability performance of the pump withoptimized internal casing diameter was also studied by analyzing the pressurefluctuation performance. Secondly, finite element method (FEM) technology wasused to study the stress safety performance of pumps with different internal casingdiameters, casing wall thickness and casing materials. Appropriate casing wall thicknessand casing materials were chosen.Reasonable CFD calculation method was set up. Fluid regions of extendedsuction nozzle, extended discharge nozzle, hub gap and shroud gap wereincluded in the geometric model. All the meshes were hexahedral type gridswith high quality. Turbulence model was set as SST k-ω in normaltemperature and normal pressure (NTNP) condition, and was set as RNG k-ε in high temperature and high pressure (HTHP) condition, which was determinedby y on blades. In the main calculation method, the working condition wasthe NTNP condition, and the seal ring was simplified as smooth ring gap. Thecalculations in HTHP condition supported the reference value of the predictionmethod in HTHP condition by combining calculation results in NTNP conditionand the Karassik correction formula. Independent calculations of diamondshape honeycomb seal ring and smooth ring gap seal ring were also developed,which supported the main calculation method. Independent calculations of sealrings provided a correction method when diamond shape honeycomb seal ringwas adopted instead of smooth ring gap, based on leakage. Pumps, with different internal casing diameters of0.750D40,0.875D40,D40and1.125D40, while D40was the internal casing diameter of the originalLUV pump, were studied by the CFD calculation method in this study. Thenormalized hydraulic efficiency of pump with0.750D40internal casingdiameter was greatly decreased by9.79%. The hydraulic performances of theother three pumps were close.0.875D40was chosen as optimized internalcasing diameter by considering both hydraulic efficiency and material costs ofpump casing.Pressure fluctuation performances of original pump and new pump withoptimized internal casing diameter were compared. No more hydraulic stabilityproblems were newly caused. At the same time, pressure fluctuationperformance in HTHP condition supported the reasonability of the assumptionthat the pressure load of pump casing’s internal surface was uniformlydistributed during the stress safety analysis.Self-coding program was completed in this study, which helped thecalculation of stress safety. The stress safety of new pump casing withoptimized internal casing diameter was validated. Based on the analysis ofstress safety performances of pumps with different internal casing diameters,different casing wall thickness and different casing materials, two optimizationcases were proposed. Case one is the pump casing with0.875D40internalcasing diameter, T0casing wall thickness and forge material. Case two is thepump casing with0.875D40internal casing diameter,0.875T0casing wallthickness and casting material.