Numerical Computations Of Viscous Oil Flow And Performance For Centrifugal Oil Pumps

This research issue is one part of a project, which was fully supported by the key Research and Development Program for Outstanding Groups at Lanzhou University of Technology in 2002.Centrifugal oil pumps have found extensive application in petroleum and chem-petrol presses in China. The prediction of the pumps performance and through understand of the feature of flow in the pumps have an important practical significance and research potential for both improvement in hydraulic design and performance optimization. However, just a few of investigations into the numerical computation of both performance and viscous oil flow dynamics in the centrifugal oil pump are available currently. As a first attempt, The viscous fluid flow field in a whole centrifugal oil pump, which was served as the test model of LDV measurements, has been calculated numerically by using CFD software-FLUENT 6.1 in this thesis. Both pump operating point and fluid viscosity have been varied respectively in the computations. The 2D and 3D viscous flows in the cascade, rotating channel with rectangular-section and centrifugal pump impeller with suction pipe have been worked out by using FLUENT in order to estimate its computational accuracy. Meanwhile, the information associated with flow separation, shear stress at wall, secondary-flow, jet-wake construction and hydraulic losses has been obtained. The head coefficient and pressure coefficient over blade have been compared with their corresponding experimental data. The following results should been shown:(1) The number of mesh cells, but residual convergence tolerance can affect numerical results;the relative error of pressure coefficient with respect to experimental data is around 15%.(2) The development of relative velocity profile computed agrees well with that of measurement along the rotating diffusing channel with rectangular section, the jet-wake construction and secondary flow patterns at various cross-sections and the effects of flow rate on them also have a good agreement with the experimental data.(3) The relative error of computational head coefficient of the centrifugal pump compared with experiments is less than 6%, the distribution of the numerical head coefficient on blades agrees well that obtained by experiment;the hydraulic loss in the impeller is dominating and the loss in the section pipe is minor, furthermore, the variation of the loss in the impeller with the flow rate differs from that in the suctionpipe significantly.(4) A zone with high-relative velocity or low absolute total pressure and static pressure exists in the bend of shroud in impeller meridional plane;a low -relative velocity or high absolute total pressure and static pressure is available in the bend of impeller hub. A zone with high pressure or low relative velocity exists in the blade pressure side in blade-to-blade plane. There is also a zone with low pressure or high relative velocity in the blade suction side The area of the zone with low relative velocity reduces and that with high-relative velocity increases. The impeller developing a higher head in part-loading point is mainly due to the reduction of relative velocity in blade pressure side.(5) The hydraulic loss occurs on blade pressure side, trailing edge of blade and inside of shroud at design point, but on blade suction side and blade inlet tip and inside of shroud at part-loading point.(6) The head-flow rate curve computed agrees well with that of test, the maximum relative error of head with respect to experimental data is 6.67%, and the minimum error is 3.4%.(7) When the flow Reynolds number is less that 2300 in the suction pipe, the flow should be in laminar regime in the impeller and volute of the pump.