The Discussion Of Disc Loss Calculation And Research Of Internal Flow Characteirstics For The Centrifugal Pump With Low Specific Speed Based On The Method Of Numerical Simulation

In recent years, with improvement of the level of computer hardware, CFDtechnology are widely used in calculation and optimization design of the pump, but ifthe calculation domains without before and after pump and mouth ring clearance forthe centrifugal pump with low specific speed, CFD technology can not accuratelypredict the performance prediction, because the disc friction loss is ignored.In this paper, the main model is a centrifugal pump with low specific speed, twokinds of calculation domain models is set up, one is compose of the impeller passagesand volute casing, and another is that of the front and back chambers,the sealclearance, the impeller passages and volute casing. FLUENT software is used tosimulate the six working condition, which is0.2Q_opt、0.3Q_opt、0.5Q_opt、0.7Q_opt、Q_opt、1.1Q_opt. And through contrasting the calculation and test, it finds that calculationdomains with before and after pump and mouth ring clearance can accurately predictthe performance prediction of centrifugal pump with low specific speed, andprediction of the shaft power and efficiency should be amended when calculationdomains didn’t contain before and after pump and mouth ring clearance,and revisedefficiency was closer to the experimental values. The method using disc friction losspower and volume losses of power to amend efficiency was more appropriate toamend efficiency.In this paper, two kinds of unsteady turbulent model, which are LES model andRNGk εmodel, are used to predict the performance and speed of impeller channelimport and export of the centrifugal pump with low specific speed, which shows thatit is not significant for the calculation results for the characteristic curve, but thetransient speed of some points have differences. And LES model can not only predictpulse phenomenon and impact phenomenon and vortex,but also can accuratelycapture the continuity of liquid flow near the leaf.By comparing the map of impellerchannel import and export speed, it is found that there is a large difference of twomodel of the point of concrete transient speed. It is found that liquid, which is close tothe tongue of the impeller, have apparent pressure pulsation. Moreover, it discussesthat grid number impact the result of LES model, and finds that the more gridnumbers, the more obvious for the separation vortex in the impeller runners andvolute casing, the more change for the amplitude of the pressure pulsation. Therefore,it think that less grid numbers can miss a lot of information.