Modeling Of Fluid Resistance And Analysis Of Flowrate In Canned Motor Of Nuclear Coolant Pump

The core feature of the 3^rd generation nuclear pump is that after introducing high pressure water into the canned motor,the pressure boundary is changed to static seal from dynamic seal,so the security level is highly improved with less chance of leak from the primary loop.What’s more,the introduced fluid can help dissipate more heat of the motor.However the introduction of fluid can bring great challenge to the reliability of canned motor.The three dimensional flow channel of the cavity inside canned motor is so complicated that it is very difficult to predict the flowrate of internal cooling circuit.The thesis aims to build the model of this circuit,simplify its channel by topology,analyze flow resistance and find out the impact of rotor rotating in real condition.So the flowrate can be predicted to provide reference for motor heat dissipation.The detailed contents of this thesis are as follows:Firstly,the model of internal cooling circuit inside canned motor was established from its design.The simplified topology circuit and its equivalent water route model were built accordingly.The hydraulic head of auxiliary impeller was estimated by theoretical analysis and experimental data.The flow field of rotor/stator can flow channel,upper journal bearing and flywheel flow channel,upper outlet flow channel,lower journal bearing flow channel,double-direction thrust bearing flow channel,throttle ring flow channel were all analyzed and their flow resistance plus heat exchanger’s resistance were calculated by computational calculation methods.The flow resistance of throttle ring flow channel was found out to be non-linear changed with respect to main size factor.Secondly,the distributions of pressure drop under different rotor speeds were measured by a scale test rig.The experimental results indicate that with the rotational speed increasing,the pressure drop between inlet and outlet also increases,the original empirical formula of friction factor in an annulus channel is no longer suitable and should be revised.The mapping relationship between the revision factor and ratio of tangential/axial Reynolds numbers was obtained through data analysis.Thus the revised formula of friction factor by tangential flow was derived.In order to verify the accuracy and universality of this new formula,the flow characteristics and pressure drop of the fluid in scaled test rig and also in canned pump were studied by CFD method.The results show that the bias of friction factor calculated by simulation and the revised formula is small enough to be considered as reasonable.The law of friction factor in the annular channel between rotor and stator of the canned pump in different conditions was found out by simple equations consequently.Finally,the flowrate and pressure predictions of internal cooling circuit were analyzed based on previous study.The throttle ring flow channel resistance was proved to show great significance to ratio of upper and lower branch flowrate.The overall flowrate was deduced considering the flow resistance revision by rotor rotating and the result was very close to actual working condition data to show that the whole modeling,calculation is reasonable.The flowrate of main channels and relative pressure of mains flow nodes under the rated operation condition were predicted accordingly.The mapping relationship between overall flowrate of internal circuit and rotating speed was found out to be just simply proportional by theoretical interpretation as well as experimental results from scaled test rig.This thesis shows some encouraging results of internal cooling circuit modeling,flow resistance calculation and flowrate prediction.These results will help predict flowrate as well as flow resistance inside canned motor so that they can have a better understanding of the design for AP1000 canned motor.