Investigation On Annular GAP Flow And Hydraulic Power Loss In Nuclear Canned Motor Pump

As new nuclear actor technology,advanced passive nuclear power plant is designed to reduce the leakage probability of primary loop,which is developed with the passive safety and simplified design concept by Westinghouse.In this system,a kind of canned motor pump(RCP)with flywheels is used to drive primary loop water(PLW)and it has distinguished integrity of pressure boundary(PB).Compared with shaft-sealed nuclear pump,the PLW goes into the narrow gap of canned motor so that the PB is significantly improved.The dynamic seal is changed into static seal under high temperature and pressure conditions.The seal's challenge is solved in the reactor coolant pump and the safety of the primary loop is highly improved,which shaft-sealed nuclear pump once faced.The system's safety is highly improved with new RCP,however,the hydraulic power loss is enlarged remarkably.According to the safety design for improving the PB integrity of RCP,this thesis mainly focuses on the hydraulic power loss of canned motor.Firstly,the velocity structures with vortexes are mainly investigated through analytical and experimental work.Second,the interface effect on energy transfer behavior is investigated in turbulent annular flow.Based on the velocity structures and energy transfer behavior,hydraulic power loss model is proposed to fast predict the energy consume of canned motor according to the separately flow model.According to this model,the energy dissipation behavior is analyzed and the high-density energy transfer behavior is revealed.(1)Velocity structures of annular gap flow with Taylor vortexTo reveal the velocity distribution along radial direction,the annular flow behavior is simulated by employing the commercial CFD codes.Firstly,the development of Taylor vortex is analyzed to reveal its effect on velocity structures with fixed and varied annular gap.The results indicate that the annular flow velocity structures are changed by Taylor vortex.The annular flow velocity gradients are reduced so that the torque behaviors are reduced when the gap width is enlarged.Second,the experimental setup is built and the experiments are conducted on this experimental rig.The simulation works have good agreement with the experimental measurements.Third,the analytical and experimental works indicate that torque behaviors increase with Taylor number;the larger the annular gap is,the slower the torque behaviors increase;besides,the torque behaviors with larger annular width are larger than that with smaller annular width.Through these works,the torque behavior of rotor can and flywheel are better evaluated in the nuclear canned motor pump.(2)Interface effect on torque behavior in turbulent annular flowTo evaluate the geometrical characteristic of micro structure effect on torque behavior,analytical work and experimental measurements are employed.First,the torque measurements are conducted to fit the exponential law.Second,the energy transfer behavior is divided into two parts,which one is viscosity energy transfer behavior and the other is convection transfer behavior based on energy transfer behavior model.Through measuring the energy transfer,the dominant energy transfer models are revealed.To evaluate the surface characteristic,the average roughness,peak roughness,Abbott Firestone curve,and surface area are employed.Based on energy transfer behavior in the annular flow,we find that peak roughness affects the convection energy behavior and surface area affects viscosity energy transfer remarkably.These work is validated on our experimental setup.(3)Predicting hydraulic power loss and efficiency of canned motorThe pressure flow and shear flow are simulated through CFD codes.The results indicate that shear flow mainly brings the hydraulic power loss.As the main loss source,the flywheel consumes one second of hydraulic power loss;the rotor consumes one third of hydraulic power loss;and the bearing consumes one sixth of hydraulic power loss.Besides,the shear hydraulic power loss has uneven distribution characteristic.Based on the prediction,the thrust bearing and cylindrical surface of flywheel have extremely large energy transfer density.Confined to the materials,the increasing rate of hydraulic power loss is larger than that of motor capacity.After the power loss distribution analysis,high-density energy transfer is identified as one of the key point when enlarging the capacity of canned motor pump.It has remarkable influence on efficiency of high-capacity canned motor pump.The investigation work mainly focuses on the velocity structures and energy transfer of annular flow through analytical and experimental works.Based on the velocity structure and energy transfer,hydraulic power loss model is proposed.After bi-level validation of scaled canned motor and AP1000 canned motor,the model is used to predict the power loss of CAP1400 canned motor pump.According to the model,the hydraulic power loss distribution is analyzed.And the high-density energy transfer is revealed in the canned motor.These works mainly try to get a comprehensive understanding the role of high turbulent internal flow of primary coolant water in canned motor and makes contribution to enlarging capacity of nuclear coolant pump.