| Nuclear power has the advantages of low pollutant discharge,energy saving,high power generation efficiency and low raw material cost.With the continuous development of engineering technology,the safety of nuclear power is getting higher and higher.The nuclear power as a future energy industry,an important direction of development has become a worldwide consensus.In China's energy structure adjustment,nuclear power has always been given high expectations.At present,China's nuclear power autonomy has achieved excellent results,but in the nuclear main pump and other key technologies on the existence of short board.The nuclear main pump(reactor coolant pump group)is one of the most important nuclear island one main equipment in the PWR nuclear power plant.It is the only rotating equipment in the nuclear island.Its function is to drive the radioactive high temperature cooling Continuous circulation of the core to achieve the heat exchange between the core and the steam generator,resulting in high-pressure steam,through the steam turbine and turbine generator to achieve power generation.The design and manufacture of nuclear main pump is a major technical problem encountered in the process of nuclear power autonomy.In order to solve the problem,the relevant researchers must devote more time and energy to further study and find a solution.In order to maximize the protection of nuclear island safety,nuclear cooling function of the main pump not only need to meet the normal work needs of the reactor,but also be able to withstand the test of various types of accident conditions,such as water,the audience power,Shaft and other serious accidents.This paper studies the running characteristics of the main pump of the AP1000 nuclear core pump in the accident process,and provides an important basis for optimizing and improving the nuclear main pump.At present,there are many researches on the small nuclear accident of nuclear main pump,but there is little research on the operation of nuclear main pump in nuclear accident.This phenomenon is caused by the difficulty of the card shaft due to the varying degrees and the performance of the card shaft.Coupler rupture,bearing lubrication system failure and other reasons caused by the shaft resistance torque must be the same,the card length and duration of the curve with the time curve is not the same.In this paper,the experimental and simulation research to overcome the above difficulties,the small break under the card shaft accident AP1000 nuclear main pump external characteristics and its flow mechanism to do a lot of research,including the following:(1)To optimize the expression of the four quadrants of the existing nuclear main pump,and to deduce and introduce the normalized expression method.This method overcomes the drawbacks of the four-quadrant curve method,which can pump the main pump in full speed.The change in external characteristics under full flow is expressed by as few curves as possible.AP1000 core main pump card shaft accident is an unsteady transient transition process,flow,head,impeller speed and other external parameters with the rapid changes over time,this process cannot use the conventional four-quadrant expression to describe,but can be used The normalization method is expressed concisely and expressly,which is of great benefit to the understanding and further study of the external characteristics of the nuclear pump shaft accident process;(2)The AP1000 nuclear main pump prototype was tested and found that the severity of the CA-axis accident had a great influence on the total speed of the impeller from the rated speed to the complete stall,and the change of the flow rate had little effect on the severity of the card shaft accident.The initial value,the final value and the change curve of the pressure pulsation in the vicinity of the upper surface of the pump chamber are almost the same,but the amplitude is different,and the pressure value near the upper surface of the pump chamber has been reduced to the lowest value until the impeller is completely stopped.The influence of the small break condition on the flow of the shaft and the change of the impeller speed is small,and the influence of the pressure pulsation in the vicinity of the upper surface of the pump chamber lies mainly in the range and amplitude of the pressure fluctuation;(3)Using CFD to simulate the CA axis of the main pump of the AP1000,it is found that the fluctuation frequency of the flow velocity and pressure at the exit of the impeller is reduced and the velocity of the flow velocity gradually decreases The vortex gradually increases,the vortex gradually reaches the peak,and then the vortex gradually diverges,the degree of eddy current,the vortex gradually increases,the pressure amplitude gradually decreases,the impeller,guide vane,the pump cavity flow gradually disorder,the flow of components within the eddy current development,decline;(4)The use of CFD simulation AP1000 nuclear main pump in the small crack under the card shaft accident found that the initial nuclear main pump head,shaft torque,power changes with a small degree of hysteresis,the more serious the lag is more obvious(Referred to herein as the low pressure zone)extending from the pump inlet to the pump outlet during the accident,where the bubble accumulation area(region with a gas content higher than 5%)is completely contained in the low pressure zone,And mainly distributed in the back of the blade,the highest gas content in the impeller at the interface between the low pressure zone and the high pressure zone,with the card shaft accident continues,the pump low pressure area and bubble distribution area is shrinking,With the blade back to the front of the front plate position;small break under the card shaft accident in the pump liquid flow caused by bubble burst collapse interference in the impeller high and low pressure area at the junction of chaos,the pump flow rate as a whole decreased Trend,but the decline and the shock situation is different,after the accident,the main pump impeller on the fluid power of the process of change and basically no small break when the conditions are basically the same,but there are also small differences,the same The process of impeller radial force coherence change is similar to that of no small break condition,but only in the first 0.1s of the accident,there is a steep process. |
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