Research On The Characteristics Of Distortion Inflow And Its Control Method On Reactor Coolant Pump With Steam Generator

Nuclear energy is a clean energy with great potential to cope with the global energy shortage in the future.Reactor coolant pump is the key equipment to maintain the normal operation of the nuclear island system.Based on the passive design concept of AP1000,there is no longer a long pipeline at the inlet of the reactor coolant pump.Due to the lack of transition pipelines,this unique layout modification allows the high-temperature and high-pressure fluid from the steam generator to be poured directly into the reactor coolant pump without being rectified,so that the inflow of the reactor coolant pump is no longer the uniform inflow assumed in the design,but forms the inflow.distortion.The AP1000 reactor coolant pump has a design life of 60 years.In such a long service period,the inflow distortion caused by the steam generator always exists.In addition,the inflow of the reactor coolant pump is affected by the steam generator lower head,and the geometry is more complicated than that of the elbow pipe.The power of a single AP1000 reactor coolant pump is about 5.2MW,and each nuclear equiment has 4 reactor coolant pumps running at the same time.The energy loss of the reactor coolant pump caused by inflow distortion is huge.Therefore,in order to avoid the blade fatigue damage caused by the inflow distortion of the reactor coolant pump during long-term service,and to guide the independent design of the domestic reactor coolant pump,it is urgent to reveal the formation mechanism of the inflow distortion of the reactor coolant pump caused by the steam generator.The law of influence on the hydraulic dynamic load of the reactor coolant pump blade.Based on the research project of the973 Program,this paper proposes a method to comprehensively characterize the inflow distortion and reveals the formation mechanism and evolution of the inflow distortion in response to the key problem of the coupling effect of the flow field between the reactor coolant pump and the steam generator.The characteristics of the inflow distortion are studied.And its impact on the flow field of the reactor coolant pump.Relevant research results have important theoretical significance and application value for the independent research and development of our country's nuclear power equipment and the safe operation of long-term service in the future.The main research contents and results are as follows:(1)A test platform was designed and built,and a joint calculation model of the steam generator lower head and the reactor coolant pump was established.The inflow distortion caused by the steam generator lower head and the reactor coolant pump were explored from both test and simulation aspects.The influence of the flow field at the inlet of the pump.The test results found that,affected by the outflow of the steam generator lower head,there is an approximately constant local low pressure zone,a local low speed zone and an eccentrically distributed vortex zone in the inlet section of the reactor coolant pump.At the same time,along the circumferential and radial directions,the axial velocity distribution at the inlet of the reactor coolant pump is greater than 40% of the average velocity;it is verified that the inflow distortion caused by the steam generator exists at the inlet of the pump,and the velocity distribution of the inflow distortion caused by the steam generator lower head is solved.Further simulation analysis of the details of the flow field in the pump,by comparing the characteristics of the reactor coolant pump flow field in the two cases of inflow distortion and uniform inflow,it is concluded that the inflow distortion reduces the head and efficiency,causing locally high turbulent kinetic energy and turbulent dissipation.The local high value indicates that the inflow distortion caused by the steam generator has deteriorated the flow field of the reactor coolant pump.Under the condition of inflow distortion,the axial force of the impeller is increased by about 1.1 times,but the amplitude of the axial force change is increased by about 10 times.The radial force of the impeller is increased by about 3 times,and the variation range of the radial force is also increased by 3.5times.In addition,the direction of the radial force changed about 90 degrees,indicating that the inflow distortion not only changed the magnitude of the load value of the fluid in the pump,but also changed the direction of the load.This shows that due to the influence of the steam generator,there is an approximately constant large-scale low-pressure zone at the inlet section of the reactor coolant pump,which reduces the axial force,but when the rotating blades periodically pass the low-pressure zone,it will be affected.The pulse load in the axial direction increases the fluctuation of the axial force.(2)The regularized spiral analysis method is used to analyze the movement structure of the flow vortex in the reactor coolant pump,and the reason for the deterioration of the flow field in the pump caused by the inflow distortion is analyzed from the perspective of the vortex.The vortex generated by the inflow distortion follows the fluid to move in the direction of the impeller.The flow passages of the impeller produce asymmetrical or even oppositely rotating vortex core regions,indicating that the inflow distortion has an adverse effect on the pump flow field.The symmetry of the flow field in the turn channel is broken,which reduces the stability of the impeller.An analysis method based on the influence relationship between the complicated geometric domain and the inflow distortion based on the adjoint solution is proposed,and it is revealed that the area with the most significant influence on the inflow distortion is concentrated in the intersecting area between the steam generator lower head and the inlet pipe of the reactor coolant pump.Three indicators of velocity distortion,average deviation angle,and vortex distortion are proposed to comprehensively evaluate the inflow distortion caused by the steam generator,quantify the inflow distortion phenomenon of the reactor coolant pump,and fully reflect the flow pattern characteristics of the inflow distortion.It provides an important reference for comprehensive evaluation of inflow distortion characteristics.(3)Based on the analysis of the formation mechanism of the inflow distortion,the idea ofimproving the negative influence of the inflow distortion on the inner flow field of the reactor coolant pump is proposed.A preliminary optimization method to reduce inflow distortion is proposed.The baffle effectively reduces the influence of the inflow distortion on the reactor coolant pump;the calculation and comparison of the flow field at the outlet of the impeller,optimizes the inlet flow field of the reactor coolant pump,verifies the feasibility of the optimization scheme,and achieves the reduction of inflow distortion and thus reduction.And based on the quasi-Newton optimization algorithm,the parameter calculation empirical formula of the baffle device is obtained,which is convenient to determine the optimal design critical dimensions in a short time.