Numerical Study On Excitation Force And Dynamics Characteristics Of Reactor Coolant Pump Wear-ring Seal

Nuclear energy is a new type of clean energy,which can be converted into electric energy by nuclear power plant.The reactor coolant pump is the key equipment of "hualong-1"(hpr1000)nuclear power plant,which plays an important role in controlling the cooling water circulation.The reasonable sealing structure is of great significance for the efficient and stable operation of the reactor coolant pump system.Under the effect of assembly,machining error and shaft bending,the rotor is eccentric in actual operation,the circumferential pressure distribution in the seal gap is uneven,and the generated seal excitation force brings unstable factors to the operation of the reactor coolant pump rotor system.Therefore,it is necessary to explore the influence of the rotor eccentricity on the seal excitation force.In this paper,through the numerical calculation method,we designed different wear-ring eccentricity schemes,considered different wear-ring seal structure,and explored the influence of the eccentricity of the reactor coolant pump wear-ring on the excitation force and dynamic characteristics of the rotor seal.Firstly,based on the plane wear-ring structure,this paper explored the influence of rotor eccentricity on the flow characteristics and seal excitation force in the clearance region of reactor coolant pump,and made a comparative study from the two aspects of no eccentricity and eccentricity.The model of reactor coolant pump was scaled reasonably,and the reliability of the selected model was verified by comparing the numerical calculation results and experimental results of the scaled model of reactor coolant pump.Three kinds of eccentric rotor models with eccentricity of 10%,30% and 50% were selected to carry out the whole basin grid division,and the gap flow under different rotor eccentricity schemes was simulated.The results show that the change of eccentricity has little effect on the hydraulic performance of the impeller.With the increase of eccentricity,the leakage of the wear-ring first decreases and then increases,and reaches the minimum value,reduced by 43.6%,when the eccentricity is 30%.When the rotor has no eccentricity,the pressure and velocity in the clearance region are uniformly distributed in the circumferential direction,and the radial force of the rotor is uniform at this time,and the operation is the most stable;with the increase of eccentricity,the distribution of the circumferential pressure and velocity in the clearance region is uneven,especially when the eccentricity is 30%The results show that the circumferential motion is strengthened,the distribution of pressure and velocity is the most uneven,the pulsating amplitude of the corresponding seal excitation force is the largest one,and the stability of the rotor is the worst one,followed by the eccentricity of 50%,and the eccentricity of 10%.Secondly,the influence of seal structure on the flow characteristics and seal exciting force in the gap region of reactor coolant pump under different eccentric schemes was studied.Three kinds of seal structure,plane seal,labyrinth seal and screw seal,were designed.The results show that when the rotor is not eccentric,the leakage of plane seal is the largest one,labyrinth seal is the second one,and spiral seal is the smallest one,which can be reduced by 93%.The pressure and velocity in the clearance area are uniformly distributed in the circumferential direction under the three kinds of wear-ring schemes,and the pulsation amplitude of sealing excitation force under the plane seal structure is the smallest one,The rotor is the most stable,labyrinth seal is the second one,and spiral seal is the worst one;Compared with plane seal,labyrinth seal and spiral seal can reduce the excitation force under the other three eccentric schemes;The labyrinth seal has the best effect,especially when the eccentricity is 30%,it can significantly reduce 61%.Finally,the influence mechanism of different parameters on t he rotor dynamic characteristics of reactor coolant pump was studied.The results show that the larger speed and pressure difference,the more pressure distribution in the clearance region and the effect of whirl ratio on sealing force is more significant;with the increase of rotating speed,the absolute values of stiffness coefficient and damping coefficient increase;with the increase of pressure difference,the absolute values of stiffness coefficient and direct damping coefficient increase,while the c ross damping coefficient first decreases and then increases;among the three kinds of wear-ring sealing structures,the stiffness and damping coefficient of plane sealing structure are the largest one,followed by spiral seal and labyrinth seal.At the sam e time,it is found that the increase of speed and pressure make the whirl coefficient increase and the instability of rotor operation increase.Among the three seal structures,the whirl coefficient of labyrinth seal structure is the smallest one,the stability is the best one,the spiral seal is the second one,and the plane seal is the worst one.