| Seal is the key part of mechanical and electrical equipment to prevent the leakage of working fluid and external impurities from entering the product.The loss caused by the clearance leakage of rotor stator can reach 22%-33% of the total loss of steam turbine,which has a great impact on the performance of steam turbine.Steam foil seal is a new type of flexible structure gas dynamic pressure seal,which has the advantages of small leakage and anti-wear,It is of great significance to the performance of steam turbine.Therefore,this paper takes the steam foil seal as the research object,and studies the dynamic and static characteristics of the seal respectively.In this paper,the velocity fluctuation in turbulent flow field is considered,the turbulence correction coefficient is introduced,and the compressible turbulent Reynolds equation suitable for high temperature and high pressure steam is obtained by combining with the equation of state of saturated steam under high temperature and high pressure.The static characteristics are solved by Newton iterative method and finite difference method.On this basis,the dynamic characteristics are solved by small disturbance method.Thus,the theoretical basis of this paper is given.By analyzing the axial velocity distribution,pressure distribution and leakage of the dimensionless seal clearance,the effects of different clearance,rotational speed,eccentricity,aspect ratio,half wave foil length and foil thickness on the static characteristics of the steam foil seal were studied.On the basis of obtaining the static characteristics of the steam foil seal,the effects of the above six parameters on the dynamic characteristic coefficients such as stiffness and damping of the steam foil seal are studied.The steam foil seal is applied to the steam turbine rotor system.The motion equations of the elastic shaft element,the rigid disk and the gas film force equation of the steam foil seal gap are established.On this basis,the motion equations of the steam turbine rotor system are obtained.Then the dynamic characteristics of the system are solved,and the finite element model of the steam foil seal rotor system is established,The unbalance response and critical speed are analyzed. |
