Design Study Of Non-contact Screw Steam Seal At The Shaft End Of Steam Turbine

Steam turbine is one of the three main engines of thermal power plant,its operation will directly affect the economic benefits of the entire thermal power enterprise,therefore,improving the operating performance of the steam turbine can improve energy utilization and promote green production.However,the existing turbine shaft sealing system is limited by the design structure,and there are still many defects,such as easy to cause rotor grinding,resulting in increased steam turbine air leakage,etc.,these defects not only reduce the overall efficiency of the steam turbine,but also affect the economy of power generation.Therefore,on the basis of not changing the shaft end length of the steam turbine,the inner and outer two sections of the three-stage straight tooth ring type steam seal of the shaft end of the original steam turbine are designed as a non-contact spiral steam seal with opposite rotations,and the thread rotation gas repulsion effect is used to reduce the steam leakage inside the cylinder and the air leakage outside the cylinder,thereby reducing the steam leakage loss of the turbine and improving the efficiency of the turbine generator set.In order to verify the sealing effect of the new spiral steam seal,the internal flow of the new and old steam seals under the same working conditions was simulated and analyzed by using finite element software,and the three-dimensional model of comb tooth steam seal and spiral steam seal of the same size was constructed,and the steam leakage and air leakage of the new and old steam seals were compared and analyzed to verify the implementability of the spiral steam seals.According to the simulation data,the air leakage of the new spiral steam seal is reduced by 13% compared with the comb-tooth type steam seal,and the air leakage is reduced by about 8%,and the fluid forms a more energy-consuming vortex movement in the spiral steam seal,which verifies the feasibility of the new steam seal.Using the single variable method,a unified reference model was established,and the effects of many parameters such as rotation speed,dynamic viscosity,sealing length,sealing gap,groove depth,relative groove width and thread elevation angle on the sealing capacity of spiral steam seals were briefly analyzed.At the same time,it also provides a theoretical basis for the operation characteristics and reliability analysis of the seal.The research results of this thesis will provide a reference for the application of new screw shaft seals on turbine shaft ends and the flexible transformation of steam turbine shaft end steam seals.