A Numerical Study Of Wet Steam Non-equilibrium Condensation Flow In Turbine Last Stage Cascade

Steam turbine is the main device to provide power for electric industry. It is ofgreat significance to improve the work efficiency and operational safety for energyconservation,emissions reduction and the improvement of life level. The existence ofnon-equilibrium condensation of wet steam flow not only restricts the economiccharacter but also poses a serious threat on the safety of the operation of steam turbine.Wet steam flow characteristics are analyzed in the paper. The establishment of wetsteam two-phase non-equilibrium condensation flow numerical model and thedevelopment of condensation and droplet growth model are reviewed. Several internaldesiccant methods inside the turbine and the study of heterogeneous condensation floware introduced. Based on the concept of double fluid model, homogeneous andheterogeneous non-equilibrium condensation flow model of wet steam is derived. TheVirial equation is used to consider the real gas effect. Secondary development interfaceof FLUENT software is used to realize the loading of real gas load model and numericalmodel.The wet steam uniform non-equilibrium condensation flow of Laval nozzle andBakhtar two-dimensional cascade is simulated respectively and the condensationmechanism and the distribution of important physical parameters in the flow field arestudied. Compared with experiment results, it shows that the calculation modeldeveloped in the paper has high precision. Two-dimensional blade with differentdehumidifying groove structures is taken as the research object in the paper. Theinfluence of different dehumidification groove structures on the condensation processare analyzed, the reasonable design of dehumidification slot can effectively slow downthe process of condensation nucleation, reduce the loss caused by the phase transition.Based on the two-dimensional cascade, the paper analyzed the change of physicalparameters of heterogeneous and homogeneous condensation flow field with particlesize of1.0×10^-9m and concentration of1.0×10¹⁸1/kg, besides this, The influence ofparticle concentration at the entrance and the change of particle size on heterogeneouscondensation flow was considered by numerical simulation. The study found thatcondensation in heterogeneous condensation flow occurred earlier and more even andheterogeneous condensation can effectively slow down the non-equilibriumcondensation.