Research On The Particle Deposition Characteristic Of Air-cooled Turbine For Gas Turbine

Marine gas turbines work in a marine environment with high salt and high humidity for a long time.The sulfide generated by the impurities mixed in the gas under high temperature working environment will chemically react with Na Cl,the main components of the salt spray,to produce Na₂SO₄ in a molten state.These molten impurity particles enter the cascade channel with the main flow,destroying the thermal insulation coating on the surface of the turbine blade,and aggravate the corrosion of the alloy.The particles deposited on the surface of the blade will not only affect the flow and heat transfer characteristics of the surface,but also cause the ablation of turbine blade.For aero engines,working in an environment with a lot of dust pollution,some volcanic ash,sand and other impurities are sucked into the engine.The deposition of molten particles formed after high temperature heating in the combustion chamber will not only reduce the turbine’s flow area,affect the performance of the engine,but also partially block the film cooling holes,causing the corresponding failure of the cooling structure.In this paper,based on the dynamics of the particles entering the turbine cascade channel with the mainstream gas and the interaction between the particles and the wall,exploring the interaction criteria for adhesion and peeling of particles after collision with the surface,as well as sedimentation and rebound interaction criteria,Including the analysis and prediction of particle-wall collision dynamics.On this basis,the corresponding particle-wall surface deposition model is constructed for numerical simulation calculation.By considering the material properties of the particles and the contacting wall surface,the particle impact speed,angle,particle size and other related factors,the restoring deformation work of the particles and the wall adhesion work are calculated,the normal and tangential recovery coefficients of the particle rebound velocity are finally obtained.and the corresponding particle collision dynamics prediction model is established.For the cascade channel with no film cooling structure,under the critical velocity model,as the momentum Stokes number increases,the particle deposition efficiency on the blade surface and end wall firstly remains unchanged and then begins to decrease.Under the critical viscosity model,as the momentum Stokes number increases,the particle deposition efficiency on the blade surface and the lower end wall continues to increase,while the upper end wall firstly increases,then decreases,and finally increases.The increase of the blowing ratio does not necessarily improve the particle impact efficiency on the blade surface.On the contrary,it may increase the particle impact efficiency,but it will reduce the particle deposition efficiency on the blade surface.The effects on the particle capture efficiency on the upper and lower endwalls and the blade surface are not same.For a flat plate,under the same blowing ratio,the particle impact efficiency increases with the increasing of the trench depth.The effects of different trench depths on particle deposition distribution and film cooling efficiency are different under the different blowing ratios.For the blade,under the same blowing ratio,the existence of 0.8d trench increases the particle impact efficiency on the pressure surface of the blade,but the particle deposition and capture efficiency decrease.Under a small blowing ratio,the existence of the trench structure makes the cold air at the outlet of the film hole deviate from the lower endwall to the upper endwall,the film cooling efficiency is improved due to the increase of the spanwise film coverage.Although the film cooling performance in the groove is decreased due to the increase of the blowing ratio,the film cooling performance downstream of the groove is better than the original structure.