Experimental And Numerical Simulation Study Of Particle Deposition On The Turbine Blade Surface

When the airplane is flying through the air containing large concentrations of sand,fly-ash and other particles,these external particles would be sucked into the aero-engine.They would undergo phase transition or maintain the solid state through the combustor and subsequently travel towards the turbine blade along with the high-temperature airflow.Deposition may occur under the interaction between particles and blade surface.It affects heat transfer and aerodynamic performance of the turbine blades,and even worse,results in blockage of film cooling holes and local ablation.Those would greatly shorten the engine performance and life.Eventually,the engine needs to be replaced ahead of schedule.Consequently,experimental and numerical simulation are carried out to investigate the behaviors and rules of particle deposition on the turbine blade surface.It is of significance to provide the theoretical basis and technical support for lowering of particle deposition and improving of service life and adaptability.First,the particle deposition was studied on the turbine blade through the actual phenomenon observation.Based on the dimensional analysis,the key nondimensional parameters for modeling of microparticle deposition behaviors were determined,and an applicability analysis was performed on the accelerated deposition test law.Experiment methods to simulate microparticle deposition were further developed at ambient and high temperatures,respectively.Then,particle phase governing equations were derived based on analysis of forces on particles.A numerical model for simulating particle deposition was developed considering the particle-wall interaction,particle transport and deposition behaviors.A set of numerical simulation methods was developed for particle deposition.Next,the particle deposition on a flat plate was simulated experimentally and numerically at ambient temperature with the experimental and numerical simulation methods developed herein,respectively.The effects of test parameters,such as wax mass flow rate,attack angle,blowing ratio,and existence of film cooling holes,were explored and the mechanism behind particle deposition affected by cooling airflow was revealed;The transverse trench configuration was designed to control the near-wall cooling air flow regime,based on the characteristics of the particle deposition on the plate affected by the cooling air.Experimental investigation and numerical simulation were conducted to explore the effect of transverse trench configuration on the deposition behavior and provide mechanistic insight into deposition inhibition.Finally,the particle deposition on a three-dimensional air cooling turbine blade was simulated both experimentally and numerically at high gas temperature.The independent effects of gas temperature and transverse trench configuration were studied to determine the change in deposition mass and thickness.Computed results were compared with experimental results to validate the numerical simulation method.The main conclusions of the above research can be summarized as follows:(1)From the experimental and numerical simulation of particle deposition on the flat plate at ambient temperature,it was found that for the pressure side,the bigger attack angle could result in the larger deposition mass by enlarging windward area for capturing particles.However,it has little effect on the deposition for the leading edge;The higher particle concentration leads to heavier deposition mass on the pressure side and leading edge of the plate;The accelerated deposition tests were conducted by increasing particle concentration and shortening test duration on the principle of equivalence,with total mass of sand particles held constant.The difference in the amount of deposition on the pressure side was below 15%,which provesthe accelerated deposition test law is satisfied,but it is imprecise to predict the mass of deposition at the leading edge.(2)For the film cooled flat plate,experimental and numerical simulations of particle deposition at ambient temperature revealed that there was evident deposition downstream of the film cooling holes on the pressure side.This is because jet vortices form after the mixing of the film-cooling jet and mainstream,further resulting in more particle deposition on the flat plate.Besides,entrainment effect is enhanced with blowing ratio increasing,which contributes to particle deposition.(3)For the flat plate with film cooling holes in various transverse trench configurations,deposition tests and numerical prediction revealed that the transverse trench configuration can lower the deposition mass.This is because the transverse trench configuration reduces the jet momentum and then the cooling air spreads spanwise,which weakens the entrainment effect and particle deposition.The narrower or deeper trench could result in lighter deposition mass on the pressure side.At the depth-to-width ratio of 0.5,there is a 25% relative deposition mass reduction.The computational predictions of the effect of different transverse trenches are consistent with the experimental simulations.(4)For particle deposition on the turbine blade with film cooling at high gas temperature,both experimental and numerical simulations indicated that deposition mainly occurs at the leading edge and regions downstream of the film cooling holes on the pressure side;The rise in the gas temperature accounts for the increase in the blade surface temperature,which further leads to larger deposition mass.Besides,as the gas temperature approaches the particle melting temperature,increasing deposition rate can be observed;A good agreement is obtained between the numerical calculation and the experimental data in terms of deposition mass varying with the gas temperature,and the relative error of the deposition mass is 4.5% at the gas temperature of 1626 K.(5)After the transverse trenches were installed on the blade,deposition decreased on the blade surface.The inhibition effect mainly occurred in the trench and downstream of the trench.Deeper trench could result in lower capture efficiency.As the depth-to-width ratio reaches 0.53,the reduction rate of the deposition mass exceeds 50%.Besides,the transverse trench configuration would not result in the rise in blade surface temperature.For transverse trench of various depths,an agreement is obtained between the numerical calculation and the experimental data in terms of deposition characteristics.This demonstrates that the transverse trench configuration is effective in inhibiting the particle deposition on the blade surface.