Numerical Investigation Of Rain Ingestion Characteristics On Axial Compressor

Rain is one of the important factors that threaten the normal operation of aircraft engines.Excessive rain ingestion leads to the deterioration of engine performance,such as stall,surge,reduction of trust power and even shut down.The modern airworthiness clause requires that the aero-engines do not extinguish after the rain ingestion,and do not descent speed,do not occur unrecoverable surge or stall,etc.So as to overcome the bad weather such as rainstorm.However,the effect mechanism of rain ingestion on engine performance has not been fully understood.Therefore,the numerical method is used to analyse the rain ingestion characteristics of engine compression components.First,based on the Eulerian-Lagrangian two-phase flow theory,this paper has considered the water droplets evaporation,break-up and collision process,and use the source items to build two-way coupling effects about quality,momentum and energy exchange between water and air.The water film model on the rotor blade surface was established,and the sand grain roughness was used to characteristic the wall water film morphology.The single-rotor compressor characteristics of rain ingestion were analyzed.Then,based on the HARIKA algorithm and the gas-liquid two-phase flow calculation modules,a one-dimensional calculation program for the two-phase flow of compressor was developed,and the rain ingestion characteristics of multistage axial compressor ware analyzed.The three-dimensional calculation results showed that,due to the big effect of inertia force,water droplets in the compressor flow path showed the movement trend that biasing to the cascade pressure side while deviating from the cascade suction side.Majority of water droplets collided with the cascade pressure surface to form more water film,while the water film formed on the suction surface is less.The area and thickness of the water film formed on the pressure surface was far greater than the suction surface.The water film on the pressure surface of the blade was mainly distributed near the front and the top of the blade,and the thickness of the water film decreased gradually along the axial direction of the blade.The pressure rise coefficient and isentropic efficiency of the compressor decreased with the water ingestion.The comparison between the numerical results and the experimental results showed that the flow loss of the boundary layer caused by the water film had a great influence on the performance of the compressor.The results of one-dimensional numerical calculation showed that the water ingestion increased the total pressure loss of the cascade flow field,and the compressor power consumption increased,resulting in deterioration of multistage compressor performance.The inlet mass flow,total pressure ratio and the compression efficiency of the compressor decreased with the increase of the precipitation and the diameter of the droplets.The evaporation intensity of water droplets in the compressor cascade channel increased with the increase of the stages,and the evaporation rate of small water droplets was greater than that of large water droplets.Compared with dry compression,the total temperature of compressor cascades decreased under the condition of rain suction,and the density of working fluid increased at a smaller rainfall.Well,when the rainfall was increased to a certain extent,the density of the working fluid will lower than that of dry compression.The flow angle of the cascade was changed due to the water ingestion,The flow angle of the cascade is changed by the pressure drop of the compressor,and the angle of attack of the front rotor blade cascade increased while the angle of attack of the rear rotor blade was reduced.The change of the angle of attack of the front and rear rotor would made the compressor easy to surge during operation,which might be the main reason for the reduction of the stability of the multistage compressor under the condition of water ingestion.With the increase of the rainfall and the diameter of the droplets,the amplitude of the angle of attack increased,and the possibility of the surge of the compressor was further increased.