Numerical Analysis Of Rain Absorption Characteristics Of Turbofan Engine Fan

The increase in the number of flights and the increase in flight distance have increased the possibility of the aircraft flying in rain.Excessive rain ingestion leads to the deterioration of engine performance,such as surge,reduction of trust power and even shut down,which seriously affects aviation safety.In order to ensure the safety of passengers,contemporary aircraft should have the ability to fly safely in rain.Therefore,the numerical method is used to analysis the rain ingestion process of intake duct and fan.First of all,with the help of Ansys CFX and Gasturb software,the Euler-Lagrangian numerical calculation method was used to calculate the rain ingestion rate of the air intake duct and the variation of water droplet velocity and particle size under typical flight conditions.The numerical results show that,when the aircraft is in the condition of high power and low flight speed,the water droplets follow the air flow to converge before reaching the air inlet,resulting in less rain absorption of the aircraft than in nature;on the contrary,in the condition of low power and high flight speed,the water droplets follow the air flow to overflow before reaching the air inlet,resulting in more rain absorption of the aircraft than in nature.Effected by aircraft flight speed and inlet air flow velocity,the particle velocity changes differently in different flight stages,but the axial velocity of particles entering the inlet is between the aircraft flight speed and inlet air velocity,and is greater than the average absolute velocity in the two directions of vertical and parallel to the ground.Because of the influence of aerodynamic breaking and air flow movement characteristics(overflow or convergence),the particle size changes in different flight stages.Then based on the research results of the particles(particle size,particle speed,and water ingestion rate),it was used as the boundary conditions of the inlet water droplets in the fan research,and the evaporation,collision,and crushing of the water droplets in the fan were fully considered.In the typical flight conditions of an airplane,the movement trajectory and particle size of the water droplets,the mass flow of the inner and outer channels after the shunt ring,and the influence of water droplets on the fan torque and the aerodynamic parameters of the internal channel outlet were explored in the typical flight conditions.Influenced by shock waves,the particle size decreases sharply after it enters along the fan blades cascade following the airflow.Water droplets inevitably collide with the fan rotor blades in the process of movement,which increases the torque of the fan,increases the power consumption of the fan,and reduces the efficiency.Due to the characteristics of water droplets and the influence of the fan structure,there are non-uniformities in the radial distribution of the water-air ratio,the total temperature and the total pressure at different heights of the exit of the inner content road.In the take-off condition,the water vapor in the middle and upper part of the inner passage outlet is relatively large,and the water vapor ratio in the area near the hub and the casing is small.Compared with the take-off condition,the water-air ratio distribution is more uniform in the descent condition.The maximum water vapor ratio distribution area gradually moves to the hub area as the flying height decreases.The rain reduces the total temperature at the outlet of the inner track,and 80% of the areas above the leaf height have the greatest decrease in total temperature.Under the influence of impact force and aerodynamic drag force,rainwater reduce the average total pressure at the outlet of the inner track.The change of total pressure near 90% of leaf height is very obvious,and the changes in other areas are more complicated.