| In the current advanced high bypass ratio turbofan engine,the fan can provide about 90% of all the thrust of the engine.Under the high bypass ratio requirements,the fan rotor blade radial size and the windward area become larger,which results in increasing probability of bird strike.So it is important to study the influence of bird impact on the aerodynamic performance of fan blades and the compliance with the relevant provisions of airworthiness in the design process.This paper analyzes the airworthness of bird strike firstly and obtains thrust loss requirement of turbofan engine after middle bird impact;Then a typical high-bypass fan rotor is selected as the research object and a damage model of the bird-impact fan rotor blade is constructed;A two-dimensional planar cascade experiment about both damaged and undamaged 70% section of blade model is carried out and the numerical method based on NUMECA is validated and calibrated.Finally,the influence on the aerodynamic performance of different number of damaged fan blades after middle bird impact is studied by annual numerical simulation.The results show: The mass flow at chock point,the peak efficiency,the stability margin,the thrust of peak efficiency point and the maximum thrust of different number of damaged blades decline inordinately compared to the undamaged blade while the magnitude increases due to the increasing number of damaged blades.Wherein,when the number of damaged blades reaches three,the thrust at peak efficiency point decreases by about 11.35% and the maximum thrust decreases by about 20.68% compared to the undamaged blade,which meets the requirement in Airworthiness Certification that thrust losses of middle bird strike damaged fan can't exceed 25%.Different amount of damaged fan blades have flow separation from the damage position to the blade tip within different degree and lead to the outlet flow field of the fan has different degrees of distortion. |
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