METHOD OF CONTROLLING TURBOMACHINE BLADE FLUTTER

摘要

METHOD OF CONTROLLING TURBOMACHINE BLADE FLUTTER A method for controlling the first torsional node line position in a rotatable blade of a turbomachine to improve its flutter stability including the steps of forming a first monolithic blade having a desired airfoil shape with convex and concave side walls; arranging several of the monolithic blades in a cascade array and subjecting the cascade array to an unsteady, supersonic, transonic and subsonic flow condition thereacross and thereafter determining the unsteady surface pressures acting on the monolithic blades; independently determining the first torsional mode vibration node line of each of the monolithic blades and comparing the resultant unsteady pressure force on the monolithic blades and its relationship to the first torsional mode vibration node line to determine whether or not the monolithic blade is absorbing or adding energy to the air flow thereacross; thereafter forming a plurality of first and thereafter modified composite blades by adding dissimilar material to the blade shape of a monolithic blade within the confines of its convex and concave side walls with the location of the dissimilar material and the amount of the dissimilar material being determined by subjecting the first composite blades and modifications thereof to unsteady, supersonic, transonic and subsonic flow conditions while the first composite blades and modification thereof are located in a cascade array and determining the resultant unsteady surface pressures thereon and comparing such unsteady surface pressures to the location of an independently determined node line position of the first composite blades and modifications thereof so as to optimize the location of their first torsional mode node line with respect to unsteady surface pressures produced thereon under unsteady, supersonic, transonic and subsonic flow conditions so as to produce a flutter stable blade.