Nonlinear Dynamics Research Of Aeroengine Bladed Disk

Varying rotating blades can be found in different engineering problems as the key component of aircraft engines.Especially in turbine engine and turbomachinery,the vibration of varying rotating blades is of continuing concern to the designers.The emphasis on engine performance under the necessary constraints of minimum weight and satisfactory life requires that vibration levels should be kept low.The vibrations in turbine engine can be a source of the fatigue failure if the vibration amplitudes of the varying rotating blades are not decreased below an acceptable limit.Furthermore,certain important design considerations require a thorough understanding of the structural dynamic characteristics of varying rotating blades.Extensive uses of varying rotating pre-twisted cantilever conical shell can be found in different engineering disciplines.The dynamic behaviors of the varying rotating pre-twisted cantilever conical shell are significant for the analysis of the whole structure of blades.The nonlinear dynamics under different excitations are extremely important to the safety and effectiveness of the aircraft equipment.The main work in this dissertation is focused on the nonlinear dynamics of bladed disks from theoretical analysis and numerical simulations.The main contents of this dissertation are as follows:In the first part,an analytical model is presented to investigate the nonlinear dynamic responses of the blade with the varying rotating speed and the thickness.The varying rotating blade is treated as a pre-twisted thin-walled rotating cantilever conical shell.Based on the first-order shear deformation theory,von Karman nonlinear relationship and Hamilton's principle,the partial differential governing equations of motion are derived.Galerkin's approach is applied to obtain the ordinary differential governing equations of motion for the shell.The method of multiple scales is exploited to derive the averaged equations under the case of 1:3 internal resonance.The amplitude-frequency response curves,bifurcation diagrams,phase portraits,time history diagrams,three-dimensional phase portraits and power spectrum densities(PSD)are obtained.Numerical simulations are performed to study the nonlinear dynamic responses of the pre-twisted thin-walled rotating cantilever conical shell with the varying thickness under the diverse velocities and different excitations.In the second part,the rotating bladed disk with two blades is settled as a springs-rotating conical shells system,and the effects of the presetting,pre-twisted angles and variable thickness are considered during the establishment of the model.In the frame of the von Karman nonlinear relationship,the first-order shear deformation theory and the Hamilton's principle,the partial differential governing equations of motion are derived.Galerkin's approach is applied to obtain the ordinary differential governing equations for the blisk.Then the method of multiple scales is exploited to derive the averaged equations for the case of 1:3 internal resonance.The amplitude-frequency response curves,bifurcation diagrams,phase portraits,time history diagrams,three-dimensional phase portraits and power spectrum densities(PSD)are obtained.In the third part,the bladed disk with four blades is settled as a springs-rotating conical shells system.Using the von Karman nonlinear relationship,the first-order shear deformation theory and the Hamilton's principle,the partial differential governing equations of motion for the bladed disk are derived.Galerkin's approach is applied to obtain the ordinary differential governing equations.Then the method of multiple scales is exploited to derive the averaged equation for the case of 1:3 internal resonance.The amplitude-frequency response curves,bifurcation diagrams,phase portraits,time history diagrams,three-dimensional phase portraits and power spectrum densities(PSD)are obtained.Numerical simulations are performed to study the nonlinear dynamic responses of the rotating bladed disk under the diverse velocities and the different excitations.