The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering t...The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering the effects of several system parameters such as the mean speed,flow velocity,axial added mass coefficient,mass ratio,slenderness ratio,tension and viscosity coefficient.Numerical results show that when the pulsation frequency of the axial speed is close to the sum of first-and second-mode frequencies or twice the lowest two natural frequencies,instability with combination or subharmonic resonance would occur.It is found that the beam can undergo the periodic-1 motion under subharmonic resonance and the quasi-periodic motion under combination resonance.With the change of system parameters,the stability boundary may be widened,narrowed or drifted.In addition,the vibration amplitude of the beam under resonance can also be affected by changing the values of system parameters.展开更多
A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the simulation....A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the simulation.The rotor investigated in this paper is ND_TAC rotor,which is the rotor of one-stage transonic compressor in the University of Notre Dame.Three varied inlet flow conditions are simulated.The inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow,while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary condition.Among the total pressure ratio curves for the three inlet flow conditions,it is found that the hub dis-torted inlet boundary condition improves the stall margin,while the tip distorted inlet boundary condition dete-riorates compressor stability.The axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further examined.It is demonstrated that the axial momentum balance is the mechanism for interface movement.The hub distorted inflow could de-crease the axial momentum ratio,suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11972167,12072119,12102139).
文摘The dynamics of an axially accelerating beam subjected to axial flow is studied.Based on the Floquet theory and the Runge-Kutta algorithm,the stability and nonlinear vibration of the beam are analyzed by considering the effects of several system parameters such as the mean speed,flow velocity,axial added mass coefficient,mass ratio,slenderness ratio,tension and viscosity coefficient.Numerical results show that when the pulsation frequency of the axial speed is close to the sum of first-and second-mode frequencies or twice the lowest two natural frequencies,instability with combination or subharmonic resonance would occur.It is found that the beam can undergo the periodic-1 motion under subharmonic resonance and the quasi-periodic motion under combination resonance.With the change of system parameters,the stability boundary may be widened,narrowed or drifted.In addition,the vibration amplitude of the beam under resonance can also be affected by changing the values of system parameters.
基金supported by National Natural Science Foundation of China with project No.51010007 and No.51106153
文摘A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the simulation.The rotor investigated in this paper is ND_TAC rotor,which is the rotor of one-stage transonic compressor in the University of Notre Dame.Three varied inlet flow conditions are simulated.The inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow,while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary condition.Among the total pressure ratio curves for the three inlet flow conditions,it is found that the hub dis-torted inlet boundary condition improves the stall margin,while the tip distorted inlet boundary condition dete-riorates compressor stability.The axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further examined.It is demonstrated that the axial momentum balance is the mechanism for interface movement.The hub distorted inflow could de-crease the axial momentum ratio,suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability.
