Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating par...Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating parameters of labyrinth seals on dynamic coefficients, a model of calculating dynamic coefficients of labyrinth seals is presented using a two control volume model. The coupling influences of parameters on cross-coupled stiffness and direct damping of labyrinth seal are discussed. In the conclusion, a reference of preventing steam-exciting vibration and optimum determination of design parameters of labyrinth seals are provided.展开更多
The arc curved beams have been widely applied in the construction industry in recent years. The calculation methods for arc curved beams provided by the industry have been varied. This paper mainly researches on the m...The arc curved beams have been widely applied in the construction industry in recent years. The calculation methods for arc curved beams provided by the industry have been varied. This paper mainly researches on the method of reckoning the force state of a curved beam with multiple straight beams. By comparing the three-dimensional stiffness matrix of the straight beam element and the curved beam element, the coupling stiffness of a curved beam is discovered. By using multiple finite element analysis software, this paper undertakes a case analysis of multiple models and subsequently provides some referential parameter for engineering design by approximating a curve by straight beams.展开更多
The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are der...The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are derived by the Hamilton principle and solved by the finite difference method. The critical axial shortness is determined by the B - R cirterion. The given example is used to highlight the influences of initial imperfection, impact velocity, stress wave and coupled stiffness. It is found that the unsymmetrically laminated bar has a quite different dynamic buckling behaviour from that of the symmetrically laminated bar.展开更多
A new mechanism is proposed to implement the synchronization of the four unbalanced rotors in a vibrating system,which consists of a main rigid frame(MRF)and two accessorial rigid frames(ARF).An analytical approach is...A new mechanism is proposed to implement the synchronization of the four unbalanced rotors in a vibrating system,which consists of a main rigid frame(MRF)and two accessorial rigid frames(ARF).An analytical approach is developed to study the coupling dynamic characteristics of the four unbalanced rotors,which converts the problem of synchronization of the four unbalanced rotors into the existence and the stability of zero solutions for the non-dimensional differential equations of the angular velocity disturbance parameters(NDDEDP).The stability of zero solutions of the NDDEDP is decomposed into that of its generalized system and a system of the three first order differential equations for the disturbance parameters of the phase differences.The coupling dynamic characteristic of the four unbalanced rotors includes the inertia coupling,the stiffness coupling of angular velocity and the load torque coupling.The non-dimensional inertia coupling matrix is symmetric,the non dimensional matrix of the stiffness coupling of angular velocity is antisymmetric and its diagonal elements are all negative.Hence,the general system of the NDDEDP automatically satisfies the generalized Lyapunov equations when the non-dimensional inertia coupling matrix is positive definite and its elements are all positive.Using Routh-Hurwitz criterion the condition of stability of differential equations for the disturbance parameters of the phase differences is obtained.The load torque coupling makes the vibrating system have the dynamic characteristic of selecting motions and self-synchronization of the four unbalanced rotors arises from the dynamic characteristic of selecting motion of the vibrating system.When the two coefficients of coupling cosine effect of phase angles are all greater than 0 and the three indexes of synchronization are all far greater than 1,the vibrating system can implement an elliptical motion of the main rigid frame required in engineering.Numeric results show that the structural parameters of the proposed mechanism can guarantee the non-dimensional inertia matrix to be always positive definite.Computer simulation is carried out to verify the results of the theoretical investigation.展开更多
基金This project is supported by National Natural Science Foundation of China(59990472). Manuscript received on November 30, 1999 r
文摘Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating parameters of labyrinth seals on dynamic coefficients, a model of calculating dynamic coefficients of labyrinth seals is presented using a two control volume model. The coupling influences of parameters on cross-coupled stiffness and direct damping of labyrinth seal are discussed. In the conclusion, a reference of preventing steam-exciting vibration and optimum determination of design parameters of labyrinth seals are provided.
文摘The arc curved beams have been widely applied in the construction industry in recent years. The calculation methods for arc curved beams provided by the industry have been varied. This paper mainly researches on the method of reckoning the force state of a curved beam with multiple straight beams. By comparing the three-dimensional stiffness matrix of the straight beam element and the curved beam element, the coupling stiffness of a curved beam is discovered. By using multiple finite element analysis software, this paper undertakes a case analysis of multiple models and subsequently provides some referential parameter for engineering design by approximating a curve by straight beams.
基金The present research work was financially supported by the National Natural Science Foundation of China.(No.19472042)
文摘The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are derived by the Hamilton principle and solved by the finite difference method. The critical axial shortness is determined by the B - R cirterion. The given example is used to highlight the influences of initial imperfection, impact velocity, stress wave and coupled stiffness. It is found that the unsymmetrically laminated bar has a quite different dynamic buckling behaviour from that of the symmetrically laminated bar.
基金supported by the National Natural Science Foundation of China(Grant No.50535010)Project of Liaoning Province College Science and Research(Grant No.2008S095)Program for Changjiang Scholars and Innovative Research Team in University
文摘A new mechanism is proposed to implement the synchronization of the four unbalanced rotors in a vibrating system,which consists of a main rigid frame(MRF)and two accessorial rigid frames(ARF).An analytical approach is developed to study the coupling dynamic characteristics of the four unbalanced rotors,which converts the problem of synchronization of the four unbalanced rotors into the existence and the stability of zero solutions for the non-dimensional differential equations of the angular velocity disturbance parameters(NDDEDP).The stability of zero solutions of the NDDEDP is decomposed into that of its generalized system and a system of the three first order differential equations for the disturbance parameters of the phase differences.The coupling dynamic characteristic of the four unbalanced rotors includes the inertia coupling,the stiffness coupling of angular velocity and the load torque coupling.The non-dimensional inertia coupling matrix is symmetric,the non dimensional matrix of the stiffness coupling of angular velocity is antisymmetric and its diagonal elements are all negative.Hence,the general system of the NDDEDP automatically satisfies the generalized Lyapunov equations when the non-dimensional inertia coupling matrix is positive definite and its elements are all positive.Using Routh-Hurwitz criterion the condition of stability of differential equations for the disturbance parameters of the phase differences is obtained.The load torque coupling makes the vibrating system have the dynamic characteristic of selecting motions and self-synchronization of the four unbalanced rotors arises from the dynamic characteristic of selecting motion of the vibrating system.When the two coefficients of coupling cosine effect of phase angles are all greater than 0 and the three indexes of synchronization are all far greater than 1,the vibrating system can implement an elliptical motion of the main rigid frame required in engineering.Numeric results show that the structural parameters of the proposed mechanism can guarantee the non-dimensional inertia matrix to be always positive definite.Computer simulation is carried out to verify the results of the theoretical investigation.
