Vibration intensity and non-dimensional amplitude parameters are often used to extract the fault trend of rotary machines. But,they are the parameters related to energy,and can not describe the fault trend because of ...Vibration intensity and non-dimensional amplitude parameters are often used to extract the fault trend of rotary machines. But,they are the parameters related to energy,and can not describe the fault trend because of varying load and conditions or too slight change of vibration signal. For this reason,three non-dimensional parameters are presented,namely waveform repeatability factor,waveform jumping factor and waveform similarity factor,called as waveform factors jointly,which are based on statistics analysis for the waveform and sensitive to the change of signal waveform. When they are used to extract the fault trend of rotary machines as a kind of technology of instrument and meter,they can reflect the fault trend better than the vibration intensity,peak amplitude and margin index.展开更多
Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumpti...Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumption of a given Q-model that is obtained by tomographic inversion. However, the resolution of the latter is low and cannot reflect the amplitude attenuation and phase distortion during wave propagation in viscoelastic media. Thus, a Q waveform inversion method is proposed. First, we use standard linear body theory to describe attenuation and then we derive the simplified viscoacoustic equation that characterizes amplitude attenuation and phase distortion. In comparison with conventional equations, the simplifi ed equation involves no memory variables and therefore requires less memory during computation. Moreover, the implementations of the attenuation compensation are easier. The adjoint equation and the corresponding gradient equation with respect to either L2-norm or the zero-lag cross-correlation objective function are then derived and the regularization strategy for overcoming the instability during numerical solution of the adjoint equation is proposed. The Q waveform inversion is developed using the limited-memory Broyden–Fletcher– Goldfarb–Shanno (L-BFGS) iteration method for known velocity. To alleviate the dependence of the waveform inversion on the initial model and overcome cycle skipping to some extent, we adopt multiscale analysis. Furthermore, anti-noise property and double-parameter inversion are assessed based on the results of numerical modeling.展开更多
According to the least square criterion of minimizing the misfit between modeled and observed data, this paper provides a preconditioned gradient method to invert the visco-acoustic velocity structure on the basis of ...According to the least square criterion of minimizing the misfit between modeled and observed data, this paper provides a preconditioned gradient method to invert the visco-acoustic velocity structure on the basis of using sparse matrix LU factorization technique to directly solve the visco-acoustic wave forward problem in space-frequency domain. Numerical results obtained in an inclusion model inversion and a layered homogeneous model inversion demonstrate that different scale media have their own frequency responses, and the strategy of using low-frequency inverted result as the starting model in the high-frequency inversion can greatly reduce the non-tmiqueness of their solutions. It can also be observed in the experiments that the fast convergence of the algorithm can be achieved by using diagonal elements of Hessian matrix as the preconditioned operator, which fully incorporates the advantage of quadratic convergence of Gauss-Newton method.展开更多
文摘Vibration intensity and non-dimensional amplitude parameters are often used to extract the fault trend of rotary machines. But,they are the parameters related to energy,and can not describe the fault trend because of varying load and conditions or too slight change of vibration signal. For this reason,three non-dimensional parameters are presented,namely waveform repeatability factor,waveform jumping factor and waveform similarity factor,called as waveform factors jointly,which are based on statistics analysis for the waveform and sensitive to the change of signal waveform. When they are used to extract the fault trend of rotary machines as a kind of technology of instrument and meter,they can reflect the fault trend better than the vibration intensity,peak amplitude and margin index.
基金supported by the Open Fund of Sinopec Multi-wave Multicomponent Key Laboratory(Grant No.GSYKY-B09-33)
文摘Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumption of a given Q-model that is obtained by tomographic inversion. However, the resolution of the latter is low and cannot reflect the amplitude attenuation and phase distortion during wave propagation in viscoelastic media. Thus, a Q waveform inversion method is proposed. First, we use standard linear body theory to describe attenuation and then we derive the simplified viscoacoustic equation that characterizes amplitude attenuation and phase distortion. In comparison with conventional equations, the simplifi ed equation involves no memory variables and therefore requires less memory during computation. Moreover, the implementations of the attenuation compensation are easier. The adjoint equation and the corresponding gradient equation with respect to either L2-norm or the zero-lag cross-correlation objective function are then derived and the regularization strategy for overcoming the instability during numerical solution of the adjoint equation is proposed. The Q waveform inversion is developed using the limited-memory Broyden–Fletcher– Goldfarb–Shanno (L-BFGS) iteration method for known velocity. To alleviate the dependence of the waveform inversion on the initial model and overcome cycle skipping to some extent, we adopt multiscale analysis. Furthermore, anti-noise property and double-parameter inversion are assessed based on the results of numerical modeling.
文摘According to the least square criterion of minimizing the misfit between modeled and observed data, this paper provides a preconditioned gradient method to invert the visco-acoustic velocity structure on the basis of using sparse matrix LU factorization technique to directly solve the visco-acoustic wave forward problem in space-frequency domain. Numerical results obtained in an inclusion model inversion and a layered homogeneous model inversion demonstrate that different scale media have their own frequency responses, and the strategy of using low-frequency inverted result as the starting model in the high-frequency inversion can greatly reduce the non-tmiqueness of their solutions. It can also be observed in the experiments that the fast convergence of the algorithm can be achieved by using diagonal elements of Hessian matrix as the preconditioned operator, which fully incorporates the advantage of quadratic convergence of Gauss-Newton method.
