5 results on '"Kai Chai"'
Search Results
2. Simulation study on the flow-induced vibration and noise in marine centrifugal pumps
- Author
-
Cunsheng Zhao and Kai Chai
- Subjects
Mechanics of Materials ,Mechanical Engineering ,Automotive Engineering ,Aerospace Engineering ,General Materials Science - Abstract
Due to the three-dimensional non-axisymmetric shape of the volute, its interaction with the impeller increases the internal flow field complexity and instability of the marine centrifugal pump, representing the main reason for pump body vibration and hydraulic noise. First, the basic principle of fluid machinery noise calculation was explained based on the Lighthill acoustic analogy method and Curle’s theory. Then, the fluid pressure pulsation and flow characteristics of centrifugal pumps were analyzed using the Fluent software, after which the Actran software was used to examine the flow-induced vibration noise properties. The results showed that the clearance size significantly impacted the pump head, while the peak value of the flow-induced vibration response was mainly twice the blade frequency. Although a larger ring clearance increased the structural vibration, it had little impact on the sound pressure level changes in the external sound field. The results provided a new method for the structural optimization and low-noise design of marine centrifugal pumps.
- Published
- 2023
3. Estimation of longitudinal excitation of propeller using a novel hybrid method
- Author
-
Kai Chai and Haiping Wu
- Subjects
Acoustics ,Measure (physics) ,02 engineering and technology ,Propulsion ,01 natural sciences ,Quantitative Biology::Cell Behavior ,Physics::Popular Physics ,0203 mechanical engineering ,vibration and noise control ,0103 physical sciences ,TJ1-1570 ,Waveguide (acoustics) ,General Materials Science ,Mechanical engineering and machinery ,010301 acoustics ,Physics ,Physics::Biological Physics ,waveguide function ,Noise (signal processing) ,Mechanical Engineering ,Propeller ,propeller excitation ,Function (mathematics) ,propulsion shafting ,Physics::Classical Physics ,Vibration ,020303 mechanical engineering & transports ,modal method ,Excitation - Abstract
Due to the limitation of working environment and structure conditions, it is difficult to directly measure the propeller excitation of ship propulsion shafting system. A method based on waveguide function and modal method combining with shafting vibration response measurement was proposed to estimate the propeller longitudinal excitation indirectly. Firstly, a waveguide transfer model for the general structure of the propulsion shafting is proposed that is suitable for estimating propeller excitation from shafting vibration response. Secondly, the longitudinal excitation of the propeller is calculated by measuring the waveguide coefficients of any shaft sections via the proposed hybrid method. Finally, the scheme is verified by a concrete example. The simulation results prove its feasibility and effectiveness for estimating propeller excitation by measuring the shafting vibration response, which provides a novel scheme for accurately grasping the propeller excitation and effectively controlling the vibration and noise of hull structure.
- Published
- 2021
4. Line spectra chaotification of the nonlinear vibration isolation system on the flexible foundation based on the open-plus-nonlinear-closed-loop method
- Author
-
Yong S Liu, Shuang Li, Kai Chai, Xiang Yu, Jun J Lou, and Chao Q Yang
- Subjects
Computer science ,Mechanical Engineering ,Nonlinear vibration ,Foundation (engineering) ,Aerospace Engineering ,01 natural sciences ,Spectral line ,010305 fluids & plasmas ,Nonlinear system ,Mechanics of Materials ,Feature (computer vision) ,Control theory ,Isolation system ,0103 physical sciences ,Automotive Engineering ,General Materials Science ,010301 acoustics ,Closed loop ,Variable (mathematics) - Abstract
Line spectra chaotification is a principal method to weaken or eliminate the line spectra feature of submarines. However, this method is difficult to obtain chaos under the variable working conditions and small amplitudes. Furthermore, there are multistable attractors in the nonlinear vibration isolation system simultaneously. So, the quality of chaos highly depends on initial conditions and systematic parameters. In this study, the attractor entrainment control and line spectra chaotification of a nonlinear vibration isolation system on the flexible foundation have been studied by using the open-plus-nonlinear-closed-loop method. First, the dynamic equation of the nonlinear vibration isolation system on the flexible foundation was formulated, and its exhaustive bifurcation characteristics were analyzed. The regulations of global characteristics and coexistent attractors were found out. Second, the entrainments between the different attractors were carried out under the open-plus-nonlinear-closed-loop control, which can ensure the system always works in the lowest line spectra intensity and the best overall vibration isolation performance. Finally, an open-plus-nonlinear-closed-loop coupling method was used to achieve generalized chaotic synchronization between the driving system and the response system, which effectively obtained sustainable chaos even under variable working conditions and small amplitudes. Simulation results validate the feasibility and validity of the open-plus-nonlinear-closed-loop method, which achieves the dual goals of effective vibration isolation in the low frequency range and line spectra chaotification under variable working conditions.
- Published
- 2020
5. Bifurcation and singularity analysis of HSLDS vibration isolation system with elastic base
- Author
-
Xiang Yu, Kai Chai, Shuyong Liu, and Yongbao Liu
- Subjects
Singularity theory ,lcsh:Mechanical engineering and machinery ,elastic base ,02 engineering and technology ,Parameter space ,Bifurcation diagram ,01 natural sciences ,0203 mechanical engineering ,singularity theory ,0103 physical sciences ,General Materials Science ,lcsh:TJ1-1570 ,010301 acoustics ,Bifurcation ,Physics ,Basis (linear algebra) ,bifurcation diagram ,Mechanical Engineering ,high-static-low-dynamic-stiffness (HSLDS) ,Mathematical analysis ,Equations of motion ,averaging method ,Base (topology) ,transition set ,020303 mechanical engineering & transports ,vibration isolation system (VIS) ,Restoring force - Abstract
In order to reveal the bifurcation mechanism and optimize the system design for high-static-low-dynamic-stiffness (HSLDS) vibration isolation system (VIS) with elastic base, the local bifurcation analyses both in unfolding parameter space and physical parameter space were carried out theoretically and numerically. Firstly, the restoring force of the HSLDS-VIS was approximated to linear and cubic stiffness by applying the Maclaurin series expansion and the motion equations of HSLDS-VIS with elastic base were established. Subsequently, the motion equations of HSLDS-VIS with elastic base were formulated to transform the system into a standard form and the averaging method was applied to obtain the single-variable bifurcation equation for the HSLDS-VIS with elastic base in case of primary resonance and 1:2 internal resonance. Furthermore, the transition sets and bifurcation diagrams in the unfolding parameter space were studied by means of singularity theory. Finally, for the engineering application, the transition sets were transferred back to the physical parameter space, thus to obtain the bifurcation diagrams of the amplitude with respect to the external force. The numerical simulation results show that the local bifurcations of HSLDS-VIS with elastic base in case of 1:2 internal resonance are considerable complex and need to be analyzed in six two-parameters spaces, meanwhile, the necessary condition of multiple solutions lies in some physical parameters, which can provide a theoretical basis and reference for design and application of the HSLDS-VIS with elastic base.
- Published
- 2018
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