The Experts below are selected from a list of 26562 Experts worldwide ranked by ideXlab platform
Chengchi Wang - One of the best experts on this subject based on the ideXlab platform.
-
bifurcation and nonlinear analysis of a flexible rotor supported by a relative short spherical Gas Bearing system
Communications in Nonlinear Science and Numerical Simulation, 2010Co-Authors: Chengchi WangAbstract:Abstract This paper employs a hybrid numerical method combining the differential transformation method and the finite difference method to study the bifurcation and nonlinear dynamic behavior of a flexible rotor supported by a relative short spherical Gas Bearing (RSSGB) system. The analytical results reveal a complex dynamic behavior comprising periodic, sub-harmonic, quasi-periodic, and chaotic responses of the rotor center and the journal center. Furthermore, the results reveal the changes which take place in the dynamic behavior of the Bearing system as the rotor mass and Bearing number are increased. The current analytical results are found to be in good agreement with those of other numerical methods. Therefore, the proposed method provides an effective means of gaining insights into the nonlinear dynamics of RSSGB systems.
-
performance analysis of high speed spindle aerostatic Bearings
Tribology International, 2005Co-Authors: Chengying Lo, Chengchi WangAbstract:The methods adopted to derive the pressure distribution and precision of Bearing rotation are fundamental issues in the arena of Gas Bearing design. The current study presents a detailed theoretical analysis of Bearing performance, in which the Gas flow within the Bearing is initially expressed in the form of simplified dimensionless Navier Stokes equations. Adopting the assumption of mass flow continuity between the Bearing clearance and the orifice, the nonlinear dimensionless Reynolds equation is then derived and subsequently discretized using the Newton method. Finally, the modified Reynolds equation is solved by means of the iterative rate cutting method. The current numerical models are valid for the analysis of the film pressure distribution, friction effects, loading capacity, rigidity, lubricating Gas flow rate, and eccentricity ratios of a variety of static and dynamic pressure aerostatic Bearings, including high-eccentricity ratio journals, high-speed non-circular journals, thrust Bearings, and slider Bearings, etc. The proposed analytical models provide a valuable means of analyzing the static and dynamic performance of a high-precision rotating Gas Bearing, and allow its design to be optimized accordingly.
Yu Lie - One of the best experts on this subject based on the ideXlab platform.
-
dynamic stiffness and damping coefficients of aerodynamic tilting pad journal Bearings
Tribology International, 2007Co-Authors: Yang Lihua, Li Huiguang, Yu LieAbstract:Abstract The dynamic Gas–film forces of aerodynamic Bearing often can be characterized by eight linear stiffness and damping coefficients. How to theoretically predict these coefficients is a very difficult issue for tilting-pad Gas Bearing design because of its structural complexity. The current study presents a novel and universal theoretical analysis method for calculating the dynamic stiffness and damping coefficients of aerodynamic tilting-pad Bearing. The Gas–film pressure within the Bearing is expressed in the form of dimensionless compressible Gas-lubricated Reynolds equation, which is solved by means of the finite element method. With the assumption that the journal and the pads are disturbed with the same frequency, the dynamic coefficients of tilting-pad Gas Bearing are computed by using the partial derivative method and the equivalent coefficient method. Finally, the investigations are conducted about the effects of Bearing number, perturbation frequency of the journal and the pads, eccentricity ratios, preload and length-to-diameter ratio of the Bearing on the dynamic coefficients of aerodynamic tilting-pad journal Bearing. The numerical results indicate that the dynamic stiffness and damping coefficients of tilting-pad Gas Bearing are closely related with these factors. The proposed analytical method provides a valuable means of predicting dynamic performances of tilting-pad Gas Bearing. The solution can be used for the purpose of prediction of dynamic behavior of the rotor systems supported by aerodynamic tilting-pad Bearings.
Xin Chang - One of the best experts on this subject based on the ideXlab platform.
-
study on the damage characteristics of Gas Bearing shale under different unloading stress paths
PLOS ONE, 2019Co-Authors: Lei Wang, Xin ChangAbstract:In order to understand the influence of unloading on the mechanical properties of shale rock, triaxial unloading tests under different stress paths were conducted. In this paper, three types of tests are completed, including: 1) Conventional triaxial compression test;2) Pre-peak constant maximum principal stress-unloading confining pressure test with different initial confining pressures and rates;3) Increasing axial stress-unloading confining pressure test. The deformation and rupture modes characteristics of shale sample under different unloading stress paths were obtained. Research results show that: 1) The confining pressure effect is obvious and the peak strength increases with the increase of initial confining pressure, under conventional triaxial compression test, the samples show obvious elastic-plastic characteristics; Under unloading confining pressure test, it shows obvious elastic brittleness characteristics.2) Compared with conventional triaxial compression test, unloading confining pressure is more prone to deformation and rupture, and the damage is more serious. Under same initial stress level, the brittle characteristics in unloading confining pressure are more obvious and the expansion is more intense. 3) Under same unloading stress path, the higher the initial confining pressure is, the more severe the sample failure is. With the increase of unloading rate, the rupture degree of the sample becomes more complex.4) The brittle rupture characteristic increases with the increase of unloading rate and initial confining pressure. Increasing axial stress-unloading confining pressure, various types of tensile and shear fractures with different mechanisms are well developed. These conclusions reveal loading and unloading mechanical properties of Gas-Bearing shale under different stress paths; it provides theoretical basis for horizontal drilling, fracturing design and long-term fracturing effect analysis of shale Gas reservoirs.
Wei Deng - One of the best experts on this subject based on the ideXlab platform.
-
Gas hydrate accumulation and occurrence associated with cold seep systems in the northern south china sea an overview
Geofluids, 2021Co-Authors: Wei Zhang, Jinqiang Liang, Qianyong Liang, Jiangong Wei, Zhifeng Wan, Junxi Feng, Wei Huang, Jing Zhao, Miaomiao Meng, Wei DengAbstract:Studying deep-water cold seep systems is of great significance to Gas hydrate exploration due to their close relationship. Various cold seep systems and related Gas hydrate accumulations have been discovered in the northern South China Sea in the past three decades. Based on high-resolution seismic data, subbottom profiles, in situ submergence observations, deep drilling and coring, and hydrate Gas geochemical analyses, the geological and geophysical characteristics of these cold seep systems and their associated Gas hydrate accumulations in the Qiongdongnan Basin, the Shenhu area, the Dongsha area, and the Taixinan Basin have been investigated. Cold seep systems are present in diverse stages of evolution and exhibit various seabed microgeomorphic, geological, and geochemical features. Active cold seep systems with a large amount of Gas leakage, Gas plumes, and microbial communities and inactive cold seep systems with authigenic carbonate pavements are related to the variable intensity of the Gas-Bearing fluid, which is usually derived from the deep strata through mud diapirs, mud volcanoes, Gas chimneys, and faults. Gas hydrates are usually precipitated in cold seep vents and deeper vertical fluid migration pathways, indicating that deep Gas-Bearing fluid activities control the formation and accumulation of Gas hydrates. The hydrocarbons collected from cold seep systems and their associated Gas hydrate reservoirs are generally mixtures of biogenic Gas and thermogenic Gas, the origin of which is generally consistent with that of deep conventional Gas. We also discuss the paragenetic relationship between the Gas-Bearing fluid and the seafloor morphology of cold seeps and the deep-shallow coupling of Gas hydrates, cold seeps, and deep petroleum reservoirs. It is reasonable to conclude that the deep petroleum systems and Gas-Bearing fluid activity jointly control the development of cold seep systems and the accumulation of Gas hydrates in the northern South China Sea. Therefore, the favorable areas for conventional oil and Gas enrichment are also prospective areas for exploring active cold seeps and Gas hydrates.
Xiangguo Kong - One of the best experts on this subject based on the ideXlab platform.
-
dynamic mechanical characteristics and fracture mechanism of Gas Bearing coal based on shpb experiments
Theoretical and Applied Fracture Mechanics, 2020Co-Authors: Enyuan Wang, Xiangguo Kong, Haifei Lin, Zhibo ZhangAbstract:Abstract To investigate the dynamic characteristics and fracture mechanisms of Gas-Bearing coal samples, a split Hopkinson pressure bar experimental system (SHPB-Gas) was built, using which dynamic impact experiments of Gas-Bearing coal were performed. Stress wave signals were collected and processed to analyze changes in strain characteristics with time. Relationships between dynamic strength, failure strain, and various factors such as axial static load, confining pressure, Gas pressure, and impact load were analyzed. Our results show that dynamic strength and failure strain increased with the increase of confining pressure and impact load, but decreased with the increase of axial static load and Gas pressure. Furthermore, evolution of dynamic cracks and failure mode of Gas-Bearing coal were analyzed, with the results indicating that samples presented axial tension fracture under the combination loading (axial static load, confining pressure, Gas pressure and impact load). The effects of these four factors on the fracture evolution in coal samples were then discussed. Under these conditions, the fracture mechanism of Gas-Bearing coal was investigated and the effects of shear stress and normal stress on the fracture surface were illustrated. Our findings show that Gas flow over the coal surface will increase shear stress along the fracture surface, in turn inducing coal fracture.
-
fractals and chaos characteristics of acoustic emission energy about Gas Bearing coal during loaded failure
Fractals, 2019Co-Authors: Xiangguo Kong, Enyuan Wang, Haifei Lin, Peng Xiao, Kaizhi ZhangAbstract:To study the damage evolution mechanism of Gas-Bearing coal and formation causes of acoustic emission signals during this process, the loaded experiments of Gas-Bearing coal were performed, and aco...
-
damage and deformation control equation for Gas Bearing coal and its numerical calculation method
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Enyuan Wang, Xiangguo KongAbstract:Abstract The dual pore structure of coal and occurrence of Gas adsorption make Gas-Bearing coal mechanical properties different from other non-adsorptive porous materials. Considering adsorbed-Gas-induced swelling stress and erosion, and pore/fracture-induced damage and failure to coal skeleton, the new effective stress equation, damage deformation control equation and constitutive model for Gas-Bearing coal is established. Based on principle of statistics and fractal theory, we combined the macro- and micro-structure characteristics of coal, and established the control equation of fracture field distribution. According to fracture mechanics and mesoscopic damage mechanics, we also established the expansion and damage evolution control equation of mesoscopic cracks. Furthermore, we revealed the relationship between meso-scale crack extension damage and macro mechanical characteristics, set up the macro-mesoscopic numerical model and calculation method of fractured rock mechanic constitutive, and developed the stress–strain numerical calculation program of Gas-Bearing coal using Comsol Multiphysics partial differential equation module and MatLab software. The model and methods were further validated in field tests. The results showed that our equations could better describe the deformation and damage process of Gas-Bearing coal and solve the fluid–solid coupling problems in Gas and coal engineering practices.
