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Chinese Journal of Mechanical Engineering 2022年第1期35卷 91-111页

作者： Xiaohui Lin Shun Wang Shuyun Jiang Shaowen Zhang School of Mechanical Engineering Southeast UniversityNanjing 210000China

The water-lubricated bearings are usually the state of turbulent cavitating flow under high-speed conditions. And the distribution of cavitation bubbles and the interface effect between the two phases have not been included in previous studies on high-speed water-lubricated bearings. In order to study the influence of interface effect and cavitation bubble distribution on the dynamic characteristics of high-speed water-lubricated spiral groove thrust bearings(SGTB).A turbulent cavitating flow lubrication model based on two-phase fluid and population balance equation of bubbles was established in this paper. Stiffness and the damping coefficients of the SGTB were calculated using the perturbation pressure equations. An experimental apparatus was developed to verify the theoretical model. Simulating and experimental results show that the small-sized bubbles tend to generate in the turbulent cavitating flow when at a high rotary speed, and the bubbles mainly locate at the edges of the spiral groove. The simulating results also show that the direct stiffness coefficients are increased due to cavitation effect, and cross stiffness coefficients and damping coefficients are hardly affected by the cavitation effect. Turbulent effect on the dynamic characteristics of SGTB is much stronger than the cavitating effect.

关键词： Spiral groove thrust bearings Water lubrication Turbulent lubrication Cavitating flow dynamic characteristics

dynamic characteristics of large permanent magnet direct‐drive generators considering electromagnetic–structural coupling effects

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International Journal of Mechanical System dynamics 2023年第1期3卷 25-38页

作者： Qinkai Han Xueping Xu Zhihong Zhang Yifeng Yan Chao Peng Fulei Chu Department of Mechanical Engineering The State Key Laboratory of TribologyTsinghua UniversityBeijingChina School of Instrumentation and Optoelectronic Engineering Research Institute for Frontier ScienceBeihang UniversityBeijingChina Institute of Research Center Xinjiang Goldwind Science and Technology Co.Ltd.XinjiangChina

dynamic characteristics of large permanent magnet direct‐drive generators(PMDGs)considering electromagnetic–structural coupling effects are analyzed in this study.Using the conformal mapping method,the scalar magnetic potential of the air gap magnetic field considering the slot effect is calculated.On the basis of the discrete current element and magnetic equivalent circuit model,the local magnetic saturation effect of the stator and rotor is quantitatively simulated and the air gap magnetic field intensity distribution is obtained via numerical simulation.A series of uniformly distributed equivalent electromagnetic springs are introduced to develop an electromagnetic–structural coupling finite element PMDG model.The proposed air gap field analysis method is verified by the finite element analysis results.On the basis of the test platform for the Goldwind 1.5MW PMDG,both modal and dynamic response tests for the stator/rotor coupling system are conducted,and the results are compared with the natural frequencies,mode shapes,and vibration responses obtained using the numerical model.The effects of the air gap length and rotor speed on the natural frequencies of the coupling system are analyzed.The proposed model has the potential to accurately evaluate the PMDG vibration energy,avoiding resonance points,and maintaining stable operations of the unit.

关键词： permanent magnet direct‐drive generators dynamic characteristics electromagnetic–structural coupling effects conformal mapping magnetic equivalent circuit model electromagnetic springs

dynamic characteristics of Functionally Graded Timoshenko Beams by Improved Differential Quadrature Method

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1647-1668页

作者： Xiaojun Huang Liaojun Zhang Hanbo Cui Gaoxing Hu School of Architecture and Civil Engineering Anhui Polytechnic UniversityWuhu241000China College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China

This study proposes an effective method to enhance the accuracy of the Differential Quadrature Method(DQM)for calculating the dynamic characteristics of functionally graded beams by improving the form of discrete node distribution.Firstly,based on the first-order shear deformation theory,the governing equation of free vibration of a functionally graded beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam axial displacement,transverse displacement,and cross-sectional rotation angle by considering the effects of shear deformation and rotational inertia of the beam cross-section.Then,ignoring the shear deformation of the beam section and only considering the effect of the rotational inertia of the section,the governing equation of the beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam transverse displacement.Based on the differential quadrature method theory,the eigenvalue problem of ordinary differential equations is transformed into the eigenvalue problem of standard generalized algebraic equations.Finally,the first several natural frequencies of the beam can be calculated.The feasibility and accuracy of the improved DQM are verified using the finite element method(FEM)and combined with the results of relevant literature.

关键词： Timoshenko beams functionally graded materials dynamic characteristics natural frequency improved differential quadrature method

dynamic characteristics of Rotor System with a Slant Crack Based on Fractional Damping

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Chinese Journal of Mechanical Engineering 2021年第2期34卷 79-96页

作者： Zhinong Li Yunlong Li Dong Wang Zhike Peng Haifeng Wang Key Laboratory of Nondestructive Testing Ministry of EducationNanchang Hangkong UniversityNanchang 330063China Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China State Key Laboratory of Mechanical Systems and Vibration Shanghai Jiaotong UniversityShanghai 200240China

The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent process.The occur of fractional order calculus just makes up for the deficiency in integer-order calculus.Therefore,a new dynamic model with a slant crack based on fractional damping is proposed.Here,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor method.The proposed model is simulated by Runge-Kutta method and continued fraction Euler method.The influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is discussed.The simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional order.With the increase of the rotating speed,the amplitude of first harmonic component becomes gradually larger,the amplitude of the second harmonic becomes smaller,while the amplitude of the other frequency components is almost invariant.The shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without overlapping.With the increase of the slant crack depth,the amplitude of the transverse response frequency in the rotor system with a slant crack increases,and the amplitude in the second harmonic component also increases significantly.In addition,the torsional excitation frequency and other coupling frequency components also occur.The proposed model is further verified by the experiment.The valuable conclusion can provide an important guideline for the fault diagnosis of rotor system with a slant crack.

关键词： Fractional calculus Slant crack Rotor system dynamic characteristics

dynamic characteristics and influencing factors of CO_(2) huff and puff in tight oil reservoirs

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Petroleum Exploration and Development 2021年第4期48卷 946-955页

作者： TANG Xiang LI Yiqiang HAN Xue ZHOU Yongbing ZHAN Jianfei XU Miaomiao ZHOU Rui CUI Kai CHEN Xiaolong WANG Lei State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China Petroleum Engineering Institute China University of Petroleum(Beijing)Beijing 102249China Exploration and Development Research Institute of Daqing Oilfield Co Ltd Daqing 163712China Exploration and Development Department China Southern Petroleum Exploration and Development CorporationPetroChinaHaikou 570100China PetroChina Coalbed Methane Company Limited Beijing 100028China

CO_(2)huff and puff experiments of different injection parameters,production parameters and soaking time were carried out on large-scale cubic and long columnar outcrop samples to analyze dynamic characteristics and influencing factors of CO_(2)huff and puff and the contribution of sweeping mode to recovery.The experimental results show that the development process of CO_(2)huff and puff can be divided into four stages,namely,CO_(2)backflow,production of gas with some oil,high-speed oil production,and oil production rate decline stages.The production of gas with some oil stage is dominated by free gas displacement,and the high-speed oil production stage is dominated by dissolved gas displacement.CO_(2)injection volume and development speed are the major factors affecting the oil recovery.The larger the injected CO_(2)volume and the lower the development speed,the higher the oil recovery will be.The reasonable CO_(2)injection volume and development speed should be worked out according to oilfield demand and economic evaluation.There is a reasonable soaking time in CO_(2)huff and puff.Longer soaking time than the optimum time makes little contribution to oil recovery.In field applications,the stability of bottom hole pressure is important to judge whether the soaking time is sufficient during the huff period.The oil recovery of CO_(2)huff and puff mainly comes from the contribution of flow sweep and diffusion sweep,and diffusion sweep contributes more to the oil recovery when the soaking time is sufficient.

关键词： tight oil CO_(2)huff and puff dynamic characteristics oil recovery influencing factors oil-displacement mechanism

dynamic characteristics OF LAG VIBRATION OF A WIND TURBINE BLADE

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Acta Mechanica Solida Sinica 2013年第6期26卷 592-602页

作者： Yinghui Li Liang Li Qikuan Liu Haiwei Lv School of Mechanics and Engineering Southwest Jiaotong University College of Mathematics Chengdu University of Information Technology

Lagwise dynamic characteristics of a wind turbine blade subjected to unsteady aero- dynamic loads are studied in this paper. The partial differential equations governing the coupled longitudinal-transverse vibration of the blade with large bending deflection are obtained by ap- plying Hamilton＇s principle. The modal problem of the coupled vibration is handled by using the method of numerical integration of Green＇s function. Influences of the rotating speed, the pitch angle, the setting angle, and the aerodynamic loads on natural frequencies are discussed. Results show that：（I） Lagwise natural frequencies ascend with the increase of rotating speed; effects of the rotating speed on low-frequencies are dramatic while these effects on high-frequencies become less. （2） Influences of the pitch angle on natural frequencies are little; in the range of the normal rotating speed, the first frequency ascends with the increase of the absolute value of the pitch angle, while it is contrary to the second and third frequencies. （3） Effects of the setting angle on natural frequencies depend on the rotating speed; influences are not significant at low speed, while they are dramatic on the first frequency at high speed. （4） Effects of the aerodynamic loads on natural frequencies are very little; frequencies derived from the model considering aerodynamic loads are smaller than those from the model neglecting aerodynamic loads; relative errors of the results corresponding to two models ascend with the increase of the absolute value of the setting angle.

关键词： wind turbine blade lag dynamic characteristics rotating speed pitch angle setting angle aerodynamic load

dynamic characteristics of resonant gyroscopes study based on the Mathieu equation approximate solution

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Chinese Physics B 2012年第5期21卷 58-65页

作者：樊尚春李艳郭占社李晶庄海涵 School of Instrument Science&Opto-electronics Engineering Beihang University Key Laboratory of Precision Opto-mechatronics Techonology of Ministry of Education Key Laboratory of Inertial Science and Technology for National Defence

dynamic characteristics of the resonant gyroscope are studied based on the Mathieu equation approximate solution in this paper.The Mathieu equation is used to analyze the parametric resonant characteristics and the approximate output of the resonant gyroscope.The method of small parameter perturbation is used to analyze the approximate solution of the Mathieu equation.The theoretical analysis and the numerical simulations show that the approximate solution of the Mathieu equation is close to the dynamic output characteristics of the resonant gyroscope.The experimental analysis shows that the theoretical curve and the experimental data processing results coincide perfectly,which means that the approximate solution of the Mathieu equation can present the dynamic output characteristic of the resonant gyroscope.The theoretical approach and the experimental results of the Mathieu equation approximate solution are obtained,which provides a reference for the robust design of the resonant gyroscope.

关键词： resonant gyroscopes dynamic characteristics Mathieu equation approximate solution

dynamic characteristics of Tracked Vehicle Power Train Considering Road Random Torsional Excitation

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Journal of Donghua University(English Edition) 2016年第1期33卷 80-86页

作者：符升平李胜波罗宁 School of Mechanical and Automotive Engineering Xiamen University of Technology

The road random torsional excitation is one type of torque rooted from the road roughness and vehicle drive system. This paper aims to study how the road random torsional excitation affects the dynamic characteristics of vehicle power train. The method of simulating the random torsional excitation of tracked vehicle is explored at first. Secondly,the road random torsional excitations under different road roughness,vehicle speeds and pre-tensions are obtained. Thirdly,the dynamic analysis model of tracked vehicle power train is constructed with the consideration of the road random torsional excitation. Eventually,the influences of this excitation on output torque,bearing support force,vibration acceleration and dynamic shear stress of transmission shafts are intensively studied.The research conclusions are helpful to correct and refine the present virtual prototype of tracked vehicle power train.

关键词： road random torsional excitation tracked vehicle power train dynamic characteristics simulation platform

Relationship between dynamic characteristics of air film of aerostatic spindle and mid-frequency of surface topography

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Advances in Manufacturing 2022年第3期10卷 428-442页

作者： Dong-Ju Chen Shu-Pei Li Xuan Zhang Jin-Wei Fan Mechanical Industry Key Laboratory of Heavy Machine Tool Digital Design and Testing Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing 100124People's Republic of China

The dynamic characteristics of the gas film of an aerostatic spindle primary affect workpiece waviness in ultra-precision machining.To improve the machining accuracy of the machine tool and provide a firm theoretical basis for the design of an aerostatic spindle,a simulation model combining transient computational fluid dynamics(CFD)analysis and transient dynamic analysis is established in this study to investigate the dynamic characteristics of the spindle under unstable operating conditions.Based on a large eddy simulation,a three-dimensional flow model of an air film in an aerostatic spindle is established.The simulation results show that the gas flow in the throttle chamber is turbulent,and that complex vortices are formed.Using dynamic grid modeling technology,a CFD numerical model for the unsteady calculation of the spindle is established,and the dynamic characteristics of the gas film are obtained.A transient dynamic simulation model of an aerostatic spindle is established,and the effect of the nonlinear dynamic characteristics of the gas film on the spindle displacement response is investigated.Subsequently,a surface morphology prediction model is established.Results show that film fluctuation significantly affects the dynamic characteristics of the spindle and subsequently affects the generation of surface ripples on the workpiece.

关键词： dynamic characteristics Aerostatic spindle Surface formation Ultra-precision flying cutting

Numerical Investigation on dynamic characteristics of Casing Deformation During Marine Hydrate Production

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China Ocean Engineering 2022年第4期36卷 638-648页

作者： CHANG Yuan-jiang WANG Kang CHEN Guo-ming SUN Bao-jiang SUN Huan-zhao JI Miao-miao Centre for Offshore Engineering and Safety Technology(COEST) China University of Petroleum(East China)Qingdao 266580China College of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China

Formation subsidence is inevitable during marine hydrate decomposition,and the consequent casing deformation seriously threatens the security of sustainable hydrate production.Owing to insufficient observed data of formation subsidence in field,displacement boundary condition of casing is undetermined.Thus the conventional static methods are inapplicable for the calculation of casing deformation in hydrate production well.The present work aims at proposing an approach to investigate dynamic deformation of the casing during hydrate production.In the proposed methodology,based on the movement theory of hydrate decomposition front,hydrate decomposition process can be simulated,in which hydrate reservoir strength formation subsidence showed time-dependent characteristics.By considering the actual interactions among casing,cement and formation,three models of hydrate production well are developed to reveal the static and dynamic deformation mechanisms of the casing.The application of the proposed methodology is demonstrated through a case study.Results show that buckling deformation and bending deformation of casing reduce the passing ability of downhole tools in deformed casing by 4.2%and 7.5%,respectively.With the progress of hydrate production,buckling deformation will increase obviously,while a little increase of bending deformation will occur,as the formation slippage induced by formation inclination is much larger than that caused by hydrate decomposition.The proposed approach can provide theoretical reference for improving casing integrity of marine hydrate production.

关键词： hydrate production casing deformation dynamic characteristics formation inclination