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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 ***,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent *** occur of fractional order calculus just makes up for the deficiency in integer-order ***,a new dynamic model with a slant crack based on fractional damping is ***,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor *** proposed model is simulated by Runge-Kutta method and continued fraction Euler *** influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is *** simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional *** 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 *** shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without *** 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 *** addition,the torsional excitation frequency and other coupling frequency components also *** proposed model is further verified by 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 of Hydrocarbon Fuel within the Channel at Supercrit- ical and Pyrolysis Condition

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Journal of Thermal Science 2017年第6期26卷 560-569页

作者： YU Bin ZHOU Weixing QIN Jiang BAO Wen Harbin Institute of Technology 150001 Heilongjiang China

Regenerative cooling with fuel as the coolant is used in the scramjet engine. In order to grasp the dynamic cha- racteristics of engine fuel supply processes, this article studies the dynamic characteristics of hydrocarbon fuel within the channel. A one-dimensional dynamic model was proved, the thermal energy storage effect, fuel volume effect and chemical dynamic effect have been considered in the model, the ordinary differential equations were solved using a 4th order Rungc-Kutta method. The precision of the model was validated by three groups of expe- rimental data. The effects of input signal, working condition, tube size on the dynamic characteristics of pressure, flow rate, temperature have been simulated. It is found that cracking reaction increased the compressibility of the fuel pyrolysis mixture and lead to longer responding time of outlet flow. The responding time of outlet flow can reach 3s when tube is 5m long which will greatly influence the control performance of the engine thrust system. Meanwhile, when the inlet flow rate appears the step change, the inlet pressure leads to overshoot, the overshoot can reach as much as 100%, such highly transient impulse will result in detrimental effect on fucl pump.

关键词： dynamic characteristics n-Decane supercritical pyrolysis

dynamic characteristics analysis and flight control design for oblique wing aircraft

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Chinese Journal of Aeronautics 2016年第6期29卷 1664-1672页

作者： Wang Lixin Xu Zijian Yue Ting School of Aeronautics Science and Engineering Beihang University

The movement characteristics and control response of oblique wing aircraft(OWA) are highly coupled between the longitudinal and lateral-directional axes and present obvious nonlinearity. Only with the implementation of flight control systems can flying qualities be satisfied. This article investigates the dynamic modeling of an OWA and analyzes its dynamic ***, a flight control law based on model-reference dynamic inversion is designed and verified. Calculations and simulations show that OWA can be trimmed by rolling a bank angle and deflecting the triaxial control surfaces in a coordinated way. The oblique wing greatly affects longitudinal motion. The short-period mode is highly coupled between longitudinal and lateral motion,and the bank angle also occurs in phugoid mode. However, the effects of an oblique wing on lateral mode shape are relatively small. For inherent control characteristics, symmetric deflection of the horizontal tail will generate not only longitudinal motion but also a large rolling rate. Rolling moment and pitching moment caused by aileron deflection will reinforce motion coupling, but rudder deflection has relatively little effect on longitudinal motion. Closed-loop simulations demonstrate that the flight control law can achieve decoupling control for OWA and guarantee a satisfactory dynamic performance.

关键词： Control allocation Decoupling dynamic characteristics Model-reference dynamic inversion Oblique wing aircraft

dynamic characteristics of High-speed Water-Lubricated Spiral Groove Thrust Bearing Based on Turbulent Cavitating Flow Lubrication Model

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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 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 LARGE FLOW RATING ELECTROHYDRAULIC PROPORTIONAL CARTRIDGE VALVE

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Chinese Journal of Mechanical Engineering 2008年第6期21卷 57-62页

作者： FU Linjian WEI Jianhua QIU Minxiu State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

A kind of cartridge servo proportional valve is discussed, which can be used for controlling large flow rate with high performance. By analyzing the structure principle of the valve, the transfer fimction of the valve is derived. With the transfer function, some structure elements that may affect its performance are investigated. Through the numerical simulation and test study, some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The test results conform to the results of the theoretical analysis and simulation, which proves the correctness of the study and simulation works. The paper provides theoretical basis for engineering applications and series expanding design works

关键词： Large flow rate electro-hydraulic proportional cartridge valve dynamic characteristics

dynamic characteristics of the Long Runout Rock-ice Avalanche at High Altitude——A Case from the Zelongnong Basin,Eastern Himalayan Syntaxis,China

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Acta Geologica Sinica(English Edition) 2024年第5期98卷 1376-1393页

作者： GAO Shaohua YIN Yueping LI Bin GAO Yang ZHANG Nan ZHANG Tiantian GAO Haoyuan LIU Xiaojie Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China China Institute of Geological Environment Monitoring Beijing 100081China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesBeijing 100081China School of Civil Engineering Lanzhou University of TechnologyLanzhou 730050China

Rock-ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic *** events commonly trigger catastrophic geohazard chains,including debris flows,river blockages,and *** study focuses on the Zelongnong Basin,analyzing the geomorphic and dynamic characteristics of high-altitude *** basin exhibits typical vertical zonation,with disaster sources initiating at elevations exceeding 4000 m and runout distances reaching up to 10 *** disaster chain movement involves complex dynamic effects,including impact disintegration,soil-rock mixture arching,dynamic erosion,and debris deposition,enhancing understanding of the flow behavior and dynamic characteristics of rock-ice *** presence of ice significantly increases mobility due to lubrication and frictional *** the disaster event of September 10,2020,the maximum flow velocity and thickness reached 40 m/s and 43 m,***,continuous deformation of the Zelongnong glacier moraine was observed,with maximum cumulative deformations of 44.68 m in the distance direction and 25.96 m in the azimuth direction from March 25,2022,to August 25,*** the future,the risk of rock-ice avalanches in the Eastern Himalayan Syntaxis region will remain extremely high,necessitating a focus on early warning and risk mitigation strategies for such basin disasters.

关键词： rock-ice avalanche dynamic characteristics mobility moraine Eastern Himalayan Syntaxis

dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

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Journal of Central South University of Technology 2004年第4期11卷 451-456页

作者：杨忠炯何清华柳波 School of Mechanical and Electrical Engineering Central South University Changsha 410083 China

Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

关键词： load-haul-dump vehicle hydraulic power steering system accumulator dynamic characteristics (simulation)

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 ***,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 ***,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 *** on the differential quadrature method theory,the eigenvalue problem of ordinary differential equations is transformed into the eigenvalue problem of standard generalized algebraic ***,the first several natural frequencies of the beam can be *** 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