Dynamic analysis of the drive train of a wind turbine based upon the measured load spectrum

Caichao Zhu,Shuang Chen,Hua iju Liu,Huaqing Huang,Guangfu Li,Fei Ma 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6

A dynamic model of the drive train of a megawatt wind turbine is proposed in which the blades, the hub, the main shaft, and the speedupgearbox are assumed as flexibilities. The external excitation due to the measured load spectrum and the internal excitations due to thetime-varying mesh stiffness, the transmission errors, and the meshing impacts within the gearbox are considered to predict the dynamicresponse of the system. Results show that the most vibration energy occurs at the speed-up gearbox, followed by the generator, and thenthe main shaft. An experimental remote real-time system is developed to monitor vibration performance of the drive train, with which theaccelerations of components are detected. The experimental results are in accordance with the theoretical results.

Dynamic analysis of a megawatt wind turbine drive train

Caichao Zhu,Shuang Chen,Chaosheng Song,Hua iju Liu,Houyi Bai,Fei Ma 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

The dynamic performance of a wind turbine drive train significantly influences the operation of an entire machine. In this work, amegawatt wind turbine drive train is subject to theoretical and experimental dynamic analysis. The method of rigid-flexible couplingmultibody dynamics was applied to develop a dynamic model of the entire drive train. This model was then used to study the naturalcharacteristics of the system. The blades, hub, main shaft, and speed-up gearbox in the dynamic model were modeled as flexible bodies. The potential resonances of the system were detected through Campbell and modal energy distribution analyses. Theoretical results showthat the first-order natural frequency of the system is approximately 1.72 Hz. This frequency represents a torsional vibration mode,Moreover, resonances are not observed within the normal operating speed range of the drive train. An experimental remote real-timesystem was developed to monitor the torsional vibration of the drive train. This vibration was used to measure the torsional vibration ofthe system overall. The experimental results are consistent with the theoretical results.

Investigation of dynamic characteristics of planetary gear stage in wind turbine considering voltage dip

Jianjun Tan,Caichao Zhu,Chaosheng Song,Xiangyang Xu,Zi Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

The transient variation of electrical parameters makes system loads fluctuate and reduces bearing capacity when the grid voltage dips. This work proposes an electromechanical coupling dynamic model of the wind turbine drivetrain to build a dynamic interconnection between the electric and drivetrain subsystems. The drivetrain subsystem that includes an improved model of the planetary gear stage is developed and validated. This improved model considers the carrier and planet bearing clearances, the connection relationship among the carrier, main shaft, and planets as well as the flexibilities of the main shaft and parallel stage shafts. The influences of the carrier bearing clearances, non-torque load and planet position angle on planet bearing loads are investigated under the low-voltage ride through (LVRT) event. The results indicate that as the LVRT occurs, the planet bearing loads reduce below the minimum requisite with a high, fluctuating system speed; considering the bearing clearances, the impacts occur in the planet bearing in the minimum load zone followed by significant stress variation; the non-torque load suppresses the planet bearing impacts in a limited range of carrier bearing clearance; the planet position angle has a significant effect on the planet bearing impacts because of the asymmetry of load and structure of the planetary gear stage.

Dynamic modeling and analysis for transmission system of high-power wind turbine gearbox

Hongfei Zhai,Caichao Zhu,Chaosheng Song,Hua iju Liu,Guangfu Li,Fei Ma 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

As a key component to adjust the speed and torque, double-fed speed up gearbox plays a vital role in reliability and stability for thewind turbine system. Considering the base helix angle, normal pressure angle, position angle, rotation of carrier and the mesh of the ringgear and planet gear, a coupled dynamic model for high-power wind turbine gearbox transmission system, which consists of two helicalplanetary stages and one helical gear stage was established using the lumped parameter method in this paper. Numerical integration applyingthe explicit 4/5th order Runge-Kutta algorithm was used to solve the proposed model and the dynamic responses of transmissionsystem were investigated. Results show that the modal frequencies for the system are not coincided with the gear mesh frequencies of thestages. Then, the dynamic mesh forces of the 1st stage in different models are compared and analyzed in frequency domain.

Effects of gear modifications on the dynamic characteristics of wind turbine gearbox considering elastic support of the gearbox

Shuaishuai Wang,Caichao Zhu,Chaosheng Song,Huachao Liu,Jianjun Tan,Houyi Bai 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

The reliability and service life of wind turbines are directly influenced by the dynamic performance of the gearbox under the timevarying wind loads. The control of vibration behavior is essential for the achievement of a 20-year service life. We developed a rigidflexible coupled dynamic model for a wind turbine gearbox. The planet carrier, the housing, and the bedplate are modelled as flexibilities while other components are assumed as rigid bodies. The actual three points elastic supporting are considered and a strip based mesh model is used to represent the engagement of the gear pairs. The effects of gear tooth modifications on the dynamics were investigated. Finally, we conducted a dynamic test for the wind turbine gearbox in the wind field. Results showed that the contact characteristics of gear pairs were improved significantly; the peak-to-peak value of transmission error of each gear pair was reduced; the amplitudes of the vibration acceleration and the structural noise of the wind turbine gearbox were lowered after suitable tooth modification.

Dynamic characteristics and experimental study on a wind turbine gearbox

Liang Xu,Caichao Zhu,Hua iju Liu,Guo Chen,Wei Long 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

A gearbox is part of the transmission chain of wind turbine, which can increase rotational speed and reduce torque. Dynamic characteristics of the gearbox directly influence the vibration and the service life of the wind turbine system. In this paper, dynamic behaviors of a megawatt level wind turbine gearbox are studied theoretically and experimentally by dividing the gearbox into a transmission sub-system and a body sub-system. The transmission sub-system, i.e., the gear-shaft-bearing sub-system, is coupled with the gearbox body using bearings which are simulated as mass-less springs. The theoretical study applies a finite element model for the gearbox, where the internal excitations are caused by time-varying stiffness, transmission errors and mesh impacts. The time-varying wind load is considered as the external excitation, collected by a remote real-time online test and transformed into load spectrums through the rain-flow counting method. With boundary conditions and working conditions being defined in the finite element model, the natural characteristic analysis and the dynamic response analysis are conducted. Results show that the operating frequencies of the gearbox are far away from the main natural frequencies of the system, thus avoiding resonances. The main vibration components of the gearbox are with meshing frequencies of the second and third gear stage and their multiplication counterparts. Moreover, the greatest vibration occurs at the bearing housing of the high-speed shaft with the root-mean-square value of its vibration speed less than 3.5 mm/s. A test rig is developed and the experimental vibration conditions are monitored by acceleration sensors. The experimental results are in accordance well with the theoretical results. In this way, the theoretical model is validated. The methodology reported in this paper can provide valuable guidance for practical industrial engineers.

Parametric studies of lubrication performance of a helical gear pair with non-Newtonian fluids

Mingyong Liu,Caichao Zhu,Hua iju Liu,Chenhui Wu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1

In this paper, Thermal elastohydrodynamic lubrication (TEHL) model of a helical gear pair is proposed to study contact performanceduring the whole meshing period. Effects of working conditions and design parameters on lubrication performance, i.e. film thickness,pressure, temperature, friction coefficient, etc. are investigated. Influence of thermal effect and non-Newtonian effect are evaluatedthrough a detailed study on three characteristic meshing positions. Results show that, the thermal effects and non-Newtonian fluid bothhave significant effects on the lubrication performance of the helical gear pair, especially in high speed, heavy load cases. The effects ofnormal pressure angle, helix angle and module on lubrication performance along the line of action are discussed.

Effects of macro-parameters on vibration and radiation noise for high speed wheel gear transmission in electric vehicles

Xi Chen,Chaosheng Song,Caichao Zhu,Jianjun Tan,Najeeb Ullah 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Considering flexible shafts, a coupled dynamic model for the gear transmission system of wheel reducer used in electric vehicle was developed. By combining the acoustics finite element modal for housing in Virtual Lab and the coupled dynamic model for gear transmission system, a simulation method was proposed for the prediction of the radiation noise for the wheel reducer. Then, the effects of different macro geometry gear parameters including pressure angle and helical angle on the dynamic response and radiation noise were investigated under the rated working condition. Results show that the peak-peak value of the transmission error dramatically falls in the starting zone, followed by an upward trend with the increase of the pressure angle for the low speed stage gear pair. The minimum transmission error and vibration acceleration occur when the pressure angle is 17°. The increase of the pressure angle does not affect the sound pressure level at the field point obviously. The design case with 17° pressure angle shows the optimum radiation noise level, which is 4.41dB less than the original model. Compared to the pressure angle, the helix angle has a major influence on the transmission error, vibration acceleration and acoustic radiation noise. With the increase of the helix angle, the time-varying transmission error curve becomes more smooth with a lower peak-peak value. Besides, the increase of helix angle results in lowering the varying and fluctuating trend of both vibration acceleration and acoustic radiation noise. The design case with 24° helix angle shows the prime radiation noise level, which is 7 dB less than the original scheme.

Mesh stiffness analysis of beveloid gears for the rotating vector transmission

Yucheng Huang,Xuesong Du,Caichao Zhu,Gaoxiang Ni,Najeeb Ullah,Hao Liu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.8

This paper investigates the meshing stiffness of beveloid gears in the beveloid rotate vector (BRV) transmission. It is a new kind of transmission evolved from rotate vector (RV) reducer. In the BRV transmission, the beveloid gear is a kind of involute gear with a bevel angle. The BRV transmission have high power density, large transmission ratio and high precision in geared coupled systems. However, there is rare systematic research conducted on the meshing stiffness analysis of the BRV transmission at present. Based on the loaded contact finite element analysis principle, a meshing stiffness analysis model for beveloid gears is established. The influence of different factors such as pitch cone angle, addendum coefficient, load and rim structure parameters of external gear on meshing stiffness are studied. The results show that the pitch cone angle and addendum coefficient have little effect on the shape of the meshing stiffness curve, but they have a significant influence on the amplitude of meshing stiffness. In contrast, the load can affect both the shape and the amplitude of the meshing stiffness curve obviously. Also, the size of scallop-hole and rim thickness have a great impact on the amplitude of the meshing stiffness. The prescribed piece of study can provide a better understanding for gear researchers in order to understand the influence of different parameters on dynamic characteristics analysis of the BRV transmission systems.

Sliding friction effect on dynamics of crossed beveloid gears with small shaft angle

Song Chaosheng,Zhu Caichao,Liu Wenji 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

We propose a new method of incorporating the gear sliding friction model and loaded mesh model into an analytical nonlinear crossed beveloid geared vibration model to evaluate the mesh and dynamic characteristics. A 3-dimensional quasi-static loaded tooth contact analysis is employed and the derivation of distributed sliding friction forces and synthesis of frictions to the effective form is applied in the nonlinear dynamic analysis. Using the proposed method, the excitation effects of frictions on tooth mesh and dynamic responses at different load levels are found and investigated. The analysis results show that the existence of sliding frictions between the engaged teeth indeed tends to affect the contact pattern, normal load distribution and maximum contact pressure, but it is unsubstantial. The torque load effect of friction is found with greater degressive influence on mesh stiffness and transmission error at heavier load case. The magnitude and directionality of sliding friction on effective total engaged teeth exhibit less obvious variations than on each tooth due to the contributions from multiple teeth effect. Also, friction excitations tend to decrease the dynamic mesh force slightly for both light and heavy load cases.