Planet Carrier Research Articles

Load sharing and distributed on the gear flank of wind turbine planetary gearbox

In the design of wind turbine gearboxes, the most important objective is to improve the durability to guarantee a service life of more than 20 years. Planetary gearsets, commonly used in wind turbine gearboxes, should have good load distribution and load sharing among gears to improve the durability. This work investigates how the optimal helix modification influence both the load distribution over the gear tooth flank and the planet load sharing. A whole system model is developed to analyze a wind turbine gearbox (WTG) that consists of planetary gearsets. The model includes the nonlinear mesh stiffness of gears and the nonlinear stiffness of bearings as well as the flexibilities of the housing, planet carriers, and ring gears. The results presented state that if the optimal helix modification is applied, the edge loading of gear tooth ends will disappear and the contact pattern will improve significantly. This is why the face load factor will decrease and the gear safety factor will increase. However, the mesh load factor is decreased slightly after helix modification. This means that the helix modification is not directly related to the mesh load factor.

Planetary Gearbox Vibration Signal Characteristics Analysis and Fault Diagnosis

Planetary gearboxes are widely used in helicopters, wind turbines, mining machinery, and so forth. The structure and motion type of a planetary gearbox are more complex in comparison with a fixed-shaft one, which makes condition monitoring and fault diagnosis of planetary gearbox a challenging issue in practical applications. In order to understand the fundamental nature of planetary gearbox vibration, this paper conducts an investigation on vibration characteristics of a single-stage planetary gearbox. Assuming that the gearbox and the sensor revolve inversely at the speed of planet carrier, the problem can be transformed into two easier parts: research on fixed-shaft gearbox signal model and research on influence of sensor spinning. Based on this assumption, a vibration signal model of planetary gearbox is obtained. Experimental data are used to validate the model.

A hybrid approach for fault diagnosis of planetary bearings using an internal vibration sensor

Planetary gearboxes exhibit unique challenges in bearing fault detection. This paper presents a hybrid approach for fault diagnosis of planetary bearings using an internal vibration sensor and novel signal processing strategies. An accelerometer is mounted internally on the planet carrier to address the issues of variable transmission path. An effective bearing faults detection algorism is developed by employing several advanced signal processing techniques, including Cepstrum whitening, minimum entropy deconvolution (MED), spectral kurtosis (SK) and envelope analysis. The adverse effect of the electromagnetic interference in the signal due to the use of a slip ring is tackled by optimizing the SK technique for demodulation band selection. The proposed method is assessed by analyzing experimental data from a planetary gearbox test rig with seeded bearing faults. The result shows that the new method can effectively detect both inner race and outer race faults of the planetary bearing.

On a Sensitivity-Analysis-Based Design Method for Shearer Parts

To improve the repeatability of CAE analysis and design on shearer parts, the author proposes a static-dynamic integration design method for shearer parts while taking into account their structural features. The idea behind this method is that the design is analysis-driven and together with network technology, parameterized technology and optimization technology, it leads to conceptual design of shearer parts and through the integrated analysis on sensitivity of shearer parts in both static and dynamic states, the best design scheme can be offered to users. The author verifies the feasibility and effectiveness of this method by analyzing here the conceptual design of the planet carrier in the cutting unit of some shearer.

Multi-objective genetic algorithms based structural optimization and experimental investigation of the planet carrier in wind turbine gearbox

To improve the dynamic performance and reduce the weight of the planet carrier in wind turbine gearbox, a multi-objective optimization method, which is driven by the maximum deformation, the maximum stress and the minimum mass of the studied part, is proposed by combining the response surface method and genetic algorithms in this paper. Firstly, the design points’ distribution for the design variables of the planet carrier is established with the central composite design (CCD) method. Then, based on the computing results of finite element analysis (FEA), the response surface analysis is conducted to find out the proper sets of design variable values. And a multi-objective genetic algorithm (MOGA) is applied to determine the direction of optimization. As well, this method is applied to design and optimize the planet carrier in a 1.5MW wind turbine gearbox, the results of which are validated by an experimental modal test. Compared with the original design, the mass and the stress of the optimized planet carrier are respectively reduced by 9.3% and 40%. Consequently, the cost of planet carrier is greatly reduced and its stability is also improved.

Mechanochemical Dechlorination of PVC by Utilizing Eggshell Waste

Within this work, the dechlorination of polyvinylchloride (PVC) chemical as a model by co-milling with eggshell was performed in a planetary ball mill in order to show that mechanochemistry can be utilized for the simultaneous treatment of two wastes, while the products of the treatment can be used in further applications. The products of the reaction are water-soluble calcium chloride (CaCl2), which can be used e.g. for de-icing of roads in winter and organic residue on the basis of ethylene, which can be recovered as energy source. The highest dechlorination yield (almost 97%) was achieved under following milling conditions: molar ratio between Ca and Cl: 2.34, ball-to-powder ratio: 65, rotation speed of the planet carrier: 550 rpm, milling time: 4 h and material of milling media: tungsten carbide. The optimum conditions were then applied for the removal of chlorine from industrial waste the abandoned PVC window parapet. In this case, 95% dechlorination was evidenced.

Planetary Gearbox Fault Diagnosis Using a Single Piezoelectric Strain Sensor


 
 
 Planetary gearboxes are widely used in the drivetrain of helicopters and wind turbines. Any planetary gearbox failure could lead to breakdown of the whole drivetrain and major loss of helicopters and wind turbines. Therefore, planetary gearbox fault diagnosis is an important topic in prognostics and health management (PHM). Planetary gearbox fault diagnosis has been done mostly through vibration analysis over the past years. Vibration signals theoretically have the amplitude modulation effect caused by time variant vibration transfer paths due to the rotation of planet carrier and sun gear, and therefore their spectral structure is complex. It is difficult to diagnose planetary gearbox faults via vibration analysis. Strain sensor signals on the other hand have less amplitude modulation effect. Thus, it is potentially easy and effective to diagnose planetary gearbox faults via stain sensor signal analysis. In this paper, a research investigation on planetary gearbox fault diagnosis via strain sensor signal analysis is reported. The investigation involves using time synchronous average technique to process signals acquired from a single piezoelectric strain sensor mounted on the housing of a planetary gearbox and extracting condition indicators for fault diagnosis. The reported investigation includes analysis results on a set of seeded fault tests performed on a planetary gearbox test rig in a laboratory. The results have showed a satisfactory planetary gearbox fault diagnostic performance using strain sensor signal analysis.
 
 

Performance Comparison of the Fabricated Planet Carrier and the Integral Planet Carrier

This paper compares the performance of the fabricated planet carrier and the integral planet carrier. By using the finite element analysis, the paper will found which planet carrier has the better performance in the same structure and load conditions. And draw the conclusions.

A CFD analysis of the oil squeezing power losses of a gear pair

Effi ciency is becoming more and more a main concern in the design of power transmissions and the demand for high effi ciency gearboxes is continuously increasing. Also the more and more restrictive euro standards for the reduction of pollutant emissions from light vehicles impose to improve the effi ciency of the engines but also of the gear transmissions. For this reason the resources dedicated to this goal are continuously increasing. The fi rst step to improve effi ciency is to have appropriate models to compare different design solutions. Even if the effi ciency of transmissions is quit high if compared with the effi ciency of the engines and appropriate models to predict the power losses due to gear meshing, to bearings and to seals already exist, in order to have a further improvement, some aspects like the power losses related to the oil churning, oil squeezing and windage are still to be investigated. In previous papers the authors have investigated by means of computational fl uid dynamic (CFD) analysis and experimental measurements the churning losses of planetary speed reducers (in which there is a relative motion between the “planets + planet carrier” and the lubricant). Also the windage power losses have been studied by the authors in previous papers. This report is focused on the oil squeezing power losses. This kind of losses is associated with the compressionexpansion process by the meshing teeth. The contraction of the volume at the gear mesh implies an overpressure that induces a fl uid fl ow primarily in the axial direction and this, for viscous fl uids, means additional power losses and a decrease of the effi ciency. In this work this phenomena has been studied by means of some CFD simulations. The infl uence of some operating conditions like the lubricant properties, the rotational speed and the temperature has been studied.

Structural Design and Finite Element Analysis for Planet Wheel Gear System

Calculation the gear bottom bending strength and the gear surface contacting stress are traditional wheel gear design method. It takes a long time to design and works out parameters for gears system. Nowadays, the optimization design and reliability theory are introduced into modern engineering, we can make full use of the calculator tool to look for the best design parameter. Modern powerful finite element analysis software packages such as ANSYS are now not only an analysis tool but a design tool as well. This kind of technology makes planet wheel gear system design quantified precisely combining with physics principles in one. In the study, we designed a planet carrier with traditional method and built three dimensional full-scale model in Pro/E software. Based on finite element analysis, the finally result of stress distribution and deformation distribution is obtained. The results indicate that the design can meet the requirement.

The dynamic behavior induced by different wind turbine gearbox suspension methods assessed by means of the flexible multibody technique

The continuous demand for increase in power output for new wind parks under strict cost constraints, the greater wind resource at elevation and the desire for fewer machines per Mega-Watt to reduce operations resulted in a demand for bigger turbines. The drive train is an important component in realizing reliable and robust wind turbines.This paper investigates a geared wind turbine. In this type a gearbox is used to convert the low rotor speed to the required high generator speed. In the market several solutions are available to constrain the gearbox in the nacelle. The used configuration significantly determines the gearbox response to rotor loads and the transmission of gearbox vibrations to the turbine. This paper investigates the effectiveness of three configurations: the three point mounting, the double bearing configuration and the hydraulic damper system. The flexible multibody modeling technique can be used to accurately characterize gearbox dynamics. The goal of this work is to use an experimentally validated multibody model of a wind turbine drive train as a starting point to characterize the ability of the three configurations to minimize the introduction of non-torque loads in the gearbox and the ability to isolate the high speed shaft initiated gearbox vibrations from the rest of the turbine.A case study with parameter variation was performed on the existing three point mounted NREL GRC drive train. Furthermore some modifications were done to simulate a two bearing configuration and a hydraulic suspension system. We performed a parametric study to visualize the trends governing suspension influences.This paper shows that the two bearing configuration and the hydraulic system generally have lower rear planet carrier bearing response amplitudes than the three point mounting configuration. In addition, the hydraulic system was able to remove an important resonance.The paper concludes with a sensitivity analysis to link the trends above to their driving parameters.

Adaptive Fixturing System for the Smart and Flexible Positioning of Large Volume Workpieces in the Wind-power Sector

Quality and productivity in a manufacturing process depend considerably on the toolkits used, whose basic functions are to position the component into a right position relative to the cutting tool and to hold the component tightly to avoid displacements during the machining. In this document the design of a smart and adaptive fixture is presented for the accurate positioning of a planet carrier with very strict requirements of tolerances and for an intelligent adjustment during the machining process when required. This device will allow the manufacturer reducing the manual inspections, automatizing the adjustment tasks and improving the machining process setup time, increasing consequently the productivity and achieving the required accuracy and the required geometrical quality of the part. The development of the intelligent fixturing will be focused mainly in the conception of a high precision actuator capable of moving the large part with the required tolerance. Moreover, a testbench has been developed that will allow validating the actuator, assuring therefore its applicability in the future industrialization of the fixture device.

基于差动轮系调速的风力发电机的动力学建模与分析

对基于无级调速原理的风力发电机动力学建模，改变传统风力发电机的齿轮箱传动比固定而采用电子方法实现变速恒频的特性，通过增加差动轮系的自由度，采用机械调速方式进行前端调速，使输出转速与转矩恒定，达到变速恒频的目的。以实现调速功能的差动轮系为主要研究对象，将整个风力发电机传动链简化成三个部分：行星架输入轴、太阳轮输出轴和齿圈调速轴，并运用拉格朗日方程和差动轮系转速约束关系，建立动力学方程。结合风力发电机并网要求，此外还研究了该情形下的动力学关系，将并网后的动力学问题即转化为：输出转速恒定条件时，可变的风轮转矩作用下，调速电机的调速问题。Based on the principle of stepless speed regulation, dynamic modeling of wind turbine has been done. Having changed fixed transmission ratio characteristic of gearbox in traditional wind turbines and the variable speed constant frequency characteristic realized by electronic method, the freedom of differential gear train is increased and the mechanical means have been used for the fore-end speed regulation in order to achieve constant output speed and torque. Taking the diffe-rential gear train as the main learning object, in this paper the wind turbine transmission chain is divided into three parts: planet carrier input shaft, sun wheel output shaft and ring gear speed- regulation shaft, and dynamic equations are established using the Lagrange equation and the speed constraint relations of differential gear train. Therefore, to satisfy the grid-connected requirement, the dynamic relationship in this circumstance is also learned. The dynamic problem can be transformed into the speed-regulation problem of speed-regulation motor under the variable wind turbine torque to achieve constant output speed.

Influence of lubricant temperature, lubricant level and rotational speed on the churning power loss in an industrial planetary speed reducer: computational and experimental study

Planetary speed reducers are applied in a wide range of applications. Their main advantages are the compact design and high power density. For this reason, the demand for high effi ciency gearboxes is continuously increasing and this is also why models to predict the additional churning loss, characteristic of this kind of gearing, are required. The particular confi guration of the planetary speed reducers, in fact, entails an additional motion with a circular path around the gearbox axis of the planetary gears due to the rotation of the planet carrier on which they are mounted and this induces an additional source of loss. Having effi ciency prediction models allows, in fact, comparison of different solutions during the design step. Literature provides some prediction models for ordinary gears but no models are still available for planetary gears. This report introduces a computational and experimental analysis of this kind of loss. Many simulations have been performed and the infl uence of many operating conditions like lubricant level and temperature and the rotational speed of the planet carrier have been studied. Moreover, the results of an experimental testing campaign on a specially designed gearbox are presented and compared with the computational ones to validate the model. The two approaches give results in good agreement.

Dynamics Simulation and Analysis of Planetary Reducer

Taking a planetary reducer in an electric vehicle as the object of study, a rigid-flexible coupling model was established to perform the dynamics simulation. The variational regularities of the meshing forces, output speed and acting forces of bearings were obtained, and then a finite element analysis of the planet carrier was carried out. This method can not only solve the problem of the boundary conditions of planet carrier which are difficult to define in finite element analysis, but also improve the accuracy of analysis results when the influence of carrier flexibility on the whole system is considered in dynamics simulation, which lays the foundation for further research on reducers.

A dynamic model of a double-helical planetary gear set

A linear, time-invariant model of a double-helical planetary gear set is proposed in this paper. The model formulation allows the analysis of a gear set with any number of planets, any planet phasing and spacing configurations and any support conditions. Torsional, transverse, axial and rotational (rocking) motions of gears and the planet carrier are included in this three-dimensional model. Planets are allowed to be positioned equally or unequally spaced around the sun gear. The natural modes are computed by solving the corresponding Eigen value problem. The modal summation technique is used to find the forced response due to periodic gear mesh excitations under constant or proportional modal damping conditions. An example gear set consisting of four equally-spaced planets is considered at the end to demonstrate the influence of key design parameters including right-to-left stagger angle, and support conditions on the dynamic response of the double-helical planetary gear system. Numerous modes with dominant tilting motions are predicted to underline the essence of using a 3D formulation for double helical gears. Staggering of gear teeth is shown to impact the dynamic response of the gear system substantially. Different values of stagger are shown excite different types of modes, resulting in different dynamic response curves. It is also found that left and right sides of double helical gears can carry equal or different dynamic load amplitudes based on the right-to-left stagger values. Likewise the influence of the sun support conditions is shown to be more pronounced for the case of a non-zero stagger.

Three‐dimensional bearing load share behaviour in the planetary stage of a wind turbine gearbox

The Gearbox Reliability Collaborative has conducted extensive field and dynamometer test campaigns on two heavily instrumented wind turbine gearboxes. In this study, the load sharing behaviour between six bearings in the planetary stage is described using a combined approach of measurement and simulation. First, planet-bearing data are analysed to characterise planetary stage behaviour in different environments. Second, a method is described for integrating the measured responses of the planetary stage into an advanced model of the bearing life that significantly changes the life prediction. Third, a sensitivity study of the planet bearings is conducted using multibody gearbox models. Various levels of gearbox flexibility and different planet assembly fits are investigated and compared with experimental observations. Measurements in the dynamometer and field show that bearing loading differs significantly between the six planet bearings. The relative loading behaviour of the planetary stage bearings is directly influenced by boundary conditions of the planet carrier pins. Assembly differences between two identically designed gearboxes cause different load sharing behaviour. Simulations are used to quantify the effect of different component flexibilities. Reduced order models are developed to accurately predict bearing loading in a cost-efficient manner.

Three-Roll Planetary Rolling Mill Motion Analysis and Test Research

Against defects of three-roll fixed axis rolling mill caused by rolled piece rotating in process of rolling, presented three-roll planetary rolling scheme, designed the planetary transmission system structure, expounded planetary mill rolling process, analyzed movement relationship between planet carrier, roll and rolled piece according to planetary gear train transmission principle. The rolls do planetary motion and spinning motion both, the former acts on the rolled piece to make it do clockwise rotation movement, the latter acts on the rolled piece to make it do anti-clockwise rotation. The actual movement of rolled piece is combination of the two motions. The theoretical analysis and calculation shows that in rolling process of planetary mill, the speeds of above two kinds of motions are very close, directions are opposite. Due to rolls are inclined compare to the rolled piece, as a result rolled piece does axial movement with a speed of vsinα, radial rotation speed is 0.0029 times of planet carrier rotational speed. Thanks to complexity of extrusion and friction between rolls and rolled piece, the actual speed of rolled piece is approximately zero. Prototype rolling test has verified correctness of theoretical analysis and calculation.

Assessment of excitation mechanisms and structural flexibility influence in excitation propagation in multi-megawatt wind turbine gearboxes: Experiments and flexible multibody model optimization

Reliable gearbox design calculations require sufficient insight in gearbox dynamics, which is determined by the interaction between the different excitation mechanisms and the gearbox modal behavior. Both external gearbox excitation originating from the wind turbine drive train and internal gearbox excitation are important. Moreover with regard to the modal behavior the different gearbox structural components: planet carrier, shafts and housing are of influence. The main objective of this article is the experimental investigation of the interaction between the different excitation mechanisms and the gearbox modal behavior. The insights gathered are used to prove the need for accurate gear mesh representation and structural flexibility within the corresponding flexible multibody gearbox simulation model. Experiments are conducted on a dynamic 13.2MW test facility on which two multi-megawatt wind turbine gearboxes are placed back to back and subjected to a speed run-up. Measurement sensors consist of bearing displacement sensors, torque sensors, encoders and accelerometers distributed over the gearbox. Excitation order amplitudes on different locations in the gearbox are determined by means of a Time Varying Discrete Fourier Transform (TVDFT) order tracking on the measured sensor signals. Moreover the propagation of this excitation throughout the gearbox is assessed. Relating the orders to the corresponding excitation source allows the definition of order influence regions within the gearbox. The interaction between the gear mesh order excitation and structural flexibility is shown.

Finite-element modeling of the failure of interference-fit planet carrier and shaft assembly

A planet carrier and shafts assembly with interference-fit was modeled based on 3-D finite element method by applying thermal loads to the shafts with orthotropic coefficients of thermal expansion. A 3-D finite element contact model verified that the contact pressure is identical compared with the calculated pressure by Lamé’s equations for the thick-wall cylinder interference-fit. A displacement history analysis by the 3-D finite element multi-contact simulation under alternate loads reveals the root cause for the interference-fit shafts coming out of the planet carrier after 65h of planetary gear reducer working test.