scholarly journals Minimum friction losses in wind turbine gearboxes

2021 ◽  
Author(s):  
José I. Pedrero ◽  
Débora Martínez-López ◽  
José Calvo-Irisarri ◽  
Miguel Pleguezuelos ◽  
Miryam B. Sánchez ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Thermal Stresses ◽  
Operating Conditions ◽  
The Other ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Tooth Root ◽  
Noise Emission ◽  
Stress Levels ◽  
Root Stress

AbstractImproving the mechanical efficiency is not the most important objective in the design of wind turbine gearboxes since the available wind energy is abundant and costless. The most important criteria for dimensioning the gearbox are the fatigue strength—bending and pitting—, noise emission, vibrations, and maintenance requirements. Nevertheless, mechanical losses increase the lubricant temperature and induce thermal stresses, which increases wear and cracking risk. This means that friction losses should be reduced as much as possible, but always regarding the contact and tooth-root stress levels, as well as the other operating parameters which should be kept for ensuring the required operating conditions.In this paper, a study on the variation of the friction losses with the tooth shift coefficients is presented. All the other geometrical parameters—number of teeth, tooth height, pressure angle, helix angle, face width, and center distance—are unalterable, since all of them have been chosen according to more important design requirements. In addition, to keep the contact and tooth-root stress levels, the shift coefficients of the sun, planets and ring are calculated in such a way that the transverse contact ratios are kept, and therefore the critical load points for bending and pitting are also unchanged. The radial clearance is also kept in order to allow the proper evacuation of the lubricant. Finally, all the geometrical constraints (undercut, pointing, root interference, secondary interference, backlash) are also imposed. With all these restrictions, the optimal shift coefficients for all the gears are calculated to minimize the friction losses.

Tooth Root Stresses of Helical Gear Pairs With Unequal and Offset Face Widths

2011 ◽  
Author(s):  
Carlos H. Wink
Keyword(s):  
Load Distribution ◽  
Element Model ◽  
Helical Gear ◽  
The Other ◽  
Gear Pair ◽  
Tooth Root ◽  
Pair Member ◽  
Face Width ◽  
The Face ◽  
Root Stress

In this study, tooth root stresses of helical gear pairs with different combinations of face width increase and offsets were analyzed. Contact face width was kept constant. The variables studied were face width and gear faces offset. The well-known LDP – Load Distribution Program was used to calculate tooth root stresses using a finite element model. The results presented show that the face width increase and offset have a significant influence on tooth root stresses. In some cases, increasing face width of one gear pair member resulted in significant increase of tooth root stress of the other member. For gear pairs with unequal and offset face widths, tooth root stresses were mostly affected when face widths were increased to the same direction of the contact line travel direction.

An Analysis of Power Characteristics of Oil-Free Scroll Vacuum Pumps

2020 ◽  
pp. 37-43
Author(s):  
A.V. Tyurin ◽  
A.V. Burmistrov ◽  
A.A. Raykov ◽  
S.I. Salikeev
Keyword(s):  
Mathematical Model ◽  
Power Efficiency ◽  
High Speed ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Total Power ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Power Characteristics ◽  
Indicator Power

This paper presents an analysis of the indicator power of an oil-free scroll vacuum pump based on the indicator diagrams obtained through high-speed pressure sensors. These values are compared with the results of calculations using a mathematical model of the pump working process. It is shown that the divergence of the calculated results and experimental values does not exceed 4%, which confirms the adequacy of the developed mathematical model. The total power of the scroll pump exceeds the indicator power by more than 2 times due to the friction losses between the face seals and disks of the reciprocal scroll elements, friction losses in the stuffing box seals and rolling bearings, as well as due to the coefficient of efficiency of the motor. The influence of the radial clearance between the scroll elements on the power consumption is considered. It is shown that at low pressures nearing the ultimate pressure, the power increases with the increased clearance, while at inlet pressures exceeding 40 kPa it decreases. The performed analysis can be used for selecting the optimal geometrical parameters of the scroll elements and increasing power efficiency of the pump depending on specific operating conditions.

Comparison between 3D FEM and Standard ISO Tooth Root Stresses

2011 ◽  
Vol 488-489 ◽  
pp. 85-88
Author(s):  
Gordana Marunić ◽  
Goran Gregov ◽  
Vladimir Glažar
Keyword(s):  
Stress Analysis ◽  
Practical Interest ◽  
Fem Analysis ◽  
Geometrical Parameters ◽  
Tooth Root ◽  
3D Fem ◽  
Stress Calculation ◽  
Stress Behaviour ◽  
Root Stress ◽  
The Web

The paper deals with the discussion how nominal spur tooth root stress of thin-rimmed gear determined in accordance with the standard ISO 6336-3:2006, method B, agrees with the results of the 3D FEM stress analysis. The procedure proposed by standard ISO for the tooth root stress calculation doesn’t identify the stress behaviour related to mutual affects of characteristic thin-rimmed gear geometrical parameters. Therefore, the 3D FEM analysis of tooth root stress has been performed for gear structures with middle and offset web with various rim and web thickness. The rim thickness has covered and slightly overcome the backup ratio defined by ISO procedure, while the web thickness has covered the range of practical interest.

scholarly journals Sustainable Self-Cooling Framework for Cooling Computer Chip Hotspots Using Thermoelectric Modules

2021 ◽  
Vol 13 (22) ◽  
pp. 12522
Author(s):  
Hamed H. Saber ◽  
Ali E. Hajiah ◽  
Saleh A. Alshehri
Keyword(s):  
Heat Generation ◽  
Electrical Power ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
The Other ◽  
Large Temperature ◽  
Geometrical Parameters ◽  
Thermoelectric Modules ◽  
Computer Chips ◽  
Wasted Heat

The heat generation from recent advanced computer chips is increasing rapidly. This creates a challenge in cooling the chips while maintaining their temperatures below the threshold values. Another challenge is that the heat generation in the chip is not uniform where some chip components generate more heat than other components. This would create a large temperature gradient across the chip, resulting in inducing thermal stresses inside the chip that may lead to a high probability to damage the chip. The locations in the chip with heat rates that correspond to high heat fluxes are known as hotspots. This research study focuses on using thermoelectric modules (TEMs) for cooling chip hotspots of different heat fluxes. When a TEM is used for cooling a chip hotspot, it is called a thermoelectric cooler (TEC), which requires electrical power. Additionally, when a TEM is used for converting a chip’s wasted heat to electrical power, it is called a thermoelectric generator (TEG). In this study, the TEMs are used for cooling the hotspots of computer chips, and a TEC is attached to the hotspot to reduce its temperature to an acceptable value. On the other hand, the other cold surfaces of the chip are attached to TEGs for harvesting electrical power from the chip’s wasted heat. Thereafter, this harvested electrical power (HEP) is then used to run the TEC attached to the hotspot. Since no external electrical power is needed for cooling the hotspot to an acceptable temperature, this technique is called a sustainable self-cooling framework (SSCF). In this paper, the operation principles of the SSCF to cool the hotspot, subjected to different operating conditions, are discussed. As well, considerations are given to investigate the effect of the TEM geometrical parameters, such as the P-/N-leg height and spacing between the legs in both operations of the TEC mode and TEG mode on the SSCF performance.

Static and Dynamic Performance of Pressure Dam Bearings With Dam Steps That Are (I) Square and (II) Filleted

2008 ◽  
Author(s):  
Dara Childs ◽  
Andrew Schaible ◽  
Bader Al Jughaiman
Keyword(s):  
Dynamic Performance ◽  
Operating Conditions ◽  
The Other ◽  
Step Test ◽  
Radial Clearance ◽  
Static Characteristics ◽  
Stiffness Coefficients ◽  
Test Conditions ◽  
Minimum Film Thickness ◽  
Direct Stiffness

Measured rotordynamic force coefficients (stiffness, damping, and added-mass) and static characteristics (eccentricity and attitude angle) are presented for two nearly identical pressure-dam bearings. One bearing has a square step at the dam; the other has a filleted step. Because of reduced manufacturing costs, the filleted-step design is used widely. The bearings’ groove dimensions are close to the optimum predictions of Nicholas and Allaire [2] and are consistent with current field applications. The bearings have a diameter of 117.1 mm (4.61 in), a length-to-diameter ratio of 0.655, and a nominal radial clearance of 0.133 mm (5.25 mils). The bottom pad has a deep, centered relief track over 25% of the pad’s axial length. The upper pad for both bearings has a step located at 130° from the horizontal and a 0.620 mm (15.75 mils) deep dam. The dam on the upper pad of one bearing has a square step; the other bearing has a filleted step. Test conditions include four shaft speeds (4000, 6000, 8000 and 10000 rpm) and bearing unit loads from 0 to 1034 kPa (150 psi). Laminar flow was produced for all test conditions within the bearing lands. For the same operating conditions, the filleted step bearing operates at a lower eccentricity ratio (has a larger minimum film thickness). The filleted step design has higher direct stiffness coefficients. Both cross-coupled stiffness coefficients are positive (favorable for stability) for both designs but the filleted design produces higher values. In regard to direct damping, the filleted-step design has higher damping in the load direction and comparable values in the unloaded direction. Hence, for the same operating conditions, a filleted step design should produce reduced amplitudes at or near a critical speed. With respect to stability as defined by WFR, the filleted design is consistently better (lower value) than the square step design, resulting in an elevated onset speed of instability for the filleted-step design.

scholarly journals Operating Behavior of Sliding Planet Gear Bearings for Wind Turbine Gearbox Applications—Part I: Basic Relations

Lubricants ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 97
Author(s):  
Thomas Hagemann ◽  
Huanhuan Ding ◽  
Esther Radtke ◽  
Hubert Schwarze
Keyword(s):  
Wind Turbine ◽  
Local Maximum ◽  
Axial Direction ◽  
Operating Conditions ◽  
Design Parameters ◽  
Radial Clearance ◽  
Wind Turbine Gearbox ◽  
Local Loads ◽  
Gear Mesh ◽  
Planet Gear

The application of sliding planet gear bearings in wind turbine gearboxes has become more common in recent years. Assuming practically applied helix angles, the gear mesh of the planet stage causes high force and moment loads for these bearings involving high local loads at the bearing edges. Specific operating behavior and suitable design measures to cope with these challenging conditions are studied in detail based on a thermo-hydrodynamic (THD) bearing model. Radial clearance and axial crowning are identified as important design parameters to reduce maximum pressures occurring at the bearing edges. Furthermore, results indicate that a distinct analysis of the gear mesh load distribution is required to characterize bearing operating behavior at part-load. Here, operating conditions as critical as the ones reached at nominal load might occur. Wear phenomena can improve the shape of the gap in the circumferential as well as in axial direction incorporating a significant reduction of local maximum pressures. The complexity of the combination of these aspects and the additionally expected impact of structure deformation gives an insight into the challenges in the design processes of sliding planet gear bearings for wind turbine gearbox applications.

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

scholarly journals Monitoring Wind Turbine Gearbox with Echo State Network Modeling and Dynamic Threshold Using SCADA Vibration Data

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 982 ◽  
Author(s):  
Xin Wu ◽  
Hong Wang ◽  
Guoqian Jiang ◽  
Ping Xie ◽  
Xiaoli Li
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Operating Conditions ◽  
Dynamic Threshold ◽  
Detection Accuracy ◽  
Echo State Network ◽  
Monitoring Method ◽  
Vibration Data ◽  
Static Monitoring ◽  
Threshold Monitoring

Health monitoring of wind turbine gearboxes has gained considerable attention as wind turbines become larger in size and move to more inaccessible locations. To improve the reliability, extend the lifetime of the turbines, and reduce the operation and maintenance cost caused by the gearbox faults, data-driven condition motoring techniques have been widely investigated, where various sensor monitoring data (such as power, temperature, and pressure, etc.) have been modeled and analyzed. However, wind turbines often work in complex and dynamic operating conditions, such as variable speeds and loads, thus the traditional static monitoring method relying on a certain fixed threshold will lead to unsatisfactory monitoring performance, typically high false alarms and missed detections. To address this issue, this paper proposes a reliable monitoring model for wind turbine gearboxes based on echo state network (ESN) modeling and the dynamic threshold scheme, with a focus on supervisory control and data acquisition (SCADA) vibration data. The aim of the proposed approach is to build the turbine normal behavior model only using normal SCADA vibration data, and then to analyze the unseen SCADA vibration data to detect potential faults based on the model residual evaluation and the dynamic threshold setting. To better capture temporal information inherent in monitored sensor data, the echo state network (ESN) is used to model the complex vibration data due to its simple and fast training ability and powerful learning capability. Additionally, a dynamic threshold monitoring scheme with a sliding window technique is designed to determine dynamic control limits to address the issue of the low detection accuracy and poor adaptability caused by the traditional static monitoring methods. The effectiveness of the proposed monitoring method is verified using the collected SCADA vibration data from a wind farm located at Inner Mongolia in China. The results demonstrated that the proposed method can achieve improved detection accuracy and reliability compared with the traditional static threshold monitoring method.

scholarly journals Testing the Validity of a Link Function Assumption in Repeated Type-II Censored General Step-Stress Experiments

Sankhya B ◽  
2021 ◽  
Author(s):  
Stefan Bedbur ◽  
Thomas Seiche
Keyword(s):  
Null Hypothesis ◽  
Statistical Tests ◽  
Operating Conditions ◽  
Link Function ◽  
Asymptotic Results ◽  
Failure Data ◽  
Stress Levels ◽  
Log Linear ◽  
Multiple Samples ◽  
General Step

AbstractIn step-stress experiments, test units are successively exposed to higher usually increasing levels of stress to cause earlier failures and to shorten the duration of the experiment. When parameters are associated with the stress levels, one problem is to estimate the parameter corresponding to normal operating conditions based on failure data obtained under higher stress levels. For this purpose, a link function connecting parameters and stress levels is usually assumed, the validity of which is often at the discretion of the experimenter. In a general step-stress model based on multiple samples of sequential order statistics, we provide exact statistical tests to decide whether the assumption of some link function is adequate. The null hypothesis of a proportional, linear, power or log-linear link function is considered in detail, and associated inferential results are stated. In any case, except for the linear link function, the test statistics derived are shown to have only one distribution under the null hypothesis, which simplifies the computation of (exact) critical values. Asymptotic results are addressed, and a power study is performed for testing on a log-linear link function. Some improvements of the tests in terms of power are discussed.

Sign in / Sign up

Export Citation Format

Share Document