Turbine Spindle Research Articles

Magnetic fluid flow rate and thermal characteristics of hydraulic turbine spindle magnetic fluid seals

The flow and temperature properties of the magnetic fluid are the primary elements impacting the seal stability in the main shaft magnetic fluid seal of the turbine. This study investigated the eddy current and heat field of the magnetic fluid at the seal gap using a mix of numerical computation and experiment and came to the following conclusions: Under the pole tooth groove and the permanent magnet, the magnetic fluid creates symmetrical vortices in the clearance of the magnetic fluid seal device. Below the pole tooth, the magnetic fluid velocity is minimal and essentially constant. The pole shoe and spindle next to the air side of the magnetic fluid seal device have the lowest temperature, and the device’s core has the greatest temperature.

Research on the Rheological Characteristics of Wind Power Grease Based on Rheological Parameters

Our research scrutinizes the impact of grease rheological properties on the lubrication performance of wind turbine spindle bearings. The rheological behavior of three distinct commercial wind turbine greases was examined with a rotational rheometer. Investigations into the viscoelastic, flow, and viscosity–temperature attributes of the grease under varying temperatures were conducted, and the rheological parameters were fitted utilizing the Herschel–Bulkley (H–B) model. Constitutive equations of the grease derived from fitting the H–B model can efficaciously predict its rheological properties and viscosity–temperature behavior for wind power spindle bearings at disparate temperatures.

Wind Turbine Spindle Operating State Recognition and Early Warning Driven by SCADA Data

An operating condition recognition approach of wind turbine spindle is proposed based on supervisory control and data acquisition (SCADA) normal data drive. Firstly, the SCADA raw data of wind turbine under full working conditions are cleaned and feature extracted. Then the spindle speed is employed as the output parameter, and the single and combined normal behavior model of the wind turbine spindle is constructed sequentially with the pre-processed data, with the evaluation indexes selected as the optimal model. Finally, calculating the spindle operation status index according to the sliding window principle, ascertaining the threshold value for identifying the abnormal spindle operation status by the hypothesis of small probability event, analyzing the 2.5 MW wind turbine SCADA data from a domestic wind field as a sample, The results show that the fault warning time of the early warning model is 5.7 h ahead of the actual fault occurrence time, as well as the identification and early warning of abnormal wind turbine spindle operation without abnormal data or a priori knowledge of related faults.

Crowning Method on Bearing Supporting Large Wind Turbine Spindle Considering the Flexibility of Structure of Shaft System

To meet the precision design of bearings on large wind turbine spindles, a crowning method of bearing on wind turbine spindles considering the flexibility of the support structure is proposed. Firstly, a finite element (FE) model of the shaft system with a flexible structure is constructed by connecting the shaft and bearing through constraint equations (CE) and multi-point constraint (MPC) algorithms and replacing the bearing rollers with nonlinear spring elements and dampers. Then, the Newmark integration algorithm is used to solve the model and analyze the effect of the structure’s rigidity on the load distribution of bearings. Then, perform convergence analysis of the sequences of the spring load distribution using a high-pass filter based on fast Fourier transform (FFT) and root mean square error (RMSE) to obtain a suitable number of replacement springs. Finally, a sub-model of the upwind bearing is constructed with structured mesh. With the maximum Von Mises stress of the roller profile as the design target, the optimal logarithmic crowning of the roller and its tolerance zone under the given working conditions are obtained. The results show that the FE model of the shaft system proposed has good convergence. The FE model of the shaft system considering the flexibility of the support structure can obtain more accurate load distributions of bearings and can make the accurate crowning design of the bearing rollers based on the actual working conditions. This provides support for the precision design of bearings in large shaft systems.

Control of Spindle Position and Stiffness of Aerostatic-Bearing-Type Air Turbine Spindle

Air turbine spindles with aerostatic bearings are widely used in ultraprecision machining equipment. Ultraprecision grinding processes using air turbine spindles with aerostatic bearings include constant-pressure dry lapping of nano-polycrystalline diamond (NPD) tools and ultraviolet irradiation polishing of chemical vapor deposition diamond films. In the dry lapping of NPD tools, it is necessary to achieve constant-pressure grinding while flexibly adjusting the contact force between the NPD tool and the truer fixed on the end face of the aerostatic spindle to form a nose bite with a cutting-edge rounding radius, R, of 0.1 nm. However, it is common for operators to manually adjust the cut depth and the air pressure supplied to the aerostatic bearing by relying on the noise and rotation speed during machining. Moreover, aerostatic spindles without a control mechanism, such as active bearings, are widely used because of their low costs and versatility. For several years, the authors have been developing a method to control air bearing stiffness by controlling the bearing supply pressure with high speeds and precision using a high-precision quick response regulator for aerostatic spindles without a control mechanism, such as active bearings. In this study, the compliance control (control of spindle position and stiffness) of aerostatic bearings was investigated using the proposed method, and the effectiveness of the method to ultraprecision grinding applications was demonstrated.

The Research on Condition Monitoring and Fault Diagnosis Method of Wind Power Spindle Bearing

With the continuous and substantial increase in the demand for wind power generation in China, the development of wind power generation units tends to be large-scale, intelligent and efficient. Besides, the working environment of spindle bearings is relatively bad and the failure rate is relatively high. Therefore, it is necessary to conduct state monitoring and fault diagnosis for wind power generation units. This paper first introduces the bearing system of wind turbine, then expounds the common faults of wind turbine spindle bearing, and carries out relevant research. According to the fault types, this paper investigates and combs the condition monitoring and fault diagnosis methods of spindle bearing. Finally, the author proposing a new condition monitoring method, which solves the vacancy of condition monitoring method based on strain.

Analysis and research on fracture cause of connecting bolt of wind turbine spindle

On a certain day in 2018, the main shaft connecting bolt of a wind turbine in a wind farm broke and failed during operation. In order to find out the cause of fracture, the fractured spindle connecting bolt was comprehensively detected and analyzed by means of appearance state analysis, chemical element composition analysis, mechanical property detection analysis, microstructure detection and fracture micro area analysis. The results show that the main reason for the fracture of the main shaft connecting bolt is that the hydrogen penetrates into the bolt surface due to improper process control during the production process, resulting in hydrogen embrittlement in the local area of the thread root. Thus, during the operation of the fan, under the combined action of bending, shear and tensile stress, the connecting bolt of the main shaft cracks at the bottom of the first thread on the side of the self rigid rod with the most concentrated stress, and expands in the form of “herringbone” brittle fracture until the overall fracture failure. It is recommended to check the bolts in the same batch to prevent hydrogen embrittlement in the whole batch.

Spindle with built-in acoustic emission sensor to realize contact detection

Recently, the demand for realizing micromachining through small-diameter tools has increased. When performing microfabrication using a numerically controlled machine tool, a machining error may be introduced if the relative position of the tool tip and workpiece surface deviates during tool change. Therefore, it is critical to determine this relative position in an actual machining condition at a specific spindle speed. We are currently developing an air bearing turbine spindle with a built-in acoustic emission sensor that can detect the contact of the tool tip with the workpiece surface in real time. The acoustic emission (AE) signal generated at the tool tip can be accurately detected by placing the AE sensor in direct contact with the tool end surface inside the main shaft floated by air. In this study, we investigated the possibility of contact detection between the tool tip and the workpiece surface at the submicrometer level through the proposed spindle. The results of the performed evaluation experiments indicated that by using the spindle with a built-in acoustic emission sensor, the contact of the small-diameter tool tip with the workpiece surface could be detected with damage to the workpiece at the submicrometer level on average.

Fabrication of Micro-end Milling Cutter Based on WEDG

The effect of unbalance caused by installation error is the one of the main reasons for tool runout in micro milling processes, especially at high-speed on the spindle. As tool runout contributes significant impact to the machining accuracy in micro milling processes, an on-machine fabrication method which could avoid the existence of installation error of spindle deviation and tool tilt caused by off-line of micro-end milling cutter has been proposed. To verify the possibility of an on-machine fabrication method based on wire electro-discharge grinding, a micro-EDM machine with an ultra-high-speed air turbine spindle and a geometrically optimized tool design were developed. Ultra-fine grain carbide end mills with the target diameter equal to 50 μm were fabricated by wire electro-discharge grinding based on the on-machine fabrication method. And some micro slot milling experiments were conducted in pure copper. The experimental results indicate that the micro cutting process using the on-machine fabricated tool by wire electro-discharge grinding is possible. Moreover, this method can improve the reliability of the cutter and the processing accuracy of the parts, avoids the error caused by the second clamping of the micro-milling cutter and improves the overall quality of micro-milling.

Design and Development of a High Efficiency Air Turbine Spindle for Small-Part Machining

This paper reports on the development of a high efficiency and low inertia miniature pneumatic turbine for ultra-high-speed manufacturing spindle applications. It is proposed that radial-inflow/axial-outflow type turbines are well suited for micro-machining spindles. To validate the turbine performance potential, a proof-of-concept prototype turbo-spindle was developed and experimentally tested. The prototype spindle produced a net mechanical power output of over 60 W at a speed of 90,000 rpm. The experimental results demonstrate a micro-turbine efficiency of over 50% and a turbine power output of approximately 100 W. This compares to a typical turbine efficiency of around 20% in commercial micro-machining spindles. Further potential improvements to both turbine and spindle energy efficiency are outlined.

Tool wear estimation method in milling process using air turbine spindle rotation-control system equipped with disturbance force observer

Tool wear estimation method in milling process using air turbine spindle rotation-control system equipped with disturbance force observer

Tool wear estimation method in milling process using air turbine spindle rotation-control system equipped with disturbance force observer

The authors investigate a disturbance-compensating and energy-saving control method for air turbine spindles equipped with a rotation control system designed for use in ultra-precision milling. The controllability and energy-conserving characteristics of the proposed method using the proposed pneumatic regulating device, called a high-precision quick-response pneumatic pressure regulator, were demonstrated experimentally previously. Herein, the proposed rotation-controlled air turbine spindle is first summarised. Subsequently, the proposed rotation-controlled air turbine spindle is set to a milling machine and applied to the milling of an alloy tool steel, to gain data and validate the effectiveness of the in-process tool wear estimation method that have been recently developed and proposed by the authors. Particularly, to evaluate the possibility of applying the proposed estimation method to three-dimensional milling, milling experiments where the air turbine spindle is set at a 45° incline were conducted and the results indicate a high possibility of the proposed method.

Study on Tool Wear In-Process Estimation for Ball End Mill Using Rotation Control Air Turbine Spindle

This paper introduces a method for in-process tool wear estimation of an air turbine spindle, which is equipped with a rotation control system for ultra-precision milling. Previous investigations revealed that the pressure of the compressed air for supply that is used to control the rotational speed and tool wear at the time when steady wear occurs, maintains a linear relationship when processing SKD61 steel. In addition, the extent to which the supply pressure changed was reduced after chipping occurred. Therefore, the possibility exists that the tool wear can be estimated by obtaining the supply pressure during processing. The purpose of this paper is to propose the evaluation of an in-process tool wear estimation method, and to evaluate its validity. An estimation method is necessary as this would allow the amount of tool wear to be estimated and abnormal wear of occurrence to be detected. Because of the linear relationship between the air pressure and the amount of tool wear, the latter can be estimated by plotting the approximately linear relationship of the tool wear as a function of the air pressure. The proposed estimation method for processing the results obtained for SKD61, is capable of estimating the relative error of the measured value within 0.2 against the estimated value at the time. Furthermore, the occurrence of abnormal wear is determined from the amount of change in the supply pressure. Thus, SKD11 steel was processed for the proposed estimation method to verify whether it is valid for cutting high hardness steel. As a result, for SKD11 the estimation method produced estimation results similar to those obtained for SKD61. Therefore, the suggested estimation method is likely to be effective for high-hardness steel cutting.

Proposal of disturbance-compensating and energy-saving control method of air turbine spindle and evaluation of its energy consumption

This paper introduces a disturbance-compensating and energy-saving control method of an air turbine spindle equipped with a rotation control system designed for use in ultra-precision milling. As one of the key components, our proposed pneumatic regulating device, called a high-precision quick-response pneumatic pressure regulator (HPQR), is used to control the air supply pressure of the air turbine spindle precisely and quickly. The rotation feedback control system including the HPQR and a disturbance force observer, which avoids changes of rotation speed due to disturbance forces applied to the air turbine spindle, is explained. In addition, a pneumatic energy assessment method using a device called an “air power meter” is explained. The effectiveness of the proposed method is demonstrated through the experimental results.

An Energy Analysis of Electric and Pneumatic Ultra-high Speed Machine Tool Spindles

There is a growing demand for ultra-high speed precision machine tool spindles to create complex miniature devices and features, in consumer markets such as medical devices, electronics and communications. The key enabling drive technologies for spindle rotational speeds in the 100,000rpm range includes electric motors, both AC and DC powered, and air turbines. In particular for high speed micromachining, turbine spindles have advantages in terms of precision and cost. A widely considered drawback of pneumatic technology though is low energy efficiency, but to date there has been little in depth analysis of commercial/state-of-art turbo-spindle energy performance. This paper provides a holistic comparative analysis of electric motor and turbine powered spindle electrical power requirements, by including the power demand of supporting systems and infrastructure. The analysis indicates that at present the energy usage associated with turbine spindles is significantly higher than electric spindles. However, a number of technically feasible energy efficiency measures are identified for turbine spindles, which would make their energy performance comparable with electro-spindles. The analysis and results will contribute towards an overall life cycle assessment of high speed turbo-spindle technology, and provide impetus to further explore energy optimization approaches and methods.

Research on aerodynamic characteristics of two-stage axial micro air turbine spindle for small parts machining

In order to meet the requirements of output torque, efficiency and compact shape of micro-spindles for small parts machining, a two-stage axial micro air turbine spindle with an axial inlet and outlet is proposed. Based on the k-ω turbulence model of SST, the flow field and operation characteristics of the two-stage axial micro air turbine spindle were studied using computational fluid dynamics (CFD) combined with an experimental study. We obtained the air turbine spindle under different working conditions of the loss and torque characteristics. When the inlet pressure was 300 KPa, the output speed of the two-stage turbine was 100,000 rpm, 9% higher than that of a single-stage turbine output torque. The total torque reached 6.39 N·mm, and the maximum efficiency of the turbine and the spindle were 42.2% and 32.3%, respectively. Through the research on the innovative structure of the two-stage axial micro air turbine spindle, the overall performance of the principle prototype has been significantly improved and the problems of insufficient output torque and low working efficiency in high-speed micro-machining can be solved practically, which laid a solid foundation for improving the machining efficiency of small parts and reducing the size of micro machine tool.

Parametric Modeling and Simulation of Taper-Lock Connection in Wind Turbine Spindle Based on ANSYS

Taking taper-lock Connection in Wind Turbine Spindle as research object, the paper analyzes the relativity of structural sizes and builds the parametric structural model by means of a way APDL. By using the non-liner finite element software ANSYS, the stress of taper-lock on the limit load conditions is analyzed, then contact stress and strain of the planet carrier and spindle are discussed. This is useful to the choice of assembly condition during taper-lock, planet carrier and spindle and providing theoretical data.

D15 エアタービンスピンドルの回転数制御による加工面への影響(第2報)(OS5-I・D1 次世代の生産技術-1-)

D15 エアタービンスピンドルの回転数制御による加工面への影響(第2報)(OS5-I・D1 次世代の生産技術-1-)

D14 エアタービンスピンドルの回転数制御による加工面への影響(第1報)(OS5-I・D1 次世代の生産技術-1-)

D14 エアタービンスピンドルの回転数制御による加工面への影響(第1報)(OS5-I・D1 次世代の生産技術-1-)

Characteristics of damaged layer in micro-machining of copper material

The study on damaged layer is necessary for improving the machinability in micro-machining because the damaged layer affects the micro mold life and micro machine parts. This study examined the ultra-precision micro-machining characteristics, such as cutting speed, feed rate and cutting depth, of a micro-damaged layer produced by an ultra-high speed air turbine spindle. The micro cutting force, surface roughness and plastic deformation layer were investigated according to the machining conditions. The damaged layer was measured using optical microscope on samples prepared through metallographic techniques. The scale of the damaged layer depends on the cutting process parameters, particularly, the feed per tooth and axial depth of the cut. According to the experimental results, the depth of the damaged layer is increased by increasing the feed per tooth and cutting depth, also the damaged layer occurs less in down-milling compared with up-milling during the micro-machining operation.