Based on the Joukowsky transformation and Theodorsen method, a novel parametric function （shape function） for wind turbine airfoils has been developed. The airfoil design space and shape control equations also have ...Based on the Joukowsky transformation and Theodorsen method, a novel parametric function （shape function） for wind turbine airfoils has been developed. The airfoil design space and shape control equations also have been studied. Results of the analysis of a typical wind turbine airfoil are shown to illustrate the evaluation process and to demonstrate the rate of convergence of the geometric characteristics. The coordinates and aerodynamic performance of approximate airfoils is rapidly close to the baseline airfoil corresponding to increasing orders of polynomial. Comparison of the RFOIL prediction and experimental results for the baseline airfoil generally show good agreement. A universal method for three-dimensional blade integration-＂ Shape function/Distribution function＂ is presented. By changing the parameters of shape function and distribution functions, a three dimensional blade can be designed and then transformed into the physical space in which the actual geometry is defined. Application of this method to a wind turbine blade is presented and the differences of power performance between the represented blade and original one are less than 0. 5%. This method is particularly simple and convenient for bodies of streamline forms.展开更多
Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct...Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.展开更多
With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the uns...With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath monitoring.The eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of stator.Then an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 kHz.Vibration tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.展开更多
This study numerically analyzes the unsteady flow around the Darrieus-type turbine by using FLUENT and deals with the application to the design of blades. Two kinds of blade sections were used in this study. Unsteady ...This study numerically analyzes the unsteady flow around the Darrieus-type turbine by using FLUENT and deals with the application to the design of blades. Two kinds of blade sections were used in this study. Unsteady RANS equation and the turbulence model, either k-e or k-co model, which are appropriate for each blade section, were employed. First for the NACA 634-021 blade that the experimental data is available, the 2-dimensional and 3-dimensional numerical analyses have been performed and compared with the experimental result. For the optimization of the turbine, the parametric study has been performed to check the performance in accordance with the changes in the number of blades, solidity and camber. It is demonstrated that the present approach could draw the turbine characteristics better in performance than the existing turbine. Next for the NACA 653-018 blade with the high lift-drag ratio from the purpose of developing highly-efficient turbine, this study has also tried to get the highly efficient turbine specifications by analyzing the performance while using 2-dimensional and 3-dimensional numerical analyses and the result was verified through the experiment. According to the present study, it is concluded that the 3-dimensional numerical analysis has simulated the experimental values relatively well and also, the 2-dimensional analysis can be a useful tool in the parametric study for the turbine design.展开更多
Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines...Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines,in-cluding Rushton turbine,concaved blade disk turbine,half elliptical blade disk turbine,and parabolic blade disk turbine.Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail.The location,size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics.The larger curvature resulted in longer residence time of the vortex at the impeller tip,bigger distance between the upper and lower vortices and longer vortex life,also leads to smaller and stronger vortices.In addition,the turbulent ki-netic energy and turbulent energy dissipation in the discharge flow were determined and discussed.High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them.Although restricted to single phase flow,the presented results are essential for reliable de-sign and scale-up of stirred tank with disc turbines.展开更多
Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigate...Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigated by using of wind turbine blade design software, PROPID. Firstly, a wind turbine blade of 2MW class was designed with DU-serics airfoils in the inner part and with aNACA series airfoil as a main airfoil in the outer part. Lift distribution was set to have near L/D maximum at each span station. Then, lift and drag curves were modified to observe effect of L/D variation. Drag and lift change with constant L/D on blade power coefficient was also studied for sensitivity investigation. Each case was optimized with Newtonian iteration incorporated in PROPID. High design lift coefficient results in less chord length and twist angle to maintain same aerodynamic load level. And, power coefficient wasn＇t improved much with high L/D. During the process, optimal inputs such as lift distribution, design lift and induction factors were suggested. As results, it was found that L/D maximization was important to obtain high efficiency. For the L/D maximization, lift maximization was important to minimize structural weight, but decreasing drag didn＇t affect the blade shape.展开更多
Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind p...Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.展开更多
The engineering analysis techniques used for the GTE （gas turbine engines） design are presented, the physical effects, which impact is not currently taken into account are described, further research directions to s...The engineering analysis techniques used for the GTE （gas turbine engines） design are presented, the physical effects, which impact is not currently taken into account are described, further research directions to strengthen core design competencies are identified, the requirements for computing power are formulated. Internal cooling techniques for gas turbine blades have been studied for several decades. The internal cooling techniques of the gas turbine blade includes： jet impingement, rib turbulated cooling, and pin-fin cooling which have been developed to maintain the metal temperature of turbine vane and blades within acceptable limits in this harsh environment.展开更多
On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piez...On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.展开更多
Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engine...Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences(IET-Wind)in order to improve both aerodynamic and structural efficiency of rotor blades.To verify the proposed design concepts,this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region.Blade models with various loading cases,inboard configurations,and core materials were comparatively studied.Furthermore,a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics.It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used.The prototype blade showed linear behavior under extreme loads in spar caps,aft panels,shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs.The inboard region of the blade showed exceptional load-carrying capacity as it survived420%extreme loads in the experiment.Through this study,potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.展开更多
基金Supported by the National Natural Science Foundation of China （ No. 50775227 ） and the Natural Science Foundation of Chongqing （ No. CSTC, 2008BC3029）.
文摘Based on the Joukowsky transformation and Theodorsen method, a novel parametric function （shape function） for wind turbine airfoils has been developed. The airfoil design space and shape control equations also have been studied. Results of the analysis of a typical wind turbine airfoil are shown to illustrate the evaluation process and to demonstrate the rate of convergence of the geometric characteristics. The coordinates and aerodynamic performance of approximate airfoils is rapidly close to the baseline airfoil corresponding to increasing orders of polynomial. Comparison of the RFOIL prediction and experimental results for the baseline airfoil generally show good agreement. A universal method for three-dimensional blade integration-＂ Shape function/Distribution function＂ is presented. By changing the parameters of shape function and distribution functions, a three dimensional blade can be designed and then transformed into the physical space in which the actual geometry is defined. Application of this method to a wind turbine blade is presented and the differences of power performance between the represented blade and original one are less than 0. 5%. This method is particularly simple and convenient for bodies of streamline forms.
基金Project(HEUCF110707)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E201216)supported by Heilongjiang Natural Science Fund,China
文摘Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.
基金National Natural Science Foundation of China(No.51775377)National Key Research and Development Plan(No.2017YFF0204800)+2 种基金Natural Science Foundation of TianJin City(No.17JCQNJC01100)Young Elite Scientists Sponsorship Program by Cast of China(No.2016QNRC001)Open Project of Key Laboratory of Underwater Information and Control(No.6142218081811)
文摘With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath monitoring.The eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of stator.Then an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 kHz.Vibration tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.
文摘This study numerically analyzes the unsteady flow around the Darrieus-type turbine by using FLUENT and deals with the application to the design of blades. Two kinds of blade sections were used in this study. Unsteady RANS equation and the turbulence model, either k-e or k-co model, which are appropriate for each blade section, were employed. First for the NACA 634-021 blade that the experimental data is available, the 2-dimensional and 3-dimensional numerical analyses have been performed and compared with the experimental result. For the optimization of the turbine, the parametric study has been performed to check the performance in accordance with the changes in the number of blades, solidity and camber. It is demonstrated that the present approach could draw the turbine characteristics better in performance than the existing turbine. Next for the NACA 653-018 blade with the high lift-drag ratio from the purpose of developing highly-efficient turbine, this study has also tried to get the highly efficient turbine specifications by analyzing the performance while using 2-dimensional and 3-dimensional numerical analyses and the result was verified through the experiment. According to the present study, it is concluded that the 3-dimensional numerical analysis has simulated the experimental values relatively well and also, the 2-dimensional analysis can be a useful tool in the parametric study for the turbine design.
基金Supported by the National Natural Science Foundation of China（20776008 20821004 20990224） the National Basic Research Program of China（2007CB714300）
文摘Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines,in-cluding Rushton turbine,concaved blade disk turbine,half elliptical blade disk turbine,and parabolic blade disk turbine.Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail.The location,size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics.The larger curvature resulted in longer residence time of the vortex at the impeller tip,bigger distance between the upper and lower vortices and longer vortex life,also leads to smaller and stronger vortices.In addition,the turbulent ki-netic energy and turbulent energy dissipation in the discharge flow were determined and discussed.High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them.Although restricted to single phase flow,the presented results are essential for reliable de-sign and scale-up of stirred tank with disc turbines.
文摘Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigated by using of wind turbine blade design software, PROPID. Firstly, a wind turbine blade of 2MW class was designed with DU-serics airfoils in the inner part and with aNACA series airfoil as a main airfoil in the outer part. Lift distribution was set to have near L/D maximum at each span station. Then, lift and drag curves were modified to observe effect of L/D variation. Drag and lift change with constant L/D on blade power coefficient was also studied for sensitivity investigation. Each case was optimized with Newtonian iteration incorporated in PROPID. High design lift coefficient results in less chord length and twist angle to maintain same aerodynamic load level. And, power coefficient wasn＇t improved much with high L/D. During the process, optimal inputs such as lift distribution, design lift and induction factors were suggested. As results, it was found that L/D maximization was important to obtain high efficiency. For the L/D maximization, lift maximization was important to minimize structural weight, but decreasing drag didn＇t affect the blade shape.
文摘Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.
文摘The engineering analysis techniques used for the GTE （gas turbine engines） design are presented, the physical effects, which impact is not currently taken into account are described, further research directions to strengthen core design competencies are identified, the requirements for computing power are formulated. Internal cooling techniques for gas turbine blades have been studied for several decades. The internal cooling techniques of the gas turbine blade includes： jet impingement, rib turbulated cooling, and pin-fin cooling which have been developed to maintain the metal temperature of turbine vane and blades within acceptable limits in this harsh environment.
文摘On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.
基金supported by the National Natural Science Foundation of China(Grant No.51405468)
文摘Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences(IET-Wind)in order to improve both aerodynamic and structural efficiency of rotor blades.To verify the proposed design concepts,this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region.Blade models with various loading cases,inboard configurations,and core materials were comparatively studied.Furthermore,a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics.It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used.The prototype blade showed linear behavior under extreme loads in spar caps,aft panels,shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs.The inboard region of the blade showed exceptional load-carrying capacity as it survived420%extreme loads in the experiment.Through this study,potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.
