Savonius型风力机结构的优化设计

对传统Savonius型垂直轴风力机各几何参量进行优化,在此基础上加入一种半自动阀门装置,得到的新型Savonius风力机,在设计风速10m／s下,对其各项空气动力学性能参数进行计算。结果表明,这种风力机具有很好的开发意义,可应用于沿海地区民宅的小型风力发电,城市公共照明及景区夜景工程的离网供电。     

Comparative study of a three-bucket Savonius rotor with a combined three-bucket Savonius–three-bladed Darrieus rotor

The vertical axis wind turbines are simple in construction, self-starting, inexpensive and can accept wind from any direction without orientation. A combined Savonius–Darrieus type vertical axis wind rotor has got many advantages over individual Savonius or individual Darrieus wind rotor, such as better efficiency than Savonius rotor and high starting torque than Darrieus rotor. But works on the combined Savonius–Darrieus wind rotor are very scare. In view of the above, two types of models, one simple Savonius and the other combined Savonius–Darrieus wind rotors were designed and fabricated. The Savonius rotor was a three-bucket system having provisions for overlap variations. The Savonius–Darrieus rotor was a combination of three-bucket Savonius and three-bladed Darrieus rotors with the Savonius placed on top of the Darrieus rotor. The overlap variation was made in the upper part, i.e. the Savonius rotor only. These were tested in a subsonic wind tunnel available in the department. The various parameters namely, power coefficients and torque coefficients were calculated for both overlap and without overlap conditions. From the present investigation, it is seen that with the increase of overlap, the power coefficients start decreasing. The maximum power coefficient of 51% is obtained at no overlap condition. However, while comparing the power coefficients (C_p) for simple Savonius-rotor with that of the combined configuration of Savonius–Darrieus rotor, it is observed that there is a definite improvement in the power coefficient for the combined Savonius–Darrieus rotor without overlap condition. Combined rotor without overlap condition provided an efficiency of 0.51, which is higher than the efficiency of the Savonius rotor at any overlap positions under the same test conditions.     

Performance analysis of a horizontal axis 3-bladed Savonius type wave turbine in an experimental wave flume (EWF)

The present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied.     

S型风力机气动设计

概述S型风力机的工作原理以及优缺点。系统分析了影响S型风轮气动性能的外形参数,总结出S型风力机达到最优气动性能时的外形参数。以最优外形参数为基础设计完成额定功率为300W的S型风力机的气动外形,所得结果可以同类型风力机的设计提供理论指导。     

小型Savonius风机的创新设计与仿真分析

Savonius风机是一种典型的垂直轴风力机。针对传统风机的发电机部分采用转子、定子一动一静的设计布局,提出了一种新型的发电机结构,从而提高风机发电效率。通过有限元分析软件ANSYS／CFX,对风力机模型进行流体分析,计算Savonius风力机的效率,验证本设计分析方法的正确性。     

An experimental investigation of a class of resistance-type,direction-independent wind turbines

The resistance-type, direction-independent wind turbine is suitable for the generation of power on a small scale in developing countries. So far, all work on this class of wind turbine seems to be restricted to the Savonius rotor. The present paper reports the findings of an experimental investigation of an entire class of wind turbines which includes the conventional Savonius rotor. The influence of four rotor-geometry parameters (i.e. number of blades, blade angle, blade location and angle of setting of the blade) is studied and discussed on the basis of two performance criteria (i.e. turbine efficiency and performance on the basis of blade area). The existence of optimum, design parameters is established and the possibility of improving substantially on the performance of the Savonius rotor is demonstrated. Some possible applications of the present class of turbines are briefly commented on.     

阻力型垂直轴风力机导风帘的优化设计

以输出功率100W的阻力型垂直轴型风力机为例,通过优化设计找寻最佳的叶片数目、高径比和折叠率等几何参量,然后加入导风帘装置,给出一个最佳结构方案。运用Fluent求解器中的有限体积法对无导风帘和三种不同长度导风帘设计的叶片周围的流场进行模拟。模拟与最佳优化方式的性能参数的计算结果表明,采用长导风帘设计的阻力型垂直轴风力机具有最好的动力学性能,可以提高运行效率。     

Investigation of 3D printed Savonius rotor performance

In this study increasing the performance of Conventional Savonius wind rotor has been investigated by a 3D (three dimensional) printer which is one of the rapid prototyping techniques. For this purpose, some design changes have been introduced to increase the performance of conventional Savonius wind rotor. Here, 3D digital designing of Savonius wind rotors have been easily manufactured tangible as a physical model by a 3D printer. Experimental data concerning produced Savonius wind rotors have been acquired by using a wind tunnel. Some numerical data have been obtained from the CFD (Computational Fluid Dynamics) analysis carried out under the same conditions. The effects of the additional blade end design have been examined to obtain more torque increase on improved classical Savonius wind rotor. Furthermore, by means of introducing straight blade, the effects of the flow compression inside the blade have been reduced and rotor performance increased. Based on such optimizations, optimum additional design parameters have been designated as that (1/r) ratio is 0.3, (s/r) is 1, and (α) additional straight blade angle is 135°. It has been determined that power coefficient is increased at a ratio of around 20% together with all these design changes.     

Influence of the deflector plate on the performance of modified Savonius water turbine

Savonius rotor is simple in design and easy to fabricate at a lower cost. The basic driving force of Savonius rotor is drag. The drag coefficient of a concave surface is more than the convex surface. Hence, the advancing blade with concave side facing the water flow would experience more drag force than the returning blade, thus forcing the rotor to rotate. Net driving force can be increased by reducing the reverse force on the returning blade. This can be realized by providing flow obstacle to the returning blade. The objective of the present work is to find out the optimal position of the deflector plate upstream to the flow which would result in maximum power generated by the rotor. Experimental investigations are carried out to study the influence of the location of the deflector plate on the performance of a modified Savonius rotor with water as the working medium at a Reynolds number of 1.32 × 10⁵. Eight different positions of the deflector plate are attempted in this study. Results conclude that deflector plate placed at its optimal position increases the coefficient of power by 50%. Maximum coefficient of power is found to be 0.21 at a tip speed ratio of 0.82 in the presence of deflector plate. Two stage and three stage modified Savonius rotors are tested to study the influence of deflector plate at the optimal position. Maximum coefficient of power improves by 42%, 31% and 17% with deflector plate for two stage 0° phase shift, 90° phase shift and three stage modified Savonius rotor respectively.     

Numerical investigation of airflow through a Savonius rotor

The aim of this report is to present a model of a rigid‐rotor system based on computational fluid dynamics (CFD), which is applied on a vertical axis wind turbine (VAWT) research. Its originality results from the use of the average value of the variable rotational speed method taken in a periodic steady‐state (PSS) of the VAWT rotor instead of the classical fixed rotational speed method. This approach was chosen in order to determine the mechanical and aerodynamic parameters of the wind turbine. The modeling method uses an implicit Euler iterative solution strategy, which resolves the coupling between fixed and moving rotor domains. The main methods that were adopted are based on the three‐dimensional modeling of the interaction of the fluid flow with a rigid‐rotor. The strategy consists of using the Reynolds averaged Navier Stokes (RANS) equations with the standard k‐ ? and SST k‐ ω models to solve the fluid flow problem. To perform the rigid‐rotor motion in a fluid, the one degree of freedom (1‐DOF) method was applied. In the present study, the steady‐state and dynamic CFD simulations of the Savonius rotor are adopted to contribute to the validation elements of the VAWT models that are used. The dynamic study allows the investigation of the rotor behavior and the relation between velocity, pressure, and vorticity fields in and around the rotor blades. The flow fields generated by the rotation of the Savonius rotor were investigated in the half revolution period of the rotor angle θ from 0° to 180°. In this range of θ, the focus is on generating and dissipating vortices. Copyright © 2013 John Wiley & Sons, Ltd.     

The use of a curtain design to increase the performance level of a Savonius wind rotors

In this study, a curtain design has been arranged so as to improve the low performance levels of the Savonius wind rotors. Designed to prevent the negative torque on the convex blade of the rotor, this curtain has been placed in front of the rotor, and performance experiments have been carried out when the rotor is with and without curtain. It has been determined from here that a significant increase can be achieved in the rotor performance by means of the curtain design. Experiments of the curtain design have been conducted in three different dimensions when the Savonius wind rotor is static, and the highest values have been obtained with the curtain 1. Therefore, the curtain designs and curtain angles in which the highest values obtained have been analyzed numerically with Fluent 6.0 program and the results obtained experimentally have been supported with numerical analysis. Moreover, performance experiments have been made for the curtain 1 with which the best performance values have been obtained when the rotor is in its dynamic position, and the results obtained have been given in figures.     

Experimental investigation of helical Savonius rotor with a twist of 180°

Conventional Savonius rotors have low performance such as low coefficient of power and low coefficient of torque. In order to increase this performance, a helical Savonius rotor with a twist of 180° is proposed. In this paper, we are interested in studying the aerodynamic behavior of the helical Savonius rotors installed in an open jet wind tunnel. Particularly we are interested in studying the influence of variation of Reynolds number and the overlap ratio on the performance of a modified Savonius rotor with aspect ratio of 1.57 at a Reynolds numbers equal to Re = 79,794, Re = 99,578, Re = 116,064 and Re = 147,059. Results conclude that the variation of Reynolds number and overlap ratio has an effect on the global characteristics of the helical Savonius rotor. A comparison between the helical one and the conventional one shows that the maximum power coefficient of the Savonius wind rotor is higher. This work is developed at Laboratory of Electro-Mechanical System (LASEM) of the National School of Engineers of Sfax (ENIS).     

Performance tests on helical Savonius rotors

Conventional Savonius rotors have high coefficient of static torque at certain rotor angles and a negative coefficient of static torque from 135° to 165° and from 315° to 345° in one cycle of 360°. In order to decrease this variation in static torque from 0° to 360°, a helical Savonius rotor with a twist of 90° is proposed. In this study, tests on helical Savonius rotors are conducted in an open jet wind tunnel. Coefficient of static torque, coefficient of torque and coefficient of power for each helical Savonius rotor are measured. The performance of helical rotor with shaft between the end plates and helical rotor without shaft between the end plates at different overlap ratios namely 0.0, 0.1 and 0.16 is compared. Helical Savonius rotor without shaft is also compared with the performance of the conventional Savonius rotor. The results indicate that all the helical Savonius rotors have positive coefficient of static torque at all the rotor angles. The helical rotors with shaft have lower coefficient of power than the helical rotors without shaft. Helical rotor without shaft at an overlap ratio of 0.0 and an aspect ratio of 0.88 is found to have almost the same coefficient of power when compared with the conventional Savonius rotor. Correlation for coefficient of torque and power is developed for helical Savonius rotor for a range of Reynolds numbers studied.     

Performance investigation of a small Savonius-Darrius counter-rotating vertical-axis wind turbine

This paper describes the study of a small vertical-axis wind turbine (VAWT) with a combined design of Darrius and Savonius counter-rotating rotors. The main purpose of this study is to improve the extraction capabilities of a single-rotor VAWT by using two distinct rotor designs while adopting the counter-rotating technique. Given that the conversion capabilities and operational speed of the existing wind turbines are still limited, the current technique is used to enhance the efficiency and expand the operating wind speed range of the VAWT. The Darrius and Savonius counter-rotating rotors were exposed to a similar upstream wind speed using a centrifugal blower. It was found that the Savonius-Darrius counter-rotating rotor was able to operate effectively, particularly at the low-speed wind. By looking at the individual performance of the rotors, it was observed that the conversion efficiency of the H-type rotor increases as the wind speed increases. However, in the case of the S-type rotor, it is higher at lower wind speed and tends to decrease as the operating speed increases. Thus, the maximum efficiency of the S-type rotor was achieved at low speed, whereas the H-type rotor has achieved its maximum efficiency at the highest operating wind speed. The average efficiency of the present Savonius-Darrius counter-rotating rotor has been improved to reach almost 42% and 30% more efficiency in terms of torque and power, respectively.     

Optimization of Savonius turbines using an obstacle shielding the returning blade

Due to the worldwide energy crisis, research and development activities in the field of renewable energy have been considerably increased in many countries. In Germany, wind energy is becoming particularly important. Although considerable progress has already been achieved, the available technical design is not yet adequate to develop reliable wind energy converters for conditions corresponding to low wind speeds and urban areas. The Savonius turbine appears to be particularly promising for such conditions, but suffers from a poor efficiency. The present study considers a considerably improved design in order to increase the output power of a Savonius turbine with either two or three blades. In addition, the improved design leads to a better self-starting capability. To achieve these objectives, the position of an obstacle shielding the returning blade of the Savonius turbine and possibly leading to a better flow orientation toward the advancing blade is optimized. This automatic optimization is carried out by coupling an in-house optimization library (OPAL) with an industrial flow simulation code (ANSYS-Fluent). The optimization process takes into account the output power coefficient as target function, considers the position and the angle of the shield as optimization parameters, and relies on Evolutionary Algorithms. A considerable improvement of the performance of Savonius turbines can be obtained in this manner, in particular a relative increase of the power output coefficient by more than 27%. It is furthermore demonstrated that the optimized configuration involving a two-blade rotor is better than the three-blade design.     

Innovative improvement of a drag wind turbine performance

Drag type wind turbines have strong potential in small and medium power applications due to their simple design. However, a major disadvantage of this design is the noticeable low conversion efficiency. Therefore, more research is required to improve the efficiency of this design. The present work introduces a novel design of a three-rotor Savonius turbine with rotors arranged in a triangular pattern. The performance of the new design is assessed by computational modeling of the flow around the three rotors. The 2D computational model is firstly applied to investigate the performance of a single rotor design to validate the model by comparison with experimental measurements. The model introduced an acceptable accuracy compared to the experimental measurements. The performance of the new design is then investigated using the same model. The results indicated that the new design performance has higher power coefficient compared with single rotor design. The peak power coefficient of the three rotor turbine is 44% higher than that of the single rotor design (relative increase). The improved performance is attributed to the favorable interaction between the rotors which accelerates the flow approaching the downstream rotors and generates higher turning moment in the direction of rotation of each rotor.     

On the performance analysis of Savonius rotor with twisted blades

The present investigation is aimed at exploring the feasibility of twisted bladed Savonius rotor for power generation. The twisted blade in a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0°). Performance analysis has been made on the basis of starting characteristics, static torque and rotational speed. Experimental evidence shows the potential of the twisted bladed rotor in terms of smooth running, higher efficiency and self-starting capability as compared to that of the conventional bladed rotor. Further experiments have been conducted in the same setup to optimize the twist angle.     

Influence of overlap ratio and aspect ratio on the performance of Savonius hydrokinetic turbine

A strong contender for the utilization of the hydropower sources is Savonius turbine because of its good starting characteristics and simplicity in fabrication. The aim of the present work is to study the effect of overlap ratio and aspect ratio on the performance of a Savonius turbine for hydrodynamic application. The findings would be useful to decide design parameters of a Savonius hydrokinetic turbine. This study is conducted in three open channels namely small laboratory channel with depth of water 270 mm, large laboratory channel with depth of water 480 mm and a real life irrigation canal with depth of water 900 mm. Influence of endplates is studied to establish the significance of their presence on rotor performance. Maximum coefficient of power is observed for an overlap ratio of around 0.11 for Savonius turbines with aspect ratio less than 0.6. For a given overlap ratio, the increasing trend of the coefficient of power is observed with the increase in the aspect ratio. However, for aspect ratios greater than 1.8, the coefficient of power becomes nearly stagnant. Copyright © 2016 John Wiley & Sons, Ltd.     

A review on the performance of Savonius wind turbines

This paper presents a review on the performance of Savonius wind turbines. This type of turbine is unusual and its application for obtaining useful energy from air stream is an alternative to the use of conventional wind turbines. Simple construction, high start up and full operation moment, wind acceptance from any direction, low noise and angular velocity in operation, reducing wear on moving parts, are some advantages of using this type of machine. Over the years, numerous adaptations for this device were proposed. The variety of possible configurations of the rotor is another advantage in using such machine. Each different arrangement of Savonius rotor affects its performance. Savonius rotor performance is affected by operational conditions, geometric and air flow parameters. The range of reported values for maximum averaged power coefficient includes values around 0.05–0.30 for most settings. Performance gains of up to 50% for tip speed ratio of maximum averaged power coefficient are also reported with the use of stators. Present article aims to gather relevant information about Savonius turbines, bringing a discussion about their performance. It is intended to provide useful knowledge for future studies.     

叶片转角对小型Savonius风机气动性能的影响

Savonius风机是一种典型的垂直轴风力发电机,通过对其进行流固耦合分析,研究叶片转角对风机气动性能的影响。利用ANSYS的CFX流体模块,流体湍流模型选择基于RANS的标准k-ε湍流模型,对风轮进行流固耦合分析,从而获得叶片产生的力矩情况,并计算了风机的功率特性。利用求解结果,得到了力矩系数与叶片转角之间的关系。分析了风机叶片在旋转一周中所产生的最大扭矩以及负扭矩所处的位置和范围。通过分析转角对风机性能的影响,可为今后的Savonius风机叶片形状优化和效率提升提供参考。