外文翻譯--螺旋薩沃紐斯轉(zhuǎn)子性能試（英文）

1、Performance tests on helical Savonius rotorsM.A. Kamoji a, S.B. Kedare a, S.V. Prabhu b,*a Department of Energy Science and Engineering, Indian Institute of Technology, Bombay b Department of Mechanical Engineering, Indi

2、an Institute of Technology, Bombaya r t i c l e i n f oArticle history:Received 27 January 2008Accepted 5 June 2008Available online 26 July 2008Keywords:Helical Savonius rotorConventional Savonius rotorCoefficient of pow

3、erCoefficient of static torquea b s t r a c tConventional Savonius rotors have high coefficient of static torque at certain rotor angles and a negativecoefficient of static torque from 135? to 165? and from 315? to 345?

4、in one cycle of 360?. In order todecrease this variation in static torque from 0? to 360?, a helical Savonius rotor with a twist of 90? isproposed. In this study, tests on helical Savonius rotors are conducted in an open

5、 jet wind tunnel.Coefficient of static torque, coefficient of torque and coefficient of power for each helical Savonius rotorare measured. The performance of helical rotor with shaft between the end plates and helical ro

6、torwithout 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 Savoniusrotor. The r

7、esults indicate that all the helical Savonius rotors have positive coefficient of static torque atall the rotor angles. The helical rotors with shaft have lower coefficient of power than the helical rotorswithout shaft.

8、Helical rotor without shaft at an overlap ratio of 0.0 and an aspect ratio of 0.88 is found tohave almost the same coefficient of power when compared with the conventional Savonius rotor. Cor-relation for coefficient of

9、torque and power is developed for helical Savonius rotor for a range of Reynoldsnumbers studied.? 2008 Elsevier Ltd. All rights reserved.1. IntroductionSavonius [1] rotor is ‘‘S-shaped’’ cross-section constructed by two

10、semi-circular buckets. The concept of Savonius rotor is based on the principle developed by Flettner. It is simple in structure, has good starting characteristics, operates at relatively low operating speeds, and has abi

11、lity to accept wind from any direction. Its aerodynamic efficiency is lower than that of other types of wind turbines such as Darrieus and propeller rotors. Savonius rotor is considered to be a drag machine. This means t

12、hat the main driving force is drag force of wind acting on its blade. However, at low angle of attacks, lift force also contributes to torque production [2]. Hence, Savonius rotor is not a pure drag machine but a compoun

13、d machine and hence can go beyond the limitation of Cp of a pri- marily drag type machine (Cpmax ¼ 0.08 for plate type turbine, Manwell et al. [3]). Although conventional Savonius rotors have low aerodynamic efficie

14、ncy, they have a high starting torque or high coefficient of static torque. Due to this they are used at starters for other types of wind turbines that have lower starting torques. Though the starting torque is high, it

15、is not uniform at all the rotor angles. At certain rotor angles, conventional Savonius rotors cannotstart on their own as the coefficient of static torque is negative. Conventional Savonius rotor is having negative torqu

16、e for the rotor angles in the range of 135–165? and from 315? to 345?. Literature suggests that two stage and three stage conventional Savonius rotors could overcome this problem of negative torque [4,5]. However, with t

17、he increase in the number of stages, the maximum coefficient of power decreases as reported by Kamoji et al. [4] and Hayashi et al. [5]. The use of three bladed single stage rotor, with each blade at 120? also reduces th

18、e torque variation in a rotor cycle but the coefficient of power decreases as reported by Shankar [6] and Sheldahl et al. [7]. Saha and JayaRajkumar [8] report that twisted three bladed Savonius rotor with a twist angle

19、of 15? has a maximum coefficient of power of 0.14 (tip speed ratio of 0.65) compared to 0.11 for a three bladed conventional Savonius rotor. Helical Savonius rotors could provide positive coefficient of static torque. He

20、lix can be defined as a curve generated by a marker moving vertically at a constant velocity on a rotating cylinder (at a constant angular velocity). Fig. 1 shows a single helical rotor blade. The inner edge remains vert

21、ical whereas the outer edge undergoes a twist of 90? (a quarter pitch turn). The blade retains its semi-circular cross-section from the bottom (0?) to the top (90?). Combination of two such blades is called as a helical

22、Savonius rotor in this study. In spite of its good promise on generating positive static torque coefficient, there is no information on helical Savonius rotor in the open literature. Hence, the main objective of the pres

23、ent study is to experimentally investigate the effect of overlap* Corresponding author. Tel.: þ91 22 25767515; fax: þ91 22 25726875,25723480.E-mail addresses: svprabhu@me.iitb.ac.in, svprabhu@iitb.ac.in (S.V. P

24、rabhu).Contents lists available at ScienceDirectRenewable Energyjournal homepage: www.elsevier.com/locate/renene0960-1481/$ – see front matter ? 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.renene.2008.06.002Rene

25、wable Energy 34 (2009) 521–529must be minimized. The seals are removed from the bearings and bearings are washed in petrol to remove the grease before mounting resulting in the reduction of friction. Wind velocity is adj

26、usted corresponding to a given Reynolds number and the rotor is allowed to rotate from no load speed. Rotational speed of the rotor is recorded by a non-contact type tachometer. Each bearing is sprayed with W-D 40 (a com

27、mercially available spray) lubricant before each reading [9]. The rotor is loaded gradually to record spring balance reading, weights and rotational speed of the rotor. A set of tests are carried to calculate the static

28、torque of the rotor at a given rotor angle using the brake drum measuring system. The static torque of the rotor is measured at every 15? of the rotor angle. At a given wind velocity, the rotor is loaded to prevent it fr

29、om rotation at a given rotor angle. The values of load and spring balance reading are recorded to calculate the static torque at a given rotor angle.3. Data reductionReynolds number based on the rotor diameter is given b

30、yRe ¼ rUD m (1)where, Re is Reynolds number , r is the density of air, U is the free stream velocity, D is the rotor diameter and m is the absolute vis- cosity of air. Tip speed ratio is given byTSR ¼ uD2U (2)w

31、here u is the angular velocity of the rotor. Torque calculated from the measured load and spring balance load is given byT ¼ ðM ? SÞ?rshaft þ rrope ?g1000 (3)where, M is the load, S is spring balance

32、load, rshaft is the radius of the shaft, rrope is the radius of the nylon string.Coefficient of torque (Ct), coefficient of static torque (Cts) and coefficient of power (Cp) are given byCt ¼ 4T rU2D2H (4)Cts ¼

33、4Ts rU2D2H (5)Cp ¼ TSR ? Ct (6)Blockage ratio (B) is given byB ¼ HDHwW (7)where, Hw is the height of the wind tunnel exit and W is the width of the wind tunnel exit. The maximum blockage ratio is within 39% for

34、 all the helical rotor models studied. The effect of blockage ratio is negligible on Cp, Ct and Cts for rotors in an open jet wind tunnel as reported by Kamoji et al. [4]. Uncertainties in various basic parameters, coeff

35、icient of static torque and coefficient of power are presented in Table 1. The uncertainties in the coefficient of static torque and coefficient of power at the maximum coefficient of power are around 4.5% and 4.8%, resp

36、ectively. Uncertainty calculations are carried out based on Moffat [10].4. Rotors covered in this studyThe helical Savonius rotors (with and without shaft in between the end plates) with a twist of 90? are fabricated in

37、a rapid proto- typing machine. Fig. 3(a) shows a helical Savonius rotor with shaft in between the end plates. Two helical Savonius rotor blades each with a twist of 90? are assembled at an appropriate overlap ratio toTab

38、le 1Uncertainties of various parametersParameter Uncertainty (%)Tip speed ratio 2.5Coefficient of static torque 4.5Coefficient of power 4.8Fig. 3. Helical Savonius rotors (a) with provision for shaft between the end plat

39、es; (b) and (c) two views of helical rotor without shaft between the end plates.Table 2Details of overlap ratio, aspect ratio and rotor diameter of helical Savonius rotorscovered in this studyRotor number Overlap ratio (