Drag type multi-bladed vertical axis wind turbine using air concentrating nozzles for power generation

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DRAG TYPE MULTI-BLADED VERTICAL AXIS WIND TURBINE USING AIR CONCENTRATING NOZZLES FOR POWER

GENERATION

SHIKHA

Centre for Energy Studies

Submitted

in fulfilment of the requirements of the degree of Doctor of Philosophy

Indian Institute ofTechnology Delhi India

August 2004

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CERTIFICATE

This is to certify that the thesis entitled DRAG TYPE MULTI-BLADED VERTICAL

AXIS W壇ND TURBINE USING AIR CONCENTRATING NOZZLES FOR POWER

GENERATION being submitted by Shikha to the Indian Institute of Technology Delhi (India) for the award of the degree of Doctor of Philosophy in Centre for Energy Studies is a bonaffide research work carried out by her under our guidance and supervision. The research reports and the results presented in this thesis have not been submitted in parts or in full to any other university or institute for the award of any degree or diploma.

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マ D.P. Kothat丁一一一 Professor

Centre for Energy Studies Indian Institute of Techno_いgy New Delhi一i i 0016

Centre for Energy Studies Indian Institute of Technology New Delhi一i i 0016

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ACKNOWLEDGEMENTS

I would like to express my deep sense of gratitude and heartfelt devotion to my advisors Dr.

T. S. Bhatti and Prof. D. P. Kothari for their invaluable guidance, constant encouragement and staunch motivation throughout this work and their involvement in bringing the manuscript to this level. I am especially thankful to them for their constructive criticisms that helped me greatly in improving the quality ofthe work.

I wish to record my indebtedness to the Head, Centre for Energy studies, lIT Delhi for all the facilities provided for conducting this research. Blessings of Prof. T. C. Kandpal shall ever be remembered.

I sincerely ao血owledge Department of Science and Technology (DST), New Delhi for funding the research infrastructure and Council of Scientiffic and Industrial Research (CSIR), New Delhi for granting me Senior Research Fellowship (SRF) for the research carried out.

I would also like to thank the in-charge of my lab Mr. V.K. Rana, who has been very kind in maintaining a suitable working atmosphere and in extending al! the lab facilities. My special thanks go to my fellow research scholars Sunil Bhat, Anshu, Prashant for always being very cordial towards me. I deeply cherish and appreciate the way my friends Anshu and Prashant cheered me up, time and again, in this hard pursuit of knowledge and research.

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This work would not have seen the light of the day but for the understanding and unfai血g support of my parents・The credit goes exclusively to my mother，魚山er, brother Si中arth and his wife Rosy. Their sincere prayers for me, loving encouragement and moral support helped to see the work ffinish smoothly. OEey have always stood by me and I hold praye_血1 and loving wishes in my heart for their welfare, for all their sacriffices. The patience, understanding, cooperation and bearing with the worst of my moods extended throughout the work by them are greatly appreciated. No words can adequately express ti元

gratitude I owe to my parents whose love and affection has been the only incentive for to attain heights of success in life.

Last but not the least I would like to thank Surya who deffinitely needs a special word of appreciation for his endless support and cooperation.

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ABSTRACT

The conventional power is utilized to meet the demand of the commercial, industrial, agricultural and domestic sectors. The a師cultural load is considerable and is distributed countrywide causing large T &D losses in addition to operational and maintenance problems. To reduce the problem of the 師d network and to improve the power situation in developing countries, it is necessary that the a師cultural load may be supplied by alternative dispersed' power generation sources. In these areas (open flelds) slow speed winds are mostly available throughout the year. Therefore the problem can be solved by harnessing power fflom slow speed winds using proper, rugged and effficient wind turbine systems.

The available slow竺磐亜nes can provide small power, which is just suffficient for running a hand pump. The agricultural irrigation load requirements generally vary fflom i to 10 kW. Therefore, a new vertical axis wind turbine has been designed which can provide the required power. The unit is of modular form expandable as per requirement.

The limitation in the existing slow wind turbines is the weight of the wheel. Therefore, to keep the size of the wind turbine runner small and to capture more power, air concentrating nozzles have been designed. The nozzles amplify the wind speed before the air contacts the blades, thus increasing the rotational speeds. OEerefore to find the optimum nozzle dimensions, a detailed theoretical and practical study. of air concentrating nozzle is conducted which involved fabrication, testing and detailed study of different nozzle models in Actual Atmospheric Conditions and Wind Tunnel. It was found out that the nozzle with inlet-outlet area ratio of around 4: 1 , having side wall length equal to the length of the intake

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gives best performance in terms ofampliffication ofwind speed and minimum power loss in the nozzle.

The ideal effficiency or the percent of maximum power extraction by a rotor placed in a free wind stream is given by Betz limit and its value is 0.5926. In this thesis, the Betz derivation was reinvestigated with the help of Euler's&Bernoulli's equations and was found out to be 0.89.

The performance of the wind rotor in terms of effficiency (power-coeffficient) and starting torque depends upon the number of blades and the blade proffile. Theoretical models for drag machines have been developed using momentum principle・メkil analysis has been carried out by considering flat, semi-circular and curved blade proffiles. It has been found out that the semi-circular proffile gives better perfonriance than the other blade proffiles considered in the study. Further, rotor models (different number of blades) were fabricated and studied using air concentrating nozzles considering semi-circular proffiles.

The theoretical veriffication of the improvement in efficiency of these rotors is also presented in the thesis. It has been found out that the six-bladed rotor using air- concentrating nozzle gave the best performance and this has been proved both practically and theoretically.

Finally, a prototype model was fabricated by using the grant provided by Department of Science and Technology, India and installed at the back of block VI at lIT Delhi. It was found that the results are quite encouraging and are in co-ordination with the study conducted earlier in the thesis.

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4.3.4 Concave Blade Analysis... i 00 Drag Force on a Stationary Semi Circular Concave Blade. . . I 00 Work done by Wind on a Moving Semi Circular Concave Blade... 101 Drag Force on a Stationary Semi Circular Concave Blade inclined at an Angle O ... i 02 4.3.5 Convex Blade Analysis...,... i 04 Drag Force on a Stationary Semi Circular Convex Blade. . . I 04 Drag Force on a Semi Circular Convex Blade inclined at an Angle. iOS 4.3.6 Maximum Power Coeffficient of Semi Circular Blades. . .. . .. . . .. . . i 07 Maximum Power Coeffficient of Semi Circular Concave Blade. . . .. 107 Maximum Power Coeffficient ofSemi Circular Convex Blade. . . i 09 Analysis ofRotor with Curved Segment Blades. . . .. 112 Thrust Analysis of Multi-Blades (Curved Proffile). . . .. . . 112 4.5 Results and Discussions... i 28 4.6 Concluding Remarks... 131

CHAPTER 5: A NEW VERTICAL AXIS WiND ROTOR

5 . 1 Introduction... ... ... ... ... 132 5.2 Drag and Liifi t即e Machines...,...．。 i 32 5.3 Savonius Rotor... ... ... i 33 5.3.1 Modiffied Savonius rotor. . .. . . ... . ... .. . . .. . .. .. . . .. . . . ... . . ... .. . . i 34 5 .4 Development of Theoretical Models.. .. . . .. .. . ... .. . .. . . .. . .. . . .. . . .. . . i 43 5 .4. 1 Two-bladed Rotor without Overlap.. .. . ... . .. . . .. .. . . .. . .. . . .. .. . .. ... . . i 43 5.4.2 Two-bladed Rotor with Overlap. . . 147 5.4.3 Two-bladed Rotor with Overlap using Air Concentrating Nozzle. . . .. 151 5.4.4 Four-bladed Rotor with Overlap using Air Concentrating Nozzle. . . .. i 54 5.4.4 Six-bladed Rotor with Overlap using Air Concentrating Nozzle. . . 157 5.5 Concluding Remarks... i 60

CHAPTER 6: STUDY OF COMPLETE SYSTEM

6. 1 Introduction....,... ... .. I 62

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6.2 Visualized Model... i 62 6.3 Fabrication ofthe Prototype Model... I 65 6.4 Amplification of Wind Velocity... i 76 6.5 Discussion...181 6.7 Concluding Remarks.. ... ... I 82

CHAPTER 7: CONCLUSION AND FUTURE SCOPE

7.1 Conclusion...,... i 83 7.2 Signifficant Contributions. ... i 84 7.3 Future Scope ofthe Work...．、．...,...,i 85 REFERENCES

Drag type multi-bladed vertical axis wind turbine using air concentrating nozzles for power generation