Savonius rotor

Fig. 2.4 Vertical axis wind turbine a Savonius rotor and b Darrieus rotor...

The Abuinaga engine features a special Darrieus or Savonlus rotor between two cylinders. Essentially, this means that the liquid pistons are formed as a column of liquid that oscillates between two cylinders. The great advantage of the Darrieus or Savonius rotors is that they maintain the same direction of rotation irrespective of the oscillation direction of the column. 

The quantity ndN)IV is the ratio of the tip speed to wind speed. Experimentally, it is found that maximum efficiency is obtained for a Savonius rotor when the gap (g) is about d 3 and (.Id is about 3. For a Savonius rotor of these proportions, the efficiency vs speed ratio curve shown in Fig. 12.10 (a) is obtained. The overall efficiency is seen to be a maximum (about 33%) when die shaft is loaded so that the speed ratio itdNyV is about unity. These results may be used to predict the behavior regardless of the fluid medium involved (air, water, etc). 

Figure 12.10. Efficiency (e) vs speed ratio [ 7idN)IV curves for several types of wind machines, a) Savonius rotor A), b) multiblade U. S. type horizontal-axis windmill E), (c) Dutch-type four blade windmill (C), d) high-speed two blade propeller (Z)), and e) vertical axis three blade high-speed wind turbine (F).

The low-speed machines, such as the Savonius rotor, can be used in water as well as in air. The Savonius rotor has been successfully used as an instrument to measure currents in the sea and is being considered as a low-head turbine to generate electrical power in regions where there is a high tidal rise (such as Passamaquoddy Bay, Maine, 18 ft Irish Sea, 22 ft West Coast of India, 23 ft East Coast of Argentina, 23 ft a river in France, 26 ft Severn River in England, 32 ft and the Bay of Fundy in Canada, 40 ft). 

A Savonius rotor 10 ft in diameter and 30 ft high operates at a speed of93 rpm in a wind of 10 mph. Using the efficiency curve of Fig. 12.10 (A) and from Table 5.1, estimate the horsepower generated. If the wind velocity increases to 30 mph, estimate the horsepower. 

Design a water turbine using a Savonius rotor for a stream of water five ft deep, 10 ft wide, and flowing with a mean stream velocity of ... 

As described in Popular Science (Oct. 1974, p. 4), a Savonius rotor has been built from oil drums (Fig. PI2.7). Ordinary 55 gallon drums measure 23 in. diameter by 35 in. high. Estimate the power generated in the rotor shown in a 10 mph wind. 

Figure 12.6. Possible applications of falling paper principle, (a) Dynamic kite made from expanded polystyrene bead material with S-shaped rotor wing, (b) Radar target consisting of pieces of aluminum foil rotating and translating in random directions, (c) Means for economic use of nucleating agent in a cloud seeding operation, (d) Auxiliary power driven Flettner rotor ship, (e) Axial view of Savonius wind driven rotor, (f) Sailboat with two collapsible nylon sails.

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