Figure 16 Comparison of power coefficient with tip speed ratio for optimized blade length, for various blade numbers at
solidity=0.05 @ pitch angle=3°
The optimum tip speed ratio was between 4 to 7 of blade number 3,5 and 7 respectively, at optimum point of solidity
0.05, many of the theoretical aspects of BEM are based on assumptions such as Prandtl's tip loss and general momentum
theory; it is useful to compare the results with other analysis methods to confirm the findings.
Glauert showed that the tip loss assumptions made by Prandtl's over predict power for low blade numbers and agree closely with exact solutions for higher blade numbers.
This would suggest that the difference in between B=3 and B=7 would increase.
Figure 14 indicated that the power coefficient decreases when the design tip speed ratio is in between 5 to 8 for all cases. Hence.
only selected designs chosen from BEM solutions were analyzed with Solidities of 3% to 10% were analyzed for blade numbers of 3, 5 and 7 and the results are shown in Figure 1 to Figure 15.
The optimum pitch angle was set according to values from the orevious BEM analysis.
11. Power velocity curve for different number of blades