Report KD 658 has been added to the menu KD-reports. The tittle of this report is: “Calculations executed for an alternative rotor of the VIRYA-4.2 windmill (lambda design = 6.5, Gö 711 airfoil) used for 24 V battery charging”. The advantage of the alternative VIRYA-4.2 rotor is that it has a higher starting torque coefficient than the original rotor which has a design tip speed ratio of 8. The starting wind speed is therefore lower. The Pel-V curve is better at low wind speeds but worse at high wind speeds. So the alternative rotor is especially meant for regions with low wind speeds.
Articles for juni 2018
KD 656 reviewed
A new chapter 6 has been added to report KD 656. In this chapter it is investigated how the rotor and the characteristics change if the 0.5 m long connecting strip which connects both blades is changed by a 0.75 m long connecting strip. It appears that the same blades can be used but that now the connecting strip has to be twisted 4 degrees in stead of 5 degrees. With this bigger rotor, the windmill is called the VIRYA-3.17. The Pel-V curve of the VIRYA-3.17 is better than the one of the VIRYA-2.92.
KD 656 added
Report KD 656 has been added to the menu KD-reports. The title of this report is: “Calculations executed for the 2-bladed rotor of the VIRYA-2.92 windmill (lambda design = 6, stainless steel tapered blades) driving the VIRYA-2.68 PM-generator for 24 V battery charging”.
Wind tunnel measurements of a similar rotor with tapered blades made out of a cylinder have already been performed in 1978. The measurements for a stainless steel rotor with a diameter of 1.8 m and with blades with a sheet thickness of 2 mm are given in report KD 616. This report has inspired me to design a bigger rotor using 3 mm stainless steel sheet for the blades and stainless steel strip size 150 * 6 mm for the connecting strip.
KD 598 reviewed again
A new chapter 7 has been added to report KD 598 about the VIRYA-0.65 floating water turbine. In this chapter it is investigated if the matching in between rotor and generator can be improved by taking a simple 2-bladed rotor with a slightly smaller rotor diameter of 0.625 m in stead of 0.65 m and a design tip speed ratio of 3.5 in stead of 3. The matching of this VIRYA-0.625 for 26 V battery charging and star rectification of the original 230/400 V winding is better than for the VIRYA-0.65. The better matching results in reduction of the cut-in water speed from 0.7 m/s to 0.6 m/s. The starting water speed is increased from 0.37 m/s up to 0.5 m/s but, as it is still lower than the cut-in water speed of 0.6 m/s, this is no problem. The maximum power at V = 2 m/s is 160 W, so the same as for the VIRYA-0.65. The negative effect of the slightly smaller rotor diameter is compensated by the better matching.