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Preliminary tests of a high speed vertical axis windmill model

Technical Report:

Abstract

This report discusses a fixed-pitch vertical axis windmill that combines the inherent simplicity of this type of machine with a high aerodynamic efficiency and a high relative velocity. A three-bladed rotor was selected as the basic design, having constant chord symmetric airfoil blades configured in a catenary curve such that the rotor diameter is equal to the rotor height. In wind tunnel tests using a 30 inch scale model, it was found that once this rotor was given a very low rotational speed, it picked up speed and ran at a rotor tip velocity/wind speed ratio greater than 1. The number of blades was varied in the testing. A maximum power coefficient of 0.67 was achieved at 17 ft/s wind speed at a tip speed/wind speed ratio of 7.25 for a 2-bladed rotor. Increasing the number of blades above 3 did not result in higher power. The rotor could operate in gusts which double the mean wind velocity. Examination of Reynolds number effects, and taking into account the scale of the model, it was concluded that a full-scale windmill could run at lower velocity ratios than those predicted by the model tests, and that it could self-start under no-load conditions  More>>
Publication Date:
Jan 01, 1971
Product Type:
Technical Report
Report Number:
NAE-LTR-LA-74; CE-02261
Reference Number:
CANM-89-000211; EDB-89-031336
Subject:
17 WIND ENERGY; DARRIEUS ROTORS; PERFORMANCE; VERTICAL AXIS TURBINES; DESIGN; AERODYNAMICS; SCALE MODELS; WIND TUNNELS; FLUID MECHANICS; MACHINERY; MECHANICS; ROTORS; STRUCTURAL MODELS; TUNNELS; TURBINES; TURBOMACHINERY; UNDERGROUND FACILITIES; WIND TURBINES; 170602* - Wind Energy Engineering- Turbine Design & Operation
OSTI ID:
6769454
Research Organizations:
National Aeronautical Establishment, Ottawa, Ontario (Canada)
Country of Origin:
Canada
Language:
English
Availability:
CANMET/TID, Energy, Mines and Resources Canada, 555 Booth St., Ottawa, Ont., Canada K1A 0G1; $0.34CAN per page, $3.40 CAN minimum.
Submitting Site:
CANM
Size:
Pages: 11
Announcement Date:

Technical Report:

Citation Formats

South, P, and Rangi, R S. Preliminary tests of a high speed vertical axis windmill model. Canada: N. p., 1971. Web.
South, P, & Rangi, R S. Preliminary tests of a high speed vertical axis windmill model. Canada.
South, P, and Rangi, R S. 1971. "Preliminary tests of a high speed vertical axis windmill model." Canada.
@misc{etde_6769454,
title = {Preliminary tests of a high speed vertical axis windmill model}
author = {South, P, and Rangi, R S}
abstractNote = {This report discusses a fixed-pitch vertical axis windmill that combines the inherent simplicity of this type of machine with a high aerodynamic efficiency and a high relative velocity. A three-bladed rotor was selected as the basic design, having constant chord symmetric airfoil blades configured in a catenary curve such that the rotor diameter is equal to the rotor height. In wind tunnel tests using a 30 inch scale model, it was found that once this rotor was given a very low rotational speed, it picked up speed and ran at a rotor tip velocity/wind speed ratio greater than 1. The number of blades was varied in the testing. A maximum power coefficient of 0.67 was achieved at 17 ft/s wind speed at a tip speed/wind speed ratio of 7.25 for a 2-bladed rotor. Increasing the number of blades above 3 did not result in higher power. The rotor could operate in gusts which double the mean wind velocity. Examination of Reynolds number effects, and taking into account the scale of the model, it was concluded that a full-scale windmill could run at lower velocity ratios than those predicted by the model tests, and that it could self-start under no-load conditions if the cut-in rpm are at least half the rpm for maximum power at the prevailing wind speed. Preliminary estimates show that a 15 ft diameter windmill of this design, designed to operate with a safety factor of 2.5 up to a maximum wind speed of 60 ft/s, would weigh ca 150 lb and could be marketed for ca $60.00, excluding the driven unit, if sufficient quantities were produced to make tooling costs negligible. Similarly, a 30 ft windmill would weigh ca 1000 lb and cost ca $400.00. 2 refs., 6 figs.}
place = {Canada}
year = {1971}
month = {Jan}
}