THEORETICAL PERFORMANCE OF WIND WHEEL TURBINES

Abstract

A wind wheel turbine designed for low wind speed applications has been analytically investigated. The turbine is simple constructed from a bladed-assembly rotor directly exposed to the free wind on the upper half and exposd to the wind through a multiple ducting system on the lower half. A theoretical analysis using an engineering model based on the impulse momentum theory is described for a range of blade numbers. The computed results of the torque and power coefficients for two-, three-. and four-blade-wheels are presented. The optimum number of blades was found to be three, using the maximum power coefficient as the performance criterion. The computed values of the power coefficients are found to be higher than those associated with other wind machines for tip speed ratios up to a value of unity. The results also show that the 3-blade-wheel, with accelerating flow through the ducting system, has increased the power coefficient by 3.5 times as much as the ideal propeller type windmill. Torque coefficients which may have potential use in some domestic applications are also described. A starting torque coefficient as high as 6.0, for example, is computed for a 2-blade-wheel.