Drag-Turbine Performance

Abstract

Abstract A previous treatise presented some basic considerations concerning the principal features of drag turbines. The conclusion was derived that this turbine type offers particular advantages for small accessory power units, where low bulk, simplicity, and high reliability are most desirable. This application was suggested since drag turbines exhibit peak efficiencies at low speeds; i.e., low u/cth), values where u denotes the wheel-tip speed and cth the spouting velocity of the gas. Presently available test data show peak efficiencies of about 35 per cent. Further studies reveal that higher efficiencies can be obtained so that this turbine type will not be restricted to applications where efficiencies are of secondary importance, but also will show merit in cases where an effective energy utilization is more critical. In this paper a simplified theory is presented which enables fair predictions of drag-turbine performance for compressible as well as incompressible media, accounting for the influence of design geometries on performance range and peak efficiency.