Tooth tip losses in external gear pumps

Abstract

The present work is concerned with a design procedure applicable to simple external gear pumps. Attention is focused on the power losses which occur in the region of the thin fluid film between the moving tips of the teeth of the gears and the adjacent stationary casing surface. A method of obtaining the value of optimum clearance between these two members is derived and the use of this value then ensures that the power loss in this region is a minimum. The results are expressed in terms of a non-dimensional operating parameter, based on the geometry of the machine and its operating conditions, the total number of teeth on each of its gears and a tooth tip clearance ratio. Contours of constant power loss are also presented for pumps having different total numbers of teeth and a method of obtaining the minimum average power loss for a machine working over a range of the operating parameter is derived.