Experiments on conical diffusers

Abstract

No systematic measurements of the efficiency of conical diffusers have been made since Gibson's tests in 1910. The present investigation was made to check this early work, and to study the variation of efficiency with Reynolds number and the changes in flow with change of cone angle. The experiments of Part I were made with cones of angles between 4 and 10 deg, of area ratio 4 between entry and exit, and with uniform flow at the entry. These showed no striking effect due to variation in cone angle and gave no sign of flow separation. The experiments of Part II were made with diffusers of area ratio 16 between entry and exit and with pipe flow at the entry, and consisted of measurements of the velocity distribution at a number of stations. The object of these later tests was to find out whether, under these different conditions from Part I, flow separation occurred at the larger cone angles, thereby giving a practical limit to the cone angle which could be used in the return circuits of wind tunnels and in other ducts.