Flow starting times in constant-area supersonic diffusers

: The efficiency of short cylindric diffusers was experimentally investigated in a supersonic wind tunnel provided with exchangeable nozzles with a conical supersonic section designed for M equals 2; 25; 30; 35; 40; and 5 0 and a half cone angle of alpha equals 8 degrees for all M numbers The diffusor lengths varied from one to eight calibers of the nozzle exit cross sections Compressed nitrogen was used as the working substance A graph of the ratio of the aerodynamic stagnation pressure during startup of a nozzle with diffusers to the relative diffuser length showed the advantage of using diffusers at higher nozzle M values A diffuser length of up to 3-4 nozzle calibers practically exhausts the possibility of decreasing the starting pressure of nozzles with calculated M values of less than 3 Diffuser lengths up to 6-7 calibers are expedient on nozzles for nearly hypersonic M values Sufficiently long cylindrical diffusers have an efficiency of 075-085 Diagrams are presented for selecting minimum diffuser lengths in the range of M equals 2-5 The experiments revealed that the maximum rarefaction attainable with cylindrical diffusers at the nozzle exit section during discharge into a normal atmosphere is 004 atm (Author)

V. E. Davidson

Papers

On the starting of supersonic nozzles with the aid of cylindrical diffusers