Revaluation of Researches on the Free Rotating Vaneless Diffusor

Abstract

After eighteen years, an attempt is now being made to revaluate the studies performed by RODGERS-MNEW and RIBAUD-FRADIN on the rotating vaneless diffuser. These two studies are complementary. The first deals with a high speed rotating vaneless diffusor fed by a swirl generating nozzle and giving high Mach numbers. The second concerns a real compressor comprising a low speed rotor followed by a rotating vaneless diffuser. The free rotation of the vaneless diffusor reduces the friction losses by about 70%. The high speed, mechanical design of the rotating vaneless diffusor is a success. The structure of the flow at the rotor outlet seems to have an important effect on the efficiency of the rotating vaneless diffusor. New types of rotating vaneless diffusors should be experimented and new comparative experiments attempted. The application of the rotating vaneless diffusor concept to low specific speeds compressors is also proposed.