Passive control of rotating stall in a parallel-wall vaned diffuser by J-grooves

In order to control and suppress instabilities caused by swirl flow, the au thors have proposed a very simple passive method utilizing shallow grooves mounted on a casing wall or diffuser wall(s) parallel to the pressure gradi ent. The groove is termed a "J-groove." The method is theoretically analyze d and experimentally proved capable of Suppressing rotating stall in a vane less diffuser. The performance curve instability is characterized by the po sitive slope of the head-capacity curve of a mixed flow pump for the entire flow range. In continuation, this work is aimed at realizing experimentall y the effect of J-grooves on suppressing rotating stall in the vaned diffus er of a centrifugal turbomachine. Thirteen double curvature vanes with vari ous radial positions, various setting angles, and J-grooves of different di mensions are tested in a parallel wall vaned diffuser with a semi-open radi al impeller with and without J-grooves. The results show that J-grooves can also suppress rotating stall in the vaned diffuser for the entire flow ran ge.