Abstract: n this paper,a test rig is set up for experiment investigation to axial double flow vaneless nozzle and three different profiles of inner-ring are designed for it.Pentahole probes and nicro-trihole bOundary layer probes are employed for measuring the radial parameters dis-tribution. The flow field of this new type of nozzle is analysed and the optimum profile of inner-ring and velocity coefficient are obtained.Additionally,the rotating effect of the inner-ring can keep the losses lower.This new type of nozzle can be applied in the large power turbines as the first stage.

Key words: axial flow vaneless nozzle, inner-ring profile, experimental data