Comparison of mixing power characteristics for curved-blade (NS-60), flat-blade and hollow-blade impellers

The paper presents the mixing power characteristics of a new type of a curv ed-blade impeller with 60 deg. angle blade, the Narcissus NS-60 based on th e impeller version reported by KRAITSCHEV et al. Experiments in a conventio nal mixing tank geometry with ID 0.4 m are described. Both Newtonian and no n-Newtonian cases are considered. Water, a 0.5 % pseudoplastic xanthan gum solution and viscoelastic 2 % carboxymethylcellulose and 1 % polyacrylamide solutions were used. The impeller rotational speed varied between 1 and 15 rps at intervals of 1 rps, and gas now rate varied between 0 and 2 vvm at intervals of 0.16 vvm. In parallel, Rushton flat-blade turbine (FB) and hol low-blade (HB) turbine were tested at similar conditions. The functions Po = f(Re) and Pg/Pu = f(Fl) corresponding to the three types of impellers wer e determined and compared. The data obtained for the FB and HB impellers ar e shown to be close to the figures reported in the literature.