The mixing of two or more liquids is very common in many industrial applications. In some cases the liquids set on the pump inlet. The mixing process of two fluids in a pump is investigated in the presented work. Different pump geometries have been studied with comparison of steady state and transient results. Turbulence closure model k-w has been used for simulations. The pump model consists of suction, impeller and discharge parts which were meshed and calculated together. This, for instance, naturally permits the effects of non-uniformity of velocity and liquids concentrations distribution on the impeller eye and on the inlet of the discharge segment to be taken into account. Commercial code Fluent 6.3.26 was used for CFD computations. A sliding mesh for transient calculations and the Multiple Reference Frame (MRF) model for steady state calculations were used with the total number of cells from four to eight million. The results show a significant change in the mixing uniformity coefficient γ, depending on where on the inlet the injected fluid is located. In the annular injection on the pump inlet, γ is close to 1 (an ideal mixture) on the outlet; whereas, γ is less than 0.9 for strong angular asymmetry injection on the pump inlet. The latter is not sufficient for some applications. Furthermore, the following transient effect is observed. Large oscillations of concentration and γ with the blade passing frequency takes place on the impeller section. However, the value of γ oscillations on the impeller – discharge interface is relatively small and fades very quickly when the distance from the impeller outlet exceeds two outlet diameters.

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