Mixed Flow Pump Impeller Research Articles

Studies on a diagonal-flow pump. (Hydraulic losses caused by a mixed-flow impeller and reasonable choice for impeller blade loading).

Hydraulic losses of mixed-flow pump impellers with four different specific speed impellers were measured near the respective best efficiency point .The measured radial variations of the hydraulic loss at the impeller exit were compared with those calculated y the two-dimensional boundary layer calculation procedure under the support of the quasi three-dimensional potential flow analysis. The calculated hydraulic losses at the impeller downstream section showed good agreement with the measured ones in the case of good agreement between the calculated and measured velocity distributions at the impeller inlet. In addition, the measured data were rearranged to get the information on the reasonable choice for the casing and hub cone angle as well as blade loading.

Experimental study on a diagonal-flow pump (Comparison between measured and calculated hydraulic losses caused by a mixed-flow impeller)

Using a five-hole pitot-tube with quick response, both upstream and downstream flow fields of a mixed-flow pump impeller were measured in order to make clear the hydraulic losses which arise in the fluid flow through an impeller. The hydraulic loss distributions at the downstream of the impeller were presented for two different specific speed impellers. The measured loss distributions were compared with the ones calculated by a simple prediction method. Moreover, the slip factors at impeller exit were also compared with the ones calculated by the existing formulae. As a result of the study, it was made clear that the ratio of the pressure rise by cascade effect to the one by centrifugal force effect is an important factor for the reasonable prediction of the hydraulic losses caused by a mixed-flow impeller.

Analyse théorique-expérimentale de l'écoulement réel dans les pompes assoradiales

The paper presents a numerical method for non-isoentropic through flow calculation in centrifugal and mixed-flow pump impellers. The analysis of incompressible fluid motion is done following Wu's general theory on 82 type surface. In particular, one of the motion equations is substituted by the geometrical condition for the flow to follow the prescribed 82 surface. Besides the flow is assumed to take place in presence of a dissipative force field locally opposite to the relative velocity vector and tangent to the stream line. Combining the basic equations of continuity, entropy production, energy and motion, defining the local geometry of the stream surface S2 (angles lambda and mu) and the stream function ψ it is possible to derive the final flow equation of the type δ2ψ/δr2 + δ2ψ/δz2 = q1 +qE ) (7) where q1 depends on velocity components and on S2 geometry and qE depends on the entropy production inside the fluid flow. The equation of stream surface is obtained starting from the blade geometry and considering its distortion due to the slip effect. For the expression of entropy gradient a local loss coefficient n ψ is defined as a ratio between the rise of total pressure in the real flow conditions and the rise of total pressure in isoentropic flow. In this way it is possible to evaluate the therm qE if a preceding isoentropic flow calculation is available. The computer numerical model for the through flow calculation perforrns the following steps : a) defmition of 82 geometry starting from the impeller geometric data and considering the slip effect. b) Iterative solution of equation (7) in the isoentropic case (qE = 0) c) Evaluation of entropy field. d) Iterative solution of equation (7) in its complete form. In the step a) three-dimensional parametric splines are used for surface representation. The discretization of the problem is done using finite element technique with isoparametric, rectangular elements (8 nodes). The solution of non-linear equation (7) is performed using Galerkin's weighted residual method. The paper finally shows an example of through flow calculation in a mixed-flow pump for the design conditions and for two off-design working points. The computed results are compared with experimental measurements.

Studies on Back-Flow Mechanism of Turbomachines : (Part 2, Back-Flow to the Suction Side of Mixed-Flow Impeller Blades)

In this paper, the mechanism of back flow to the suction side of mixed-flow pump impeller was studied by measuring the pressure distribution and the flow direction on the outside of impeller blades. Furthermore, the effect of setting angle of impeller blades on the back flow mechanism was investigated. The obtained results are mainly as follows : (1) The pump performance was made clear. (2) Pressure distributions and flow patterns on the outside of impeller blades were made clear. (3) The difference of flow on the outsides of axial-flow and mixed-flow impellers was made clear. (4) Two different reasons for the beginning of the back flow were discovered with the mixed-flow impeller.

Experimental Study on Cavitation in Mixed Flow Pump Impellers

Several mixed-flow pump impellers were tested in a test pump for the purpose of studying the effects of the number of vanes and the inlet edge shape on their performance and cavitation characteristics. The shockless entry flow rates were obtained from the incipient cavitation conditions and inlet flow deviation angles were found, their degree varying with the number of vanes. There was very little effect of the inlet edge shape on the overall performance, but it proved to be considerably influential on the cavitation characteristics. For the blunt inlet edge, cavitation was observed on both sides of the edge simultaneously, while for the sharp inlet edge it occurred on one side at a given rate of flow. The values of cavitation parameter kd for the impellers with the blunt inlet edge were about twice as large as those for the ones with a sharp inlet edge when compared at the critical point of the total head drop.

Experimental Study on Cavitation in Mixed-Flow Pump Impellers

Several mixed-flow pump impellers were tested in a test pump for the purpose of studying the effects of the number of vanes and the inlet edge shapes on their performance and cavitation characteristics. The impact-free-entry flow rates were obtained from the incipient cavitation conditions and inlet flow deviation angles were found, their degree varying with the number of vanes. There was very little effect of the inlet edge shapes on the normal performance, but they proved to be considerably influential on the cavitation characteristics. For the blunt inlet edge cavitation was observed on both sides of the edge simultaneously, while for the sharp inlet edge it occurred on one side. The values of cavitation parameter kd for the impellers with the blunt inlet edge were about twice as large as those for the ones with the sharp inlet edge when compared at the beginning of the total head drop.