Investigation of flow through centrifugal pump impellers 1

[...]... of the centrifugal pump Therefore, pump head -flow curve, which is described as one of the most important characteristic curves of centrifugal pumps (Karassik et al., 19 76), were not presented and discussed fully in their research work It was also found that few researchers compared flow field and performance between different types of pumps to give a full description of the behaviour of different pumps... different pumps As for numerical approach, most of previous numerical work 11 Chapter 1 Introduction focused on the use of the standard k − ε model to simulate water flow through pump impellers However, as pointed out by Menter (19 92), the standard k − ε model had accuracy problems in predicting adverse pressure gradient flows, which will usually occur under pump off-design conditions, and sometimes even... types of centrifugal pump impellers with various vane numbers are selected and the flow patterns and pressure distribution in these impellers are studied and compared at pump design and off-design conditions Different turbulence models will also be adopted to investigate their influence on the pump performance In addition, the present study implements numerical computation for two-phase turbulent flow through. .. turbulent flow through the pump impellers After careful consideration, four commonly used turbulence models were selected for turbulence modeling: the standard k − ε turbulence model, RNG k − ε turbulence model, the Wilcox k − ω turbulence model and the shear stress transport (SST) turbulence model 1. 4 Objective and Scope The main objective of this work is to study flows in centrifugal pump impellers. .. investigating the influences of different turbulence models to the pump performance is also a necessity On the other hand, the accurate prediction of the performance drop caused by two-phase flow in the centrifugal pump impellers is currently still a problem (Kosyna and Kecke, 2002) The influence of the gas fraction on the pump performance is still not clear yet Therefore, there is a lot of work to do in these... computation for two-phase turbulent flow through pump impellers by using Eulerian multiphase flow model The effect of the gas fraction on the pump performance will be investigated and the gas fraction distribution in the impellers will be presented and analyzed The computations first started with single-phase flow (water) through two identical but scaled radial flow pumps with five straight blades The numerical... the main contribution of this thesis 1. 3 Overview of Some Turbulence Models It is well known that the flow in the centrifugal pump impeller is threedimensional and turbulent flow characterized by diffusion and strong swirl Thus selection of the turbulence model is a very important step for obtaining accurate numerical results As pointed out by some researchers such as Menter (19 92) and Zhou et al (2002),... 12 Chapter 1 Introduction and adverse pressure gradients These eight turbulence models are Jones and Launder (JL) k − ε model (Jones and Launder, 19 72), Launder and Sharma k − ε model (Launder and Sharma, 19 74), Lam and Bremhorst (LB) k − ε model (Lam and Bremhorst, 19 81) , Chien (CH) k − ε model (Chien, 19 82), Yang and Shih (YS) k − ε model (Yang and Shih, 19 93), Fan (FL) k − ε model (Fan et al., 19 94),... principal turbulent shear stress The new model was called the shear14 Chapter 1 Introduction stress transport (SST) model and led to major improvements in the prediction of adverse pressure gradient flows Keimasi and Mohammad (20 01) performed calculation of a three-dimensional turbulent flow of square jets injected perpendicularly into a crossflow The Reynoldsaveraged Navier-Stokes equations in the general... and the other two with six twisted blades The predicted results of pump performance curves for these pump cases were validated by the experimental data over the entire flow range The calculated results for velocity and pressure distribution through these impellers were also presented and compared at pump design and off-design conditions 17 . 1 CHAPTER 1 INTRODUCTION 1. 1 Background A centrifugal pump consists of a set of rotating vanes enclosed within a casing. The vanes impart energy to fluid through centrifugal. flows in centrifugal pump are three-dimensional turbulent flows, and a clear understanding of turbulent flow structures is essential for the optimization of the performance of centrifugal pumps volumetric flow and the total breakdown of the flow may occur when the gas fraction reaches about 8 -10 % of the total volumetric flow rate. For two-phase flow applications of centrifugal pumps,