In this paper, the design methodology of a new type of three-dimensional surface return diffuser (3DRD) is presented and described in detail. The main goal was to improve the hydrodynamic performance of the deep-well centrifugal pump (DCP). During this study, a two-stage DCP equipped with two different type diffusers was simulated employing the commercial computational fluid dynamics (CFD) software ANYSY-Fluent to solve the Navier-Stokes equations for three-dimensional steady flow. A sensitivity analysis of the numerical model was performed in order to impose appropriate parameters regarding grid elements number and turbulence model. The flow field and the static pressure distribution in the diffusers obtained by numerical simulation were analyzed, and the diffuser efficiency was defined to quantify the pressure conversion capability. The prototype experimental test results were acquired and compared with the data predicted from the numerical simulation, which showed that the performance of the pump with 3DRD is better than that of the traditional cylindrical return diffuser (CRD) under all operating conditions. The efficiency and single-stage head of the pump with 3DRD have been significantly improved compared with the standard DCP of the same class.

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The present work aims to simulate the solidification process during beam blank continuous casting, to determine the causes of defects, and to optimise the process parameters. A transient finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. It has been found that the surface temperature fluctuated greatly and that the equivalent stress and strain have their highest values at the flange tip and the web. By comparing the calculated values with metallurgical constraints, the key factor causing surface cracks on the web was determined and an optimum cooling regime was proposed. Online verification of this optimisation project has led to a reduction in the incidence of web surface cracks. List of symbolsc(T) specific heat , J kg 21 uC 21 f s solid fraction h heat transfer coefficient, W m 22 K 21 H(T) enthalpy, J m 23 k(T) thermal conductivity, W m 21 uC 21 L latent heat of fusion, J kg 21 q heat flow density, kW m 22 q latent heat source, W m 23 t casting time, s T temperature, uC T 0 pouring temperature, uC T a air temperature, uC T s surface temperature of blank, uC T w cooling water temperature, uC x,y,z rectangular coordinates, m e strain e' emission ratio, e'50?8 r(T) density, kg m 23 r(T) s density of solid, kg m 23 s stress, MPa s' Boltzman constant, s'55?765610 28 , W m 22 uC 24

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