The operating range of centrifugal pumps is a very important information for the long service life and risks regarding various premature failures. The pump cannot always operate within the permitted range, for example, it must start and shut down the operation. When developing and selecting a pump, it is necessary to take into account the fact that the pump should be operated close to the best efficiency point (BEP) as often as possible. In this paper, we discuss the kinematic causes for the formation of the so-called hump zone in the pump H(Q) characteristic, where the Flow rates are smaller than at the BEP. For the case of a reversible pump turbine, the detailed course of the pump characteristic at different relative openings of the guide vanes was numerically analyzed. The article presents the detailed Flow field of velocity vectors and streamlines in front of the runner, inside the runner, and behind the runner.

In this paper a laminar Flow of water on an ice layer subjected to a slip condition is considered numerically. The paper describes a parametric mathematical model to simulate the coupled heat and mass transfer events occurring in moving boundary problems associated with a quasi steady state steady Flow process. The discretization technique of the elliptic governing differential equations of mass, momentum and energy is based on the control volume finite difference approach and enthalpy method. The results illustrate, the distribution of heat transfer coefficient, ice melting thickness, slip velocity at solid moving boundary and boundary layer thickness for some values of slip velocity coefficient cu.

This paper presents a novel model to simulate the Flow-current characteristic curve of an electro-hydraulic servo valve in steady state condition. This characteristic curve has three major zones: dead zone, linear zone and saturation zone. By using the presented approach, we can simulate the behavior of all types of valves including under lapped, critical center (zero lapped) and over lapped valves. A hydraulic tester has been designed and constructed for validation of the results. It can test the performance of Flow-current and some other properties of the valve. Comparison of experimental and simulated curves describes that the model has an acceptable accuracy in determining the four important valve characteristics: Flow gain, saturation Flow, saturation current and dead zone. As a result, the model can be used for other studies such as geometrical sensitivity analysis (the ultimate objective of this modeling) or design optimization. Since this model is presented in a computer based algorithm, it can be easily used to observe and measure the effects of change in the parameters of interest (particularly geometrical parameters of the valve) on the Flow-current curve.

As a cost-effective option for subsea gas and oil fields development, multiphase pump has been widely used and plays an important role in promoting field production especially for those brownfields. The objective of this research is to study the variations of Flow parameters at the inlet of each stage in a five-stage helico-axial pump under design conditions by using commercial CFD packages. The numerical results show that inlet volume Flow rate, gas volume fraction (GVF) and Flow angle of each stage both decreases from the first stage to the fifth stage because of the compression. The variations of these parameters along the Flow direction are susceptible to the effect of rotational speed and initial gas volume fraction at inlet of the first stage. These inlet Flow parameters from inlet to outlet of the five-stage pump just change little when the initial inlet GVF is lower than 10% or higher than 90%. While the variation is obvious when inlet GVF is from 20% to 80%. Based on numerical simulation results, the stage-by-stage design method is proposed and geometry parameters such as inlet impeller hub diameter and inlet angle of blade in the second stage are modified according to its inlet Flow conditions. The comparison results between the modified pump and original pump show that pressure distribution at leading edge of impeller blades in each stage becomes uniform in the modified multistage pump. The inlet incident Flow loss of each stage is diminished and internal Flow conditions has been significantly improved. Thus, the pump’s boosting capacity is enhanced. These research results in this paper are instructive for the performance optimization of multistage pumps used in gas oil fields.

In this paper, a numerical study on Flow characteristics in configurations of sudden expansion with central restriction and fence viewed as annular Flow dump combustor has been carried out for Reynolds number (Re) ranging from 50 to 200, percentage of central restriction (CR) from 10% to 40% and aspect ratio (AR) from 2 to 6 with a fixed fence subtended angle (FSA) of 10 degree and with a fixed distance of fence from throat respectively. The effect of each variable on streamline contour and velocity profile has been studied in detail. Results have been compared with the configuration of sudden expansion with central restriction only. From the study it is concluded that the configuration of sudden expansion with central restriction and fence with higher Flow Reynolds number, higher central restriction and higher aspect ratio offers more benefit in terms of the mixing possibility compared to the case of sudden expansion with central restriction only.