amir farhad najafi

Using inducers in order avoiding pressure reduction at the centrifugal pump impeller inlet and consequently increasing pump performance at high suction speeds are important in many applications. The inducer which is an axial pump with lower number blades than impeller’s (usually 3 or 4), located on the upstream impeller and rotates with the same rotational speed and direction as the pump. In this research, changing inducer design parameters such as the blade pitch and the length to the diameter ratio on its and pump hydraulic performance is investigated, numerically. The results show that using inducer and changing its blade pitch ratio from 0.24 to 0.48, causes average pressure ratio increasing from %10 up to %34 at the pump impeller inlet. Unlike the pitch ratio changing effects, increasing the length to blade diameter ratio from 7/12 to 16/12 show a fairly constant average pressure ratio increasing up to %23. For the large pitch ratio, pump impeller induced head; decreases for low flow rate. Meanwhile, decreasing pitch ratio in high flow rate causes flow counter rotation at the pump impeller inlet that increases the pump impeller head.

Recently, use of PAT (pump as turbine) in mini hydro power plants (

Pumps consume about 20% of whole electricity power in the world. Centrifugal pump is one of the most common pumps that works by the transfer of angular momentum to the fluid. The behavior of such a fluid flow in the side chamber, may affect the pump performance. The side chamber is defined the free space between the fixed (pump casing) and the rotating (pump impeller) parts. Steady, fully 3D computations of the Reynolds-averaged Navier-Stokes equations using a commercial CFD code are conducted in order to study the flow field in the whole pump including both side chambers. Numerical results are validated by comparison with the existing experiments. The impact of fluid flow in hub and shroud side chambers with the volute is investigated qualitatively by using 2D stream lines. Evaluation of the empirical equations shows that the frictional torque may be decreased more than 10%, by using the proper gap size. Considering this situation, the changes in the flow pattern and the value of power loss resulting from friction in hub and shroud side chamber is studied. It reveals that the variation in friction depends on the initial flow pattern in cavity. Finally, in order to obtain the relationship between the power loss and the flow rate, nondimensional coefficients are derived. These coefficients show that the change in the power loss due to the volumetric flow rate, is the same as its change with the gap changing, but their slopes are not equal.

slip factor is one of the most important parameters used in centrifugal pumps performance prediction. Knowing this parameter as a function of flow rate seems essential for off-design performance prediction. In this paper, it is intended to establish the slip factor dependence upon flow rate for a centrifugal pump using computational fluid dynamics. For this purpose, the full 3D-RANS equations in coupled with RNG k-ε turbulence model were solved for several flow rates ranging from 45% to 120% of rated condition by means of a commercial code, CFX. In the steady state, this simulation is defined by means of the multi-reference frame technique, in which the impeller is situated in the rotating reference frame, and the volute is in the fixed reference frame. The validity of the numerical model was confirmed by matching the calculated characteristic curves with the associated experimental data. It was found that there is a good coincidence between the numerical results and available experimental data of global performance, local velocity distribution and slip factors. A comparison was performed among the well-known slip models which reveals, that the slip factor variations can be predicted very well using CFD analysis.

In this study, a suction tube performance under the influence of horizontal Francis turbines Shklgrfth eddy current in the output of the turbine wheel, when functioning outside of the turbine design point occurs, the form has been studied numerically. Capabilities to ensure high numerical analysis, the first step was having experimental data. Hence the design and construction of a probe) probe (S·hhfrhyy pressure distribution, axial and rotational speeds in the two sections, inside the suction tube was measured. The values obtained at the entrance of the suction pipe) First stage (as boundary conditions in numerical analysis three dimensions were used. Because the eddy currents, viscosity) viscosity (flow Ghyrayzvtrvp is confusing for the accuracy Replies Atmynanyaftn RSM zethod for the Reynolds stress model is used. experimental and numerical results for axial and rotational velocity component in the second stage, were coordinated with acceptable. eddy current effect on performance for the three-point suction pipe turbine performance numerical method was demonstrated to reduce the efficiency of the suction tube was such a flow. Clearly, then can also reduce turbine production finds.