Numerical Study of Unsteady Flow Characteristics in Regenerative Pump (original) (raw)
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Experimental and CFD Analysis of Regenerative Pump
Regenerative pump is rotodynamic turbomachine capable of developing high head at low flow rates. In this paper, an experimental and CFD analysis is carried out in order to investigate the effect of varying flow rate on the performance of pump like head generation, power input and overall efficiency. For this purpose, experiment is carried out by operating pump at five different flow rate. The result showed that head generated by pump and power input decreases with increase in flow rate. As the flow rate increases the overall efficiency increases up to 31 LPM and then it decreases. The maximum efficiency obtained from experimentation is 19.61 at 31 LPM. CFD analysis is used to investigating the complex flow field within pump, visualize the recirculating flow zones and other flow losses .CFD result shows that vortices are formed at outlet region, Straight radial impeller vanes causes flow direction changes abruptly hence pressure losses occurs and from pressure contour observed the water pressure increases continuously as it passes from inlet port to outlet port because water moves helically in the casing chamber and re-enters in the impeller vane passage many times in its peripheral path.
Introduction to Design and Analysis of High Speed Pumps
2006
: The physical mechanisms which govern the flow characteristics in a turbo-machine and specifically a pump are complex, numerous and partially explained. Flow conditions are generally three dimensional, viscous and non stationary and for the case of cavitating flow, one have to take into account two or multiphase conditions. The non stationary character of the flow is obvious if one consider rotor-stator or rotor-volute interactions. In the case of non uniform inlet conditions or intrinsic heterogeneity created by off design conditions and/or two phase flow, the phenomena is more complicated to understand. Transient regimes also lead to non stationary phenomena. The correct understanding and evaluation of these physical mechanisms become more and more important because of the high level of concurrence between pump manufacturers. They have to deal with high efficiencies, extended stabilised operating zones, more compact and reliable machines with severe geometrical constrains.
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EPJ Web of Conferences, 2014
This work deals with the experimental and numerical investigation of cavitating and noncavitating flow inside a mixed-flow pump and its influence on performance curves of this pump. The experimental research has been carried out in the closed horizontal loop with the main tank capacity of 35 m 3. The loop is equipped with both the compressor and the vacuum pump capable of creating different pressure levels while maintaining constant volume flow rate. Pump investigated in this project has been equipped with transparent windows, which enabled the visualization of flow and cavitation phenomena for a wide range of flow conditions. A comprehensive CFD analysis of tested pump has been done both in the cavitating and noncavitating regimes. The ANSYS CFX commercial CFD package has been used to solve URANS equations together with the Rayleigh-Plesset model and the SST-SAS turbulence model. Both the experimental research and the CFD analysis have provided a good illustration of the flow structures inside the pump and their dynamics for a wide range of flow rates and NPSH values. Flow and cavitation instabilities have been detected at suboptimal flow rates which correspond to increased values of noise and vibrations. The calculated results agree well with the measurements.
Reynolds Number Effect on Regenerative Pump Performance in Low Reynolds Number Range
International Journal of Fluid Machinery and Systems, 2008
The effect of Reynolds number on the performance of a regenerative pump was examined in a low Reynolds number range in experiment. The head of the regenerative pump increased at low flow rates and decreased at high flow rates as the Reynolds number decreased. The computation of the internal flow was made to clarify the cause of the Reynolds number effect. At low flow rates, the head is decreased with increasing the Reynolds number due to the decrease of the shear force exerted by the impeller caused by the increase of leakage and hence local flow rate. At higher flow rates, the head is increased with increasing the Reynolds number with decreased loss at the inlet and outlet as well as the decreased shear stress on the casing wall.
International Journal for Numerical Methods in Fluids, 2011
The capability of centrifugal pumps to operate as centripetal turbines was established by several authors many years ago (Kittredge, Knapp, Stepanoff) [1-3]. More recently, Shafer, Engeda and Priesnitz [4-6] have demonstrated how the efficiency as a pump can be maintained when the machine runs as a turbine. Also, they offered relations between the flow rate and head for optimum conditions in both modes. These works concern the overall performances of these machines, based on experimental methodologies. The purpose of this paper is to investigate the flow pattern in a centrifugal pump when it works as a centripetal turbine, with special interest in the unsteady behaviour, in order to explain the shape of the performance curves. Also, we focus on the determination of the radial thrust and other mechanical loads over a pump-design machine. The pump studied is commercial, with single axial suction and a vaneless spiral volute casing. A numerical study has been carried out in order to obtain more information about the flow into the volute and the impeller. A numerical 3D unsteady simulation has been developed using a commercial code that solves the URANS set of equations with a standard k- turbulence model. The results show the non-axisymmetric flow developed in the volute, which implies a significant radial thrust, the interaction between the tongue and the impeller generates force fluctuations, the velocity and pressure distributions inside the impeller, and the exit flow, with post-rotation and lowpressure. These flow results allow us to understand the behaviour of the machine, by comparing it with the pump mode. Complementarily, an experimental study has been developed in a hydraulic setup designed specifically according to standards. It uses an auxiliary pump that supplies the flow rate and head required for the pump to work as a turbine, which is further coupled to an electric generator. This test facility allows us to characterize the pump-turbine performances in order to compare the characteristic curves in both modes and determine the performance curves at constant head. Furthermore, pressure taps located around the impeller at the front side of the volute allow the measurement of stationary and non-stationary circumference pressure distributions in order to calculate the steady radial thrust and its fluctuations. Finally, a three-hole probe, placed at the suction outlet, is used to measure the radial distribution of the velocity circumference component, which enables us to explain the loss of efficiency when postrotation appears, as well as the susceptibility to cavitation.
Numerical and Experimental Analysis of a TurboPiston Pump
2010
The TurboPiston Pump was invented to make use of merits such as, high flow rates often seen in centrifugal pumps and high pressures associated with positive displacement pumps. The objective of this study is to manufacture a plastic model 12†TurboPiston Pump to demonstrate the working principle and a metal prototype for performance testing. In addition, this research includes the study of the discharge valve to estimate the valve closing time and fluid mass being recycled back into the cylinder through hand calculations. Furthermore, a transient simulation was performed in CFD using Fluent to provide a better estimate of what will happen in the actual pump while running. Additionally, an experimental rig was designed to investigate the performance of the first generation valve on the TurboPiston Pump known as the flapper valve. Means to improve the hydrodynamic performance of both valves have been identified for future study.
Design optimisation of a regenerative pump using numerical and experimental techniques
International Journal of Numerical Methods for Heat & Fluid Flow, 2011
Regenerative pumps are the subject of increased interest in industry as these pumps are low cost, low specific speed, compact and able to deliver high heads with stable performance characteristics. The complex flow-field within the pump represents a considerable challenge to detailed mathematical modelling. This paper outlines the use of a commercial CFD code to simulate the flow-field within the regenerative pump and compare the CFD results with new experimental data. A novel rapid manufacturing process is used to consider the effect of impeller geometry changes on the pump efficiency. The CFD results demonstrate that it is possible to represent the helical flow field for the pump which has only been witnessed in experimental flow visualisation until now. The CFD performance results also demonstrate reasonable agreement with the experimental tests. The ability to use CFD modelling in conjunction with rapid manufacturing techniques has meant that more complex impeller geometry configurations can now be assessed with better understanding of the flow-field and resulting efficiency.