CFD Analysis for Cavitation of a Centrifugal Pump Impeller

2000

A mini turbo-pump, which is defined as the size having its impeller diameter between 5 mm and 50 mm by the authors, is needed for cooling small electronic devices and fuel cells, etc. Since the mini pump will act as a key part in these systems, the hydraulic performance including cavitation performance is of great importance. The authors' group has demonstrated that an impeller having more vanes than the conventional is favorable for a mini pump, using a 34 mm dia. semi-open impeller. In the present study, the proposed design concept is examined whether it is appropriate from the viewpoint of cavitation performance.

A method, based on quasi three-dimensional analysis, of describing pump cavitation behaviour is proposed. Cavitation performance is related to impeller entrance design and the influence of the angle of attack of the leading edges on the flow is studied. Coefficients are derived from the pressure drop due separately to the vanes and shroud. The influence of incident angle on cavitation is shown as a function of the blade geometry and discussed. By comparison with experimental data on centrifugal pumps, it is shown that the present model can simulate the characteristics of inception cavitation at design and off-design conditions.

International Journal of Fluid Machinery and Systems, 2011

The paper presents a new method for the analysis of the cavitation behaviour of hydraulic turbomachines. This new method allows determining the coefficient of the cavitation inception and the cavitation sensitivity of the turbomachines. We apply this method to study the cavitation behaviour of a large storage pump. By plotting in semi-logarithmic coordinates the vapour volume versus the cavitation coefficient, we show that all numerical data collapse in an exponential manner. By analysis of the slope of the curve describing the evolution of the vapour volume against the cavitation coefficient we determine the cavitation sensitivity of the pump for each operating point.

Journal of fluids …, 2002

A multi-phase CFD method is used to analyze centrifugal pump performance under developed cavitating conditions. The differential model employed is the homogeneous two-phase Reynolds-Averaged-Navier-Stokes equations, wherein mixture momentum and volume continuity equations are solved along with vapor volume fraction continuity. Mass transfer modeling is provided for the phase change associated with sheet cavitation. Quasi-three-dimensional (Q3D) and fully-three-dimensional analyses are performed for two impeller configurations. Using Q3D analysis, steady and time-dependent analyses were performed across a wide range of flow coefficients and cavitation numbers. Characteristic performance trends associated with offdesign flow and blade cavitation are observed. The rapid drop in head coefficient at low cavitation numbers (breakdown) is captured for all flow coefficients. Local flow field solution plots elucidate the principal physical mechanisms associated with the onset of breakdown. Results are also presented which illustrate the full three dimensional capability of the method.

Applied Mathematical Modelling, 2021

An important flow mechanism that can affect the performance and efficiency, as also the maintenance cost of centrifugal pumps is cavitation. Scientific research has been focusing on the mechanisms that govern cavitation in order to develop experimental and numerical tools that are able either to detect the phenomenon or to anticipate its appearance. In this study, a computational model is used in order to study the cavitation performance of a radial flow centrifugal pump with a semi open impeller. The numerical model includes and studies the effects of the blade tip clearance and its thickness, and it is validated against corresponding laboratory measurements and visualization data obtained for this pump under normal and cavitating flow conditions. The total head drop variation curves versus cavitation parameter are extracted both numerically and experimentally, and compared for various pump loading conditions with satisfactory agreement. A non-periodic pattern of flow and cavitation bubbles between the impeller blades, which is caused by the inlet pipe bending, is also well reproduced by the model. The numerical results display in detail the complex flow field and the secondary flows developed in the tip clearance area, close to the blades leading edge. The effects of the latter on the onset and development of cavitation at the suction side of the impeller, as well as on the backflow cavitation phenomenon are presented and analyzed. Backflow cavitation is found to affect the suction ability of the pump, especially for moderate cavitation conditions, as far as the pressure differences between the two blade sides remain significant.

Journal of Physics: Conference Series, 2017

Centrifugal pumps are considered as machines of high importance in a wide range of industries, hence several strategies and methods have been developed in order to ensure their optimum performance under different operating conditions. An important mechanism that can affect pump's steady and dynamic operation is cavitation, which appears in the low static pressure zone at the inlet of the impeller. Several researchers have studied experimentally the physics of the phenomenon in order to develop different methodologies for its safe detection. The aim of this paper is to study the onset and evolution of cavitation in a centrifugal pump with unshrouded impeller by performing of flow visualization and acoustic emission measurements. The results showed that the acoustic emission technique is able to detect the onset of cavitation, while the leakage backflow through the clearance affects the development of cavitation between the impeller blades. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Journal of computational fluids engineering, 2015

Journal of Power Technologies, 2016

Cavitation is an abnormal physical phenomenon which can be generated in relatively low pressure regions in centrifugal pumps. In predicting and understanding cavitation in the pumps, it is important to secure their efficiency and reliability. The purpose of this study is to analyze the cavitation flows in centrifugal pumps with variable speeds through numerical methods. The Rayleigh–Plesset cavitation model was adapted as the source term for inter-phase mass transfer in order to predict and understand the cavitation performances. The Reynolds-average Navier-Stokes (RANS) equations were discretized by the finite volume method. The two-equation SST turbulence model was accounted for turbulent flows. The numerical analysis results were validated with experimental data and it was found that both results were in good accordance. The cavitation performances were obtained for variable speeds with different temperatures and the effects on cavitation were described according to different cavitation numbers. Cavitation performances were also observed for different centrifugal pump stages (1st and 2nd). The performances of cavitation decreased with the increase of rotational speed. In addition, the development of cavitation is elucidated according to the different temperatures, and the effects of water vapor volume fraction are discussed.

ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, Volume 3, 2010

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

This paper presents the effect of outlet blade angle on cavitation in centrifugal pump. The experiment is performed on a centrifugal pump test rig consisting of backward bladed impeller at different operating conditions and characteristics of the pump are predicted. Modeling of the centrifugal pump along with the different configuration of the impeller having different exit blade angles is carried out using Creo Parametric. Numerical simulation is carried out using ANSYS CFX and standard k-
turbulence model is implemented for the analysis purpose. Cavitation is clearly predicted in the form of water vapor formation inside the centrifugal pump from the simulation results. Analytical analysis is carried out in order to find out NPSHr of the pump and Cavitation number (
c) which indicates the cavitation phenomenon in the centrifugal pump. From the results it has been found that the pump having low value of the blade exit angle will have less chances of getting affected by the cavitation phenomenon

Journal of Applied Fluid Mechanics, 2019

In this current study, the transient numerical calculations using CFD are carried out under different number of impeller blades for the flow field within a centrifugal pump under single-phase and cavitation condition. Both qualitative and quantitative analyses have been carried out on all of these results in order to better understand the flow structure within a centrifugal pump under both single-phase and cavitation. Also, the investigation using different number of impeller blades relating to the static pressure, velocity magnitude and vapour volume fraction variations have been analysed. Fluctuations pressure in both time and frequency domains at the impeller and volute of the pump also investigated. As a result, the pressure and velocity were gradually increased from inlet to outlet of the pump. Pressure at the impeller outlet was higher than the pressure at other parts due to high interaction between impeller and volute tongue region. The distribution of volume fraction first occurs at the inlet eye of impeller. Furthermore, the cavitation increases as the number of impeller blades and flow rate increase. The length of the cavity was increased when low pressure at the inlet impeller (eye) decreased at Z=5 blades cavitation was affected highly at the suction of impeller compared to other number of blades particularly at high flow rate.

Volume 1: Symposia, Parts A, B and C, 2009

Fuel spray atomization strongly affects diesel engine performance and emissions, which in turn is significantly influenced by transient cavitation behavior inside an injector nozzle. In this study, a coupled experimental and numerical study on cavitating flow inside a nozzle was carried out. Numerical simulation was performed using OpenFOAM which employs homogeneous equilibrium model (HEM) with a barotropic correlation for modeling cavitation phenomena. Cavitation in a two-dimensional nozzle was visualized using high-speed camera and liquid velocity was measured by a Laser Doppler Velocimetry (LDV). Numerical results were validated with the experimental results in terms of the comparison of cavitation and velocity distributions in the nozzle. The results attained in numerical calculations indicate that the homogeneous equilibrium model with an appropriate computational mesh and sub-models gives a good prediction for cavitation thickness and length.

The occurrence of cavitation is one of the main limiting factors in the operation and design of centrifugal pumps. In this paper a model for the prediction of sheet cavitation is described. This model has been implemented in a three-dimensional finite-element package, employing the potential-flow approximation of the governing flow equations. At the interface between vapor and liquid, pressure equilibrium is required. The closure region of the cavity is modeled as the collapse of a bubble, whose motion is described by the Rayleigh-Plesset equation. The effect of displacement of the flow due to presence of the sheet cavity is incorporated by the transpiration technique. This is a linearised approach which is well-known from techniques for coupling inviscid-flow methods to boundary-layer methods. The model gives the location of the sheet cavity (if present); its length is thus also predicted. The model has been validated by comparing sheet cavitation at the blades of a centrifugal pump impeller, obtained from CFD-computations and from visual observations in a model test.

Cavitation Effects in Centrifugal Pumps - A Review, 2016

Cavitation is one of the most challenging fluid flow abnormalities leading to detrimental effects on both the centrifugal pump flow behaviors and physical characteristics. Centrifugal pumps' most low pressure zones are the first cavitation victims, where cavitation manifests itself in form of pitting on the pump internal solid walls, accompanied by noise and vibration, all leading to the pump hydraulic performance degradation. In the present article, a general description of centrifugal pump performance and related parameters is presented. Based on the literature survey, some light were shed on fundamental cavitation features; where different aspects relating to cavitation in centrifugal pumps were briefly discussed.

2018

Machines that cater the everyday needs of mankind tend to be of inevitable and the researches that focus on improvements on such unique machinery are never ending. One among such machines is a pump that is ineludible for household, industrial, and automobile applications. Centrifugal pump is one such category. The type of impeller being used in centrifugal pump and also the contour of the casing adapted plays a hefty role in its performance. In an attempt to modify the contour of the casing and combine it with a semi-closed impeller, this research work has progressed in design and experimental analysis. A semi-closed impeller type centrifugal pump was designed with a tailor-made annular casing and the axial clearance of the pump was made the key parameter in the experimental analysis. This research work is hence an experimental analysis that would possibly conclude an optimum axial clearance that would maximize the performanceof the centrifugal pump. Performance plots were recorded ...