Effect of Blade Angle on Cavitation Phenomenon in Axial Pump

International Journal of Manufacturing, Materials, and Mechanical Engineering, 2014

This paper presents an experimental and three-dimensional numerical study of unsteady, turbulent, void growth and cavitation simulation inside the passage of the axial flow pump. In this study a 3D Navier-Stokes code was used (CFDRC, 2008) to model the two-phase flow field around a four blades axial pump. The governing equations are discretized on a structured grid using an upwind difference scheme. The numerical simulation used the standard K-e turbulence model to account for the turbulence effect. The numerical simulation of void growth and cavitation in an axial pump was studied under unsteady calculating. Pressure distribution and vapor volume fraction were completed versus time at different condition. The computational code has been validated by comparing the predicated numerical results with the experiment. The predicted of cavitation growth and distribution on the impeller blade also agreed with that visualized of high speed camera.

In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k   model to predict the parameters of hydraulic performance. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux (BVF) is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.

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

2015

For water jet systems operating in marine ships cavitation are phenomenon that often occur. The presence of vapour in the flow affects the performance of the pump and as the cavity grows the pump efficiency drastically reduces to a level where the pump cannot operate normally. Due to this influence on the pump performance it is of main interest to be able to predict the behaviour of the cavitation process. In many engineering applications, cavitation has been the subject of extensive theoretical and experimental research since it has predominantly been perceived as an undesirable phenomenon. This is mainly due to the detrimental effects of cavitation such as erosion, noise and vibrations, caused by the growth and collapse of vapour bubbles. The ability to model cavitator flows has drawn strong interest in CFD community. It covers a wide range of applications, such as pumps, hydraulic turbines, inducers and fuel cavitation in orifices as commonly encountered in fuel injection systems...

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.

IOP Conference Series: Earth and Environmental Science, 2014

A double-suction pump operating at relatively low suction head and with poorly designed suction chambers was analysed by the computational fluid dynamics (CFD). Two impeller geometries were considered -one with thicker and one with thin layer of predicted vapour cavity on blades. Steady-state simulations (SSS) were performed with shear-stresstransport (SST) turbulence model with curvature correction (CC). Transient simulations were performed with scale-adaptive-simulation SST (SAS-SST) model with CC. For both analysed geometries, transient simulations predicted higher maximal thickness of cavities than SSS. In transient simulations it was observed that, because of poor design of suction chambers, near the rib of the suction chambers two stronger (non-cavitating) vortices appeared. Near the main vortical structures, vortices with smaller intensity appeared, with direction of rotation opposite to the main vortices. Depending on their position and direction of rotation, the vortices either decreased or increased the extent of cavitation. The most important adverse effect was to increase the size of the sheet cavity by local elongation and thickening. The local effect seemed to be more pronounced for impeller with smaller thickness of sheet cavity.

Centrifugal pumps are generally used in pumping systems like water supply, sewage, and so forth. Depending on the system working conditions, centrifugal pumps can be victim to different pump failures, cavitation among others. Recent researches have been mostly oriented to the contribution of different pump parameters, be it geometrical or working parameters, to the pump performance under non-cavitating conditions. This study on the other side, intends to numerically study the contribution of the same parameters to the cavitation performance in centrifugal impellers. A numerical study was carried out with a CFD commercial code ANSYS Fluent14.5 on three impellers with different blades numbers (three, six, and nine blades) at different speeds (2120 rpm, 2560 rpm, and 3000 rpm) under cavitating conditions. The pump transient flow behaviors and related fluid mass transfer were studied, where Reynolds-Averaged Navier Stokes (RANS) equations were solved through the realizable k-Ɛ turbulence model and the Pressure Implicit with splitting of Operators (PISO) algorithm together with Schnerr and Sauer cavitation model, with water at 25 degree Celsius as the working fluid. Cavitation zones within the inter-blades flow fields constantly increased in size with both the increase in impeller blades number and rotational speed, with a thorough gradual pump head drop, leading to an almost complete inter-blades flow blockage at higher values. Low static pressure zones were merely found at each blade’s suction side and gradually got wider with both parameters increase. Both parameters showed a very big effect on pump cavitation dynamics

Transstellar Journals, 2019

A centrifugal pump's function is to transport fluid from one system to another system, within minimum time. Impeller is a key component in centrifugal pump, it intakes fluid through hub of impeller axially and distributes the fluid, radially. The configuration of the impeller blades directly effects the performance. The current paper investigates the characteristics of the pump by altering the blade profile and exit blade angles. A destructive phenomenon of cavitation is greatly influenced by blade profile. Generally, the blades of impeller will have a steep fall from hub to tip or remain in same height from hub to tip. The present project investigates the performance by employing a volute rim connecting all highest points of the blade tips. The blades also rise from tub to tip allowing the fluid to have enough space to accumulate large volumes of fluid with minimal impact on the blades to hub. Any alteration in the geometry, blade profile has a significant influence on the performance of the pump. Npsh denotes the net pressure suction head that is the amount of energy at the pump suction available to exert pressure on the fluid, if the pressure required at the pump inlet to make the liquids flow through suction side without cavitation. This can greatly reduce the cavitation effects, helping the pump to sustain to the calculated service life. Simulation is carried out using ANSYS R 15 software in FLUENT module, with ICEM meshing and SST k-Ω turbulence model.

Journal of Mechanical Science and Technology, 2019

In this study, a numerical analysis was carried out to investigate the effects of blade thickness on hydraulic performance and cavitation phenomenon of a mixed-flow pump. The three-dimensional Reynolds-averaged Navier-Stokes equation, which was discretized using the finite volume method, was applied to solve a steady-state analysis. For cavitation analysis, the Rayleigh-Plesset equation was applied to calculate the transition between liquid and vapor phases. The hydraulic performance of a mixed-flow pump changes depending on the blade thickness and was systematically analyzed under various operating conditions. Blade thickness was defined as a blockage, and the cavitation coefficient was considered to express the suction performance. Cavitation characteristics were analyzed for each blockage in relation to the vapor volume fraction. The amount and pattern of vapor were different for each blade thickness case. Furthermore, in this paper, detailed flow analyses that consider the angle of incidence are presented and discussed. To verify the numerical analysis results, an experimental test was conducted at specific points.

Journal of Fluids Engineering, 2022

The blade leading edge is a design variable that can affect the local flow patterns and pressure peaks, implying a direct effect on the cavitation performance. This study was conducted to analyze the effect of the blade leading edge shape on the cavitation and noncavitation states. A total of four sets, including the square shape, were selected under the definition of ellipse ratio, and the main focus was on the cavitation state rather than the noncavitation state. In the noncavitation state, the square set denoted a remarkable negative influence, while the other three sets obtained almost the same performance despite different ellipse ratios. In the cavitation state, the square set obtained a relatively low net positive suction head required, related to the inlet flow pattern with the cloud cavity. The other three sets contained the sheet cavity, and their suction performance tended to improve as the cavity blockage decreased. As a parallel focus, an in-depth analysis of cavitation surge and pressure gain was presented with the head drop slope for the other three ellipse sets. The numerical results included the off-design flow rate points and were validated through an experimental test.