Effect of Blade Angle on Cavitation Phenomenon in Axial Pump

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.

Journal of Marine Science and Engineering, 2022

Disc pumps with radial straight blade are unconventional designs that have been developed for hard-to-pump mixtures for many industrial applications. They are frequently used in chemical industries, sub-sea petroleum pumping systems with multi-phase media and so on. Due to the radial straight blade arrangement, they may suffer from cavitation onsets when being used under different pressure conditions. To study the influence of cavitation characteristic inside the present disc pump flow passages, experimental data analysis on a radial blade disc pump for a wide flow rate range (0 to 110 m 3 /h) is obtained. In addition, the Reynolds averaged (RANS) approach using the RNG k-ε turbulence model, is carried out under different working conditions with and without cavitation modelling. Two different pump meshing models are also implemented: the first one without hub and shroud side channels between the discs and the volute casing, the second one with both side channels corresponding to the complete real case geometry. The comparisons between experimental and numerical results reveal first that the complete geometry meshing must be used to recover the experimental performance curve especially at low flow rates whatever the rotational speed. Secondly, the cavitation effect is found to take place in precise locations (straight blade and connection column) inside the impeller at high rotational speed and high flow rates. Their effects correspond to the unexpected performance curve deterioration found for the highest rotational speed and high flow rates. Moreover, with the decrease of the inlet absolute pressure, the cavitation degree becomes serious, and the coupling phenomenon of straight blade cavitation and connection column cavitation is formed, which enlarges the scope and enhances the degree of cavitation. The present study proposes a data reduction procedure when open loop experimental testing procedure is used for specific disc pump design and the importance of the impeller-side channels interactions on head pump decrease at low flow coefficients.

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.

The KSFM Journal of Fluid Machinery, 2015

The pumped storage plant operates with quick change of the discharge as well as quick changes between pump mode and turbine mode. This study focuses on the cavitation analysis of a pump-turbine model because in turbo-machinery, cavitation can reduce the performance and shorten service life. The pump-turbine model system consists of 7 blades, 20 stay vanes (including tongue) and 20 guide vanes. This study adopts the Rayleigh-Plesset model as a cavitation model, which illustrates cavitation by using the air volume fraction method. The pump mode and turbine mode at the operating condition of partial loading, normal and excessive loading are analyzed to investigate the cavitation performance of the pump-turbine. It was observed that this pump-turbine design showed very good cavitation characteristics with no cavitation bubbles in all operating conditions. Overall value of air volume fraction of both mode at different operating condition are lower than 1, which confirms low possibility of cavitation occurrence at current situation.

2019

Centrifugal Pumps are the most common appliances used in various industries, agriculture and domestic application& thus its impeller design thus required a very precise understanding of the internal flow at rated and part load operating conditions. Design and development of turbo machines like centrifugal pump is highly complex due to turbulence flow structure, unsteadiness and cavitation inside the pump. The pump suffers with loss of efficiency, erosion of material, degradation of its useful life caused by cavitation. The Phenomenon of cavitation can be described as the vapor bubbles formation in an originally liquid flow, this change of phase is carried through at constant temperature and local drop pressure, generated by flow conditions. Turbo machines like centrifugal pumps suffer with loss of performance, degradation of its useful life caused by the cavitation. Under the analytical point of view the cavitation phenomenon shows very complex, bringing great physical and numerical...

International Journal of Advance Engineering and Research Development, 2014

New computational methods are continuously developed in order to solve problems in different engineering fiel ds. One of these fields is centrifugal pump, where the challenge is to make centrifugal pump more efficient and to reduce cavitation in the pump. One of the main parts of a centrifugal pump that can be improved is the impeller. In order to optimiz e the centrifugal pump, both experimental and numerical methods are called for. An important topic is here to perform grid sensitivity studies to make sure that the model yields mesh independent results. Another topic of interest is the choice of turbulence model and how this choice affects the grid sensitivity. After this project we made a model that is numerically reliable, mesh independent and fast. This thesis presents a computational study of the flow field generated in centrifugal pump and how that flow field convicts through the impeller. Specifically, the effect that the flow fied acting on the impeller was studied. Data from a modern centrifugal pump manufacturer was used to design a realistic, low speed, large scale efficiency test section. This paper presents the results of computational simulations done in parallel with experimental simulations of the impeller flow field. In comparisons of computational predictions with experimental data, reasonable agreement of the mean flow and generates cavitation in the centrifugal pump. After finding the cavitation area by numerical method, changing the angle of the blade or changing the number of blade the direction of the inlet and outlet flow has been changed.