Blade Outlet Angle Research Articles

Francis Turbine Blade Design on the Basis of Port Area and Loss Analysis

In this study, a Francis turbine with specific speed of 130 m-kW was designed on the basis of the port area and loss analysis. The meridional shape of the runner was designed focusing mainly on the combination of the guide vane loss analysis and experience. The runner blade inlet and outlet angles were designed by calculation of Euler’s head, while the port area of blade was modified by keeping constant angles of the blade at inlet and outlet. The results show that the effect of the port area of runner blade on the flow exit angle from runner passage is significant. A correct flow exit angle reduces the energy loss at the draft tube, thereby improving the efficiency of the turbine. The best efficiency of 92.6% is achieved by this method, which is also similar to the design conditions by the one dimension loss analysis.

Application of different surrogate models on the optimization of centrifugal pump

An optimization process for impellers was carried out based on numerical simulation, Latin hypercube sampling (LHS), surrogate model and Genetic algorithm (GA) to improve the efficiency of residual heat removal pump. The commercial software ANSYS CFX 14.5 was utilized to solve the Reynolds-averaged Navier-Stokes equations by using the Shear stress transport turbulence model. The impeller blade parameters, which contain the blade inlet incidence angle Δβ, blade wrap angle φ, and blade outlet angle β 2, were designed by random sample points according to the LHS method. The efficiency predicted under the design flow rate was selected as the objective function. The best combination of parameters was obtained by calculating the surrogate model with the GA. Meanwhile, the prediction accuracies of three surrogate models, namely, Response surface model (RSM), Kriging model, and Radial basis neural network (RBNN), were compared. Results showed that the calculated findings agree with the experimental performance results of the original pump. The RSF model predicted the highest efficiency, while the RBNN had the highest prediction accuracy. Compared with the simulated efficiency of the original pump, the optimization increased efficiency by 8.34% under the design point. Finally, the internal flow fields were analyzed to understand the mechanism of efficiency improvement. The optimization process, including the comparison of the surrogate models, can provide reference for the optimization design of other pumps.

Investigation of Pump Impeller Performance using CFD

Objectives: Impeller is the rotating component of a centrifugal pump which imparts kinetic energy on the working fluid. The present work is concentrated on the optimization of geometry of the impeller to increase the efficiency of centrifugal pump. Methods/Statistical Analysis: The L9 orthogonal array table is formed by taking the parameters such as impeller width, number of blades and inlet diameter and outlet blade angle as control factors and efficiency as response. The impeller is modelled using the software Pro_E and the analysed using CFD software Fluent 6.3 by assuming the steady, incompressible and viscous flow condition for the working fluid. Findings: The optimization technique is carried out based on taguchi concept with the aid of CFD software. From the contribution ratio values it is found that the parameter Number of Blades contributes a significant portion in affecting the pump efficiency. Based on the values of pressure, discharge and torque obtained from the software, the corresponding values of efficiencies are calculated. Application/Improvement: Using larger the better quality characteristics, the geometry of the impeller is optimized for maximum efficiencyKeywords: CFD and Optimization, Efficiency, Impeller, Vane

Numerical Investigation of Cavitation Improvement for a Francis Turbine

Cavitation in hydraulic machine is undesired due to its negative effects on performances. To improve cavitation performance of a Francis turbine without the change of the best efficiency point, a model runner geometry optimization was carried out. Firstly, the runner outlet diameter was appropriately increased to reduce the flow velocity at runner outlet region. Then, to avoid the change of the flow rate at the best efficiency point, the blade shapes were carefully adjusted by decreasing the blade outlet angles and increasing the blade wrap angles. A large number of the modified runners were tested by computational fluid dynamic (CFD) method. Finally the most appropriate one was selected, which has the runner outlet diameter 10% larger, the blade outlet angles 3 degrees smaller and the blade wrap angles 5 degrees larger. The results showed that the critical cavitation coefficient of the model runner decreased at every unit rotational speed after the optimization, and the effect was much remarkable at relative high flow rate. Besides, by analysing the internal flow field, it was found that the zone of the low pressure on pressure surface of the optimized turbine blades was reduced, the backflow and vortex rope in draft tube were reduced, and the cavitation zone was reduced obviously.

CFD Simulation of the Air Flow Field in the Multi Blade Centrifugal Fan

In this paper, the multi blade centrifugal fan parameter CAD/CFD was developed. Before treatment with the traditional design method as the foundation, use AutoCAD as development of the embedded language. The work of this regulation to establish a set of more perfect design and optimization program of axial flow fan in air, improve its economy, and provided a shortcut for energy saving and noise reduction of multi blade centrifugal machine. Also in the establishment and the simplification of complex models, mesh generation, calculation and other aspects of the use of the model to do some beneficial exploration, hoping to provide reference of the similar simulation numerical type. Influence on the performance of multi blade centrifugal fan impeller is the largest parameters such as the blade outlet angle, inlet angle and blade number. As the numerical simulation application in modern design method, in order to improve the performance of pressure air fan as the optimization objective, the optimization of the fan, the fan impeller optimization parameters more reasonable flow field distribution, air pressure with better performance is obtained, and the formula to determine the recommended number of leaves.

Multi-objective hydraulic optimization and analysis in a minipump

Minipump is widely used in microfluidics system, active cooling system, etc. But building a high efficiency minipump is still a challenging problem. In this paper, a systematic method was developed to design, characterize and optimize a particular mechanical minipump. The optimization work was conducted to cope with the conflict between pressure head and hydraulic efficiency by an improved back-propagation neural network (BPNN) with the non-dominated sorting genetic algorithm-II (NSGA-II). The improved BPNN was utilized to predicate hydraulic performance and, moreover, was modified to improve the prediction accuracy. The NSGA-II was processed for minipump multi-objective optimization which is dominated by four impeller dimensions. During hydraulic optimization, the processing feasibility was also taken into consideration. Experiments were conducted to validate the above optimization methods. It was proved that the optimized minipump was improved by about 24% in pressure head and 4.75% in hydraulic efficiency compared to the original designed prototype. Meanwhile, the sensitivity test was used to analyze the influence of the four impeller dimensions. It was found that the blade outlet angle β2 and the impeller inlet diameter D0 significantly influence the pressure head H and the hydraulic efficiency η, respectively. Detailed internal flow fields showed that the optimum model can relieve the impeller wake and improve both the pressure distribution and flow orientation.

Theoretical research of hydraulic turbine performance based on slip factor within centripetal impeller

The impeller of hydraulic turbine is a kind of centripetal impeller. The slip phenomenon within centripetal impeller is different with centrifugal impeller. In this study, the velocity distribution and the flow form of fluid within centripetal impeller are analyzed, the slip factor within centripetal impeller is calculated, and the basic energy equation of hydraulic turbine is deduced when the slip within centripetal impeller is considered. The results of theoretical calculation, the results of experiment, and the results of computational fluid dynamics calculation are compared. The formula of slip factor within centripetal impeller is obtained, and the relative error between the results of theoretical calculation using the formula and experimental data is less than 5%. The effect factors of slip factor have entrance diameter of centripetal impeller, blade numbers, entrance and outlet blade angles, rotating speed of centripetal impeller, and flow rate.

Numerical and Experimental Study on the Tonal Noise Generation of a Radial Fan

The main focus of this work is on the geometrical modifications can be made to the fan wheel and to the volute tongue of a radial fan to reduce the tonal noise. The experimental measurements are performed by using the in-duct method in accordance with ISO 5136. In addition to the experimental measurements, CFD (computational fluid dynamics) and CAA (computational aeroacoustics) simulations are carried out to investigate the effects of different modifications on noise and performance of the fan. It is shown that by modifying the blade outlet angle, the tonal noise of the fan can be reduced without impairing its aerodynamic performance. Moreover, it is indicated that increasing the number of blades leads to a significant reduction in the tonal noise and also an improvement in the aerodynamic performance. However, this trend is only valid up to a certain number of blades, and a further increment might reduce the aerodynamic performance of the fan. Besides modifying the impeller geometry, new volute tongues are designed and tested on the rig. It is demonstrated that the shape of the volute tongue plays an important role in the tonal noise generation of the fan. Moreover, in order to find out whether or not it is possible to reduce the tonal noise level through a destructive phase-shift generation, stepped tongues are comprehensively investigated by means of numerical simulations and experimental measurements.

Improving slip factor prediction for centrifugal pumps using artificial neural networks

Slip factor is an important parameter in the performance prediction of centrifugal pumps. This paper presents a new approach improving slip factor estimation of centrifugal pumps. In order to understand the effects of geometrical parameters of impeller (i.e. blade number, blade outlet angle, radius ratio, and blade turning rate) on slip factor, a set of computational fluid dynamics based analyses were carried out for over 70 different impellers by means of a commercial code, CFX. The numerical model was validated with the available experimental data. Subsequently, a multilayer feed-forward neural network, as a popular neural network based fitting tool, was used to generate a mapping between blade geometrical parameters as input variables and slip factor as output variable. The ANN (i.e. artificial neural network) model generalization capability was assessed by comparing the network predictions with those calculated from the test data. The comparative assessment of different slip models showed that the neural network model has succeeded in improving the accuracy of previous slip factor models for centrifugal pumps.

Design, Numerical Analysis and Manufacture of Radial Pump Impellers with Various Blade Geometries

Impeller blade geometry plays a dominant role on the velocity profile of the fluid flowing through the pump. Although blades’ design is based on fluid dynamics considerations, it is sometimes limited by the available manufacturing methods, due to the required complexity in the geometry. In the present paper, the evolution of the velocity field in the blade passages of two anew designed radial pump impellers with different curvature and outlet blade angle is examined in order to verify their optimum design and characteristics. The numerical solution of the discrete three-dimensional, incompressible Navier-Stokes equations over a structured grid is accomplished with a commercial CFD finite-volume code. For each impeller, pressure and relative velocity distributions are presented and analyzed. The flow patterns in the blade passages are monitored and the mechanisms that dominate the flow field in the different regions of the impeller geometry are discussed. Furthermore, the new impellers that were tested numerically are manufactured in a CNC Milling Centre under the operation of sculptured surfaces; thus the feasibility of manufacturing the improved geometries is exhibited.

Component Analysis of Unsteady Hydrodynamic Force of Closed-Type Centrifugal Pump with Single Blades of Different Blade Outlet Angles

Single-blade centrifugal impellers for sewage systems undergo both unsteady radial and axial thrusts. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces and determine the generation mechanism behind them. In this study, we conducted component analyses of radial and axial thrusts of closed, single-blade centrifugal pumps with different blade outlet angles by numerical analysis while considering leakage flow. The results revealed the effect of the blade outlet angle on the components of radial and axial thrusts. For increased flow rates, the time-averaged values of the pressure component were similar for all impellers, although its fluctuating components were higher for impellers with larger blade outlet angles. Moreover, the fluctuating inertia component of the impeller with a blade outlet angle of 8° decreased as the flow rate increased, whereas those with 16° and 24° angles increased. Therefore, the radial thrust on the hydraulic part was significantly higher for impellers with high blade outlet angles.

Two-point Hydraulic Optimization of Pump Impeller Based on Kriging Model and Neighborhood Cultivation Genetic Algorithm

To enlarge the high efficiency area of the residual heat removal pump(RHRP), an optimization process is proposed based on Kriging model and neighborhood cultivation genetic algorithm(NCGA). 16 design cases containing three main parameters, which are incidence angle ?β, are angle φ and outlet blade angle β_2, are designed by using the Latin hypercube sampling(LHS) methods. The efficiencies are calculated by steady numerical simulation. The efficiencies under the design point 1.0Q_d and 1.62 Q_d are selected as the objective functions. Approximation models between the efficiencies and the parameters are built by Kriging model. The neighborhood cultivation genetic algorithm is applied to optimize the approximation models to obtain the best combination of parameters. The results show that the predicted performance has a good agreement with that of the experiment of the original pump. The efficiencies of the optimal pump are 5.53% and 2.29% higher than those of the original one under 1.0Q_d and 1.62 Q_d, respectively. Meanwhile, the relative velocity distributions are more uniform in the optimal impeller. The optimization method can provide an effective reference to the improvement of pump's performance.

G0501002 多翼前向き羽を持つ羽根車流れに発生する流体振動

The experimental and numerical studies were performed to clarify the fundamental flow characteristics of a fan with forward-inclined multi-blades. A Sirocco fan and crossflow fan are rotated in the open space, i.e. without casing. The crossflow fan simulates a Sirocco fan with a closed inlet. Using fan's height is 115mm, the inlet and outlet radii are 160 and 180 mm, respectively. The inlet and outlet blade angles are 90 and 150 degrees, respectively. The impller includes 52 blades. The rotational frequency is set to 24 Hz. The radial velocity fluctuations at the impeller outlet are measured using a hot-wire anemometry. The experimental and numerical results show good agreements with respect to frequencies and cell numbers. The FFT spectra of the experimental and numerical results show two peaks in the Sirocco fan and one peak in the crossflow fan. The two- and three-cell oscillations occur for the Sirocco fan, and the one-cell for the crossflow fan.

A model for precessing helical vortex in the turbine discharge cone

The decelerated swirling flow in the discharge cone of hydraulic turbine develops various self-induced instabilities and associated low frequency phenomena when the turbine is operated far from the best efficiency regime. In particular, the precessing helical vortex ("vortex rope") developed at part-load regimes is notoriously difficult and expensive to be computed using full three-dimensional turbulent unsteady flow models. On the other hand, modern design and optimization techniques require robust, tractable and accurate a-priori assessment of the turbine flow unsteadiness level within a wide operating range before actually knowing the runner geometry details. This paper presents the development and validation of a quasi-analytical model of the vortex rope in the discharge cone. The first stage is the computing of the axisymmetrical swirling flow at runner outlet with input information related only to the operating point and to the blade outlet angle. Then, the swirling flow profile further downstream is computed in successive cross-sections through the discharge cone. The second stage is the reconstruction of the precessing vortex core parameters in successive cross-sections of the discharge cone. The final stage lies in assembling 3D unsteady flow field in the discharge cone. The end result is validated against both experimental and numerical data.

Numerical Research about Influence of Blade Outlet Angle on Flow-Induced Noise and Vibration for Centrifugal Pump

A hybrid numerical method was used to calculate the flow-induced noise and vibration of the centrifugal pump in the paper. The unsteady flows inside the centrifugal pumps with different blade outlet angles were simulated firstly. The unsteady pressure on the inner surface of the volute and the unsteady force applied on the impeller were analyzed. Then the vibration of the volute and sound field were calculated based on an acoustic-vibro-coupling method. The results show that the pump head has increased 7% while the hydraulic efficiency decreased 11.75% as blade outlet angles increased from 18° to 39°. The amplitude of pressure fluctuation at the first blade passing frequency has decreased but increased at the second-order blade passing frequency as the angle growing. The total fluctuation power near volute tongue goes up about 12% every 3° increment of blade outlet angle. The results also show that vibrating-velocity of the volute at second-order blade passing frequency is much higher than at other frequencies, and the velocity increases rapidly as blade outlet angle varies from 18° to 39°. At the same time, the sound pressure level outside the pump has increased about 8.6 dB when the angle increased from 18° to 39°.

Effect of Blade Outlet Angle on Unsteady Hydrodynamic Force of Closed-Type Centrifugal Pump with Single Blade

Geometrically, the single-blade centrifugal impeller, commonly used today as a sewage pump, is not axially symmetric. For this reason, the static pressure around the impeller fluctuates greatly when the impeller is rotating, and not only the radial thrust but also the axial thrust shows large fluctuations. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces. In this study, we investigated the unsteady hydrodynamic forces in a closed-type centrifugal pump with a single blade for different blade outlet angles using a numerical analysis that takes into account both experiment and the leakage flow. The results clearly showed the effect of the blade outlet angle on that act on the impeller. The root-mean-square value of the fluctuating component of the total radial thrust was roughly the same for whichever impeller at low flow rate, but at high flow rates, the value increased for impellers with larger blade outlet angles. Moreover, when the leakage flow rate increased with increasing static pressure around the impeller, such that the rear and front shroud parts were subject to high pressure, the absolute value of the axial thrust on both these parts increased.

20604 超小型遠心圧縮機内部流れの数値解析 : 羽根車出口翼角度の影響

For an ultra micro centrifugal compressor, the applicability of two-dimensional (2D) blade has been investigated with the consideration of productivity in the downsizing of impeller. On the other hand, the improvement of the pressure recovery ratio in the diffuser is also required to increase the overall pressure ratio of a centrifugal compressor system. In this study, the flows in three types of centrifugal compressor impeller with the 2D blade which are different in the impeller outlet blade angle were analyzed numerically because the outlet blade angle is the most important design parameter to specify the shape of such impeller. The computed results clarified that the increase of impeller outlet blade angle reduces the tip leakage flow and the reversed flow at the impeller outlet, but increases the wall friction loss due to the increase of the cascade passage length.

Research of factors influencing centrifugal pump external characteristics based on orthogonal test

In order to investigate the impact on external characteristics of single-stage and single-suction centrifugal pump, four parameters: cutwater gap(δ), blade number(z), impeller outlet width(b) and blade outlet angle(β) were taken into account. Orthogonal test method is a method which can make a comprehensive comparison among factors we are interested in. Thereby, it can't be more appropriate to adopt this approach to study the influence of the four factors referred above. Based on the prototype pump's geometric parameters, each of these factors took four levels. According to the principle of selecting orthogonal array, the L16(45) array was selected and 16 models were designed. After that, commercial CFD software CFX was used to calculate the head and efficiency under different conditions to determine the optimal operating condition Qr. The 16 models' rated flow rates were basically smaller than the prototype's. Considering this difference, in order to analyze the influence on the head under similar condition, the flow rate was made dimensionless and 3 conditions are chosen(Qr/Q=1, 1.25 and 1.375). Through the analysis of averaged respond head and efficiency, the laws of head and efficiency changing with the variation of the factors were obtained. Commonly, if a dependent's change cause by a independent variable is smaller than 5%, we can neglect the independent variable's effect. Thus the paper presents a research showing the factors' changing limitations considering the head changing by a percentage smaller than 5%. The conclusion of this article has important reference value for design of centrifugal pumps.

Performance analysis of mini centrifugal pump with splitter blades

Design method for a mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Then, a semi-open impeller for the mini centrifugal pump with 55mm impeller diameter is adopted in this research to take simplicity and maintenance into consideration. Splitter blades are adopted in this research to improve the performance and internal flow condition of mini centrifugal pump having large blade outlet angle. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on the performance and internal flow condition of the mini centrifugal pump. A three dimensional steady numerical flow analysis is conducted to analyze rotor, volute efficiency and loss caused by a vortex. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Flow condition at outlet of the rotor becomes uniform and back flow regions are suppressed in the case with the splitter blades. Further, the volute efficiency increases and the vortex loss decreases. In the present paper, the performance of the mini centrifugal pump is shown and the flow condition is clarified with the results of the experiment and the numerical flow analysis. Furthermore, the performance analyses of the mini centrifugal pumps with and without the splitter blades are conducted.

Numerical Optimization of Impeller for Backward-Curved Centrifugal Fan by Response Surface Methodology (RSM)

A numerical optimum study on three-dimensional unsteady viscous flow in a centrifugal fan with backward-curved blades was performed. The influence of the inlet angle, the outlet blade angle and blade number on aerodynamic performance of the centrifugal fan was analyzed concerning the whole impeller-volute configuration. Response Surface Methodology (RSM) based on a three-level, three -variable Box-Behnken Design (BBD) was used to evaluate the interactive effects of factors such as inlet blade angle (37°-41°), outlet blade angle (61°-65°) and number of blade (10-14) on the efficiency. The optimum factors deriving via RSM were: inlet blade angle 37°, outlet blade angle 61.7° and blade number 14. The maximum efficiency was 93.7%, under optimum conditions. The method of reliable CFD technique in combination with RSM can be effectively applied to the improvement and experiment design of centrifugal fans.