Low Specific Speed Centrifugal Pump Research Articles

A Study on the Effects of Blade Thickness on the Performance of Low Specific Speed Centrifugal Pump

The effects of blade thickness on impeller performance is seldom considered when design the low specific speed centrifugal pump and only considered crowding coefficient when use the speed coefficient method calculate the head of the impeller was designed. It was didn't consider the fundamental relationship how leaf thickness and low specific speed centrifugal impeller performance effect each other. The three-dimensional of flow area would have large influence if the leaf thickness changes . Here the best true thickness of the low specific speed centrifugal impeller blade was obtained though study how the thickness of blade influence on the performance of low specific speed centrifugal pump.

Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Performance Comparison of Four Geometric Models

For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, there exist several problems including how to design geometrical shape of the calculation model to represent the real pump and how to predict pump performance accurately to guide the design of pump. To solve these problems, four kinds of geometric models were designed. The performance of a low specific speed solid-liquid centrifugal pump was predicted, and the results showed that the improved prediction methods are more accurate than the traditional method. Moreover, the simulation results of the entire flow field of the geometric model including balance holes and the lateral clearances of impeller in which liquid rotates with half speed of impeller are closer to the real situation.

Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

Optimization Research on Low Specific Speed Centrifugal Impeller Based on Incomplete Sensitivities Method

According to the limitation of the traditional optimization design method for centrifugal impeller, the optimization method for low specific speed centrifugal pump impeller based on incomplete sensitivities is proposed. In this method, the affection of the control parameters perturbation on the flow state variation can be neglected while calculating the gradient of the design objective function with the control variable of the impeller passages shape. So the flow filed only need to be simulated once in one optimization cycle, it avoids the calculation of the flow field repeatedly in finite difference method. It also avoids deducing and solving the adjoint equation in adjoint method. Therefore, the calculation cost is greatly reduced. The calculation case is the low specific speed centrifugal impellers; the two dimensional blade is parameterized by Taylor expansion. The coefficients in the Taylor function are taken as the control variable. The moment acting on the blade are considered as the objective function. Using the incomplete sensitivities method the gradient of the objective function with respect to the control variable can be evaluated easily, and the blade shape can be renewed according to the inverse direction of the gradient vectors. The optimum design of impeller can be achieved while the objective function is minimized. The calculation case results show that the proposed incomplete sensitivities theory for the optimization of low specific speed centrifugal impeller is rational.

Hydraulic performance of a low specific speed centrifugal pump with Spanwise-Slotted Blades

The hydraulic efficiency of a low specific speed centrifugal pump is low because of the long and narrow meridian flow passage, and the severe disk friction. Spanwise slotted blade flow control technology has been applied to the low specific speed centrifugal pump. This paper concluded that spanwise slotted blades can improve the pump performance in both experiments and simulations. In order to study the influence to the impeller and volute by spanwise slotted blade, impeller efficiency and volute efficiency were defined. The minimum volute efficiency and the maximum pump efficiency appear at the same time in the design flow condition in the unsteady simulation. The mechanism of spanwise slotted blade flow control technology should be researched furthermore.

Applied Micro Genetic Algorithm to Optimize Design Low Specific Speed Pump Impeller

The combination of enlarged flow design and micro-genetic algorithm constitute a new optimization design method, which be applied to optimization design of low specific speed pump impeller. It improves enlarged flow design deficiencies, and making overall performance of the pump better. The experimental results of a low specific speed centrifugal pump impeller designed by proposed method show that pump high efficiency range is extended, the hump phenomenon is eliminated, and shaft power overload phenomenon has been resolved.

Analysis of inner flow in low specific speed centrifugal pump based on LES

To investigate unsteady flow in the low specific speed centrifugal pump, a three-dimensional model of a pump that n s is equal to 50 is modeled with the software Pro/E. With standard k-ɛ, SST k-ω and RNG k-ɛ turbulence model, the testing performance of pump is compared with the simulated results. Based on the result of steady flow, the unsteady flow of RNG k-ɛ turbulence model and large eddy simulation (LES) are calculated at both design and off-design conditions. The time domain of pressure fluctuation value of indicator points, which are located interfaces between volute and impeller, has been investigated numerically. The unsteady flow characteristic of pump with RNG k-ɛ turbulence model is compared with LES. The distribution of vortex in the volute is discovered. The results show that in steady flow, an error of 2.6% of RNG k-ɛ is the lowest, SST k-ω of 3.65% is second and the worst is standard k-ɛ of 4.78% at design condition. The calculated precision using RNG k-ɛ model is highest in steady condition. Because of the interaction of relative movement between volute and impeller, the pressure fluctuation can clearly be observed. The flow separation of the blade pressure surface and the stall channels in off-designed condition is the reason that the efficiency of pump operating under off-design condition is low. The vortex intensity is obviously different in the eight sections of the volute and is gradually increasing from first section to eighth section. Large eddy simulation can discover the unsteady flow of the centrifugal pump effectively.

Investigation on Flow-Induced Noise due to Backflow in Low Specific Speed Centrifugal Pumps

Flow-induced noise causes disturbances during the operation of centrifugal pumps and also affects their performance. The pumps often work at off-design conditions, mainly at part-load conditions, because of frequent changes in the pump device system. Consequently numerous unstable phenomena occur. In low specific speed centrifugal pumps the main disturbance is the inlet backflow, which is considered as one of the most important factors of flow-induced noise and vibration. In this study, a test rig of the flow-induced noise and vibration of the centrifugal pump was built to collect signals under various operating conditions. The three-dimensional unsteady flow of centrifugal pumps was calculated based on the Reynolds-averaged equations that resemble the shear stress transport (SST) k-ω turbulence model. The results show that the blade passing frequency and shaft frequency are dominant in the spectrum of flow-induced noise, whereas the shaft component, amplitude value at shaft frequency, and peak frequencies around the shaft increase with decreasing flow. Through flow field analysis, the inlet backflow of the impeller occurs under 0.7 times the design flow. The pressure pulsation spectrum with backflow conditions validates the flow-induced noise findings. The velocity characteristics of the backflow zone at the inlet pipe were analyzed, and the dynamic characteristics of the backflow eddy during one impeller rotating period were simultaneously obtained by employing the backflow conditions. A flow visualization experiment was performed to confirm the numerical calculations.

Flow in a Low Specific Speed Centrifugal Pump Using PIV

The interflow plays important roles in centrifugal pump design. In order to study the effect of rotation and z-axis on internal flow, two-dimensional particle image velocimetry (PIV) measurements have been performed to measure the steady velocity field on three planes in all impeller passages of a low specific-speed centrifugal pump. The results show that the relative velocity flows in blade passages are obviously different in terms of the positions of the blade relative to the tongue. The interaction between the impeller and tongue changes the occurrence and development of low velocity region with time. From shroud to hub, the relative velocity gradually increases, and the minimum value moves toward the suction surface. On the midplane, the magnitude increases with increased flow rate from pressure surface to suction surface, while at the shroud and hub, the measured velocity first increases with decreased flow rate from the blade pressure surface to nearly ζ = 0.5 to 0.6.

Hydraulic design and performance analysis of low specific speed centrifugal pump

Since low specific speed centrifugal pump with long narrow flow divergent channels has positive slope of head-capacity characteristic curve, low flow rate instability and high flow rate power overload, special events about its hydraulic design are still under study. This paper demonstrates a method for hydraulic design of low specific speed centrifugal pump complex impeller (with splitter blades) which is based on 2D flow theory. In this method, obtain the basic geometry parameters by empirical correlation, adjust impeller profile according to given flow cross section area distribution and wrapping angles distribution, relate the position of splitter blades to slip factor. Based on this method, low specific speed centrifugal pump impellers have been designed using the same design parameters (Head, Capacity, Rotation Speed, etc) with different factors. And 3D turbulent flow fields in design pumps have been solved by using RANS equations with RNG k-epsilon turbulence model. The investigation to the effects of different splitter blades on velocity distributions and pressure distributions along the flow channels and hydraulic performance of centrifugal pumps are presented. The result shows that properly placed splitter blades by choosing suitable design factors will improve the flow in the pump and enhance the hydraulic performance of it.

Applicability of eddy viscosity turbulence models in low specific speed centrifugal pump

The accuracy of numerical simulation determines the performance prediction whether to be successful or not in the research of centrifugal pump. In order to study the applicability of different turbulence models in the low specific speed centrifugal pump, the object was based on XST45-200 stamping and welding centrifugal pump. Five different kinds of standards which are k-ϵ model, RNG k-ϵ model, Realizable k-ϵ model, Standard k-ω model and SST k-ω model are adopted in steady numerical simulations of the centrifugal pump flow fields. Then, inner and outside characteristics of the centrifugal pump were gotten .And it also provides the calculation of pressure distribution using different turbulence models in the five conditions. Lastly, the performance curves of head, power and efficiency are compared with the test. The results show a good agreement between five kinds of turbulence models and tests obtained in small flow and design condition. In large flow, the standard k-ε model is worse than the other four, which is larger than the tested head with a relative deviation of 47.9% and efficiency with 50%.The calculation accuracy which used RNG k-ϵ model is highest. SST k-ω model takes the second place. Standard k-ω model can be used for the numerical simulation in the low specific speed centrifugal pump.

The analysis of unsteady characteristics in the low specific speed centrifugal pump with drainage gaps

The gap drainage impeller is a new structure of impeller which is based on the idea of flow control, and it has been validated in experiments that this structure can increase the pump efficiency. The purpose of this paper is to explore a valid numerical analysis method for the simulation of low specific speed centrifugal pump, and then investigate the unsteady characteristics of the gap drainage impeller pump. The internal flow numerical simulations were done at multi-flow rates, and the calculated results were analyzed based on comparison with the experimental data of hydraulic performance, pressure pulsation and vibration acceleration. It was confirmed that: the results from the simulation tend to agree well with the experiments; the unsteady method is generally superior to the steady method in computing robustness and prediction accuracy at partial flow rates; the wall friction and clearance leakage should be considered in the performance prediction of the low specific centrifugal pump; the frequency spectra of pressure fluctuation is mainly controlled by the rotor-stator interaction, and the overall energy of pressure fluctuation and vibration is increased in part-load working conditions, especially at large flow rates; the pressure pulsation and the impeller radial fluid force are uneven in circumference, and they propagate in the opposite direction of the shaft rotating; however, the calculation error is considerable when comparing with experiments, and the reasons for which should be researched furthermore.

The optimization of low specific speed centrifugal pump based on incomplete sensitivities

In this research, the optimization method for low specific speed centrifugal pump impeller based on incomplete sensitivities was proposed. The main feature of the algorithm is that it avoids solving the flow field repeatedly in one optimization cycle in finite difference method and it avoids solving the adjoint equation in adjoint method. The blade meridional plan is considered as constant, and the blade camber line was parameterize by Taylor function. The coefficients in the Taylor function were taken as the control variable. The moment acting on the blade was considered as the objective function. With the incomplete sensitivities we can get the gradient of the objective function with respect to the control variable easily, and the blade shape can be renewed according to the inverse direction of the gradient. We will find the optimum design when the objective function is minimized. The computational cost is greatly reduced. The calculation cases show that the proposed theory and method is rotational.

Cavitating suppression of low specific speed centrifugal pump with gap drainage blades

This paper aims to clarify the cavitation suppression mechanism of the gap structure impeller based on the analysis of cavitation characteristics in a low specific speed centrifugal pump. In order to obtain reliable and consistent numerical results, some numerical considerations and modeling methodology were demonstrated and researched, and a check of the time and space resolution were also conducted. Hence the predicted cavitation performance of the two centrifugal pumps were investigated and compared with experimental results, and they were in qualitative agreement. It was confirmed that the new gap structure impeller has a very good characteristic of inhibiting cavitation, especially in large flow area, the present numerical method can effectively capture the major internal flow features in the centrifugal pump, through the comparison of the two type impeller flow fields, the cavitation suppression mechanism of the gap impeller may be the combination effects of the small vice blade's guiding flow and gap tunnel's auto-balancing of pressure.

Experimental studies on the optimization design of a low specific speed centrifugal pump

Start your abstract here... For a low specific speed centrifugal pump with the requirement of high efficiency of 68% and non-overload power characteristics, series experimental studies, by matching 9 volutes with 19 impellers were done. By combining the former research results about the splitters and the non-overload theory in centrifugal pump, the theoretical conditions to achieve the property of non-overload in a centrifugal pump with splitters was analyzed, and formulas to estimate the maximum shaft power and its position are derived. Based on the requirement of high efficiency and non-overload, blade outlet angle β 2, blade outlet width b 2, volute throat area Ft and the inlet diameter of splitters Di were chosen with three levels to design a normal L9 (34) orthogonal test scheme. Meanwhile, the optimized design scheme was determined, and corresponding test was done also, it demonstrates that the experiment purpose was reached, the design method to combine the splitters and non-overload theory is reasonable, which can get the property of high efficiency and non-overload.

Numerical Simulation of Low Specific Speed American Petroleum Institute Pumps in Part-Load Operation and Comparison With Test Rig Results

A low specific speed centrifugal pump is investigated by means of numerical simulation, especially in deep part-load operation. The 3D computational fluid dynamics (CFD) model includes the front and back cavities, a 360 deg impeller and a double volute, as well as suction and pressure pipes. Stationary calculations show a strong clocking effect and lead to an overprediction of the head close to zero flow rate. A one-dimensional estimation of the head at the closed valve operation point is compared to the 3D CFD results and also a series of test rig results. In a second step, the whole head curve is calculated by a fully transient calculation using the shear stress transport–scale-adaptive simulation (SST–SAS) turbulence model. For the net positive suction head (NPSH) estimation, the histogram method is applied providing good correlation to the test rig measurement—as do the head curve and the efficiency.

Transient Hydraulic Performance and Numerical Simulation of a Centrifugal Pump with an Open Impeller during Shutting Down

In this paper, the transient behavior of a low specific speed centrifugal pump with straight blades during shutting down is studied through the experimental test, theoretical calculation, and numerical simulation. The variations of the rota- tional speed, flow rate, and head with time are obtained in experiment. Based on the experimental results of the rota- tional speed and flow rate, the additional theoretical heads are quantitatively calculated and analyzed. The experimental results of the rotational speed and flow rate are worked as the boundary conditions to accurately accomplish the nu- merical simulation of the transient flow during shutting down. The experimental results show that the decrease history of the flow rate evidently lags behind that of the rotational speed, while the rotational speed slightly lags behind the head. Theoretical analysis shows that there exists a clear negative head impact phenomenon in the process of stopping. The transient behavior of the centrifugal pump with straight blades mainly comes from the rotation deceleration of im- peller, and has nothing to do with the fluid deceleration. The numerical simulations show that a large area backflow can be seen when the rotational speed decreases to zero due to the flowing inertia. In conclusion, the numerical simulation of the flow field is in good agreement with the internal flow theory of centrifugal pumps.

Design and Analysis on Hydraulic Model of The Ultra -low Specific-speed Centrifugal Pump

The Super-low specific-speed centrifugal pump has been used widely in most industrial fields of petroleum, chemical industry, aviation, pharmaceutical industry, metallurgy, etc. With the development of the petrochemical industry and the space technology, the lower ultra high speed centrifugal pump is gradually developed, its speed is much higher and the flow rate is much lower than the low-specific speed centrifugal pump [1,2]. Based on the foundation of the former researcher, I have designed and developed GSB20-380 hydraulic model of the ultra-low specific-speed centrifugal pump. In order to rich the achievements on the ultra-low specific-speed centrifugal pump in theory, CFD(Computational Fluid Dynamics)numerical simulation and performance tests were adopted to study the model of the centrifugal pumps, to analysis the hydraulic properties of the ultra-low specific-speed centrifugal pump.

Analysis on Effects of the Blade Wrap Angle and Outlet Angle on the Performance of the Low-Specific Speed Centrifugal Pump

In order to research the effect of the blade wrap angle and outlet angle on the hydraulic performance of the low-specific speed sewage pump, the Reynolds time-averaged Navier-Stokes equations was discretized based on the finite volume method, and the modified k-ε turbulence model were chosen in FLUENT. Numerical simulation of the internal flow within the centrifugal pump with the specific speed of 60 at different blade wrap angle and outlet angle is carried out. The analysis of the velocity and the turbulent kinetic energy distribution in different cases, and predicts the external characteristics of the several cases based on the loss analysis method. The study results show that the efficiency of pumps increase with decreasing the outlet angle and increasing the wrapping angle at the design of sewage pumps. According to the analysis, changing the blade outlet Angle has much more influence on the performance of the pump than changing the wrap angle.

Numerical Design and Performance Prediction of Low Specific Speed Centrifugal Pump Impeller

Abstract In this paper, Based on Two-dimensional Flow Theory, adopting quasi-orthogonal method and point-by-point integration method to design the impeller of the low specific speed centrifugal pump by code, and using RANS (Reynolds Averaged N-S) Equation with a standard k-e two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the impeller of the low specific speed pump. An analysis of the influences of the blade profile on velocity distributions, pressure distributions and pump performance and the investigation of the flow regulation pattern in the impeller of the centrifugal pump are presented. And the result shows that this method can be used as a new way in low speed centrifugal pump impeller design. Key words : Low Specific Speed, Centrifugal Pump impeller, Two-dimensional Flow Theory, Numerical Design ， Performance Prediction 1. Introduction Centrifugal pump is the most widely used vane pump, and a wide variety of centrifugal pump types are used in many different applications in industry and other technical sectors. After long-term research and practice in centrifugal pump, a wealth of experience of slope of head-capacity characteristic curve which bring about low flow rate instability and high flow rate power overload [1]. Traditional impeller design methods, which are mainly based on the similarity theory, empirical correlation, combination of model testing, and engineering experience, their design process are difficult task, mainly due to the great number of free geometric parameters. [2, 3, 4] So well hydraulic design of low specific pump impeller becomes more difficult and more necessary. Regardless of the design process used, the final decision of a new pump impeller design is usually made following physical testing. These tests are often time and resources consuming. In addition, the flow field in impeller channels is very complicated, so that no simple mathematic model can be established to well predict the performance of impellers. For these reasons CFD (computational fluid dynamics) analysis is currently being carried out on centrifugal impeller. [5, 6, 7, 8] By using it can provide quite accurate information on the fluid behaviour, and thus helps the engineers to obtain a thorough performance evaluation of the design. In this paper, based on Two-dimensional flow theory low specific speed pump impeller design method, which adopting quasi-orthogonal method and point-by-point integration, is put forward. 3D turbulent flow field in the designed impeller is calculated numerically by using RANS (Reynolds Averaged N-S) Equation with standard k-e turbulence model and log-law wall function. And predicting result of impeller according to the flow is presented.