Original Impeller Research Articles

Influence of impeller staggered arrangement on radial force and pressure fluctuation for a double-suction centrifugal pump

Influence of impeller arrangement on performance, radial force, and pressure fluctuation for a double-suction centrifugal pump is investigated. In comparison of the original impeller with staggered angle α of 0°, the maximum improvement of pump efficiency is 2.19% for impeller with α of 30°, and the maximum improvement of pump head is 1.76% for impeller with α of 20°. The radial force vector on impeller is related to the staggered angle, and the phase angle of radial force vector is equal to the staggered angle. The staggered arrangement can effectively reduce the amplitude of radial force fluctuation. In comparison of case 0, the maximum amplitude of radial force fluctuation for case 30 reduces by 15.8%. The dominant frequencies of the radial force fluctuation for α = 0°, 10°, and 20° are fBP, while the dominant frequency for α = 30° is 2 fBP. An empirical formula is proposed to predict the radial fluctuation amplitude at specific staggered angle. For a point of the volute far from the exit volute, in comparison of case 0, the maximum amplitudes of pressure fluctuation for case 10, case 20, and case 30 are reduced by 13.1%, 49.8%, and 93.3%.

The Performance of Pump as Turbine with Machined Impellers

Pump as turbine (PAT) is a type of micro hydro power plant, which uses a commercial pump as a turbine in order to generate electricity. Most of PAT facilities used centrifugal pump. The main component of the pump is impeller, which commonly produced by using casting process. However, this paper describes a manufacturing process to produce PAT impeller by using machining process. Four impellers were produced from two variations of materials (brass and AA-7075), each with 5 and 6 blades. The impellers were tested in a laboratory scale PAT power-plant facility, and the performance of each impeller was compared to its original impeller. The experiment results show that the impeller with 6 blades made of brass material improves 48.9% of power generated.

Optimization design of multiphase pump impeller based on combined genetic algorithm and boundary vortex flux diagnosis

A novel optimization design method for the multiphase pump impeller is proposed through combining the quasi-3D hydraulic design (Q3DHD), the boundary vortex flux (BVF) diagnosis, and the genetic algorithm (GA). The BVF diagnosis based on the Q3DHD is used to evaluate the objection function. Numerical simulations and hydraulic performance tests are carried out to compare the impeller designed only by the Q3DHD method and that optimized by the presented method. The comparisons of both the flow fields simulated under the same condition show that (1) the pressure distribution in the optimized impeller is more reasonable and the gas-liquid separation is more efficiently inhibited, (2) the scales of the gas pocket and the vortex decrease remarkably for the optimized impeller, (3) the unevenness of the BVF distributions near the shroud of the original impeller is effectively eliminated in the optimized impeller. The experimental results show that the differential pressure and the maximum efficiency of the optimized impeller are increased by 4% and 2.5%, respectively. Overall, the study indicates that the optimization design method proposed in this paper is feasible.

Theoretical, experimental, and numerical study of special impeller used in turbine mode of centrifugal pump as turbine

The pump-as-turbine (PAT) technique is limited by its undesirable performance and narrow range of high efficiency due to the mismatch between the conventional backward-curve centrifugal impellers and the turbine running condition. This study aims to significantly improve the performance of PAT by designing a special impeller with forward-curve blades for the turbine working condition, and investigating the method for determining the blade inlet and outlet angles that play important roles in the energy conversion. The performance tests of PATs with the designed special impeller and an original backswept blade impeller were performed. The improved performance after replacing the original impeller with the special impeller was demonstrated by numerically investigating the PATs of specific speed of 18.1 with different impellers by use of a verified computational fluid dynamics technique. The suitability of the proposed methods to other cases was verified by designing and experimenting on two other special impellers used in two other centrifugal pumps as turbines with various specific speeds. Compared with the original backward-curve impellers, the experimental maximum efficiencies of special forward-curve impellers of three various specific speeds are more significantly increased and the flow-efficiency curve is flatter, suggesting the obvious superiority of the forward-curve impeller in PAT. The experimental flow rate of best efficiency point (BEP) is very close to the theoretically designed flow rate, indicating that the theoretical relationship expression between the blade inlet angle and design flow rate provides an effective prediction method of BEPs' flow rate in PAT's turbine operating mode with special impeller. A low-cost and convenient way to significantly improve the efficiency of PAT in turbine mode is provided in this study.

Effect of splitter leading edge location on performance of an automotive turbocharger compressor

Design of centrifugal compressors can be accomplished using methods provided in text books and open literature. In this general approach, after determination of dimensions in meridional plane, blade profiles are designed using aerodynamic methods. Then, some blades are trimmed at the beginning to avoid inlet blockage. But there is no clear guidance on how this trimming must be performed. With this widely implemented method, splitter blades have the same profile as main ones.In this research, blade profiles and dimensions of the compressor impeller are not changed while the effect of changes in the position and angle of splitters leading edge are investigated. An optimization scheme is performed to find the best configuration over the complete operating curve of the compressor using genetic algorithm and considering structural aspect of the problem. CFD codes with experimental support are used to predict the compressor performance and flow field specifications with the original impeller as well as the modified one. After taking into account some geometrical details, a new impeller is manufactured based on the modified design and tested in a wide range of operating conditions. Results show 2.7 points improvement in efficiency at the nominal point and 5% decrease in impeller moment inertia. No change in choke behavior, but notable improvement in surge margin of the modified compressor is observed. This is an important achievement in all applications of centrifugal compressors, especially in turbochargers.

Optimization on the impeller of a low-specific-speed centrifugal pump for hydraulic performance improvement

In order to widen the high-efficiency operating range of a low-specific-speed centrifugal pump, an optimization process for considering efficiencies under 1.0Q d and 1.4Q d is proposed. Three parameters, namely, the blade outlet width b 2, blade outlet angle β 2, and blade wrap angle φ, are selected as design variables. Impellers are generated using the optimal Latin hypercube sampling method. The pump efficiencies are calculated using the software CFX 14.5 at two operating points selected as objectives. Surrogate models are also constructed to analyze the relationship between the objectives and the design variables. Finally, the particle swarm optimization algorithm is applied to calculate the surrogate model to determine the best combination of the impeller parameters. The results show that the performance curve predicted by numerical simulation has a good agreement with the experimental results. Compared with the efficiencies of the original impeller, the hydraulic efficiencies of the optimized impeller are increased by 4.18% and 0.62% under 1.0Q d and 1.4Qd, respectively. The comparison of inner flow between the original pump and optimized one illustrates the improvement of performance. The optimization process can provide a useful reference on performance improvement of other pumps, even on reduction of pressure fluctuations.

Additive Manufacturing and Performance of Functional Hydraulic Pump Impellers in Fused Deposition Modeling Technology

Would it be possible for an additively manufactured impeller of fused deposition modeling (FDM) technology to have a functional behavior and a similar performance to that of the original impeller of a close-coupled centrifugal pump? In this research paper, different tests are conducted to answer this question and to evaluate the manufacturing process of FDM functional parts. Three performance experiments with the same centrifugal pump, using an open test rig, are carried out and compared, first using the original impeller provided by the manufacturer of the pump, second using an FDM replication of the original one without post-treatment, and third using a chemically dimethyl ketone post-treated FDM replication. The results obtained in the tests demonstrate the functional behavior of both additive FDM impellers in comparison with the one fabricated by means of conventional technology (subtractive manufacturing). Additionally, analogous head-flow curves (and also with an improved performance to the one of the original impeller) are obtained. This research paper introduces significant information concerning a low-cost and low-time manufacturing process of additive functional parts. Moreover, new results are presented regarding the performance of chemically post-treated FDM parts working in functional applications. FDM impellers of high complexity and quality, which meet performance criteria, can be achieved.

Effects of impeller diameter and rotational speed on performance of pump running in turbine mode

The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant.Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500rpm with original (∅ 250mm), 10% trimmed (∅ 225mm) and 20% trimmed (∅ 200mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational speed in non-dimensional form.

Performance impact of impeller blade trimming on centrifugal compressors

Centrifugal impeller blade trimming can be used to modify an existing impeller design to meet a new flow or pressure ratio design point. In flow trimming, the passage area is reduced from inlet to outlet along the entire meridional length of the impeller to reduce the flow coefficient of the impeller while maintaining the pressure ratio of the untrimmed impeller. Axial trimming is a method of reducing the blade height at the impeller exit while maintaining the shroud profile of the original impeller in order to reduce the head coefficient of the impeller while maintaining the original flow range. In this work, computational fluid dynamics was employed to numerically model four impellers of varying geometries, speeds, and performance characteristics to study the performance effects and limits of modifying the impeller geometry by either flow or axial trimming. Flow trimming was found to be capable of reducing the flow coefficient by between 20 and 50% while maintaining the pressure ratio and efficiency of the baseline impeller. The suitability of an impeller for flow trimming was found to correlate strongly with flow incidence angle. Reducing the exit blade height of a centrifugal impeller by trimming the blades axially may be used to reduce the pressure ratio of a compressor while maintaining flow range; however, the amount of pressure ratio reduction was limited to between 9 and 13% before choking in the passage reduced the choked flow rate. Impeller performance was found to respond differently to axial trimming based on the diffusion ratio of the baseline impeller.

Hydrodynamic Efficiency Improvement of High-Specific-Speed Centrifugal Pump Impeller

The high-specific-speed centrifugal pumps are very common in industrial factory for transporting fluids all day long. However, oversized pumps with low performance still could meet the purpose of fluid transporting. The aim of this study was to reduce the existed commercial impeller energy consumption by optimizing the performance of impeller through CAE processes. The impeller model was first generated by BladeGen software and analyzed by CFX in Turbo-mode. The optimized model then exported to machine center to cut the precise aluminum mold. A regular sand die casting processes were used to manufacture the impeller. The original pump which only impeller was replaced with the new one was tested with performance measurement system again. The results show that when the mass flow rate between 40-90kg/s the CFD software predicted very well pump heads and efficiencies with experimental data, which was called optimized impeller. But around the minimum and maximum flow rate region, the recirculation flow between blades and frictional loss model used still need further investigation to shrink the difference. Compare to the original impeller, the optimized one had increased efficiency 6% at the mass flow rate of 80kg/s. Also the high efficiency region (nearby of BEP) of the new impeller had broadened 50%. And the maximum mass flow rate increased 13% than the original one.

A Reverse Design Method of Geometric Model for Fan's Impeller Based on Geomagic Studio and SolidWorks

t is introduced that the point cloudy data of the fans impeller is analyzed systematically and the one of its blades is preprocessed in Geomagic Studio, its surface fitting with NURBS. The IGS file formed finally in Geomagic Studio is input to SolidWorks to reconstruct original impeller model, which expresses that the combination of CAD and reverse engineer (RE) software has important application value in model design of complex geometry products.

Advanced impeller design: Anti-ragging impeller, ARI2

The waste water treatment plant anoxic denitrification process employs agitated vessels which contain process fluids contaminated with fibrous, rag-like materials that have a tendency to collect on impeller blades and adversely affect mixing performance. The existing Philadelphia Mixing Solutions Ltd. anti-ragging impeller made from fiberglass reinforced plastic is not cost effective for this low torque application. The challenge was to design an impeller that replicated the performance of the original impeller but utilized common industrial manufacturing processes to reduce cost. The flexible construction technology chosen was sheet metal fabrication. The design effort produced a highly skewed, forward raked, hydrofoil impeller with applications that extend beyond the waste water treatment industry. The performance of the new impeller was evaluated by comparing it to the fiberglass impeller as well as three other common impeller types used in stirred tanks. Impeller pumping capacity was measured using 2-D Particle Image Velocimetry and impeller power draw was measured using a load cell and tachometer. The characteristic dimensionless impeller power and flow number, Np and Nq, were computed to be 0.17 and 0.42, respectively.

Performance and Internal Flow Condition of Mini Centrifugal Pump with Splitter Blades

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the 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. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-CFX) to investigate the internal flow condition in detail. It is clarified from experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Blade-to-blade low velocity regions are suppressed in the case with the splitter blades and total pressure loss regions are decreased. The effects of the splitter blades on the performance and the internal flow condition are discussed in this paper.

Unsteady internal flow conditions of mini-centrifugal pump with splitter blades

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the 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. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional unsteady numerical flow analysis was conducted to investigate the change of the internal flow according to the rotor rotation. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the splitter blades. The blade-to-blade low velocity region was suppressed in the case with the splitter blades. In addition to that, the unsteady flows near the volute casing tongue were suppressed due to the splitter blades. In the present paper, the performance of the mini centrifugal pump is shown and the unsteady flow condition is clarified with the results of the numerical flow analysis. Furthermore, the effects of the splitter blades on the performance and the unsteady internal flow condition are investigated.

Effects of Hub Profiles on Efficiency and Flow of Jet Fan with Single Stage Impeller

The traditional jet fans have equipped with the tandem impellers and the exclusive motors, and such designs are associated with the expensive initial cost. This serial research proposes how to simplify the fan profile for reducing the initial cost without the performance deteriorations. The paper discusses the effects of the hub profiles installed in the traditional/commercial jet fan, on the performances in the several type single-stage work. The hub with the long tail corn gives the best efficiency, and not only the stay vanes but also the cooling fins deteriorate more or less the performances, accompanying the impeller works as follows. The efficiency at the reverse rotation of the original impeller, namely at the flow condition running from the outlet to the inlet, is doubtlessly lower than one at the original rotation. The unique cascade, where the leading and the trailing edges of the blade are alternated in the tangential direction, was prepared in anticipation of improving the performances. These results advise the desirable profile of the jet fan equipped with the single-stage impeller, and the numerical simulation provides the optimum blade profile for the bidirectional flow.

Study on measures to improve gas-liquid phase mixing in a multiphase pump impeller under high gas void fraction

Rotodynamic multiphase pump can transport crude gas-liquid mixture produced from oil well, and is regarded as the good choice of oil-gas multiphase transportation in offshore product system, for its advantages that compact structure, large flow rate, not sensitive to solid particles in the fluid. However, it is prone to bring about gas-liquid separation within the impeller under high gas void fraction. To solve the problem, this paper presents several measures to break gas packet and inhibit gas-liquid separation, such as, depositing the short blades, opening holes at the blades where gas packets gather, using T-shaped blades, etc. Then, CFD software was used to simulate the flow fields which were added measures to inhibit gas-liquid separation. The results show that streamlines in three new impellers distribute more evenly than in original impeller, the gas-liquid two phases mixed degree was improved, and the gas-liquid separation was inhibited to some extent. However, adding the short blades and using T-blade impeller failed to improve the differential pressure of impellers. So the placement and the geometrical parameters of the measures inhibiting gas-liquid separation should be further optimized.

Performance and internal flow condition of mini centrifugal pump with splitter blades

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the 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. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-CFX) to investigate the internal flow condition in detail. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. The blade-to-blade low velocity regions are suppressed in the case with the splitter blades and the total pressure loss regions are decreased. The effects of the splitter blades on the performance and the internal flow condition are discussed in this paper.

A parametric study for improving the centrifugal pump impeller for use in viscous fluid pumping

Essentially, performance of centrifugal pumps is affected when pumping viscous fluids. In this paper a new idea is proposed to overcome the undesirable effects of viscosity on the pump performance parameters. This idea based on this matter that one specific impeller can be designed, made and installed on the pump for pumping of one fluid with specific viscosity. Therefore a specific pump can be used for pumping of different fluids with different viscosity, by replacement of pump impeller. Replacement of the impeller is more cost effective in comparison to the replacement of the whole of the pump. Passage width and outlet angle of impeller are considered as design variables and the effects of such variables investigated using experimentally validated numerical model. The H–Q, P–Q and η–Q graphs are extracted experimentally for the improved impeller, which show good improvement in comparison with original impeller.

Effects of impeller trimming influencing pump as turbine

Pump manufactures normally do not provide performance curves of their pumps working as turbines, especially performance curves of trimmed impellers. Impeller trimming is necessary to adapt to a certain operating condition. Therefore, establishing the correlation of PAT’s performance curve and impeller trims is essential. In this paper, a laboratory model of a pump as turbine (PAT) open test rig was set up. Experimental research was carried out on a single stage centrifugal PAT, performance curves of original impeller, impeller after once and twice trims were acquired. Numerical simulation and analysis were performed on the PAT. The accuracy of CFD was validated through comparison between numerical and experimental data. As impeller diameter is cut down, its geometrical parameters of impeller diameter, blade wrap angle, impeller inlet width and blade inlet angle are changed. So, research on effects of the above four parameters to the performance influence of PAT were carried out using CFD. Through analysis of the predicted performance curves, the reasons for the variation of performance curves after impeller trimming were explored.

Study of Flow-Induced Hemolysis Using Novel Couette-Type Blood-Shearing Devices

To assist the development and application of blood-contacting medical devices, two novel flow-through Couette-type blood-shearing devices have been developed to study the quantitative relationship between blood damage indexes and flow-dependent parameters. One device is an axial flow-through Couette-type device supported by a pair of pin bearings adapted from the adult Jarvik 2000 blood pump. The other is a centrifugal flow-through Couette-type device supported with magnetic bearings adapted from the CentriMag blood pump. In both devices, a rotor spindle was used to replace the original impeller blades so that a small gap was created between the housing and the rotating spindle surface. Computational fluid dynamics simulations have shown that a uniform, high shear stress region can be generated inside the small gap while the shear stresses elsewhere are relatively low. The possibility of secondary blood damage caused by mechanical seals was eliminated due to the use of a magnetic rotor system. Blood flow through the gap was driven by an externally pressurized reservoir. By adjusting the rotational speed and blood flow rate, shear-induced hemolysis was quantified at a matrix of exposure time (0.039 to 1.48 s) and shear stress (50 to 320 Pa). All of the experiments were conducted at room temperature using heparinized ovine blood with a hematocrit value of 30%. The measured hemolysis levels were much lower than those published in the literature, and the overestimation of those earlier studies may be attributable to device-related secondary blood-damaging effects. A new set of coefficients for the power law model was derived from the regression of the experimental data.