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1
Kareem Sakran, Hayder. "A Numerical Investigation of the Effect of Increasing Blade Numbers on Cavitation and Performance of Centrifugal Pumps at Constant Parameters." University of Thi-Qar Journal for Engineering Sciences 8, no. 3 (2017): 1–19. http://dx.doi.org/10.31663/utjes.v8i3.89.
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In the present paper, a numerical study has been investigated by using computational fluid dynamics (CFD) to analyze pressure, head, head coefficient, pressure coefficient, input power, and volume fraction of cavitation at three cases of simulation in which each one has constant parameters; however, with modifying number of blades which is changed from five to sixteen. The constant parameters are rotating speed, volume flow rate, mass flow rate, outlet diameter, suction specific speed Nss, Reynolds number and NPSHr. These parameters have been fixed to have the same conditions for each case. The shear stress transport (SST) turbulence model has been used to inspect a steady state incompressible flow through centrifugal pump numerically. The simulation has done by using ANSYS®, Vista CPDTM Release 15.0. The results are plotted and discussed to describe and find a relation among cavitation, pump behavior, and variation of blade numbers at constant conditions. The results show a strong relation among increasing blade numbers, centrifugal pump performance and reducing pump cavitation.
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Li, Hong, Zhenhua Shen, Nicholas Engen Pedersen, and Christian Brix Jacobsen. "Experimental and unsteady numerical research of a high-specific-speed pump for part-load cavitation instability." Advances in Mechanical Engineering 11, no. 3 (2019): 168781401982893. http://dx.doi.org/10.1177/1687814019828932.
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Net positive suction head peak is a well-known cavitation instability phenomenon in high-specific-speed pumps. Both non-cavitating performance and cavitating performance of a high-specific-speed pump were investigated by experiments and numerical simulations. According to the cavitating performance results, net positive suction head peak is found at 80% of nominal flow. The head curves of non-cavitating performance also have saddle-type instabilities near 70%–80% of nominal flow. Water vapor volume fraction distributions show that cavitation region at net positive suction head peak flow only covers 3% of the blade length when head drops 6%. It proves that net positive suction head peak is not caused by huge amounts of cavitation bubbles, which indicates that net positive suction head peak does not represent excessive cavitation. The velocity vector and pressure distribution plots reveal that net positive suction head peak is related to recirculation near the trailing edge. With inlet pressure decreasing, the flow pattern is sensitive to the cavitation bubbles, and recirculation region from the pressure side to the suction side becomes larger and larger.
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YOSHIDA, Yoshiki. "G405 A Consideration of Inducer's Specific Speed from an Aspect of Impeller's Suction Specific Speed." Proceedings of the Fluids engineering conference 2007 (2007): _G405–1_—_G405–4_. http://dx.doi.org/10.1299/jsmefed.2007._g405-1_.
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YOSHIDA, Yoshiki. "G405 A Consideration of Inducer's Specific Speed from an Aspect of Impeller's Suction Specific Speed." Proceedings of the Fluids engineering conference 2007 (2007): _G405—a_. http://dx.doi.org/10.1299/jsmefed.2007._g405-a_.
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Cao, Weidong, Zhixiang Jia, and Qiqi Zhang. "Near-Wall Flow Characteristics of a Centrifugal Impeller with Low Specific Speed." Processes 7, no. 8 (2019): 514. http://dx.doi.org/10.3390/pr7080514.
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In order to study the near-wall region flow characteristics in a low-specific-speed centrifugal impeller, based on ANSYS-CFX 15.0 software, Reynolds averaged Navier-Stokes (RANS) methods and renormalization group (RNG) k-ɛ turbulence model were used to simulate the whole flow field of a low specific speed centrifugal pump with five blades under different flow rates. Simulation results of external characteristics of the pump were in good agreement with experimental results. Profiles were set on the pressure side and suction side of impeller blades at the distances of 0.5 mm and 2 mm, respectively, to study the distributions of flow characteristics near the wall region of five groups of blades. The results show that the near-wall region flow characteristics of five groups of blades were similar, but the static pressure, relative velocity, cross flow velocity, and turbulent kinetic energy of profiles on the pressure side were quite different to those on the suction sides, and these characteristics also changed with the alternation of flow rate. As the flow rate was 13 m3/h or 20 m3/h, within the radius range of 40 to 50 mm, there was an extent of negative relative velocity of the profiles on the pressure side, and a counter-current happened not on the suction side, but on the pressure side in the low specific speed centrifugal impeller. The flow characteristics of profiles at the distances of 0.5 mm and 2 mm also showed a small difference.
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Mosshammer, Markus, Helmut Benigni, Helmut Jaberg, and Juergen Konrad. "Maximum Efficiency Despite Lowest Specific Speed—Simulation and Optimisation of a Side Channel Pump." International Journal of Turbomachinery, Propulsion and Power 4, no. 2 (2019): 6. http://dx.doi.org/10.3390/ijtpp4020006.
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Side channel pumps provide high pressure at relatively low flow rates. This comes along with a quite low specific speed and thus with the known disadvantage of a quite poor maximum efficiency. This paper describes the detailed analysis and optimisation of a typical 1-stage side channel pump with an additional radial suction impeller by means of computational fluid dynamics (CFD) simulations. In a first step, the model was successively generated and it was obvious that it has to contain all details including suction impeller and main stage (both 360° models) as well as the pressure housing and all narrow gaps to provide useful simulation results. Numerical simulations were carried out in a stationary and transient way with scale resolving turbulence models to analyse the components in detail. Finally the CFD-simulations were validated with model tests. For the optimisation process it was necessary to generate a reduced numerical model to analyse the effects of more than 300 geometry variations. The findings were then combined to establish the desired objectives. Finally the best combinations were validated again with the full numerical model. Those simulations predict a relative efficiency increase at best efficiency point (BEP) and part load >30% with respect to all given limitations like identical head curve, suction behavior, and dimensions.
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Wang, Cong, Yongxue Zhang, Zhiwei Li, Ao Xu, Chang Xu, and Zhicheng Shi. "Pressure fluctuation–vortex interaction in an ultra-low specific-speed centrifugal pump." Journal of Low Frequency Noise, Vibration and Active Control 38, no. 2 (2018): 527–43. http://dx.doi.org/10.1177/1461348418817697.
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To provide a comprehensive understanding of the pressure fluctuation–vortex interaction in non-cavitation and cavitation flow, in this article, the unsteady flow in an ultra-low specific-speed centrifugal pump was investigated by numerical simulation. The uncertainty of the numerical framework with three sets of successively refined mesh was verified and validated by a level of 1% of the experimental results. Then, the unsteady results indicate that the features of the internal flow and the pressure fluctuation were accurately captured in accordance with the closed-loop experimental results. The detailed pressure fluctuation at 16 monitoring points and the monitoring of the vorticity suggest that some inconsistent transient phenomena in frequency spectrums show strong correlation with the evolution of vortex, such as abnormal increasing amplitudes at the monitoring points near to the leading edge on the suction surface and the trailing edge on the pressure surface in the case of lower pressurization capacity of impeller after cavitation. Further analysis applies the relative vortex transport equation to intuitionally illustrate the pressure fluctuation–vortex interaction by the contribution of baroclinic torque, viscous diffusion and vortex convection terms. It reveals that the effect of viscous diffusion is weak when the Reynolds number is much greater than 1. Pressure fluctuation amplitude enlarges on the suction side of blade near to the leading edge due to the baroclinic torque in cavitation regions, whereas the abnormal increase of pressure fluctuation after cavitation on the pressure surface of blade approaching the trailing edge results from the vortex convection during vortices moving downstream with the decrease of available net positive suction head at the same instance.
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Friedrich, Martin G., Ioannes Bougioukas, Peter Wenig, Steffen Vormfelde, and Theodor Tirilomis. "New device for intraoperative blood suction avoiding turbulences." BMJ Innovations 4, no. 2 (2018): 91–97. http://dx.doi.org/10.1136/bmjinnov-2017-000201.
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IntroductionBleeding during surgery is common. Increased bleeding may disturb procedure, induces haemodynamic instability and results in need for blood transfusion. Allogenic blood transfusions increase mortality and morbidity, especially risk of infections, pulmonary and renal complications, as well as thromboembolic events. Autotransfusion is in many cases a solution but forced suction may destroy or alter blood cells because of turbulences, shear forces and contact of the blood to extrinsic surfaces. The aim of the study was the analysis of turbulence profile and development of a new suction device reducing (or avoiding) turbulences.MethodsWe registered turbulences with a microphone placed in different positions within the blood suction during surgery and analysed the spectrum. Then, we modified the circuit adding signals from optical sensors and pressure transducer to avoid air mixing and tight suction. Finally, we created the algorithm for the suction circuit regulating individualised suction modes.ResultsWe developed a new suction system based on a roller pump. We used a piezo sensor and registered the acoustic signals. The optimal position for this element was into the suction handle. After filtering the signal and further processing, we used it for regulation of the roller pump. Additionally, an optical sensor minimises air mixing due to further regulation of motor speed. Finally, a negative pressure transducer gives in case of tight suction information to the circuit stopping motor speed and equalising pressure by opening a valve before suctions starts again. The algorithm allows various suction modes in an individualised manner for specific situations in operating field.ConclusionsWe developed a new blood suction device based on a roller pump. The system is turbulence-controlled and its algorithm allows several individualised suction modes. Additional features avoid tight suction and reduce air mixing.
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Wang, Zhe, Ruizhi Zhang, Jiajian Zhou, and Xianwu Luo. "Cavitating flow investigation in low specific speed axial flow waterjet pumps." Journal of Physics: Conference Series 2217, no. 1 (2022): 012008. http://dx.doi.org/10.1088/1742-6596/2217/1/012008.
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Abstract In this paper, the cavitating flow in low specific speed axial flow waterjet pumps are treated at different cavitation conditions. In order to analyze the cavitating turbulent flow comprehensively, three axial flow waterjet pumps with the specific speed less than 650 min-1·m3s-1·m are chosen to compare the internal flow phenomenon. The investigations are conducted by numerical simulation, where RANS method is applied with k-ω SST turbulence model and homogeneous cavitation model. The results show that there are several types of cavitation such as tip leakage vortex cavitation, sheet cavitation attached on blade suction surface, and shedding cavity in the pumps. The vortex structure in the low specific speed waterjet pump contains tip leakage vortex, shedding vortex downstream of the sheet cavitation and perpendicular cavitation vortex. It is noted that the cavity firstly occurs at the leading edge near blade tip, and the sheet cavity covering the blade suction surface extends from leading edge to the middle part, while the tip leakage vortex cavitation develops with the decreasing cavitation number. Further analysis using relative vortex transport equation depicts that the vortex stretching term is the main contributor for the vorticity production in the pump, and the vortex dilation and baroclinic torque occur at the interface between cavity and water.
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Calgaro, Marcelo, Adroaldo Dias Robaina, and Márcia Xavier Peiter. "CURVAS DE DESEMPENHO OPERACIONAL DE BOMBAS CENTRÍFUGAS DETERMINADAS A PARTIR DAS CARACTERÍSTICAS FÍSICAS DO ROTOR I - VALORES NOMINAIS." IRRIGA 9, no. 1 (2004): 19–30. http://dx.doi.org/10.15809/irriga.2004v9n1p19-30.
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CURVAS DE DESEMPENHO OPERACIONAL DE BOMBAS CENTRÍFUGAS DETERMINADAS A PARTIR DAS CARACTERÍSTICAS FÍSICAS DO ROTORI - VALORES NOMINAIS Marcelo Calgaro1; Adroaldo Dias Robaina1; Márcia Xavier Peiter21Departamento de Engenharia Rural, Universidade Federal de Santa Maria, Santa Maria, RS, calgaro@mail.ufsm.br2Curso de Engenharia Agrícola, Universidade Regional Integrada do Alto Uruguai e das Missões – URI, Santiago, RS. 1 RESUMO Este trabalho teve como objetivo desenvolver uma metodologia com a finalidade de determinar os valores nominais da vazão, altura manométrica, rendimento, potência requerida e NPSH requerido no ponto de maior eficiência para diversos modelos de bombas, a partir das medidas das características físicas dos rotores (d1, d2, b2, e2 e β2). Para alcançar esse objetivo foi executada uma série de medidas nos rotores das bombas hidráulicas, uma metodologia de cálculo com base na teoria das bombas hidráulicas e em coeficientes experimentais fornecidos pela literatura especializada disponível. Os resultados obtidos permitiram verificar que um método simples, rápido e de baixo custo pode fornecer os valores nominais ou de projeto dos modelos de bombas avaliados. A conclusão do trabalho é que a metodologia proposta foi capaz de estimar os valores nominais da vazão Q0, da altura manométrica H0, da potência P0, do NPSH requerido NPSHr0, do rendimento Rg0 e da velocidade específica Nq0, a partir das medidas das características físicas dos rotores dos modelos de bombas estudados. UNITERMOS: sistemas de bombeamento, irrigação, agricultura. CALGARO, M., ROBAINA, A. D., PEITER, M. X.OPERATIONAL PERFORMANCE CURVES OF CENTRIFUGAL PUMPS DETERMINED FROM THE PHYSICAL CHARACTERISTICS OF THE IMPELLER I - NOMINAL VALUES 2 ABSTRACT This work aimed to develop a methodology to determine the nominal values of the outflow, manometric height, output, required potency and required NPSH in the highest point of efficiency for several pump models, from the measurements of the physical characteristics of the rotors (d1, d2, b2, e2 and ß2). To reach this objective a series of measurements was done in the hydraulic pump rotors, the used calculation methodology was based on the hydraulic pump theory and on experimental coefficients, which were supplied by the available specialized literature. The obtained results allowed to verify that a simple, fast, low cost method can supply either the nominal or project values of the evaluated pump models. This work concluded that the proposed methodology was capable of estimating the nominal values of the outflow Q0, the manometric height H0, the potency P0, the Net Positive Suction Head required NPSHr0, the output Rg0 and the specific speed Nq0 starting from measurements of the physical characteristics of the rotors of the studied pump models. KEYWORDS: pump’s system, irrigation, agriculture.
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Zhang, Jinfeng, Guidong Li, Jieyun Mao, Shouqi Yuan, Yefei Qu, and Jing Jia. "Effects of the outlet position of splitter blade on the flow characteristics in low-specific-speed centrifugal pump." Advances in Mechanical Engineering 10, no. 7 (2018): 168781401878952. http://dx.doi.org/10.1177/1687814018789525.
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To elucidate the influences of the outlet position of splitter blades on the performance of a low-specific-speed centrifugal pump, two different splitter blade schemes were proposed: one located in the middle of the channel and the other having a deviation angle at the trailing edge of splitter blade toward the suction side of the main blade. Experiments on the model pump with different splitter blade schemes were conducted, and numerical simulations on internal flow characteristics in the impellers were studied by means of the shear stress transport k- ω turbulence model. The results suggest that there is a good agreement between the experimental and numerical results. The splitter blade schemes can effectively optimize the structure of the jet-wake pattern and improve the internal flow states in the impeller channel. In addition, the secondary flow and inlet circulation on the pressure surface of main blade, the flow separation on the suction side of splitter blade, the pressure coefficient distributions on blade surface can achieve an evident amelioration when the trailing edge of splitter blade toward the suction side of the main blade is mounted at an appropriate position.
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Deban, Stephen M., Roi Holzman, and Ulrike K. Müller. "Suction Feeding by Small Organisms: Performance Limits in Larval Vertebrates and Carnivorous Plants." Integrative and Comparative Biology 60, no. 4 (2020): 852–63. http://dx.doi.org/10.1093/icb/icaa105.
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Abstract Suction feeding has evolved independently in two highly disparate animal and plant systems, aquatic vertebrates and carnivorous bladderworts. We review the suction performance of animal and plant suction feeders to explore biomechanical performance limits for aquatic feeders based on morphology and kinematics, in the context of current knowledge of suction feeding. While vertebrates have the greatest diversity and size range of suction feeders, bladderworts are the smallest and fastest known suction feeders. Body size has profound effects on aquatic organismal function, including suction feeding, particularly in the intermediate flow regime that tiny organisms can experience. A minority of tiny organisms suction feed, consistent with model predictions that generating effective suction flow is less energetically efficient and also requires more flow-rate specific power at small size. Although the speed of suction flows generally increases with body and gape size, some specialized tiny plant and animal predators generate suction flows greater than those of suction feeders 100 times larger. Bladderworts generate rapid flow via high-energy and high-power elastic recoil and suction feed for nutrients (relying on photosynthesis for energy). Small animals may be limited by available muscle energy and power, although mouth protrusion can offset the performance cost of not generating high suction pressure. We hypothesize that both the high energetic costs and high power requirements of generating rapid suction flow shape the biomechanics of small suction feeders, and that plants and animals have arrived at different solutions due in part to their different energy budgets.
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Liu, Yongchao, Jintian Jiang, Yanyan Yuan, Qinglong Jiang, and Chao Yan. "Vertically Aligned NiCo2O4 Nanosheet-Encapsulated Carbon Fibers as a Self-Supported Electrode for Superior Li+ Storage Performance." Nanomaterials 9, no. 9 (2019): 1336. http://dx.doi.org/10.3390/nano9091336.
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Binary transition metal oxides (BTMOs) have been explored as promising candidates in rechargeable lithium-ion battery (LIB) anodes due to their high specific capacity and environmental benignity. Herein, 2D ultrathin NiCo2O4 nanosheets vertically grown on a biomass-derived carbon fiber substrate (NCO NSs/BCFs) were obtained by a facile synthetic strategy. The BCF substrate has superior flexibility and mechanical strength and thus not only offers a good support to NCO NSs/BCFs composites, but also provides high-speed paths for electron transport. Furthermore, 2D NiCo2O4 nanosheets grown vertically present a large contact area between the electrode and the electrolyte, which shortens the ions/electrons transport distance. The nanosheets structure can effectively limit the volume change derived from Li+ insertion and extraction, thus improving the stability of the electrode material. Therefore, the synthesized self-supporting NCO NSs/BCFs electrode displays excellent electrochemical performance, such as a large reversible capacity of 1128 mA·h·g−1 after 80 cycles at a current density of 100 mA·g−1 and a good rate capability of 818.5 mA·h·g−1 at 1000 mA·g−1. Undoubtedly, the cheap biomass carbon source and facile synthesis strategy here described can be extended to other composite materials for high-performance energy-storage and conversion devices.
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Moravec, Prokop, Lukáš Zavadil, Jakub Stareček, Tomáš Krátký, and Milan Sedlář. "Multiphase numerical analysis of the vortex formation near the suction of the vertically mounted axial-flow pump with influence of the free water level." EPJ Web of Conferences 269 (2022): 01041. http://dx.doi.org/10.1051/epjconf/202226901041.
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Presented paper deals with the numerical investigation of a flow in a complete hydraulic system of a pump station. The station uses a recently developed high-efficiency axial-flow pump with the specific speed ns=680 min-1. The pump is vertically mounted in the suction object with the free water level and equipped with the suction bell and the suction cone with one rib. For the numerical simulations, the lowest possible water level is considered. Such scenario is the most limiting for the pump station design and need to be analysed properly. The unsteady multiphase numerical simulations were focused on the creation of the complex vortical structures at the suction part of the mentioned axial-flow pump. This phenomenon strongly influences the pump performance (hydraulic efficiency, delivery and suction head, etc.) and operation (especially the vibrations and noise) characteristics. The unsteady flows inside the investigated domains are simulated using Ansys Fluent with appropriate solver settings. The Scale Resolving Simulations (SRS) are used to model large vortices and the interaction between stationary and rotating parts.
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Zhu, Di, Zilong Hu, Yan Chen, et al. "Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement." Water 15, no. 9 (2023): 1785. http://dx.doi.org/10.3390/w15091785.
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Two-stage double-suction centrifugal pumps have both a large flow and high head. However, due to the complexity of their flow passage components, efficiency has always been a major problem, and the corresponding head is also prone to insufficiency. In this study, an improved design for a two-stage double-suction centrifugal pump unit with a specific speed of 25.9 was developed with the help of a computer. The computational fluid dynamics (CFD) method was used to evaluate the performance and loss of the unit in the process of improvement. The unit’s inlet division section, two semi-spiral suction chambers, two impellers for the first stage, two inter-stage channels, a double-suction impeller for the second stage, and the volute were able to be improved. Through a total of 39 improvements, the efficiency under multiple working conditions was comprehensively improved, and the head had a reasonable margin in meeting the requirements. After the improvements, the flow pattern in the inter-stage channel and volume were significantly improved through the check of the streamline. This research successfully improved the performance of a two-stage double-suction centrifugal pump unit, and it has significant engineering value.
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Setiawan, Rachman. "PARAMETRIC ANALYSIS ON OFF-SHORE DREDGING PROCESS USING CUTTER SUCTION DREDGERS." ASEAN Engineering Journal 6, no. 1 (2015): 37–46. http://dx.doi.org/10.11113/aej.v6.15477.
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Nowadays, cutter-suction dredgers are widely used in off-shore tin mining around South East Asia region, especially in Indonesia. So far, the effectiveness of the dredging process is arguably due to the skills and experience of individuals who operate the dredgers. No sufficient guidelines, standard operating procedures exist on how to operate the dredgers effectively based on scientific facts and factual data on the mining environment. This paper discusses the effectiveness of the dredging process in a cutter suction dredger (CSD). The influence of various parameters is studied through parametric simulation based on theoretical approach developed by Miedema and Vastbloom, with a number of adaptations from the original model in order to obtain a better approximation. A specific CSD design is used as a case study. From the parametric analysis, it is found that, dredging capacity is highly affected by the cutting thickness and swing speed, rather than the dredging depth. With the limit of pump capacity and dredge power, the optimum cutting thickness is approximately 75% for the dredger in question, adjustable through the swing speed during operation. Moreover, the dredging forces are highly affected by the cutter rotational speed and soil type, whilst lightly affected by the dredging depth. For dredging harder soils, the dredge forces increase by up to 68%, for the dredger in question, hence the operational parameters must be adjusted, i.e. by lowering the swing speed, however maintaining higher rotational speed, in order to have a safe and optimum operation.
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Yang, Wei, Xiaoyu Lei, and Benqing Liu. "Three-Dimensional Inverse Design of Low Specific Speed Turbine for Energy Recovery in Cooling Tower System." Energies 11, no. 12 (2018): 3348. http://dx.doi.org/10.3390/en11123348.
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A three-dimensional inverse design of a low specific speed turbine is studied, and a set of design criteria for low specific speed turbine runner is proposed, including blade loading distributions and blade lean angles. The characteristics of the loading parameters for low specific speed turbine runner are summarized by analyzing the suction performance of different loading positions, loading slopes and blade lean angles based on the orthogonal experiment design and range analysis. It is found that the blade loading distribution at the band plays a more important role than it does at the crown and it should be fore loaded for both band and crown. The blade lean angle at the blade leading edge should be negative. Then, the blade is optimized through the inverse method by fixing blade lean angle, based on the response surface method. After seeking the optimal value of the response surface function, the optimal result of the design parameters is obtained, which is in conformity with the design criteria and verifies the rationality of the established design criteria for low specific speed turbine.
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Cui, Baoling, Xiaotian Han, and Yinchu An. "Numerical Simulation of Unsteady Cavitation Flow in a Low-Specific-Speed Centrifugal Pump with an Inducer." Journal of Marine Science and Engineering 10, no. 5 (2022): 630. http://dx.doi.org/10.3390/jmse10050630.
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Cavitation is an undesirable phenomenon in the pumps. In this paper, unsteady cavitation flow in a low-specific-speed centrifugal pump with an inducer is investigated based on the full cavitation model and standard k-ε turbulence model using the commercial software PumpLinx. The numerical results of external performance curve and cavitation performance curve of design condition agree well with that of the experiment. The bubbles in the inducer mainly appear on the outer blade leading edge. The regions of larger vapor volume fraction in the inducer and impeller increase with the decreasing of NPSHa. The regions of larger vapor volume fraction in the inducer expand from the outer edge of the blade inlet to the hub on suction surface. Under very low NPSHa, the impeller may be filled with bubbles in the passage and the pump head drops drastically, and there exist distinct back flows near the suction surface of the blade and impeller outlet. Affected by pre-swirl of inducer outlet and the circle flow of impeller blade inlet, the amplitude of pressure fluctuation near the impeller inlet is obviously larger than that at the inlet in the inducer. The dominant frequency of pressure fluctuation for four monitoring points is shaft frequency. Compared with the non-cavitation flows, the maximum amplitudes of pressure pulsation increase for cavitating flow.
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Selim, O., and C. Bruecker. "Detecting separation pre-cursors using on-board optical tracking of flexible pillar sensors." Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (July 11, 2022): 1–17. http://dx.doi.org/10.55037/lxlaser.20th.175.
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A novel approach for characterising specific flow phenomena unique to incipient stall in real-time on small scale UAVs and aerodynamic systems operating at low to medium Reynolds numbers is introduced. Flexible pillar sensors emanating from the suction side of an aerofoil of length approx. 3% of chord length are installed on a NACA0012 and tested at City, University of London's wind-tunnel facilities. The sensors are tracked in real-time using a high-speed camera in a simulated 'on-board' position, acting as ‘digital tufts’, and the results subsequently processed. The results show the pillars reacting to specific flow phenomena that are unique to incipient stall, and scale with angle of incidence. Namely, these are low-frequency oscillations of local streamwise velocity components which are hypothesised to be resulting from quasi-periodic vortex shedding/shear layer flapping from the breathing of the laminar separation bubble over the suction side.
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Wang, Yu, Wenhang Zhang, Xiwen Luo, et al. "Effect of Vibration Conditions on the Seed Suction Performance of an Air-Suction Precision Seeder for Small Seeds." Agriculture 14, no. 4 (2024): 559. http://dx.doi.org/10.3390/agriculture14040559.
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The air-suction precision seeder for small seeds is a planting machine, characterized by precision, high efficiency, and ease of operation, that uses air suction technology to sow small grain seeds at set intervals and depths into the soil. However, the forced vibration, enhanced by the increase in the operating speed, affects the seeding accuracy of the seeder and limits the seeding efficiency. To study the influence of vibration conditions on the seed suction performance of the air-suction precision seeder, we developed a computational fluid dynamics–discrete element coupling method to construct a bidirectional fluid–solid coupling numerical simulation model of the seed suction process under vibration conditions. Within the range of operating speeds from 0.6 km/h to 8 km/h, we quantitatively studied the population movement under different vibration frequencies, vibration amplitudes, negative pressure values, and seeding disc speeds and verified the simulation model and its analysis results through bench tests. The numerical results show that the interaction between the vibration frequency, vibration amplitude, and negative pressure value has the most significant impact on the single-seed rate. In addition, via variance analysis and response surface analysis, the optimal range of negative pressure values for achieving high single-seed rates under different vibration frequencies (4~10 Hz), vibration amplitudes (3~7.5 mm), and seeding disc speeds (4~50 rpm) was determined. The results indicate that, rather than the higher the negative pressure value, the higher the seed suction rate, the optimal negative pressure value for achieving a high seed suction rate varies with the specific vibration frequencies and amplitudes.
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Wang, Yong, Kaikai Luo, Houlin Liu, Jie Chen, Yu Li, and Jun Yan. "Effect of suction chamber baffles on pressure fluctuations in a low specific speed centrifugal pump." Journal of Vibroengineering 21, no. 5 (2019): 1441–55. http://dx.doi.org/10.21595/jve.2018.18943.
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BANDO, Kiyoshi, Takuji TSUGAWA, Yutaka MIYAKE, and Masahide KONISHI. "Development of Axial-Flow Pump Having High Suction Specific Speed and Its Performance Test Results." Transactions of the Japan Society of Mechanical Engineers Series B 57, no. 537 (1991): 1712–18. http://dx.doi.org/10.1299/kikaib.57.1712.
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Liu, Jianhua, Xiangyang Zhao, and Miaoxin Xiao. "Study on the Design Method of Impeller on Low Specific Speed Centrifugal Pump." Open Mechanical Engineering Journal 9, no. 1 (2015): 594–600. http://dx.doi.org/10.2174/1874155x01509010594.
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In this work, the comparative study has been done for five kinds of design methods of the low specific speed centrifugal pump impeller adopted numerical simulation method by software of Fluent, so that the problems can be solved. Many different design methods exists for the low specific speed centrifugal pump impeller, which caused the design effect difficult to control. The numerical simulation method based on the Reynolds time averaged N-S equations (RANS) and RNG κ-ε turbulence models. Results revealed the inner flow pattern of these impeller, and these results were verified by external characteristic experiment. The research results showed that the design method, which adopted compound impeller with short blades and these short blades turned to the suction surface of long blades. Results proved that its flow distribution is even and external characteristic curve is more ideal.
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Van Wassenbergh, Sam, James A. Strother, Brooke E. Flammang, Lara A. Ferry-Graham, and Peter Aerts. "Extremely fast prey capture in pipefish is powered by elastic recoil." Journal of The Royal Society Interface 5, no. 20 (2007): 285–96. http://dx.doi.org/10.1098/rsif.2007.1124.
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The exceptionally high speed at which syngnathid fishes are able to rotate their snout towards prey and capture it by suction is potentially caused by a catapult mechanism in which the energy previously stored in deformed elastic elements is suddenly released. According to this hypothesis, tension is built up in tendons of the post-cranial muscles before prey capture is initiated. Next, an abrupt elastic recoil generates high-speed dorsal rotation of the head and snout, rapidly bringing the mouth close to the prey, thus enabling the pipefish to be close enough to engulf the prey by suction. However, no experimental evidence exists for such a mechanism of mechanical power amplification during feeding in these fishes. To test this hypothesis, inverse dynamical modelling based upon kinematic data from high-speed videos of prey capture in bay pipefish Syngnathus leptorhynchus , as well as electromyography of the muscle responsible for head rotation (the epaxial muscle) was performed. The remarkably high instantaneous muscle-mass-specific power requirement calculated for the initial phase of head rotation (up to 5795 W kg −1 ), as well as the early onset times of epaxial muscle activity (often observed more than 300 ms before the first externally discernible prey capture motion), support the elastic power enhancement hypothesis.
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Wei, Yangyang, Yang Yang, Ling Zhou, Lei Jiang, Weidong Shi, and Gaoyang Huang. "Influence of Impeller Gap Drainage Width on the Performance of Low Specific Speed Centrifugal Pump." Journal of Marine Science and Engineering 9, no. 2 (2021): 106. http://dx.doi.org/10.3390/jmse9020106.
Full textAbstract:
The centrifugal pump is one of the most important pieces of energy-consuming equipment in various hydraulic engineering applications. This paper takes a low specific speed centrifugal pump as the research object. Based on the research method combining numerical calculation and experimental verification, the influence of the gap drainage structure on the performance of the low specific speed centrifugal pump and its internal flow field distribution were investigated. The flow field inside the low specific speed centrifugal pump impeller under different gap widths was studied. The comparison between the numerical calculation results and the experimental results confirms that the numerical calculations in this paper have high accuracy. It was found that the gap drainage will reduce the head of the low specific speed centrifugal pump, but increase its hydraulic efficiency. Using a smaller gap width could greatly improve the performance of the low specific speed centrifugal pump on the basis of a slight reduction in the head. The high-pressure leakage flow at the gap flows from the blade pressure surface to the suction surface can effectively suppress the low-pressure area at the impeller inlet. The flow rate of the high-pressure leakage flow increases with the gap width. Excessive gap width may cause a low-pressure zone at the inlet of the previous flow passage. These results could serve as a reference for the subsequent gap design to further improve the operating stability of the low specific speed centrifugal pump.
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Julfrianto, Julfrianto, and Edilla. "Implementation analysis of vacuum area gripping system in pick and place machinery in wooden door company." JTTM : Jurnal Terapan Teknik Mesin 4, no. 2 (2023): 172–83. http://dx.doi.org/10.37373/jttm.v4i2.574.
Full textAbstract:
Companies must grow in order to boost efficiency and production quality due to competition in the wood industry, particularly in the production of increasingly hard wooden doors. The issue that businesses face frequently is the occurrence of product flaws during the manufacture of wooden doors. A method for lifting, positioning, and moving door goods has been created by PT XYZ, one of the export-quality wooden door firms. By reducing product flaws, this study hopes to raise the quality of wooden doors. The pick and place machine's grasping system is the primary cause of the high prevalence of impairment. There are specific flaws in the door-gripping mechanism that increase the likelihood of product failures from falling and workplace accidents. After reworking the vacuum area gripping system, which uses suction technology, one of the Schmalz brands manufactured in Germany is outfitted with an external suction motor as a source of suction energy. The tool can lift loads up to 50 kg in accordance with specifications at a consistent speed, according to development results
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Dupuy, F., R. Mendonça, E. Costa, et al. "A CFD/experimental comparative database to feed a predictive model for ground vortex characteristics." IOP Conference Series: Materials Science and Engineering 1226, no. 1 (2022): 012011. http://dx.doi.org/10.1088/1757-899x/1226/1/012011.
Full textAbstract:
Abstract Most modern aircraft engines rely on the use of high Bypass Ratios (BPR) turbofans to achieve both high thrust and low specific fuel consumption. However, such configurations are prone to the formation of ground vortices during low-speed operations. This phenomenon arises under specific combinations of wind direction, velocity or inlet air speed, generating engine vibrations and leading to the suction of damaging abrasive particles. Its characterization in early design stages is crucial. In this work, a joint experimental and numerical exploration of operating conditions leading to ground vortex presence is carried out on a scaled wind tunnel configuration. Flow details are investigated for several working points obtained from a specific set of input parameters (intake speed, wind speed, ground clearance). A methodology suitable for both experimental and Computational Fluid Dynamics (CFD) works is developed to extract vortex characteristic quantities, based on a local pressure minimum and Q-criterion contours topology. A very good agreement is obtained when comparing vortex predictions stemming from CFD and experiments. This database shall be used to transpose experimental data probed outside of the nacelle to data within the nacelle using data analytics techniques, paving the way for future data driven predictive models.
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Kim, Hye In, Tae-Seong Roh, Hwanil Huh, and Hyoung Jin Lee. "Development of Ultra-Low Specific Speed Centrifugal Pumps Design Method for Small Liquid Rocket Engines." Aerospace 9, no. 9 (2022): 477. http://dx.doi.org/10.3390/aerospace9090477.
Full textAbstract:
With the growth of the satellite industry, the demand for a propulsion system for small launch vehicles and spacecraft has increased. Small liquid rocket engines may require Ultra-Low specific speed centrifugal pumps due to the low required thrust and volumetric flow rate and high combustion chamber pressure. Therefore, in this study, a design method of Ultra-Low specific speed centrifugal pumps for several hundred Newton class small liquid rocket engines was developed by combining various empirical formulas. In addition, centrifugal pump impellers were designed using the Stepanoff method, which is typically used in pump design, and the circular arc method. The most appropriate method for designing Ultra-Low specific speed centrifugal pumps was determined through a comparative analysis with other methods and validated through CFD. As a result, the pump designed using the proposed method exhibited a performance of pumping and suction superior to the Stepanoff method. Although the number of arcs did not considerably influence the pump performance, the single arc method was confirmed to be the most appropriate design approach in terms of the design productivity and simplicity.
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Lv, Weiling, Yang Zhang, Wenbin Zhang, et al. "Experimental Research on Pressure Pulsation and Flow Structures of the Low Specific Speed Centrifugal Pump." Energies 17, no. 18 (2024): 4730. http://dx.doi.org/10.3390/en17184730.
Full textAbstract:
The low specific speed centrifugal pump plays a crucial role in industrial applications, and ensuring its efficient and stable operation is extremely important for the safety of the whole system. The pump must operate with an extremely high head, an extremely low flow rate, and a very fast speed. The internal flow structure is complex and there is a strong interaction between dynamic and static components; consequently, the hydraulic excitation force produced becomes a significant factor that triggers abnormal vibrations in the pump. Therefore, this study focuses on a low specific speed centrifugal pump and uses a single-stage model pump to conduct PIV and pressure pulsation tests. The findings reveal that the PIV tests successfully captured the typical jet-wake structure at the outlet of the impeller, as well as the flow separation structure at the leading edge of the guide vanes and the suction surface. On the left side of the discharge pipe, large-scale flow separation and reverse flow happen as a result of the flow-through effect, producing a strong vortex zone. The flow field on the left side of the pressure chamber is relatively uniform, and the low-speed region on the suction surface of the guide vanes is reduced due to the reverse flow. The results of the pressure pulsation test showed that the energy of pressure pulsation in the flow passage of the guide vane occurs at the fBPF and its harmonics, and the interaction between the rotor and stator is significant. Under the same operating condition, the RMS value distribution and amplitude at fBPF of each measurement point are asymmetric in the circumferential direction. The amplitude of fBPF near the discharge pipe is lower, while the RMS value is higher. A complex flow structure is shown by the larger amplitude and RMS value of the fBPF on the left side of the pressure chamber. With the flow rate increasing, the energy at fBPF of each measurement point increases first and then decreases, while the RMS value decreases, indicating a more uniform flow field inside the pump.
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Jiang, Linglin, Houlin Liu, Yong Wang, Yanhong Mao, Runze Zhou, and Jianbin Gu. "Experimental Study on the Effect of Gas Volume Fraction on the Cavitation Performance of a Low-Specific-Speed Centrifugal Pump." Water 14, no. 5 (2022): 798. http://dx.doi.org/10.3390/w14050798.
Full textAbstract:
In order to study the cavitation performance of centrifugal pumps with low specific speeds under the condition of gas–liquid two-phase flow, a cavitation test rig for pumping gas–liquid two-phase flow was set up. The cavitation performance of the pump with a specific speed of 32 was studied. The variation of the head, pressure pulsation intensity, and vibration intensity with the cavitation allowance NPSHa (Net Positive Suction Head available) of the centrifugal pump were obtained at different inlet gas volume fraction (IGVF) conditions of 0, 1%, 2%, and 3%. The results show that the cavitation performance of a low-specific-speed centrifugal pump can be improved obviously in a certain liquid flow range when the IGVF is 1%, especially at a low liquid flow rate. When cavitation did not occur or the degree of cavitation was low, a lower IGVF can reduce pressure pulsation intensity at the pump outlet and the vibration intensity at the pump inlet under design flow rate and high flow rate conditions. Additionally, all performances of the low-specific-speed pump are more sensitive to gas when the liquid flow rate is low. The results can provide a reference for improving the cavitation performance of low-specific-speed pumps for transporting gas–liquid two-phase flow and single-phase liquids.
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Kampowski, Tim, Lara-Louise Thiemann, Lukas Kürner, Thomas Speck, and Simon Poppinga. "Exploring the attachment of the Mediterranean medicinal leech ( Hirudo verbana ) to porous substrates." Journal of The Royal Society Interface 17, no. 168 (2020): 20200300. http://dx.doi.org/10.1098/rsif.2020.0300.
Full textAbstract:
Haematophagous ectoparasites must ensure a reliable hold to their host during blood meals and, therefore, have evolved a broad spectrum of versatile and effective attachment mechanisms. The Mediterranean medicinal leech ( Hirudo verbana ), for example, uses suction on both smooth and textured air-tight substrates. However, preliminary studies showed that H. verbana is also capable of attaching itself to air-permeable substrates, where suction does not work. Using high-speed videography and mechanical tests, we comparatively investigated the attachment of H. verbana on both smooth and textured air-tight as well as on porous artificial substrates, also considering the influence of mucus on sucker surfaces. In general, the leech-specific locomotion cycle did not differ between the tested surfaces, and the leeches were able to reliably attach to both air-tight and porous substrates. From our results, we conclude that suction is presumably the primary attachment mechanism of H. verbana . However, secondary mechanisms such as mechanical interlocking with surface asperities and pores or capillary forces occurring at the interface between the mucus-covered suckers and the substratum are also employed. In any case, the rich repertoire of applicable attachment principles renders the organs of H. verbana functionally highly resilient.
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Pochylý, František, Pavel Jandourek, Simona Fialová, and Pavel Rudolf. "Analysis of the inlet recirculation in centrifugal pumps." IOP Conference Series: Earth and Environmental Science 1483, no. 1 (2025): 012042. https://doi.org/10.1088/1755-1315/1483/1/012042.
Full textAbstract:
Abstract Conference article is focused on theoretical and practical deepening of knowledge associated with inlet recirculation in centrifugal pumps, especially with higher specific speed pumps. The conditions of instability of the vortex structures and the causes of recirculation are studied theoretically and experimentally. The methodology is based on the analysis of the Navier-Stokes equations for an incompressible fluid depending on the boundary conditions. The result of the theoretical analysis is the design of various types of dampers in the suction part of the pump, to limit the occurrence of recirculation. Their effect is demonstrated experimentally in laboratory conditions. An article presents individual types of the vortex structures depending on the operating parameters of the pump, including its characteristics. The interest of the research is a plastic model of the pump with specific speed nq = 90 rpm which is made by 3D printing technology.
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Yang, Yang, Ling Zhou, Hongtao Zhou, et al. "Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test." Journal of Marine Science and Engineering 9, no. 2 (2021): 121. http://dx.doi.org/10.3390/jmse9020121.
Full textAbstract:
Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps.
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Mdee, Ombeni, Cuthbert Kimambo, Torbjorn Nielsen, and Joseph Kihedu. "Analysis of Performance Characteristics Predicted From Several Experimental Data and Conversion Methods for Pumps as Turbine Application Using Statistical Techniques." Tanzania Journal of Engineering and Technology 39, no. 2 (2020): 213–26. http://dx.doi.org/10.52339/tjet.v39i2.706.
Full textAbstract:
Different performance characteristics have been indicated when running centrifugal pumps in the reverse direction. The water flows from the discharge side of the pump to the suction side to run in the reverse direction and generate the mechanical rotational energy for the micro-hydropower plant. The current study evaluates the extent of variation of performance characteristics predicted by several experimental data from different pump-specific speeds and conversion methods. The performance characteristics discussed include the head, flow rate, efficiency and specific speed. The flow rate and head of a pump operating in pump mode divided with the characteristic of the pump operating in the reverse mode, at the best efficiency point, the resulting coefficient of determination (R 2 ) values were of 0.890 and 0.708, respectively. Also, the graph of head versus flow rate coefficients, which is a second- order polynomial function, has shown the value of R 2 of 0.954 for pump-specific speed ranging between 9 and 94 rpm. However, the pump in the reverse mode has smaller performance characteristics for efficiency and specific speed compared to the pump mode operation with R 2 of 0.966 and 0.999, respectively. Furthermore, schematic empirical statistical models were developed to predict the performance characteristics of several conversion methods using pump data obtained from the manufacturers.
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Ohta, Y., E. Outa, and K. Tajima. "Evaluation and Prediction of Blade-Passing Frequency Noise Generated by a Centrifugal Blower." Journal of Turbomachinery 118, no. 3 (1996): 597–605. http://dx.doi.org/10.1115/1.2836707.
Full textAbstract:
The blade-passing frequency noise, abbreviated to BPF noise, of a low-specific-speed centrifugal blower is analyzed by separating the frequency response of the transmission passage and the intensity of the noise source. Frequency response has previously been evaluated by the authors using a one-dimensional linear wave model, and the results have agreed well with the experimental response in a practical range of the blower speed. In the present study, the intensity of the noise source is estimated by introducing the quasi-steady model of the blade wake impingement on the scroll surface. The effective location of the noise source is determined by analyzing the cross-correlation between measured data of the blower suction noise and pressure fluctuation on the scroll surface. Then, the surface density distribution of a dipole noise source is determined from pressure fluctuation expressed in terms of quasi-steady dynamic pressure of the traveling blade wake. Finally, the free-field noise level is predicted by integrating the density spectrum of the noise source over the effective source area. The sound pressure level of the blower suction noise is easily predicted by multiplying the free-field noise level by the frequency-response characteristics of the noise transmission passage.
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Checcucci, Matteo, Federica Sazzini, Michele Marconcini, et al. "Assessment of a Neural-Network-Based Optimization Tool: A Low Specific-Speed Impeller Application." International Journal of Rotating Machinery 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/817547.
Full textAbstract:
This work provides a detailed description of the fluid dynamic design of a low specific-speed industrial pump centrifugal impeller. The main goal is to guarantee a certain value of the specific-speed number at the design flow rate, while satisfying geometrical constraints and industrial feasibility. The design procedure relies on a modern optimization technique such as an Artificial-Neural-Network-based approach (ANN). The impeller geometry is parameterized in order to allow geometrical variations over a large design space. The computational framework suitable for pump optimization is based on a fully viscous three-dimensional numerical solver, used for the impeller analysis. The performance prediction of the pump has been obtained by coupling the CFD analysis with a 1D correlation tool, which accounts for the losses due to the other components not included in the CFD domain. Due to both manufacturing and geometrical constraints, two different optimized impellers with 3 and 5 blades have been developed, with the performance required in terms of efficiency and suction capability. The predicted performance of both configurations were compared with the measured head and efficiency characteristics.
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Yokoi, T., D. Kang, M. Nohmi, T. Tsuneda, J. Okajima, and Y. Iga. "Visualization of rotating cavitation in a centrifugal pump." Journal of Physics: Conference Series 2217, no. 1 (2022): 012019. http://dx.doi.org/10.1088/1742-6596/2217/1/012019.
Full textAbstract:
Abstract In this study, unsteady cavitation in a centrifugal pump that had 3 blades was visualized in experiments. Cavitation behavior was photographed by using a high-speed camera from the axial direction. To observe rotating cavitation, its aspects were visualized using a high-speed camera. The experiment was performed at rotational speed of 825 rpm with a centrifugal pump under reduced pressure. Rotating cavitation occurred on the suction side of blades under the condition of flow rates lower than the best efficiency point. In addition, observed rotating cavitation was super-synchronous rotating cavitation, which rotates at a faster speed than the impeller in absolute coordinate form. As a result of frequency analysis of the brightness value on the channel, propagation velocity ratios, which is the ratio of the propagation velocity of the cavity to the rotational velocity of the impeller were 1.2 - 1.3. It was confirmed that the propagation velocity ratio of rotating cavitation in the centrifugal pump is close to that of rotating cavitation in the inducer even when the specific speed and Reynolds number are different.
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Lehr, Christian, Andreas Linkamp, Daniel Aurich, and Andreas Brümmer. "Simulations and Experimental Investigations on the Acoustic Characterization of Centrifugal Pumps of Different Specific Speed." International Journal of Turbomachinery, Propulsion and Power 4, no. 3 (2019): 16. http://dx.doi.org/10.3390/ijtpp4030016.
Full textAbstract:
Subject of discussion are simulations and experimental investigations on the acoustic characterization of three single stage centrifugal pumps of different specific speed. In operation, these pump-types generate pressure pulsation at blade passing frequency, primarily due to rotor-volute-interaction. In order to determine the acoustic excitation it is necessary to know about the pumps’ acoustic transmission parameters. In this paper, a one-dimensional numerical model for transient time-domain simulation is presented, which takes into account the pump geometry as well as the volutes’ structural behaviour by means of the local effective speed of sound. Numerical results for the transmission characteristics of the three different pumps are shown in terms of scattering matrices and evaluated against parameters calculated from measurement results. The experimental analyses are carried out using dynamic pressure sensors in both the suction and the discharge pipe. Assuming solely plane wave propagation, the complex acoustic field on each side is evaluated independently. The so called “two source” method is then used to determine the transmission parameters of the pumps in standstill for a range of frequencies experimentally. Subsequently, the acoustic excitation at varying rotational speed is evaluated by means of measurements at the pumps in operation and presented as monopole and dipole source types for cavitation-free conditions.
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Zhang, Ning, Bo Gao, Zhong Li, and Qifeng Jiang. "Cavitating flow-induced unsteady pressure pulsations in a low specific speed centrifugal pump." Royal Society Open Science 5, no. 7 (2018): 180408. http://dx.doi.org/10.1098/rsos.180408.
Full textAbstract:
With the development of cavitation, the high-energy pressure wave from a cavitation bubble collapsing is detrimental to the stable operation of centrifugal pumps. The present paper concentrates on pressure pulsations under cavitation conditions, and pressure amplitudes at the blade-passing frequency ( f BPF ) and RMS values in the 0–500 Hz frequency band are combined to investigate cavitation-induced pressure pulsations. The results show that components at f BPF always dominate the pressure spectrum even at the full cavitation stage. For points P1–P7 on the volute side wall, with a decreasing cavitation number, the pressure energy first remains unchanged and then it rises rapidly after the critical point. For point In1 in a volute suction pipe located close to the cavitation region, the pressure energy changes slightly at high cavitation numbers; then for a particular cavitation number range, the pressure energy decreases, and finally increases again. For different flow rates, the pressure energy at the critical point is much lower than the initial amplitude at the non-cavitation condition for In1. This demonstrates that the cavitation cloud in the typical stage is partially compressible, and the emitted pressure wave from a collapsing cavitation bubble is absorbed and attenuated significantly. Finally, this leads to the pressure energy decreasing rapidly for the measuring point In1 near the cavitation region.
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Li, Wen-Guang, and Yu-Liang Zhang. "Computational cavitating viscous liquid flows in a pump as turbine and Reynolds number effects." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, no. 3 (2018): 536–50. http://dx.doi.org/10.1177/0954408918770057.
Full textAbstract:
Cavitating flows of viscous oils in an experimental centrifugal pump with low specific speed are modeled and simulated by using the time-averaged Navier–Stokes equations and standard [Formula: see text] turbulence model as well as full cavitation model based on the computational fluid dynamics method, when the pump operates in the reverse direction as turbine to generate power. The cavitation characteristics are identified at part-load, best efficiency and over-load points and five viscosities. Effects of viscosity on net positive suction head required are clarified. Net positive suction head required correction factor and conversion factor curves are obtained and correlated to impeller Reynolds number. The flow and cavitation models are validated with the existing experimental results and empirical correlations. Pressure and helix angle profiles at the draft tube entrance, cavity shape, swirling flow pattern in the draft tube, and the pressure coefficient distribution over the blade surfaces are presented. The presented results can be useful for design, selection, performance prediction, and impeller redesign of a pump as turbine.
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Zangeneh, M., A. Goto, and T. Takemura. "Suppression of Secondary Flows in a Mixed-Flow Pump Impeller by Application of Three-Dimensional Inverse Design Method: Part 1—Design and Numerical Validation." Journal of Turbomachinery 118, no. 3 (1996): 536–43. http://dx.doi.org/10.1115/1.2836700.
Full textAbstract:
This paper describes the design of the blade geometry of a medium specific speed mixed flow pump impeller by using a three-dimensional inverse design method in which the blade circulation (or rVθ) is specified. The design objective is the reduction of impeller exit flow nonuniformity by reducing the secondary flows on the blade suction surface. The paper describes in detail the aerodynamic criteria used for the suppression of secondary flows with reference to the loading distribution and blade stacking condition used in the design. The flow through the designed impeller is computed by Dawes’ viscous code, which indicates that the secondary flows are well suppressed on the suction surface. Comparison between the predicted exit flow field of the inverse designed impeller and a corresponding conventional impeller indicates that the suppression of secondary flows has resulted in substantial improvement in the exit flow field. Experimental comparison of the flow fields inside and at exit from the conventional and the inverse designed impeller is made in Part 2 of the paper.
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Wang, Biaobiao, Haoyang Zhang, Fanjie Deng, Chenguang Wang, and Qiaorui Si. "Effect of Short Blade Circumferential Position Arrangement on Gas-Liquid Two-Phase Flow Performance of Centrifugal Pump." Processes 8, no. 10 (2020): 1317. http://dx.doi.org/10.3390/pr8101317.
Full textAbstract:
In order to study the internal flow characteristics of centrifugal pumps with a split impeller under gas-liquid mixed transportation conditions, this paper conducted a steady calculation of the flow field in the centrifugal pump under the conditions of different inlet gas volume fractions based on the Eulerian-Eulerian heterogeneous flow model, using air and water as the working media and the Schiller Nauman model for the interphase resistance. This paper takes a low specific speed centrifugal pump as the research object, through the controlling variables, using the same pump body structure and pump body geometric parameters and setting three different arrangements of long and short blades (each plan uses the same long and short blades) to explore the influence of the short blade arrangement on the low specific speed centrifugal pump performance under a gas-liquid two-phase flow. The research results show that, under pure water conditions, the reasonable arrangement of the short blade circumferential position can eliminate the hump of the centrifugal pump under low-flow conditions, can make the flow velocity in the impeller more uniform, and can optimize the performance of the pump. Under the design conditions and the gas-liquid two-phase inflow conditions, when the circumferential position of the short blades is close to the suction surface of the long blades, some of the bubbles on the suction surface of the long blade can be broken under the work of the pressure surface of the short blade and flow out of the impeller with the liquid, which improves the flow state of the flow field in the impeller.
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Gan, Gongchang, Wenhao Shi, Jinbao Yi, Qiang Fu, Rongsheng Zhu, and Yuchen Duan. "The Transient Characteristics of the Cavitation Evolution of the Shroud of High-Speed Pump-Jet Propellers under Different Operating Conditions." Water 15, no. 17 (2023): 3073. http://dx.doi.org/10.3390/w15173073.
Full textAbstract:
Pump-jet propellers are currently the mainstream propulsion method for underwater vehicles, and cavitation is an important factor limiting the high speed and miniaturization of pump-jet propellers. In order to explore the cavitation performance of high-speed pump-jet propellers, based on the modified SST turbulence model and the Zwart cavitation model, a three-dimensional numerical simulation of unsteady internal cavitation flow was carried out by comparing the impeller with specific speed ns = 1920 using FLUENT 2020R2 software. At the same time, the occurrence and development process of cavitation under 0.95 Q, 1.0 Q, and 1.05 Q conditions were analyzed (Q is the mass flow), the changes in gas volume fraction in the impeller channel were captured, the distribution characteristics of cavitation under different NPSH values were explored, and the change law of cavitation with time was determined. The results show that, when NPSH dropped to 95 m, the impeller cavitation first occurred under the 1.05 Q operating condition, and the impeller cavitation volume fraction was 0.0379525. When NPSH dropped to 85 m, the impeller cavitation occurred under the 1.0 Q operating condition, and the impeller cavitation volume fraction was 0.0185164. When NPSH dropped to 80 m, the impeller cavitation occurred under the condition of 0.95 Q, and the volume fraction of the impeller cavitation was 0.013541. The high-speed pump-jet propeller had better anti-cavitation ability with a small flow rate. The cavitation distribution law under the three operating conditions was similar; cavitation was first generated on the impeller inlet edge and near the shroud, and the vacuoles with large volumes were mostly concentrated on the impeller inlet side. As the NPSH gradually decreased, the entire flow channel was gradually occupied by vacuoles. As the flow decreased, the corresponding NPSH also decreased. When NPSH dropped to 50 m, the volume fraction of the impeller under all three operating conditions reached around 0.4. As the cavitation only occurred on the suction surface, the volume fraction of the cavitation on the suction surface exceeded 0.8, at which time the impeller had already undergone severe cavitation. Within a complete cycle, bubbles first appeared at the inlet edge of the impeller (measured near the shroud) and gradually spread toward the middle and rear of the impeller, ultimately covering the suction surface of the impeller. Under the design condition, the experimental results of the model pump were consistent with the numerical simulation results, and the error was only 2.68%, thus verifying the reliability of the numerical simulation. The research results provide a reference for the in-depth study of the cavitation performance of high-speed pump-jet propellers and provide a good theoretical basis and practical significance in the engineering field for the high-speed and miniaturization process of high-speed pump-jet propellers.
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Li, Bowen, Xiaojun Li, Xiaoqi Jia, Feng Chen, and Hua Fang. "The Role of Blade Sinusoidal Tubercle Trailing Edge in a Centrifugal Pump with Low Specific Speed." Processes 7, no. 9 (2019): 625. http://dx.doi.org/10.3390/pr7090625.
Full textAbstract:
Pressure pulsations may cause high-amplitude vibrations during the process of a centrifugal pump. The trailing edge shape of the blade has a critical influence on the pump’s pressure fluctuation and hydraulic characterization. In this paper, inspired by the humpback whale flipper, the authors research the impact of applying the sinusoidal tubercles to the blade suction side of the trailing edge. Numerical calculation and experiments are carried out to investigate the impact of the trailing edge shape on the pressure pulsations and performance of a centrifugal pump with low specific speed. Two designed impellers are tested, one is a sinusoidal tubercle trailing edge (STTE) impeller and the other is the original trailing edge (OTE) prototype. The detailed study indicates that the sinusoidal tubercle trailing edge (STTE) reduces pressure pulsation and enhances hydraulic performance. In the volute tongue region, the pressure pulsation amplitudes of STTE at fBPF decrease significantly. The STTE impeller also effectively changes the vortex structure and intensity in the blade trailing edge area. This investigation will be of great benefit to the optimal design of pumps.
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Chaichan, Miqdam Tariq. "EGR Effect On Performance of a Spark Ignition Engine Fueled with Blend of Methanol-Gasoline." Wasit Journal of Engineering Sciences 1, no. 2 (2013): 110–92. http://dx.doi.org/10.31185/ejuow.vol1.iss2.19.
Full textAbstract:
This paper examines the results of performance of a single cylinder spark- ignition engine fuelled with 20% methanol +80% gasoline (M20), compared to gasoline. The experiments were conducted at stoichiometric air–fuel ratio at wide open throttle and variable speed conditions, over the range of 1000 to 2600 rpm. The tests were conducted at higher useful compression ratio using optimum spark timings and adding recirculated exhaust gas with 20% to suction manifold.
 The test results show that the higher compression ratio for the tested gasoline was 7:1, 9.5:1 for M20 and 9:1 for M20 with added EGR. M20 at higher useful compression ratio (HUCR) and optimum spark timing (OST) characteristics are significantly different from gasoline. Within the tested speed range, M20 consistently produces higher brake thermal efficiency by about 6%. Also it resulted in approximately 3.06% lower brake specific fuel consumption compared with gasoline. Adding EGR to M20 caused reduction in HUCR and advancing the OST. This addition increased brake specific fuel consumption (BSFC), reduced brake thermal energy, volumetric efficiency and exhaust gas temperatures.
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Zhao, Bo. "Investigation of Fiber Diameter in Spunbonding Process via Mathematical Modeling." Applied Mechanics and Materials 33 (October 2010): 567–70. http://dx.doi.org/10.4028/www.scientific.net/amm.33.567.
Full textAbstract:
The polymer air-drawing model of polypropylene (PP) spunbonding nonwovens has been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have been studied. The effects of the processing parameters on the final filament fiber diameter have also been investigated. A lower polymer throughput rate, a higher polymer melt temperature, a higher primary air temperature, a higher primary cool air velocity, and a higher air suction speed can all produce finer fibers, while fiber diameters first decrease with increases in the venturi gap and then increase with increases in the venturi gap.
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Walsh, Christian, and Parmar Bhavesh. "CFD Analysis on the Performance of Centrifugal Pump." Research and Applications of Thermal Engineering 8, no. 1 (2025): 32–44. https://doi.org/10.5281/zenodo.15221887.
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<em>The CFD-code FLUENT, version 5.4, was used to analyze the flow of two test pumps of the end-suction volute type, one with a low specific speed and the other with a medium specific speed. Head as a function of flow rate at constant rotational speed is known for both, according to experiments. For the analysis of turbomachinery flows, FLUENT offers three different calculation methods: the Multiple Reference Frame technique (MRF), the Mixing Plane method (MP), and the Sliding Mesh method (SM). In all three methods, the rotor flow is computed in a revolving reference frame, whereas the stator flow is approximated in an absolute reference frame. While unsteady flow equations are solved using the SM method, stable flow equations are solved using the MRF and MP approaches. Physical approximations are not introduced by the SM technique. The unstable interaction between the rotor and stator is approximated by the steady approaches. However, the cost of the unsteady method is often 30 to 50 times more than that of the steady method. It is discovered that for flows that are far from the optimal efficiency point, the MRF and MP approaches produce entirely inaccurate flow field predictions. Because of this, the steady approaches cannot be used to predict performance in general.</em>
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Ma, Yang, Yaodong Zhou, and Zhenkun Zhu. "The Investigation of Two-Phase Expansion Performance with Indicator Diagram in a Twin-Screw Expander." Processes 11, no. 6 (2023): 1862. http://dx.doi.org/10.3390/pr11061862.
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Volumetric expanders are proven to be more suitable for small-scale waste heat recovery applications because of their simplicity, reliability, lower rotational speed and lower cost. Unlike turbines, volumetric expanders can work in the two-phase fluid state, which broadens their application fields. To investigate the two-phase performance of volumetric expanders, a specific twin-screw expander was chosen and modeled. The leakage loss and the suction pressure loss were primary concerns in this research. The two-phase expansion process in the expander is presented in detail using the developed mathematical model with an indicator diagram. The influence of several factors, including inlet vapor quality, rotational speed and intake pressure, are investigated. The influence mechanism of the vapor phase and the liquid phase on expander performance is clarified. In brief, this paper presents an illustrative understanding of the two-phase expansion process in twin-screw expanders.
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Ismail, Mohd Azlan, Al Khalid Othman, Shahidul Islam, and Hushairi Zen. "End Suction Centrifugal Pump Operating in Turbine Mode for Microhydro Applications." Advances in Mechanical Engineering 6 (January 1, 2014): 139868. http://dx.doi.org/10.1155/2014/139868.
Full textAbstract:
This paper reviews the current research works on the end suction centrifugal pump coupled with induction generator running in turbine mode for microhydro application. The information can be used by practicing engineers, researchers, and plant managers to understand the potential of pump running as turbine. Review on experimental and simulation works was carried out encompassing end suction single stage low specific speed which is less than 10 kW. This is followed by review of their efficiency improvement through modifications. The results show that centrifugal pump can operate in turbine modes without any modification on mechanical components. However, to achieve the best efficiency point (BEP), it requires higher flow rate and head than pumping rating. Efficiency improvement is viable through geometric modification to improve hydraulic characteristic. The studies also show that pump as turbine (PAT) can be directly coupled with modified induction motor as generator by adding capacitor and electric control system, regulating voltage and frequency at the output terminal. It was found that PAT offers the best low cost solution for microhydro application especially for third world countries that do not have local microhydro manufacturer.
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Lemell, Patrick, Christoph Lemell, Peter Snelderwaard, Michaela Gumpenberger, Robert Wochesländer, and Josef Weisgram. "Feeding patterns ofChelus fimbriatus(Pleurodira:Chelidae)." Journal of Experimental Biology 205, no. 10 (2002): 1495–506. http://dx.doi.org/10.1242/jeb.205.10.1495.
Full textAbstract:
SUMMARYThe kinematics of feeding on fish have been studied in the aquatic feeding specialist Chelus fimbriatus, the fringed turtle, to provide a basic description of complete feeding cycles. Anatomical findings supplement the kinematic results. High-speed video (500 frames s-1) recordings and X-ray film (150 frames s-1) are used to analyse the kinematic variables characterizing head, hyoid, oesophageal and prey movements. The high velocities, especially of mouth opening, the forward thrust of the head and suction of the prey, are unique among turtles and comparable with those of aquatic salamanders and certain fishes (unidirectional feeders, in contrast to Chelus fimbriatus). The expandability of the pharynx and the anterior half of the oesophagus enables a specific type of unidirectional flow, at least during the early stages of the feeding cycle. This considerably improves the feeding performance compared with that of other aquatic turtles. The streamlined shape of the skull, the large hyoid apparatus, the highly reduced tongue and the extremely distensible oesophagus support the kinematics to a great extent, making C. fimbriatus a specialized suction feeder that can be regarded as one endpoint in the feeding evolution of aquatic reptiles.