Volume 3B: Fluid Applications and Systems最新文献

{"title":"Mitigation of Flow-Induced Pressure Fluctuations in a Francis Turbine Using Water Injection","authors":"Muhannad Altimemy, Bashar Attiya, Cosan Daskiran, I-Han Liu, A. Oztekin","doi":"10.1115/ajkfluids2019-4867","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4867","url":null,"abstract":"\u0000 Computational fluid dynamics simulations are conducted to characterize the spatial and temporal characteristics of the turbulent flow fields inside Francis turbine operating at the design and partial load regimes. High-fidelity large eddy simulations turbulence model is applied to investigate the flow-induced vibrations in the draft tube of the unit. The water injection at 4% rate from the runner cone is implemented to control the flow-induced pressure fluctuations. The simulations are conducted at the turbine design point and two partial load operations with and without water injection. It has been demonstrated that the water injection has a profound influence in the turbulent flow structure and the pressure field inside the draft tube at the partial load operating conditions. To evaluate the effectiveness of the water injection techniques in mitigating flow-induced fluctuations, the probes at various locations along the wall of the draft tube are used to monitor the pressure signals. It appears to be a reduction in the level of pressure fluctuations by the water injection at both partial load operating regimes. However, we could not draw a firm conclusion about the level of mitigation of flow-induced vibrations. Simulations should be carried out for much longer flow time. Water injection hardly influenced the unit power generation. Hence water injection can be employed effectively without a major liability on the power generation.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"87 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114128311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Transient Characteristics Analysis of Pump During Rapid Valve Opening and Closing","authors":"Shuai Yang, Shiyang Li, Dazhuan Wu, Kai Zhang, Qiao Li, Xu Zhongtian","doi":"10.1115/ajkfluids2019-5180","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5180","url":null,"abstract":"\u0000 The dynamic characteristics of pump response to transient events were investigated by combining the Method of Characteristic (MOC) and Computational Fluid Dynamics (CFD) together. In a typical pump–pipeline–valve system, similar to the reactor system, the pump is treated as three-dimensional CFD model using Fluent code, whereas the rest is represented by one-dimensional components using MOC code. Meanwhile, a description of the coupling theory and procedure ensuring proper communication within the two codes is given. Then the pump transient characteristics caused by downstream valve closing and opening were analyzed and compared with the steady characteristic to study the effect of fluid inertia on the pump transient performance. It was found that the H-Q curve in transient operation evidently deviates from the steady-state value and shows two distinct patterns of deviation, and the cause of the deviation was further explained by the comparison of pump internal and external characteristics. All the results showed that MOC–CFD is an efficient and promising way for simulating the interaction between pump model and piping system.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122368417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research on the Performance of Check Valve at a Long Distance Pumping System","authors":"H. Bi, Honggang Fan, Bin Cao, Yu Xu","doi":"10.1115/ajkfluids2019-5668","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5668","url":null,"abstract":"\u0000 Experimental investigations of dynamic characteristics of the check valve are a contribution work to provide boundary condition to check valve mathematical simulation. The closure process of the check valve was tested. The changing processes of inlet and outlet pressure were performed.\u0000 Based on the experiment system and the measured quantities, mathematical models were established to study the test. Numerical calculation was mainly focus on when valve starting to close and the closing characteristic time.\u0000 The paper simulated the different minimum velocities that the valve started to close at. Simulation results approximated to test data when the check valve started to close at a larger flow velocity and a shorter closing characteristic time. The closing characteristic time was discussed when check valves closing on a certain velocity.\u0000 Following the closure rule of check valve got during the simulation, the paper studied the check valve acting on a long distance pumping system. Two part contents were studied: only check valve arranged along pipeline, both air admission valve and check valves arranged.\u0000 Along the pipeline seven check valves were arranged, the pump power failure condition was calculated and check valves were closed because of the flow velocity decreased. The result showed negative pressure was large when installed just a finite number of check valves along pipeline.\u0000 Gas admission valves were arranged to negative pressure prevention. Two check valves were respectively arranged at the pump outlet and pipeline. The pressure transient peak at pump outlet will be dropped a lot with the check valve at pipeline closed; the maximum pressure transient peak along pipeline is appeared at check valve outlet on the pipeline under the pump power failure condition. The negative pressure in front pipes could be prevented by installing gas admission valve. Through the check valves and gas admission valves combined action, both the pressure and backflow were well controlled.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121287264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Visualization of Gas-Liquid Flow Patterns in a Centrifugal Rotor","authors":"H. Stel, E. Ofuchi, Rafael F. Alves, S. Chiva, R. Morales","doi":"10.1115/ajkfluids2019-5029","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5029","url":null,"abstract":"\u0000 Centrifugal pumps operating with gas-liquid flows can undergo severe performance degradation. This can be attributed to an effect of the gas phase on the liquid flow orientation in the pump impeller channels, which induces additional hydraulic losses that negatively affect the delivered head and flow rate. Effort to investigate the effect of many operating parameters on the pump performance under multiphase flows can be found on numerous experimental investigations. Few studies, however, bring together flow visualization to understand the physics behind the behavior of centrifugal pumps with gas-liquid flows. One issue is that pumps involve rotating parts, metallic casing and limited visual access, sometimes making it hard to interpret flow patterns and to understand complex phenomena, such as bubble breakup and coalescence. Such issues usually lead to unsatisfactory image quality, which in turn makes it difficult to extract quantitative data from the obtained images, such as gas volume fraction and bubble size distribution. In an attempt to overcome many difficulties of previous investigations, this work presents an experimental study aimed to visualize gas-liquid flow patterns in a centrifugal rotor prototype using a novel approach. The experimental apparatus uses a plane and transparent rotor, assembled with an intake pipe and a discharge chamber by means of a dynamic seal system that dismisses the use of an enclosing pump casing. This makes possible to use back illumination of the impeller for visualization, which in turn is done by using a camera attached to the impeller axis for filming in a rotating frame of reference. This setup, which is new in the open literature, provides high image contrast and sharpness for clear interpretation of the flow patterns found inside the rotor channels for a wide range of operating conditions. This advantage, in turn, allows using image processing for quantitative assessment of gas volume fraction distributions. Pressure rise versus flow rate curves are measured together to investigate the rotor performance degradation associated with the gas-liquid flow patterns for a range of liquid and gas flow rates. Information obtained with the designed experimental setup at controlled conditions help not just to bring further understanding to the complex phenomena involved with multiphase flows in rotating devices, but also in the direction of validating a numerical model for reliable simulations of gas-liquid flows in centrifugal pumps, which is lacking in the current literature.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114996795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large Eddy Simulation of a Submerged Vortex in a Simplified Computational Model","authors":"Y. Yamade, C. Kato, T. Nagahara, J. Matsui","doi":"10.1115/ajkfluids2019-5205","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5205","url":null,"abstract":"\u0000 The flow structures of a submerged vortex that appears in a model pump sump were numerically investigated by performing large eddy simulation (LES) of a model vortex in a simplified computational model with a sufficiently fine grid that could resolve the vortex core. The simplified model is designed to simulate the flow under the bellmouth in a model pump sump. The model pump sump is composed of a 2,500 mm-long water channel of rectangular cross section with a width of 300 mm, a water height of 150 mm and a vertical suction pipe with a diameter of 100 mm installed at its downstream end. Our previous large eddy simulations, which used approximately 2 billion grids and were applied to the model pump sump, have fully clarified the origin and formation mechanism of a submerged vortex. In these computations, however, the static pressure in the vortex core decreased only by as much as 4 kPa at a channel velocity of 0.37 m/s. The decrease in the static pressure was far smaller than the one for which one can expect initiation of cavitation in the vortex core. The static pressure drop was most likely to be underpredicted in our previous LES. Insufficient grid resolution was assumed to be one of the reasons for this underprediction. In the present study, LES with a sufficiently fine grid was applied to the simplified computational model that represents the stretch of a submerged vortex under a constant acceleration of the vertical velocity. Case studies for which the grid resolution was varied between 3.25 and 150 micrometres were performed while the size of the vortex core appeared in the simplified model was 500 micrometres. As a result, we confirmed the grid resolution finer than 15 micrometres is needed to resolve the vortex core with a diameter of 500 micrometres. Vertical and tangential velocities obtained by averaging those distributions of a submerged vortex that was computed in our previous LES were prescribed at the bottom wall of the computational domain as the inlet boundary conditions. In the present LES with the grid resolution finer than 15 micrometres, the static pressure decreased by more than 100 kPa. In addition, the parametric studies where the initial swirl numbers were changed have fully clarified the change in the dynamics of a submerged vortex. We found that a strong submerged vortex appears only at a relatively small range of the swirl-number from 1 to 3.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128612902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research of Unsteady Characteristics of Torque in Centrifugal Pumps","authors":"Luo Yin, Han Yuejiang, Dong Jian","doi":"10.1115/ajkfluids2019-4914","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4914","url":null,"abstract":"\u0000 Torque is one of the most important operating parameters of centrifugal pumps which reflects the internal flow rate of centrifugal pumps. In order to explore the unsteady characteristics of torque of centrifugal pumps based on sensorless monitoring technology, a series of accurate measurements of torque of experimental centrifugal pump were carried on based on the test data collected. The frequency characteristic spectrums of torque were established and analyzed under different operation conditions. The analysis results shows that the torque of the experimental centrifugal pump varies approximately linearly with the increase of flow rate in time domain. Besides, a gentle trend of the torque fluctuation is also founded. Through frequency domain, the analysis results show that the dominant frequencies under different flow rates and cavitation conditions are all axial frequencies. The magnitude of amplitude has nothing to do with the flow rates or the cavitation conditions, and the internal flow rates of centrifugal pumps have no obvious effects on the fundamental frequency of torque of centrifugal pumps.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121519870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predictive Model for Two-Phase Flow Performance of Mixed Flow Pumps","authors":"Abhay V. Patil, Burak Ayyildiz, S. Pirouzpanah, Adolfo Delgado, G. Morrison","doi":"10.1115/ajkfluids2019-5486","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5486","url":null,"abstract":"\u0000 Multiphase pumps are increasingly being used to transport gas-liquid multiphase flow in the oil and gas industry. Complexity of two-phase flow interaction and varying designs of multiphase pumps pose significant challenges to developing generalized performance prediction tool similar to the affinity laws. The goal of this study is to characterize the performance of two multiphase pumps with different specific speeds using experimental data to develop generalized prediction models. Initially, the performance is investigated in the terms of head, power input and efficiency for different Gas Volume Fractions (GVF). Dimensional analysis is performed to evaluate the effect of pump geometry and GVF. Head degradation due to the presence of gas is presented in the terms of dimensionless numbers. These numbers represent the systematic change in the energy loss due to two phase flow interaction and inherent characteristics of the pump design. This is utilized to develop a generalized model for two phase flow. The study is concluded by validating the model using experimental data.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125346366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of the Pump, Dissipation and Inverse Turbine Operating Modes Using the CATHARE-3 One-Dimensional Rotodynamic Pump Model","authors":"L. Matteo, A. Dazin, N. Tauveron, F. Cerru","doi":"10.1115/ajkfluids2019-4961","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4961","url":null,"abstract":"\u0000 A predictive transient one-dimensional rotodynamic pump model is currently developed into the CATHARE-3 thermal-hydraulic system code at CEA Saclay, France. Flow is computed in each part of the pump (suction, impeller, diffuser, volute and discharge pipe) based on the definition of a mean stream line. Several cells are used to mesh each part of the rotodynamic pump, which makes this model different from usually called “1D models”. In this study, the model is tested on a medium specific speed centrifugal pump in every operating modes encountered in the first quadrant (positive flow rate and rotational speed). A flow rate evolution is performed at the nominal rotational speed and also at rotational speed equal to zero in order to produce complete first quadrant homologous curves. Relative discrepancy between computation and experiment is respectively less than 10% and 15% on the whole obtained homologous head and torque curves.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116006169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of Turbulence Models in Transient Simulations of Inducers Under Steady Operation","authors":"Björn Gwiasda, M. Mohr, Dennis Herrmann-Verspagen, M. Böhle","doi":"10.1115/ajkfluids2019-4640","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4640","url":null,"abstract":"\u0000 A significant uncertainty in full transient 3D-CFD simulations of inducers is the used turbulence model. To investigate the influence of different turbulence models (Spalart-Allmaras, SST, SSG) on the transient effects experiments and simulations are performed for two inducers. In this paper the results of simulations are represented that are performed under noncavitating conditions to exclude the additional influence of the cavitation model in order to gain an isolated understanding for the influence of turbulence models. Comparison of transient data from simulations as well as experiments determines the influence of the turbulence model. For the investigations two different inducers are designed with different leading edges. One inducer with a straight leading edge and one with a back swept leading edge. All other geometrical parameters are kept constant, such as the hub contour which is purely axial.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127689710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsteady Flow in the Vaned Diffuser of a Low Specific Speed Centrifugal Pump With an Unshrouded Impeller","authors":"Asuma Ichinose, Tomoki Takeda, K. Miyagawa, Y. Ogawa, H. Negishi, Kazuki Niiyama","doi":"10.1115/ajkfluids2019-5599","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5599","url":null,"abstract":"\u0000 The unsteady internal flow in a low specific speed centrifugal pump was experimentally and numerically investigated. Unshrouded impellers enable high head designs but on the other hand, they exhibit complicated internal flow and an efficiency decline compared to shrouded impellers. Furthermore, the complicated impeller outlet flow induces unsteady internal flow in the vaned diffuser. Therefore, a detailed investigation of the internal flow is required in order to increase the efficiency of these low specific speed centrifugal pumps. The aims of this paper are to clarify the loss mechanisms in the impeller and to investigate the effect of impeller outlet flow to the diffuser internal flow at the design point. The detailed pump internal flow is investigated using unsteady computation, which enables the computation of the 3D flow pattern. The reversed flow and the secondary flow are induced by the tip leakage flow, and this creates a high loss region in the blade-to-blade region. On the other hand, the mixing effect is remarkable at the impeller outlet, and this affects the creation of the wake. This flow behavior makes the internal flow of the diffuser unsteady and the diffuser performance fluctuates due to the impeller wake at the design point.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"237 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134543614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}