Volume 3B: Fluid Applications and Systems最新文献

{"title":"Numerical Analysis of Contraction Geometry Effects on Cavitation Choking in a Piping System","authors":"M. Nohmi, S. Kagawa, T. Tsuneda, W. Tsuru, K. Yokota","doi":"10.1115/ajkfluids2019-5359","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5359","url":null,"abstract":"\u0000 There is a contraction portion in the water supply pipe line system, and cavitation may occur in the contraction when the flow velocity is increased. Such a situation occurs widely in the throat of the fluid machineries and in the vicinity of the valve body of the valve. In operation of the valve, it is well known that a phenomenon occurs in which the flow rate does not increase even if the static pressure difference upstream and downstream of the valve is increased due to the growth of cavitation in the contraction, which is well known as choking . It is not clear what phenomena occurs when cavitation surge occurs in the pipe system in the situation where choking is occurring in the contraction. In this study, cavitation CFD was performed on pipes those have three different geometry contractions. It was revealed that choking occurred when cavitation occurred in any shape. Also, in the case with the sharp contraction part and the sudden expansion, the flow fluctuation at the upstream of the contraction is much weaker than that at the downstream, but in the contraction with the bent part where the centrifugal force acts on the flow, the flow fluctuation at the upstream was found to be strong.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133833225","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":"Validation of a Developed Assessment Procedure for the Functional Performance of Wastewater Pumps","authors":"M. Poehler, Ümit Hasirci, Tim Rese, P. Thamsen","doi":"10.1115/ajkfluids2019-5439","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5439","url":null,"abstract":"\u0000 To date, there is no standardised test available, which assesses the actual performance of a pump for wastewater (especially its clog-resistance) as well as providing references about its efficiency. The developed testing procedure presented in this paper can display the different levels of performance for different pumps. The functionality of the pump, together with its efficiency is aggregated to the Functional Efficiency Index (FEI). The developed testing procedure is validated with two pumps from the field. Both are considered to be very prone to clogging by their respective wastewater network operators.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121847747","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":"Improvement of Film Cooling Effectiveness in the Gas Turbine Endwall by Use of Optimization Framework","authors":"D. Hata, Kazuto Kakio, Y. Kawata, Masahiro Miyabe","doi":"10.1115/ajkfluids2019-5368","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5368","url":null,"abstract":"\u0000 Recently, the number of gas turbine combined cycle plants is rapidly increasing in substitution of nuclear power plants. The turbine inlet temperature (TIT) is constantly being increased in order to achieve higher effectiveness. Therefore, the improvement of the cooling technology for high temperature gas turbine blades is one of the most important issue to be solved.\u0000 In a gas turbine, the main flow impinging at the leading edge of the turbine blade generates a so called horseshoe vortex by the interaction of its boundary layer and generated pressure gradient at the leading edge. The pressure surface leg of this horseshoe vortex crosses the passage and reaches the blade suction surface, driven by the pressure gradient existing between two consecutive blades. In addition, this pressure gradient generates a cross-flow along the endwall. This all results into a very complex flow field in proximity of the endwall. For this reason, burnouts tend to occur at a specific position in the vicinity of the leading edge. In this research, a methodology to cool the endwall of the turbine blade by means of film cooling jets from the blade surface and the endwall is proposed. The cooling performance is investigated using the transient thermography method. CFD analysis is also conducted to investigate the phenomena occurring at the endwall and calculate the film cooling effectiveness.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"206 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122605768","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":"Flow Field and Performance Analysis of a Centrifugal Pump During Unstable Operating Conditions","authors":"R. Prunières, C. Kato","doi":"10.1115/ajkfluids2019-4886","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4886","url":null,"abstract":"\u0000 Centrifugal pump performance curves instability, characterized by a local dent, can be the consequence of flow instabilities in rotating or stationary parts. Such flow instabilities often result in abnormal operating conditions, causing severe problems such as increased pressure pulsation, noise and vibration which can damage both pump and system. For the pump to have reliable operation, it is necessary to understand the onset and the mechanism of the phenomenon resulting in performance curves instability.\u0000 Present paper focuses on performance curves instability of a centrifugal pump of low specific speed (ωs = 0.65, Ns = 1776) and aims at a better understanding of the mechanism leading to the head drop observed during tests at part load. For that purpose, Computation Fluid Dynamic (CFD) was performed using a Large-Eddy Simulation (LES) approach. The geometry used for present research is in fact the first stage of a multi-stage centrifugal pump and is composed of a suction chamber, a closed-type impeller, a vaned diffuser and return guide vanes to next stage (not included). Leakages at wear ring and stage bush were also included in the computed geometry in order to consider their potential influence on pump stability.\u0000 The occurrence of the instability in CFD is found at a higher flow rate than in the experiments. It is observed that the pre-swirl angle is under-predicted by several degrees which leads to change the impeller operating conditions.\u0000 Nevertheless, the analysis of the CFD results is still useful to have a better understanding of the onset of the head drop. When the head drops, a switching of low radial and axial velocities at the impeller outlet from the hub side to the shroud side is observed. This change of flow pattern goes along with a strong increase of the diffuser inlet throat recirculation and the development of stall, that impairs pressure recovery between the impeller outlet and the diffuser inlet.\u0000 As the pump flow rate is further decreased below the head drop flow rate, recirculation at the diffuser throat extend toward the impeller outlet and impact Euler head. Conversely, the pressure recovery from the impeller outlet to the diffuser inlet throat increases again as the flow velocity slowdown can be effective again. Consequently, the pump head increases again.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115293406","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":"Dynamic Characteristics of Unshrouded Impellers Equipped With Balance Piston Systems for Rocket Turbo Pumps","authors":"Tomoyuki Hayashi, M. Yoshimura, Keisuke Matsumoto, K. Miyagawa, S. Kawasaki, J. Takida, H. Hiraki, Naohito Suwa","doi":"10.1115/ajkfluids2019-5600","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5600","url":null,"abstract":"\u0000 Turbo pumps for rocket engines often equipped balance piston (BP) systems at the back-shroud of the impellers for cancelling their axial thrust. The BP system is self-balancing and stable under quasi-static conditions, but it is known that the BP systems can be unstable under certain dynamic conditions. The performance characteristics of turbo pumps equipped with unshrouded impellers might be affected by the axial position of the rotor. Thus it is necessary to consider this effect when calculating the balance of axial thrust. Few experiments have determined the characteristics of unshrouded impellers equipped with BP systems yet.\u0000 In this research, an experimental study of a model turbo pump for rocket engines was carried out. This pump had an unshrouded impeller, a BP system, a vaned diffuser, and a volute. Axial forced oscillations were applied on the rotor of the pump by an active magnetic bearing (AMB) test facility. This setup can oscillate with freely-selected amplitude and frequency applying thrust to the rotor. During the oscillations, the fluctuation of axial thrust under the operating conditions was monitored using strain gauges. The axial thrust compensation ability and the response of the BP system were evaluated by analyzing the magnitude, amplitude and phase delay of the axial position of the rotor. Moreover, 3D simulations and 1D simulations were carried out for the model pump. In the 3D simulations, computational fluid dynamics (CFD) was used to calculate the internal flow of the model pumps. The BP system was equipped with an impeller on which were applied forced oscillations. The impeller movement was modeled using a mesh morphing method. The 1D simulation predicted the axial thrust by calculating the mass flow balance using the geometry of the model pump.\u0000 The phase lag between the axial position and the thrust was dominated by the pressure fluctuation at the BP chamber caused by the mass flow balance. The 3D simulations well predicted the fluctuation, but the characteristics of the BP system estimated by the 3D simulations were more stable than those determined by the experiments. On the other hand, the characteristics estimated by the 1D simulation was less stable than those by the experiments. However, these simulations grasped the tendency of the BP system to become unstable as the oscillation frequency increases, and are effective in predicting the characteristics.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130882847","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":"Leakage Rate Performance Mapping of Smooth Stator/Grooved Rotor Labyrinth Seals Using Statistical Tools","authors":"Hanxiang Jin, A. Untăroiu","doi":"10.1115/ajkfluids2019-5429","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5429","url":null,"abstract":"\u0000 As one of the most widely used annular pressure seals, labyrinth seals are used to reduce the fluid leakage between different pressure stages. They are multi-toothed seals with circumferential grooves located on the rotor surfaces and/or stator surfaces, which are distributed along the axial direction. The intricacy of the surface geometry and directionality of the seal pattern assist in converting pressure into dissipated kinetic energy without rotor-stator rub effects. The majority of previous studies focused on annular labyrinth liquid seals with smooth rotor/grooved stator (SR/GS) case, whereas this paper attempts to elucidate the effects of geometric variables modification for smooth stator/grooved rotor (SS/GR) case using Computational Fluid Dynamics (CFD) and design of experiments (DOE) techniques. In this study, a smooth stator/grooved rotor liquid seal was modeled and validated against experimental data. The model was then used as a baseline case for a sensitivity analysis of its geometry variations. Simulation results under different pressures/rotor speeds were used to validate the CFD setup. Four geometric parameters of the seal were then selected as design variables to adapt the baseline geometry for potential performance improvements. The design space was discretized using the DOE technique. Similar mesh/simulation setups were automatically generated for each design point. Regression analysis was applied based on the CFD results for a better understanding of the effects associated with different design variables. These results can be used to improve the current design of smooth stator/grooved rotor annular pressure seals in order to achieve lower leakage rates.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"274 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122935888","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":"Suppression of the Surging Phenomenon by Modifying Tongue Shape of Air Conditioner Mounted With Cross-Flow Fan","authors":"Haruki Nukaga, Hiroshi Maita, H. Daisaka","doi":"10.1115/ajkfluids2019-4958","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4958","url":null,"abstract":"\u0000 Energy saving of room air-conditioner (RAC) is strongly required due to growing environmental concern. It is difficult to work a cross flow fan (CFF) at the most efficient operating point (OP) because a surging phenomenon occurs near this efficient OP. The conventional method for suppressing the surging phenomenon by increasing a rotation speed is unfavorable because a fluidic noise and a fan power consumption increase. Therefore, we investigated the new method for suppressing the surging phenomenon focusing on a structure of a fan casing.\u0000 It is known that the surging phenomenon is likely to occur from both right and left ends of the CFF. However, an area where surging occurs and a flow pattern in this area have not been revealed in detail. In this study, we experimentally investigated the area where surging occurs by measuring the outlet air velocity distribution across the CFF. In addition, the flow pattern in this area was compared with that of the center area using simulation. Simulation results showed that an area ratio of a vortex flow inside the CFF is high at both ends of the CFF, and a part of the mainstream flows back to the upstream side through a gap between the tongue and the CFF. Therefore, we thought that the function of the tongue, which divide inflow and outflow, is not sufficient.\u0000 The influence of modifying the tongue shape was experimentally evaluated. The test results showed that the surging limit shifted to the low flow rate and high static pressure side, and the noise at the condition of the surging limit decreased. The surging phenomenon was suppressed by modifying the tongue shape at both ends of the CFF compared to the center area. This technique makes it possible to work the CFF in a more efficient OP.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133812143","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":"Cryogenic Pumps Monitoring, Diagnostics and Expert Systems Using Motor Current Signature Analyses and Vibration Analyses","authors":"P. Popaleny, N. Peton","doi":"10.1115/ajkfluids2019-4716","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4716","url":null,"abstract":"\u0000 The paper discusses the Cryogenic Pumps Condition Monitoring and Machinery Diagnostics Systems, including the automated Expert Diagnostics Systems. The Cryogenic Pump construction differs by design, failure modes and criticality and no single solution will suit all designs. Therefore, two approaches are discussed: Motor Current Signature Analyses and Vibration Analyses. The paper further shows the real case studies, diagnostics and findings on Cryogenic Pumps using both analyses.\u0000 The article addresses common failure types and proposes applicable solutions. The Cryogenic Pumps mechanical and electrical malfunctions are discussed, their reflection on the dynamic current spectrum using improved Motor Current Signature Analysis (MCSA), aka. Model-Based Voltage and Current (MBVI) Analyses and vibration spectrum using Vibration Analyses (VA). The article contrasts the similarities vs. differences and advantages vs. disadvantages of both methods and may be of value for field engineers to understand the pros. and cons. of each technology.\u0000 The paper outlines the Expert Diagnostics System based on MBVI, able to distinguish automatically among different malfunctions. The Expert System uses the power spectral density of the difference between the expected current obtained from the model and the actual current. These differences include only abnormalities generated by the motor anomaly. Therefore, they are immune to the noise or harmonics present in the supply voltages.\u0000 The presented results, using both approaches: Model-Based Voltage and Current Analyses and Vibration Analyses, prove the potential of both techniques and the advantages of their combined use for reaching a maximum reliable Condition Monitoring and Diagnostics of Cryogenic Pumps.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"160 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133917908","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 Tests With Centrifugal Pumps: Degradation of Performance, Instability and Dynamic Phenomena With Non-Newtonian Suspensions of Kaolin in Water","authors":"Matteo Occari, Enrico Munari, V. Mazzanti, M. Pinelli, F. Mollica, A. Suman","doi":"10.1115/ajkfluids2019-4939","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4939","url":null,"abstract":"\u0000 The performance of pumps when working with non-Newtonian fluids significantly change with respect to water. In several experimental tests with non-Newtonian fluids, significant deration of head and the presence of head instability were observed. The present work aims to better understand this phenomenon since the reasons that originate it are not clear. Two small size centrifugal pumps were experimentally tested with different mixtures of kaolin-in-water, which showed a verified non-Newtonian behavior. The rheology of the mixtures and the particle size distribution of kaolin powder were measured to characterize the fluids. Similar to previous tests, a strong reduction of head and the appearance of instability were observed at low flow rates and, in some cases, also at higher flow rates. This behavior was related to the presence of air trapped into the fluid that, within the pump, generated a phenomenon known as gas-locking, which in literature it has been studied in detail with water but not with non-Newtonian fluids. Moreover, in some working conditions, non-stable time-varying phenomena are observed and their consequence on performance commented. Comparing the two pumps, characterized by a similar specific speed but by a different geometry, the head drop manifested itself with different intensity.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"296 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121124224","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":"Stabilizing Pump-Turbine Operations Using Water Injection Passive Control","authors":"Muhannad Altimemy, Bashar Attiya, Cosan Daskiran, I-Han Liu, A. Oztekin","doi":"10.1115/ajkfluids2019-4866","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4866","url":null,"abstract":"\u0000 Computational fluid dynamics simulations are carried out to characterize the spatial and temporal characteristics of the velocity and pressure field of turbulent flows through a pumpturbine unit operating with the turbine mode. The high-fidelity large eddy simulations turbulence model is utilized to examine the flow-induced vibrations in the draft tube of the unit. The water injection from the runner cone is considered as the control strategy to mitigate the flow-induced fluctuations. The simulations are conducted for the turbine flow rate of 0.2 m3/s without and with the water injection at a rate of 0.008 m3/s. The pressure along the surface of the draft tube is probed at various locations to access the effectiveness of the water injection to mitigate fluctuations. Water injection at 4% rate is demonstrated to be effective in attenuating the pressure fluctuation inside the draft tube. The amplitude of fluctuations is reduced by nearly 50% by the water injection. The generated power is hardly influenced by water injection. Thus, the control strategy considered here could be employed effectively without a penalty on the power generation.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133616796","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}