Volume 3B: Fluid Applications and Systems最新文献

{"title":"Effects of Trailing Edge Position of Splitter Blade on the Pressure Pulsation in a Low Specific Centrifugal Pump","authors":"Jinfeng Zhang","doi":"10.1115/ajkfluids2019-4875","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4875","url":null,"abstract":"\u0000 A combination of experimental and numerical simulation was carried out to analyze influence of trailing edge position of splitter blade on the pressure fluctuation in low specific pumps with and without splitter blades under different flow rates. Performance experiments and PIV tests were performed to verify the results of numerical calculation. Several monitor points were placed in the calculation model pump to collect the pressure fluctuation signals, which were processed by Fast Fourier Transform to obtain the frequency results for further analysis. Besides, turbulence intensity and relative velocity distribution were also analyzed in regions of impeller and volute. The results showed that compared with prototype without splitter blade and the splitter blade schemes, when the trailing edge of splitter blade deviates to the suction side of main blade, the maximum pressure pulsation amplitudes are the lowest at different monitoring points of model pump. And the variation of pressure pulsation amplitude in this scheme is relatively stable with the change of flow rates compared with other schemes. Furthermore, the splitter blade scheme with an appropriate trailing edge position has the lowest average turbulence intensity and optimal relative velocity distribution in main flow passage component. Therefore, this paper proposes a reference scheme of the trailing edge position of the splitter blade to effectively decrease predominate pressure pulsation amplitude.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"2 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":"114065207","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":"Theoretical Optimization of Splitter Blade Geometry in High-Efficiency Centrifugal Turbopumps","authors":"A. Apollonio, Francesco Maddaluni, A. Pasini, D. Valentini, L. d'Agostino","doi":"10.1115/ajkfluids2019-5616","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5616","url":null,"abstract":"\u0000 The introduction of splitter blades (splitters) in the impeller represents a possible way to improve the head and efficiency of centrifugal turbopumps. Splitters decrease flow slip, deviation, blockage and losses at the impeller discharge by reducing the displacement flow and the adverse pressure gradient it induces on the boundary layers (BLs) developing on the pressure sides of the full blades. These benefits are to be balanced against the introduction of additional flow blockage and losses. It is therefore of interest to investigate which splitter blade geometry (position and length), if any, is most effective to best exploit the potential advantages of adding splitter blades to a centrifugal impeller. To this purpose a quasi-3D, reduced-order method, previously developed for preliminary prediction of the geometry and performance of centrifugal turbopumps, is extended to account for the introduction of splitter blades for the purpose of investigating their influence on the hydraulic performance of these machines. Splitters with radial leading edges and the same shape as the full blades are introduced in the six-bladed backswept impeller of the VAMPIRE turbopump, a high-efficiency machine previously used for experimental validation of the original version of the flow model. The results highlight the most relevant action mechanisms of splitter blades in affecting the turbopump performance and provide general indications on their most effective design for performance improvement. As a consequence of the evolution of the BLs in the blade channels, relatively longer splitters located closer to the pressure sides of the full blades are more efficient at and above design flow, while the reverse is the case at high blade loadings. The results also indicate that the introduction of splitter blades only marginally improves the performance of the already optimized VAMPIRE pump in view of its small residual margins for performance gains.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"19 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":"114655152","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":"Numerical Investigation of the Influence of Impeller-Diffuser Gap (A- and B-Gaps) on Unsteady Flow in a Centrifugal Pump at Part Flows","authors":"T. Takamine, S. Watanabe","doi":"10.1115/ajkfluids2019-5372","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5372","url":null,"abstract":"\u0000 Because of the high energy density of multi-stage centrifugal pump, it is really important to ensure the reliability of the pumps thus the stability of rotor system in the wide flow rate range. Rotating stall is a well-known unsteady flow phenomenon in which one or several stall cell structures propagate circumferentially in impeller and/or diffuser. Rotating stall alters the peripheral pressure distribution of rotors, and therefore it is often regarded as one of the primary trigger of unstable fluid force acting on the rotor system. One possible factor which could affect the rotating stall is a geometrical relationship between the rotor and the stator. In the present study, unsteady RANS simulations of internal flow in a centrifugal pump are carried out. The pump is the partial model of the final stage of the three-stage centrifugal pump used in our previous study. In order to investigate the effect of the gap between impeller trailing edge and diffuser leading edge on the unsteady flow of the pump, three cases of impeller-diffuser gap is simulated; one is the smaller gap case with original impeller. The other cases are two larger gap cases with only cutting the impeller blades and with cutting the both impeller blades and impeller shroud walls. For all gap cases, the computations are conducted for the nominal flow rate and the low flor rate with 10% of the nominal flow rate.\u0000 As a result, the rotating stall is observed only in the larger gap case with the cut shroud walls, indicating that the key phenomenon for the stable formation of the stall cell is not only the weakened rotor-stator interaction, but also the other phenomenon attributed to the enlarged gap between the impeller shroud walls and the diffuser walls. In the shroud cut case, a part of the main flow blocked by the stalled region and the secondary flow on the diffuser walls tend to flow into the side gaps more easily than other cases. They might be the important phenomenon associated with the diffuser rotating stall in the enlarged wall gap condition.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"59 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":"124855965","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":"Investigations Into Wet Wipe Related Clogging Phenomena of Wastewater Pumps","authors":"Raja-Louisa Mitchell, S. Busche, P. Thamsen","doi":"10.1115/ajkfluids2019-5446","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5446","url":null,"abstract":"\u0000 To gain a better understanding of the operational problems confronting wastewater pumps due to nonwoven wet wipes, experimental data generated in a laboratory setting were compared with data collected in the field. Pump blockages from a wastewater pump operating in the field under normal conditions were collected and analysed. The types of wet wipes occurring in the blockages were identified and were categorised according to their (claimed) flushability. The clogging effect of comparable wet wipes was then investigated in the laboratory using a wastewater pump with a low resilience against clogging. Profound differences in the clogging effect of the nonwoven wet wipes could be observed. It could also be shown that wet wipes labelled as “flushable” have different clogging effects, depending on whether or not they comply with industry flushability guidelines.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"6 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":"131729931","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":"Two Flow Models for Designing Hydrostatic Bearings With Porous Material","authors":"M. Böhle, Y. Gu, A. Schimpf","doi":"10.1115/ajkfluids2019-4657","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4657","url":null,"abstract":"\u0000 The numerical prediction of load capacity, stiffness, power loss of hydrostatic journal bearings must be performed for technical applications. In this contribution hydrostatic bearings consisting of porous material are considered. Porous hydrostatic bearings have the advantage that no pressure erosion occurs and that the flow medium can be led homogenously to the gap between shaft and bearing. It is still a problem to design such bearings because the flow in the porous material must be taken into account. There is a simple flow model (SFM) available to calculate quickly the load capacity, stiffness, power loss. This model which is based on the assumption that the flow inside the porous material is axially symmetric works well provided that the eccentricity is small (dimensionless eccentricity e/h0 < 0.5). For large eccentricities — larger than e/h0 > 0.5 the axially symmetric assumption is too strong violated and the results for load capacity, stiffness become inaccurate. Therefore an improved model was developed which is described in the present contribution. This improved model couples the Reynolds equation for hydrodynamic lubrication (REHL) with Darcy Law as it had already been done for the aforementioned fast working SFM. The improved model is not based on the axially symmetric assumption but models the flow completely inside the porous material, i.e. Darcys Law is applied for the porous material without making any assumptions. By the application of the new model, its short name is Full Darcy’s Law (FDL) Model, bearings with high eccentricities can be designed. The application of Darcys Law leads to a Laplace equation for the static pressure distribution in the porous material which is coupled with the REHL. It is described how the resulting equation system is solved by a finite difference method. In this contribution the fast working SFM is described shortly again. The main emphasis lies on the introduction of the FDL-model which needs more computer resources for designing a porous bearing than the SFM. It is explained in detail how the coupling between Darcy Law (Laplace equation) and the REHL is realized. A comparison between the results of both models is shown and the differences are interpreted. Additionally, CFD results are used in order to validate the results of the FDL-model.","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":"132719076","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":"Operational Performance and Locally Resolved Outflow of Brush Seals","authors":"F. Schur, J. Friedrichs","doi":"10.1115/ajkfluids2019-4877","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4877","url":null,"abstract":"\u0000 As a result of the superior leakage efficiency of brush seals compared to conventional labyrinth seals, compliant contacting filament seals are used to increase the efficiency of jet engines as well as stationary gas and steam turbines. The widespread application of brush seals at different and varying pressure differences combined with variable contacting velocities at the rotor surface requires a profound understanding of the influences of different design parameters on the operational leakage performance. In order to systematically investigate the impact of different design parameters on sealing performance, a new cold air test rig was developed. The new test rig with rotating shaft enables hot-wire anemometry measurements downstream of the seals. These measurements provide insight into the locally resolved flow structure in addition to the integral leakage measurements. For the investigations, one welded and five different clamped brush seals at rotational speeds up to 3000rpm and pressure differences across the seals up to 500kPa are considered. Therefore, the influence of two different designs on the flow through the bristles is presented. For the clamped brush seals, variations of the front and backing plate are investigated. Additionally, the effects of bristle diameter and three different axial inclinations of the bristle pack on the sealing efficiency are shown. Furthermore, initial wear development during the first 30 to 60 hours of brush seal operation at varying experimental conditions is presented and linked to the design parameters. Consequently, the effects of major design aspects on the operational performance of brush seals are examined and presented.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"49 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":"116484858","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":"Development of High-Efficiency Half-Ducted Propeller Fan for Air-Conditioners by Blade Tip Shape Modification","authors":"M. Yoshikawa, Hiroyuki Toyoda, H. Daisaka","doi":"10.1115/ajkfluids2019-4908","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4908","url":null,"abstract":"\u0000 We developed a high-efficiency half-ducted propeller fan to reduce the electric power consumption of the outdoor unit of air conditioner by using computational fluid dynamics (CFD). Total pressure loss coefficient on the cylindrical surface of blade tip started increasing at the middle of the blade, and the region of high total pressure loss coefficient was formed after trailing edge. Therefore, we assumed that decreasing this region helped increasing static pressure efficiency. Limiting stream lines on the pressure surface showed that the flow from leading edge leaked at the middle of the blade tip, so it was assumed that the region of the high total pressure loss coefficient arose from the leakage at the middle of the blade tip. We confirmed that static pressure at the middle of blade tip, which was the leakage point, was low. We assumed that low inward force to the flow caused the leakage. On the other hand, static pressure at trailing edge of the blade tip was high. Therefore, it was found that the inward force could be increased by making the static pressure higher at the meddle of the blade tip. In order to make the static pressure higher at the middle of the blade tip, we attempted to move the maximum camber position of the blade tip from trailing edge side to leading edge side. Calculation results showed leakage at the blade tip decreased and the static pressure efficiency increased by 0.5%. Experimental results showed that the static pressure efficiency increased by 1.7 % and sound pressure level was almost the same. For the above reasons, we found leakage of flow from leading edge could be decreased by adjusting the maximum camber position of the blade tip. Decreasing leakage contributed to increasing static pressure efficiency and decreasing electric power consumption.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"46 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":"124594491","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":"Predicting Cooling Fan Noise of Electric Motor Using Compressible Large Eddy Simulation","authors":"Kimihisa Kaneko, Tsutomu Yamamoto","doi":"10.1115/ajkfluids2019-4699","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4699","url":null,"abstract":"\u0000 This paper describes prediction of aeroacoustics from a rotating machinery fan using compressible Large Eddy Simulation (LES). The fan is installed semi-opened space located between the fan cover and the body of rotating machinery such as a electric motor. The fan distributes air from the fan cover intake onto the cooling fins. The Reynolds number of the rotating fan is 9 × 105; its Mach number is approximately 0.1. Under the low Mach number regime, hybrid computational aeroacoustics (hybrid CAA) method, which is solved turbulent flow and acoustics separately, is generally used. However, we used a direct CAA method because interaction between pressure fluctuation from the turbulence and sound propagation should be considered.\u0000 For the direct CAA method approach, compressible Navier–Stokes equations are solved. Density is calculated from the ideal gas law. To compute turbulence phenomena, LES is used as the turbulence model. The Dynamic Smagorinsky Model is used for the subgrid scale. The sound propagation speed is approximately 10 times faster than the flow speed.\u0000 Therefore, the numerical schemes, time step, and computational grids size were evaluated with line sound source in the two-dimensional domain as a fundamental study to determine the numerical schemes. Subsequently we evaluated the sound pressure level with the electric motor fan, which is an experimental structure.\u0000 Through verification of the direct CAA model, we obtained the following results. (1) The predicted pressure fluctuation spectra show good agreement with the experimentally obtained spectra. Specifically, the blade passing frequency (BPF) and trend of the pressure fluctuation decay in the inertial turbulence subrange were predicted. (2) The predicted sound pressure spectra also show good agreement with BPF. Specifically, the acoustic mode and broadband turbulence noise level were predicted.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"45 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":"130205684","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 Blade Surface Cavitation on Various Types of Hydrofoils","authors":"H. Horiguchi, Masakazu Toyoshima, T. Matsuda, K. Sugiyama","doi":"10.1299/JSMEFED.2018.OS8-6","DOIUrl":"https://doi.org/10.1299/JSMEFED.2018.OS8-6","url":null,"abstract":"\u0000 In high speed turbopumps, various types of cavitation such as blade surface cavitation, tip leakage vortex cavitation, and backflow vortex cavitation occurs. When cavitation responses to encourage fluctuation of pressure and flow rate, the oscillation of flow rate called cavitation surge can occur. Therefore, clarification of dynamic characteristics of cavitation is desired to obtain higher reliability of turbopumps. Focusing on blade surface cavitation as one of fundamental cavitation, we investigated dynamic characteristics of blade surface cavitation on Clark-Y 11.7% hydrofoil and NACA0015 hydrofoil in addition to a flat plate hydrofoil in experiments. Several interesting characteristics of blade surface cavitation were clarified.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"19 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":"130371264","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":"Thermal Cavitation Instability Analysis in Axial Inducers by Means of Casing and Hub-Mounted Pressure Sensors","authors":"Ruzbeh Hadavandi, A. Pasini, D. Valentini, G. Pace, L. d'Agostino","doi":"10.1115/ajkfluids2019-5620","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5620","url":null,"abstract":"\u0000 The effects of thermal cavitation on the flow instabilities developing in a three-bladed, tapered-hub, variable-pitch space turbopump inducer are described by illustrating the results of similarity experiments in water carried out at Sitael in the Cavitating Pump Rotordynamic Test Facility (CPRTF). The operating conditions have been varied as required for investigating the onset and response of the fluid dynamic instabilities occurring in the test inducer over a wide range of cavitation numbers from noncavitating to heavy cavitation conditions, both at design and off-design flow. The CPRTF water temperature has been varied from room conditions to 80 °C ca. in order to induce thermal cavitation effects of increasing intensity capable of reproducing in the experiments the occurrence of typical cavitation phenomena in cryogenic space propellants. A wide variety and number of axial and rotating fluid dynamic instabilities have been detected, identified and characterized by spectral analysis of the pressure measurements obtained from statoric and rotoric transducers flush-mounted on the casing and the hub of the test inducer. The results indicate that thermal cavitation significantly affects the types of flow instabilities developing in cavitating inducers and the range of flow and suction conditions for their occurrence.","PeriodicalId":270000,"journal":{"name":"Volume 3B: Fluid Applications and Systems","volume":"1 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":"130583636","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}