The objective of this research is to suppress pressure fluctuation by machining slits to the diffuser vanes and clarify its effect on the diffuser rotating stall from the hydrodynamics point of view. In order to investigate pressure fluctuations due to the diffuser rotating stall, both experiment and CFD (Computational Fluid Dynamics) calculations were conducted. In the experiment, two kinds of pump (one is original and another is with slit vanes) characteristics and time history of static pressure were measured. Then, data processing of wave form were conducted by FFT (Fast Fourier Transform) analysis. The static pressure transducers were mounted at casing-side of diffuser inlet in two passages. On the other hand, the CFD calculations were carried out to investigate the behavior of the diffuser rotating stall and the effect of slit vanes using a commercial CFD software, ANSYS CFX. A positive slope of head-flow characteristics is confirmed around at ϕ = 0.036 in the case of original pump. On the other hand, it has been shifted to lower flow rate, ϕ = 0.020 in the case of slit vanes. The periodic pressure fluctuations were observed for both cases at those flow rate, respectively. Then, it was confirmed that the diffuser rotating stall occurs and the number of cell is one from the co-relation between pressure wave form of two flow passages. The unsteady RANS (Reynolds-averaged Navier-Stokes) calculations were conducted for two kinds of pump. Then the internal flow within the diffuser were compared and the differences were clarified.
{"title":"Suppression of Diffuser Rotating Stall in a Centrifugal Pump by Use of Slit Vane","authors":"Shunya Takao, S. Konno, S. Ejiri, Masahiro Miyabe","doi":"10.1115/fedsm2021-65519","DOIUrl":"https://doi.org/10.1115/fedsm2021-65519","url":null,"abstract":"\u0000 The objective of this research is to suppress pressure fluctuation by machining slits to the diffuser vanes and clarify its effect on the diffuser rotating stall from the hydrodynamics point of view.\u0000 In order to investigate pressure fluctuations due to the diffuser rotating stall, both experiment and CFD (Computational Fluid Dynamics) calculations were conducted. In the experiment, two kinds of pump (one is original and another is with slit vanes) characteristics and time history of static pressure were measured. Then, data processing of wave form were conducted by FFT (Fast Fourier Transform) analysis. The static pressure transducers were mounted at casing-side of diffuser inlet in two passages.\u0000 On the other hand, the CFD calculations were carried out to investigate the behavior of the diffuser rotating stall and the effect of slit vanes using a commercial CFD software, ANSYS CFX.\u0000 A positive slope of head-flow characteristics is confirmed around at ϕ = 0.036 in the case of original pump. On the other hand, it has been shifted to lower flow rate, ϕ = 0.020 in the case of slit vanes. The periodic pressure fluctuations were observed for both cases at those flow rate, respectively. Then, it was confirmed that the diffuser rotating stall occurs and the number of cell is one from the co-relation between pressure wave form of two flow passages. The unsteady RANS (Reynolds-averaged Navier-Stokes) calculations were conducted for two kinds of pump. Then the internal flow within the diffuser were compared and the differences were clarified.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81889078","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}
Micro air vehicles (MAVs) have been developed for many fields. The MAVs usually receive strong impact from a velocity change in time or space, and facilities for aerodynamic experiments of MAVs under a gusty environment have been required. The present study has developed a gust wind tunnel to generate unsteady and non-uniform flows. We developed a small wind tunnel with eight multi-fans and a shutter mechanism at the upstream of the test section. We controlled the outputs of the fans independently and obtained a linear shear layer with an error of 5 percent. The velocity gradient of the shear layer was from 5 to 8 s−1. The shutter mechanisms provided a longitudinal gust with the velocity change from 2 m/s to 10 m/s within 0.3 seconds.
{"title":"Design of Gust Wind Tunnel With Unsteady and Shear Main-Flows","authors":"Y. Nishio, Ryotaro Miyazaki, T. Ogawa","doi":"10.1115/fedsm2021-65946","DOIUrl":"https://doi.org/10.1115/fedsm2021-65946","url":null,"abstract":"\u0000 Micro air vehicles (MAVs) have been developed for many fields. The MAVs usually receive strong impact from a velocity change in time or space, and facilities for aerodynamic experiments of MAVs under a gusty environment have been required. The present study has developed a gust wind tunnel to generate unsteady and non-uniform flows. We developed a small wind tunnel with eight multi-fans and a shutter mechanism at the upstream of the test section. We controlled the outputs of the fans independently and obtained a linear shear layer with an error of 5 percent. The velocity gradient of the shear layer was from 5 to 8 s−1. The shutter mechanisms provided a longitudinal gust with the velocity change from 2 m/s to 10 m/s within 0.3 seconds.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74751818","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}
M. Khan, Sambhaji T. Kadam, A. Kyriakides, Ibrahim Hassan, A. Papadopoulos, M. A. Rahman, P. Seferlis
Vapor absorption refrigeration (VAR) is a sustainable alternative to the conventional vapor compression refrigeration (VCR) cycle, owing to its lower non-renewable energy requirements and potentially for exploitation of renewable energy sources. Traditionally, the coefficient of performance (COP) of the conventional single effect VAR cycle is considerably lower than VCR cycles. This provides room for improvement which can be attained through double effect VAR cycles that provide relatively higher performance. The COP of the dual effect VAR cycle is enhanced due to the waste/rejected heat energy utilization from the condenser or the absorber into a secondary generator. Models that correlate the COP of the double effect VAR cycle with operating parameters are not available in the open literature, with Iyer’s correlation being the only exception. This work applies this COP correlation using literature data for double effect VAR that operate with a variety of refrigerant and absorbent pairs. A comprehensive Mean Absolute Percentage Error (MAPE) analysis is performed for more than 2028 data points of various fluid pairs. Results reveal that MAPE (86.6–839%) values appear to be quite high for the reported correlation. Furthermore, the model is optimized using the proposed data set, considerably reducing the MAPE up to 36.03%. The results also indicate that due to the lack of fluid-specific parameters, the application of this correlation may not support the development of new double effect VAR cycles. Therefore, it is crucial to establish a performance-based correlation that considers both operational parameters and fluid parameters to assess the performance of new and efficient dual effect VAR cycles.
{"title":"Modified Operating Parameter-Based Iyer Correlation for the Coefficient of Performance (COP) Prediction of Different Fluid Pairs in Double-Effect Vapor Absorption Refrigeration (VAR) Cycles","authors":"M. Khan, Sambhaji T. Kadam, A. Kyriakides, Ibrahim Hassan, A. Papadopoulos, M. A. Rahman, P. Seferlis","doi":"10.1115/fedsm2021-65709","DOIUrl":"https://doi.org/10.1115/fedsm2021-65709","url":null,"abstract":"\u0000 Vapor absorption refrigeration (VAR) is a sustainable alternative to the conventional vapor compression refrigeration (VCR) cycle, owing to its lower non-renewable energy requirements and potentially for exploitation of renewable energy sources. Traditionally, the coefficient of performance (COP) of the conventional single effect VAR cycle is considerably lower than VCR cycles. This provides room for improvement which can be attained through double effect VAR cycles that provide relatively higher performance. The COP of the dual effect VAR cycle is enhanced due to the waste/rejected heat energy utilization from the condenser or the absorber into a secondary generator. Models that correlate the COP of the double effect VAR cycle with operating parameters are not available in the open literature, with Iyer’s correlation being the only exception. This work applies this COP correlation using literature data for double effect VAR that operate with a variety of refrigerant and absorbent pairs. A comprehensive Mean Absolute Percentage Error (MAPE) analysis is performed for more than 2028 data points of various fluid pairs. Results reveal that MAPE (86.6–839%) values appear to be quite high for the reported correlation. Furthermore, the model is optimized using the proposed data set, considerably reducing the MAPE up to 36.03%. The results also indicate that due to the lack of fluid-specific parameters, the application of this correlation may not support the development of new double effect VAR cycles. Therefore, it is crucial to establish a performance-based correlation that considers both operational parameters and fluid parameters to assess the performance of new and efficient dual effect VAR cycles.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91137308","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}
Many pumping stations require an urgent rehabilitation from hydraulic, energetic, and economic point of view, being older than 30 years. Some urban stations for the water supply are nowadays under-dimensioned compared with the necessary consumption. Such an example is the pumping station of the Buzau City, realized in 1986. Its population has grown in the last decades by about 30% due to industrial development and its water pumping station from the treatment plant is currently totally insufficient. The hydraulic losses through the control discharge valve have become too high. This pumping station ensures the water supply for the south and east part of the city. Firstly, some characteristics of the pumping station equipped with pumps 12NDS- Normal-Double spiral casing-Single-layer of 160kW and 18NDS of 400kW and 500 kW, all from domestic production, are presented. Modernization of the pumping station has started few years ago and being realized in steps, so as not interrupt the city’s water supply. To establish the optimal operating point some algorithms are presented, developed based on the experimental data and using functions with one or two independent variables. Firstly, the interpolation function is determined, followed by its numerical calculation. To establish the characteristics’ equations H = f(Q), P = f(Q), and η = f(Q) starting from experimental results obtained by direct measurements, a polynomial approximation was chosen by the method of the least squares, using the polynomials Lagrange and Bezier. For optimization, the fuzzy technique is adopted regarding the flow fusing, intervals between start and stop following some policies concerning the aggregates’ starting. For a year, the energy saved between these intervals was calculated. Finally, the obtained yields of about 90% proved that the pumps modernization adopting new functioning techniques is more advantageous in some situations than the purchase of new equipment.
{"title":"Fuzzy Method Applied at Energetic and Economic Rehabilitation of Pumping Station","authors":"V. Radulescu","doi":"10.1115/fedsm2021-65616","DOIUrl":"https://doi.org/10.1115/fedsm2021-65616","url":null,"abstract":"\u0000 Many pumping stations require an urgent rehabilitation from hydraulic, energetic, and economic point of view, being older than 30 years. Some urban stations for the water supply are nowadays under-dimensioned compared with the necessary consumption. Such an example is the pumping station of the Buzau City, realized in 1986. Its population has grown in the last decades by about 30% due to industrial development and its water pumping station from the treatment plant is currently totally insufficient. The hydraulic losses through the control discharge valve have become too high. This pumping station ensures the water supply for the south and east part of the city. Firstly, some characteristics of the pumping station equipped with pumps 12NDS- Normal-Double spiral casing-Single-layer of 160kW and 18NDS of 400kW and 500 kW, all from domestic production, are presented. Modernization of the pumping station has started few years ago and being realized in steps, so as not interrupt the city’s water supply. To establish the optimal operating point some algorithms are presented, developed based on the experimental data and using functions with one or two independent variables. Firstly, the interpolation function is determined, followed by its numerical calculation. To establish the characteristics’ equations H = f(Q), P = f(Q), and η = f(Q) starting from experimental results obtained by direct measurements, a polynomial approximation was chosen by the method of the least squares, using the polynomials Lagrange and Bezier. For optimization, the fuzzy technique is adopted regarding the flow fusing, intervals between start and stop following some policies concerning the aggregates’ starting. For a year, the energy saved between these intervals was calculated. Finally, the obtained yields of about 90% proved that the pumps modernization adopting new functioning techniques is more advantageous in some situations than the purchase of new equipment.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86793715","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}
Tatsunori Hayashi, H. F. Farahani, A. Rangwala, H. Sakaue
Arctic oil spills are particularly detrimental as they could cause extensive ice melting in addition to the environmental pollution they create. Floating oil slicks amongst ice floes absorb ambient energy and transfer that energy to the ice to aggravate melting in the thaw season. However, few studies have been undertaken to reveal how oil-ice interactions impact ice melting. This research employs a measurement technique to investigate the heat transfer pathways from oil slicks to the ice. Dual-luminescence imaging and particle imaging velocimetry (PIV) in a side cooled cavity is performed for temperature and velocity measurements of Toluene, respectively. Dual-luminescence imaging captured the spatial temperature distribution of the fuel. Consecutive imaging of the seeding particles in PIV provided the spatial velocity field of the fuel in the cavity. The results show that the convective field is directly coupled with the temperature field, i.e., the temperature difference instigates a flow in the liquid. Successful implementation of the two measuring techniques together is a step toward analyzing heat transfer pathways in a liquid fuel adjacent to an ice body, indicating the extent of melting.
{"title":"Dual-Luminescence Imaging and Particle Tracking Velocimetry for Simultaneous Temperature and Velocity Field Measurements in Hydrocarbons Liquid","authors":"Tatsunori Hayashi, H. F. Farahani, A. Rangwala, H. Sakaue","doi":"10.1115/fedsm2021-61460","DOIUrl":"https://doi.org/10.1115/fedsm2021-61460","url":null,"abstract":"\u0000 Arctic oil spills are particularly detrimental as they could cause extensive ice melting in addition to the environmental pollution they create. Floating oil slicks amongst ice floes absorb ambient energy and transfer that energy to the ice to aggravate melting in the thaw season. However, few studies have been undertaken to reveal how oil-ice interactions impact ice melting. This research employs a measurement technique to investigate the heat transfer pathways from oil slicks to the ice. Dual-luminescence imaging and particle imaging velocimetry (PIV) in a side cooled cavity is performed for temperature and velocity measurements of Toluene, respectively. Dual-luminescence imaging captured the spatial temperature distribution of the fuel. Consecutive imaging of the seeding particles in PIV provided the spatial velocity field of the fuel in the cavity. The results show that the convective field is directly coupled with the temperature field, i.e., the temperature difference instigates a flow in the liquid. Successful implementation of the two measuring techniques together is a step toward analyzing heat transfer pathways in a liquid fuel adjacent to an ice body, indicating the extent of melting.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89578012","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}
The presence of excessive swirl at the runner outlet in Francis turbines operating at part load leads to the development of flow instabilities such as the rotating vortex rope (RVR). The presence of RVR causes severe pressure pulsations, power swings, and fatigue damage in the turbine unit. Air and water injection in the draft tube have been reported to reduce the detrimental effects of RVR formation in the Francis turbines. Air injection is one of the oldest and most widely used methods. In contrast, water jet injection is a relatively new methodology. The present work reports the numerical simulations performed to compare the respective effectiveness of these methods to mitigate the RVR and the related flow instabilities. The efficacy of the two methods has been compared based on the pressure pulsations and pressure recovery in the draft tube cone. The results show that the air and water injection influence the draft tube flow field in different ways. Both air and water injection led to a reduction in pressure pulsation magnitudes in the draft tube cone. However, the air injection led to a negative pressure recovery while the water injection improved the draft tube action.
{"title":"Comparison of Axial Water and Air Injections in the Draft Tube of a Francis Turbine for RVR Mitigation","authors":"S. Khullar, K. Singh, M. Cervantes, B. Gandhi","doi":"10.1115/fedsm2021-65503","DOIUrl":"https://doi.org/10.1115/fedsm2021-65503","url":null,"abstract":"\u0000 The presence of excessive swirl at the runner outlet in Francis turbines operating at part load leads to the development of flow instabilities such as the rotating vortex rope (RVR). The presence of RVR causes severe pressure pulsations, power swings, and fatigue damage in the turbine unit. Air and water injection in the draft tube have been reported to reduce the detrimental effects of RVR formation in the Francis turbines. Air injection is one of the oldest and most widely used methods. In contrast, water jet injection is a relatively new methodology. The present work reports the numerical simulations performed to compare the respective effectiveness of these methods to mitigate the RVR and the related flow instabilities. The efficacy of the two methods has been compared based on the pressure pulsations and pressure recovery in the draft tube cone. The results show that the air and water injection influence the draft tube flow field in different ways. Both air and water injection led to a reduction in pressure pulsation magnitudes in the draft tube cone. However, the air injection led to a negative pressure recovery while the water injection improved the draft tube action.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90830592","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}
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