Plunging jets have been extensively studied for their relatively simple set-up but complex multiphase interactions. This phenomenon includes gas carry-under and mixing, which occurs when shear effects between the plunging liquid jet and surrounding gas are sufficient to entrain gas at the impact site. Previous investigations typically assume the floor has an infinite depth and neglect compressive effects caused by the jet interacting with the catch tank floor. While this assumption is ideal for breaking waves in the middle of the ocean, many other applications have to contend with floor effects. These include waterfalls, wastewater treatment, dams, fish farms, mineral separation, and molten metal pouring. It is hypothesized that floor interactions will significantly affect the multiphase flow hydrodynamics, especially in places where the uninhibited jet would approach or pass the floor region. Using a large catch tank with an adjustable floor region designed to hold a constant water level, data were collected using high-speed backlit stereographic imaging to capture and compare the effects of three separate tank depths with those found using an infinite pool assumption. To identify bubbles in each stereographic projection, a uniform bubble recognition procedure was developed that was used across all data sets. This allowed for the automated identification of bubble entrainment regions, which could be compared with different flow conditions. Preliminary results are inconclusive as to the effects of the floor region on the bubble plume dynamics; however, the results showed consistent measurements between trials and the two stereographic cameras, implying the time variation of the jet dynamics was the primary source of uncertainty in the results and not the identification procedure. Therefore, the identification methods have provided a method for plume volume and shape estimation, which will be used in future studies using 3D imaging techniques.
{"title":"Stereographic Backlit Imaging and Bubble Identification From a Plunging Jet With Floor Interactions","authors":"Roy A. Pillers, T. Heindel","doi":"10.1115/fedsm2021-65313","DOIUrl":"https://doi.org/10.1115/fedsm2021-65313","url":null,"abstract":"\u0000 Plunging jets have been extensively studied for their relatively simple set-up but complex multiphase interactions. This phenomenon includes gas carry-under and mixing, which occurs when shear effects between the plunging liquid jet and surrounding gas are sufficient to entrain gas at the impact site. Previous investigations typically assume the floor has an infinite depth and neglect compressive effects caused by the jet interacting with the catch tank floor. While this assumption is ideal for breaking waves in the middle of the ocean, many other applications have to contend with floor effects. These include waterfalls, wastewater treatment, dams, fish farms, mineral separation, and molten metal pouring. It is hypothesized that floor interactions will significantly affect the multiphase flow hydrodynamics, especially in places where the uninhibited jet would approach or pass the floor region.\u0000 Using a large catch tank with an adjustable floor region designed to hold a constant water level, data were collected using high-speed backlit stereographic imaging to capture and compare the effects of three separate tank depths with those found using an infinite pool assumption. To identify bubbles in each stereographic projection, a uniform bubble recognition procedure was developed that was used across all data sets. This allowed for the automated identification of bubble entrainment regions, which could be compared with different flow conditions. Preliminary results are inconclusive as to the effects of the floor region on the bubble plume dynamics; however, the results showed consistent measurements between trials and the two stereographic cameras, implying the time variation of the jet dynamics was the primary source of uncertainty in the results and not the identification procedure. Therefore, the identification methods have provided a method for plume volume and shape estimation, which will be used in future studies using 3D imaging techniques.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84845703","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}
Pump clogging is a well-known problem due to the increasing amount of nonwoven wet wipes in the wastewater system. In addition, the usage of water decreases which causes higher concentration of solids in the wastewater. Based on the high variation of sewage flow many operators of sewer systems and sewage pumping stations were motivated to act that the wastewater is pumped as needed. It means that with reducing costs of frequency-controlled drives the usage of pumps with speed variation became a more state of the art application. The current operation mode when speed variation in wastewater pumps are used, affects the pumping of sewage water depending on inflow and the minimum velocity in the pipes. Until now, there is no answer which functionality and clogging occurs in the pump when speed changes. The study investigates how speed influences the clogging phenomena of wastewater pumps. The pumps have been approved at a test stand in a laboratory that is designed for proving wastewater pumps. The test includes several speeds with different quantities of wipes in a short-time and long-time functional performance test. The effects on the pumps and their clogging behavior are very different.
{"title":"Effect of Speed Variation on Clogging of Sewage Pumps","authors":"Enrico Müller, T. Pensler, P. Thamsen","doi":"10.1115/fedsm2021-65515","DOIUrl":"https://doi.org/10.1115/fedsm2021-65515","url":null,"abstract":"\u0000 Pump clogging is a well-known problem due to the increasing amount of nonwoven wet wipes in the wastewater system. In addition, the usage of water decreases which causes higher concentration of solids in the wastewater. Based on the high variation of sewage flow many operators of sewer systems and sewage pumping stations were motivated to act that the wastewater is pumped as needed. It means that with reducing costs of frequency-controlled drives the usage of pumps with speed variation became a more state of the art application.\u0000 The current operation mode when speed variation in wastewater pumps are used, affects the pumping of sewage water depending on inflow and the minimum velocity in the pipes. Until now, there is no answer which functionality and clogging occurs in the pump when speed changes.\u0000 The study investigates how speed influences the clogging phenomena of wastewater pumps. The pumps have been approved at a test stand in a laboratory that is designed for proving wastewater pumps. The test includes several speeds with different quantities of wipes in a short-time and long-time functional performance test. The effects on the pumps and their clogging behavior are very different.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80289901","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}
High efficiency is strongly demanded for gas turbines to reduce CO2 emissions. In order to improve the efficiency of gas turbines, the turbine inlet temperature is being raised higher. In that case, the turbine blade loading is higher and secondary flow loss becomes a major source of aerodynamic losses due to the interaction between the horseshoe vortex and the strong endwall cross flow. One of the authors have optimized a boundary layer fence which is a partial vane to prevent cross-flow from pressure-side to suction-side between blade to blade. However, it was also found that installing the fence leads to increase another loss due to tip vortex, wake and viscosity. Therefore, in this paper, we focused on the endwall contouring and the positive effect findings from the boundary layer fence were used to study its optimal shape. Firstly, the relationship between the location of the endwall contouring and the internal flow within the turbine cascade was investigated. Two patterns of contouring were made, one is only convex and another is just concave, and the secondary flow behavior of the turbine cascade was investigated respectively. Secondly, the shape was designed and the loss reduction effect was investigated by using optimization method. The optimized shape was manufactured by 3D-printer and experiment was conducted using cascade wind tunnel. The total pressure distributions were measured and compared with CFD results. Furthermore, flow near the endwall and the internal flow of the turbine cascade was experimentally visualized. The internal flow in the case of a flat wall (without contouring), with a fence, and with optimized endwall contouring were compared by experiment and CFD to extract the each feature.
{"title":"Secondary Flow Loss Reduction Method by Use of Endwall Contouring in Gas Turbine Cascade Using Optimization Method","authors":"Kazuki Yamamoto, Ryota Uehara, Sho Mizuguchi, Masahiro Miyabe","doi":"10.1115/fedsm2021-65787","DOIUrl":"https://doi.org/10.1115/fedsm2021-65787","url":null,"abstract":"\u0000 High efficiency is strongly demanded for gas turbines to reduce CO2 emissions. In order to improve the efficiency of gas turbines, the turbine inlet temperature is being raised higher. In that case, the turbine blade loading is higher and secondary flow loss becomes a major source of aerodynamic losses due to the interaction between the horseshoe vortex and the strong endwall cross flow. One of the authors have optimized a boundary layer fence which is a partial vane to prevent cross-flow from pressure-side to suction-side between blade to blade. However, it was also found that installing the fence leads to increase another loss due to tip vortex, wake and viscosity. Therefore, in this paper, we focused on the endwall contouring and the positive effect findings from the boundary layer fence were used to study its optimal shape. Firstly, the relationship between the location of the endwall contouring and the internal flow within the turbine cascade was investigated. Two patterns of contouring were made, one is only convex and another is just concave, and the secondary flow behavior of the turbine cascade was investigated respectively. Secondly, the shape was designed and the loss reduction effect was investigated by using optimization method. The optimized shape was manufactured by 3D-printer and experiment was conducted using cascade wind tunnel. The total pressure distributions were measured and compared with CFD results. Furthermore, flow near the endwall and the internal flow of the turbine cascade was experimentally visualized. The internal flow in the case of a flat wall (without contouring), with a fence, and with optimized endwall contouring were compared by experiment and CFD to extract the each feature.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81110544","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}
Juan J. Campos Manzo, Nicole J. Wagner, K. Anderson
Twin wire arc spraying (TWAS) is a plasma spraying process that offers low workpiece heating and high deposition rates at a lower cost. Variations in TWAS process conditions cause the substrate temperature to fluctuate and even melt. Therefore, the motivation of this project was to simulate the heat transfer from the TWAS torch to the substrate during spraying and layer formation of a coating. Simulations using ANSYS FLUENT Computational Fluid Dynamics (CFD) software were used to model the heat transfer in a TWAS system. The results of this paper are meant to augment and improve the database of TWAS technology. A CFD numerical heat transfer model is presented that was used to investigate the substrate surface temperature during the TWAS process. The results for the different pressure models showed that for a 3 second simulation, substrate surface temperatures increased as nozzle inlet pressure was decreased. For the upper and lower bound pressures of 75 psia and 29 psia, substrate surface temperature resulted in 946 °C and 1010 °C, respectively.
{"title":"Multiphysics Modeling and Simulation of an Arc-Jet Sprayer","authors":"Juan J. Campos Manzo, Nicole J. Wagner, K. Anderson","doi":"10.1115/fedsm2021-65319","DOIUrl":"https://doi.org/10.1115/fedsm2021-65319","url":null,"abstract":"\u0000 Twin wire arc spraying (TWAS) is a plasma spraying process that offers low workpiece heating and high deposition rates at a lower cost. Variations in TWAS process conditions cause the substrate temperature to fluctuate and even melt. Therefore, the motivation of this project was to simulate the heat transfer from the TWAS torch to the substrate during spraying and layer formation of a coating. Simulations using ANSYS FLUENT Computational Fluid Dynamics (CFD) software were used to model the heat transfer in a TWAS system. The results of this paper are meant to augment and improve the database of TWAS technology. A CFD numerical heat transfer model is presented that was used to investigate the substrate surface temperature during the TWAS process. The results for the different pressure models showed that for a 3 second simulation, substrate surface temperatures increased as nozzle inlet pressure was decreased. For the upper and lower bound pressures of 75 psia and 29 psia, substrate surface temperature resulted in 946 °C and 1010 °C, respectively.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"321 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77783426","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}
A single-camera synthetic Schlieren method is introduced here to measure two-dimensional topography and depth of dynamic free liquid surfaces. The method is simple and easy to implement. Because of light refraction (following Snell’s law), markers on a flat bottom which are seen through the surfaces of a transparent liquid are virtually displaced. This leads to a governing equation that the liquid surface depth (and its topography) is associated with the marker displacement. In the equation, the refractive index of the liquid (e.g. water) can be obtained by a refractometer (or from a technical reference), and the displacements of the markers can be obtained by a cross-correlation method which is usually used in particle image velocimetry. In the equation, the only unknown, the depth of the surface, can be obtained by solving the governing equation with boundary conditions. Unlike free-surface synthetic Schlieren (FS-SS) of Moisy et al. (Exp. Fluids, 1021, 46, 2009), our method does not require a reference depth (which is obtained before or after experiments), so that flows with temporally evolving depth can be measured. Experiments of liquid ripples and dam-break flows were performed to test the method. The results agree well with those obtained with FS-SS and visualization measurements.
{"title":"A Single-Camera Synthetic Schlieren Method for Measuring Two-Dimensional Liquid Surfaces","authors":"Duo Xu, Huixin Li, M. Avila","doi":"10.1115/fedsm2021-66507","DOIUrl":"https://doi.org/10.1115/fedsm2021-66507","url":null,"abstract":"\u0000 A single-camera synthetic Schlieren method is introduced here to measure two-dimensional topography and depth of dynamic free liquid surfaces. The method is simple and easy to implement. Because of light refraction (following Snell’s law), markers on a flat bottom which are seen through the surfaces of a transparent liquid are virtually displaced. This leads to a governing equation that the liquid surface depth (and its topography) is associated with the marker displacement. In the equation, the refractive index of the liquid (e.g. water) can be obtained by a refractometer (or from a technical reference), and the displacements of the markers can be obtained by a cross-correlation method which is usually used in particle image velocimetry. In the equation, the only unknown, the depth of the surface, can be obtained by solving the governing equation with boundary conditions. Unlike free-surface synthetic Schlieren (FS-SS) of Moisy et al. (Exp. Fluids, 1021, 46, 2009), our method does not require a reference depth (which is obtained before or after experiments), so that flows with temporally evolving depth can be measured. Experiments of liquid ripples and dam-break flows were performed to test the method. The results agree well with those obtained with FS-SS and visualization measurements.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75786183","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}
Yi-xiang Xu, Qiang Ru, Huai-yu Yao, Zhi-jiang Jin, J. Qian
The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.
{"title":"Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes","authors":"Yi-xiang Xu, Qiang Ru, Huai-yu Yao, Zhi-jiang Jin, J. Qian","doi":"10.1115/fedsm2021-65674","DOIUrl":"https://doi.org/10.1115/fedsm2021-65674","url":null,"abstract":"\u0000 The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76656869","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}
Conventional studies usually assume that the train surface is smooth, so as to simplify the numerical calculation. In fact, the surface of the train is irregular, which will change the flow characteristics in the boundary layer and further affect the aerodynamic performance of a train. In this work, roughness is applied to the roof of a 1:25 scaled train model in the form of longitudinal strips. Firstly, the improved delayed detached eddy simulation (IDDES) method is adopted to simulate the aerodynamic performance of the train model with both smooth and rough surface, which are subjected to crosswind. Results show that the side force coefficient and the roll moment coefficient subjected to rough model decreased by 3.71% and 10.56% compared with the smooth model. Then, the width, height and length of the strips are selected as variables to design different numerical simulation schemes based on the orthogonal experimental design method. Through variance analysis, it can be found that four design parameters have no significant effect on the side force coefficient. Meanwhile, for the roll moment coefficient, the length of the strips in the straight region of the train has a significant effect and the width of the strips has a highly significant effect on it. These conclusions can provide a theoretical basis to improve the aerodynamic performance of the high-speed train subjected to crosswind.
{"title":"Influence of Rectangular Strips’ Size on Aerodynamic Performance of a High-Speed Train Subjected to Crosswind","authors":"Mengying Wang, Zhenxu Sun, S. Ju, Guowei Yang","doi":"10.1115/fedsm2021-65692","DOIUrl":"https://doi.org/10.1115/fedsm2021-65692","url":null,"abstract":"\u0000 Conventional studies usually assume that the train surface is smooth, so as to simplify the numerical calculation. In fact, the surface of the train is irregular, which will change the flow characteristics in the boundary layer and further affect the aerodynamic performance of a train. In this work, roughness is applied to the roof of a 1:25 scaled train model in the form of longitudinal strips. Firstly, the improved delayed detached eddy simulation (IDDES) method is adopted to simulate the aerodynamic performance of the train model with both smooth and rough surface, which are subjected to crosswind. Results show that the side force coefficient and the roll moment coefficient subjected to rough model decreased by 3.71% and 10.56% compared with the smooth model. Then, the width, height and length of the strips are selected as variables to design different numerical simulation schemes based on the orthogonal experimental design method. Through variance analysis, it can be found that four design parameters have no significant effect on the side force coefficient. Meanwhile, for the roll moment coefficient, the length of the strips in the straight region of the train has a significant effect and the width of the strips has a highly significant effect on it. These conclusions can provide a theoretical basis to improve the aerodynamic performance of the high-speed train subjected to crosswind.","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":"78222070","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}
A stable and reliable pump-turbine operation under continuously expanding operating range requirement often imposes challenges on the hydraulic design of the pump-turbines and requires new developments. During a previous study carried out at the HSLU (Lucerne University of Applied Sciences, Switzerland), the flow instabilities of a low specific speed (i.e., nq = 25) pump-turbine were analyzed while a CFD methodology was developed through taking different numerical approaches and applying several turbulence models. The goal was to predict the turbine-mode characteristics of the reversible pump-turbines in the S-shaped region (at speed no load conditions) accurately as well as analyzing the flow features especially at off-design conditions. This CFD model was validated against the experimental data at different guide vane openings in turbine operating mode. Based on the analysis of the experimental data, flow visualization, and CFD results focusing especially on the flow features in the vaneless space and at the runner inlet, the onset and development of the flow instabilities were explored. Furthermore, a flow control technology that entailed injecting air and water in the vaneless space of a model pump-turbine was implemented for suppressing the flow instabilities and thus extending the operating range of the pump-turbine. Both air- and water-injection were applied by using an external energy source (compressor and pump) and discrete nozzles that are distributed in the vaneless space circumferentially. The S-shaped pump-turbine characteristics in turbine operating mode were modified so that the slope at speed no load conditions was no more positive indicating an improvement in the stability behavior. The analysis of the unsteady pressure data indicates the suppression of flow instability such as rotating stall with fluid injection in the vaneless space. The positive effect of fluid injection on the pump-turbine characteristics was also demonstrated in the CFD calculations. CFD was able to predict the pump-turbine dimensionless discharge, Kcm1, - speed, Ku1, characteristic curve with water injection correctly. After the CFD tool is validated for the prediction of the pump-turbine characteristics with fluid injection, further CFD simulations were carried out in order to improve the effectiveness of flow control and if possible, using less amount of injected fluid in the vaneless space. The goal was to optimize the fluid injection so that the instabilities can be suppressed with the lowest possible water/energy consumption. Parameters such as number of injection nozzles, nozzle position, nozzle diameter, and injection direction are varied. Several configurations of water injection system i.e., changing the number, location, and distribution of injection nozzles circumferentially and radially, direction of flow injection with respect to the main flow in the vaneless space, symmetrical and asymmetrical circumferential distribution of the nozzles i
{"title":"Improvements of Flow Control With Fluid Injection for the Suppression of Flow Instabilities in Pump-Turbines","authors":"S. Deniz, Fabio Asaro","doi":"10.1115/fedsm2021-65115","DOIUrl":"https://doi.org/10.1115/fedsm2021-65115","url":null,"abstract":"\u0000 A stable and reliable pump-turbine operation under continuously expanding operating range requirement often imposes challenges on the hydraulic design of the pump-turbines and requires new developments. During a previous study carried out at the HSLU (Lucerne University of Applied Sciences, Switzerland), the flow instabilities of a low specific speed (i.e., nq = 25) pump-turbine were analyzed while a CFD methodology was developed through taking different numerical approaches and applying several turbulence models. The goal was to predict the turbine-mode characteristics of the reversible pump-turbines in the S-shaped region (at speed no load conditions) accurately as well as analyzing the flow features especially at off-design conditions. This CFD model was validated against the experimental data at different guide vane openings in turbine operating mode.\u0000 Based on the analysis of the experimental data, flow visualization, and CFD results focusing especially on the flow features in the vaneless space and at the runner inlet, the onset and development of the flow instabilities were explored. Furthermore, a flow control technology that entailed injecting air and water in the vaneless space of a model pump-turbine was implemented for suppressing the flow instabilities and thus extending the operating range of the pump-turbine. Both air- and water-injection were applied by using an external energy source (compressor and pump) and discrete nozzles that are distributed in the vaneless space circumferentially. The S-shaped pump-turbine characteristics in turbine operating mode were modified so that the slope at speed no load conditions was no more positive indicating an improvement in the stability behavior. The analysis of the unsteady pressure data indicates the suppression of flow instability such as rotating stall with fluid injection in the vaneless space. The positive effect of fluid injection on the pump-turbine characteristics was also demonstrated in the CFD calculations. CFD was able to predict the pump-turbine dimensionless discharge, Kcm1, - speed, Ku1, characteristic curve with water injection correctly.\u0000 After the CFD tool is validated for the prediction of the pump-turbine characteristics with fluid injection, further CFD simulations were carried out in order to improve the effectiveness of flow control and if possible, using less amount of injected fluid in the vaneless space. The goal was to optimize the fluid injection so that the instabilities can be suppressed with the lowest possible water/energy consumption. Parameters such as number of injection nozzles, nozzle position, nozzle diameter, and injection direction are varied. Several configurations of water injection system i.e., changing the number, location, and distribution of injection nozzles circumferentially and radially, direction of flow injection with respect to the main flow in the vaneless space, symmetrical and asymmetrical circumferential distribution of the nozzles i","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78828128","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}
In order to characterize wastewater pumps regarding their clogging behaviour, a wide variety of test procedures with artificial wastewater exist. These tests provide a good insight into the clogging characteristics of a pump. However, conclusions about the clogging mechanisms and their sources cannot be drawn. This paper deals with the design and implementation of an optical access on the suction side of a wastewater pump to allow visualisation of the interaction between impeller and textile via high-speed recordings. The optical access is realized by an endoscope and a connected high-speed camera with a frame rate of 2000 fps and a resolution of 1024 × 1024 pixels. To ensure sufficient illumination of the impeller, a light ring assembled from 12 high power LEDs with a luminous flux of 5595 lumen are circumferentially arranged around the suction side of the pump. The light ring concept is scalable to fit any pump size. A clogging-affine impeller is developed, 3D printed and used for experimental investigations. For the investigated impeller, the blade’s upper area is identified to be crucial for pump clogging. Optical accessibility provides an important contribution to develop non-clogging impellers.
{"title":"Visualisation of Interactions Between Impeller and Textile in a Wastewater Pump","authors":"M. Steffen, P. Thamsen","doi":"10.1115/fedsm2021-65427","DOIUrl":"https://doi.org/10.1115/fedsm2021-65427","url":null,"abstract":"\u0000 In order to characterize wastewater pumps regarding their clogging behaviour, a wide variety of test procedures with artificial wastewater exist. These tests provide a good insight into the clogging characteristics of a pump. However, conclusions about the clogging mechanisms and their sources cannot be drawn.\u0000 This paper deals with the design and implementation of an optical access on the suction side of a wastewater pump to allow visualisation of the interaction between impeller and textile via high-speed recordings. The optical access is realized by an endoscope and a connected high-speed camera with a frame rate of 2000 fps and a resolution of 1024 × 1024 pixels. To ensure sufficient illumination of the impeller, a light ring assembled from 12 high power LEDs with a luminous flux of 5595 lumen are circumferentially arranged around the suction side of the pump. The light ring concept is scalable to fit any pump size. A clogging-affine impeller is developed, 3D printed and used for experimental investigations. For the investigated impeller, the blade’s upper area is identified to be crucial for pump clogging. Optical accessibility provides an important contribution to develop non-clogging impellers.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"291 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75197367","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}
Sambhaji T. Kadam, I. Hassan, L. Wang, M. A. Rahman
Rapid urbanization resulted in the drastic expansion of the built infrastructure in urban areas. This eventually led to an increase in energy consumption in the residential and commercial sectors. An appropriate selection of the convective heat transfer coefficient correlation at the design stage is of vital importance as it directly affects the cooling load of the building and consequently buildings’ energy demand. In this context, the comparative analysis of existing convective heat transfer coefficient correlations (CHTCs) used in building simulation programs such as EnergyPlus, ESP-r, IES, IDA, and TAS, are assessed. These correlations are tested against the data of Liu et al.’s [1]. It is observed that some of CHTCs correlations show lower error and others exhibit a significant deviation. In the case of the CHTCs used EnergyPlus, it is observed that the TARP algorithm shows overall better prediction ability for windward, leeward, and roof surface. On the other hand, in the case of the ESP-r, different correlations show a good prediction ability for different surfaces. For windward surface: MoWiTT; for leeward surface: MoWiTT and McAdams; and for roof surface: Liu and Harris show closer prediction with an error of less than 30% among other correlations. The correlation used in IES, IDA, and TAS shows a large deviation for windward, leeward, and roof surfaces under considered input. Based on this analysis, it can be concluded that the choice of such CHTCs uses in the BES tool can lead to the significantly higher energy consumption of the building and hence need the expertise to make the appropriate selection.
{"title":"Impact of Urban Microclimate on Air Conditioning Energy Consumption Using Different Convective Heat Transfer Coefficient Correlations Available in Building Energy Simulation Tools","authors":"Sambhaji T. Kadam, I. Hassan, L. Wang, M. A. Rahman","doi":"10.1115/fedsm2021-65589","DOIUrl":"https://doi.org/10.1115/fedsm2021-65589","url":null,"abstract":"\u0000 Rapid urbanization resulted in the drastic expansion of the built infrastructure in urban areas. This eventually led to an increase in energy consumption in the residential and commercial sectors. An appropriate selection of the convective heat transfer coefficient correlation at the design stage is of vital importance as it directly affects the cooling load of the building and consequently buildings’ energy demand. In this context, the comparative analysis of existing convective heat transfer coefficient correlations (CHTCs) used in building simulation programs such as EnergyPlus, ESP-r, IES, IDA, and TAS, are assessed. These correlations are tested against the data of Liu et al.’s [1]. It is observed that some of CHTCs correlations show lower error and others exhibit a significant deviation. In the case of the CHTCs used EnergyPlus, it is observed that the TARP algorithm shows overall better prediction ability for windward, leeward, and roof surface. On the other hand, in the case of the ESP-r, different correlations show a good prediction ability for different surfaces. For windward surface: MoWiTT; for leeward surface: MoWiTT and McAdams; and for roof surface: Liu and Harris show closer prediction with an error of less than 30% among other correlations. The correlation used in IES, IDA, and TAS shows a large deviation for windward, leeward, and roof surfaces under considered input. Based on this analysis, it can be concluded that the choice of such CHTCs uses in the BES tool can lead to the significantly higher energy consumption of the building and hence need the expertise to make the appropriate selection.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73781858","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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