The transport of a flow from a static system into a rotating system can be realized by means of orifices in the rotating wall. In this paper the experimental study of a liquid flowing through a radial, sharp-edged orifice with a l/d-ratio of 1.56 in a rotating shaft is presented. The discharge coefficient cd for (circumferential) orifice speeds of up to 24 m s−1 and Reynolds numbers ranging from Red = 1.2 × 104 to 3.4 × 104 is evaluated for an oil with a density of 920 kg m−3 and a kinematic viscosity of 5.3 × 10−6 m s−2. A modular test rig was designed, consisting of two concentric rotating shafts forming an annular duct. The outer shaft is fitted with the orifices through which the liquid passes from the static into the rotating system. The modularity allows the exchange of the shaft element containing the orifices. For this study two shaft elements with 5 or 12 radial, cylindrical, sharp-edged orifices were used. Thus, a wider range of flow velocities through a single orifice was achieved. This study is the first to illustrate the effect of cavitation in a rotating orifice. Outside the cavitation regime a change of the approaching flow represented by the velocity ratio causes a change of the discharge coefficient while within the cavitation regime cd additionally depends on the cavitation parameter. A relationship for the flow contraction in the cavitation regime depending on the orifice velocity and the pressures upstream and downstream of the orifice is derived. For a second set of orifices, where the liquid exits the rotor into the surrounding air, a significant regime change depending on the ratio of orifice rotational speed and flow velocity occurs. For higher flow velocities through the orifice this change occurs for lower orifice speeds. A likely cause is the onset of cavitation.
流动从静态系统进入旋转系统可以通过旋转壁上的孔来实现。本文对液体在转轴中流过l/d比为1.56的径向锐边孔进行了实验研究。对于密度为920 kg m - 3，运动粘度为5.3 × 10 - 6 m s - 2的油，(周向)孔口速度高达24 m s - 1，雷诺数范围为Red = 1.2 × 104至3.4 × 104的流量系数cd进行了评估。设计了一个模块化的试验台，由两个同心旋转轴组成一个环形管道。外轴装有孔，液体通过孔从静态系统进入旋转系统。模块化允许交换包含孔的轴元件。在这项研究中，使用了两个具有5或12个径向，圆柱形，锋利边缘孔的轴元件。因此，通过单个孔板实现了更大范围的流速。本研究首次阐明了旋转孔内空化的影响。在空化区外，以流速比表示的接近流的变化引起流量系数的变化，而在空化区内，cd还取决于空化参数。导出了空化区流动收缩与孔板速度和孔板上下游压力的关系。对于第二组孔，其中液体离开转子进入周围的空气，一个显着的制度变化取决于孔转速和流速的比率发生。当通过孔板的流速较高时，这种变化发生在孔板速度较低时。一个可能的原因是空化的开始。
{"title":"Experimental Investigation of the Discharge Behavior of Cavitating and Non-Cavitating Flow Through Rotating Radial Orifices","authors":"Laura Cordes, C. Schwitzke, H. Bauer","doi":"10.1115/gt2019-90213","DOIUrl":"https://doi.org/10.1115/gt2019-90213","url":null,"abstract":"\u0000 The transport of a flow from a static system into a rotating system can be realized by means of orifices in the rotating wall. In this paper the experimental study of a liquid flowing through a radial, sharp-edged orifice with a l/d-ratio of 1.56 in a rotating shaft is presented. The discharge coefficient cd for (circumferential) orifice speeds of up to 24 m s−1 and Reynolds numbers ranging from Red = 1.2 × 104 to 3.4 × 104 is evaluated for an oil with a density of 920 kg m−3 and a kinematic viscosity of 5.3 × 10−6 m s−2.\u0000 A modular test rig was designed, consisting of two concentric rotating shafts forming an annular duct. The outer shaft is fitted with the orifices through which the liquid passes from the static into the rotating system. The modularity allows the exchange of the shaft element containing the orifices. For this study two shaft elements with 5 or 12 radial, cylindrical, sharp-edged orifices were used. Thus, a wider range of flow velocities through a single orifice was achieved.\u0000 This study is the first to illustrate the effect of cavitation in a rotating orifice. Outside the cavitation regime a change of the approaching flow represented by the velocity ratio causes a change of the discharge coefficient while within the cavitation regime cd additionally depends on the cavitation parameter. A relationship for the flow contraction in the cavitation regime depending on the orifice velocity and the pressures upstream and downstream of the orifice is derived.\u0000 For a second set of orifices, where the liquid exits the rotor into the surrounding air, a significant regime change depending on the ratio of orifice rotational speed and flow velocity occurs. For higher flow velocities through the orifice this change occurs for lower orifice speeds. A likely cause is the onset of cavitation.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123142179","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 flow inside a gas turbine engine has unique complexities. One of the important characteristics of such flow field is the existence of periodic unsteady wakes, originating from stator–rotor interaction. The unsteady wakes, with their highly vortical core, impinge on the downstream blade surfaces and cause an intermittent transition of the boundary layer from laminar to turbulent. The relative intermittency value corresponding to the wake vortical core and the calm region outside the wake, irrespective of freestream turbulence intensity and wake frequency, exhibits a universal behavior which is best described by the universal intermittency function of Chakka and Schobeiri [1, 2]. This study aims at introducing a new physics-based universal intermittency function that in conjunction with the current turbulence models accurately predicts the unsteady behavior of an intermittent flow. For that reason, a transport equation for turbulence intermittency was proposed based on this function and was integrated into a RANS based solver with k-ω turbulence model. The model was tested for reliability. Experimental aerodynamics and heat transfer measurements conducted at Turbomachinery Performance and Flow research Lab (TPFL) at Texas A&M University, were used as benchmark tests. For experimental measurements, an unsteady linear cascade facility in TPFL was used to produce the periodic unsteady flow condition. Moving wakes, originating from upstream blades, were simulated in this facility by rods attached to two parallel timing belts in front of the turbine blades. Heat transfer measurements along the suction surface were conducted utilizing a specially manufactured blade with an internal heater core, instrumented with liquid crystal. All Measurements and calculations were conducted at Reynolds number of 264,000. The computational results, obtained from implementing the new enhanced intermittency transport equation into the solver, are compared with (a) experimental measurements and (b) with the computational results from RANS that incorporates Langtry-Menter [3, 4] method.
{"title":"A New Physics Based Unsteady Transition Model Using the Universal Intermittency Function","authors":"Ali Nikparto, M. Schobeiri","doi":"10.1115/gt2019-90585","DOIUrl":"https://doi.org/10.1115/gt2019-90585","url":null,"abstract":"\u0000 The flow inside a gas turbine engine has unique complexities. One of the important characteristics of such flow field is the existence of periodic unsteady wakes, originating from stator–rotor interaction. The unsteady wakes, with their highly vortical core, impinge on the downstream blade surfaces and cause an intermittent transition of the boundary layer from laminar to turbulent. The relative intermittency value corresponding to the wake vortical core and the calm region outside the wake, irrespective of freestream turbulence intensity and wake frequency, exhibits a universal behavior which is best described by the universal intermittency function of Chakka and Schobeiri [1, 2]. This study aims at introducing a new physics-based universal intermittency function that in conjunction with the current turbulence models accurately predicts the unsteady behavior of an intermittent flow. For that reason, a transport equation for turbulence intermittency was proposed based on this function and was integrated into a RANS based solver with k-ω turbulence model. The model was tested for reliability. Experimental aerodynamics and heat transfer measurements conducted at Turbomachinery Performance and Flow research Lab (TPFL) at Texas A&M University, were used as benchmark tests. For experimental measurements, an unsteady linear cascade facility in TPFL was used to produce the periodic unsteady flow condition. Moving wakes, originating from upstream blades, were simulated in this facility by rods attached to two parallel timing belts in front of the turbine blades. Heat transfer measurements along the suction surface were conducted utilizing a specially manufactured blade with an internal heater core, instrumented with liquid crystal. All Measurements and calculations were conducted at Reynolds number of 264,000. The computational results, obtained from implementing the new enhanced intermittency transport equation into the solver, are compared with (a) experimental measurements and (b) with the computational results from RANS that incorporates Langtry-Menter [3, 4] method.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124337511","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. Krumme, Clemens Buske, Johannes R. Bachner, J. Dähnert, M. Tegeler, F. Ferraro, S. Gövert, F. Kocian, F. Mare, A. Pahs
Within the scope of European Commission FP7 project FACTOR, dedicated to combustor-turbine-interaction research, a clean-sheet design of a rotating turbine test rig featuring a non-reacting combustor simulator was created and built among the partners. German Aerospace Center DLR provided the operational facility NG-Turb to which the rig was adapted and was responsible for global rig integration and operation, also including aerodynamic probe measurements of the flow field. The rig and experimental set-up is described and post-processed results from probe traverses in several measurement planes are presented and discussed. Special attention is paid to the comparison and influence of two combustor-NGV clocking positions on the periodic turbine flow field, made possible by rig adaptation during the campaign. The strongly distorted and nonuniform turbine inlet flow created by the combustor simulator proved challenging for the probe measurements, but at the same time set a realistic boundary condition enabling the analysis of ‘CTI’ by flow structures migrating through the blade rows.
{"title":"Investigation of Combustor-Turbine-Interaction in a Rotating Cooled Transonic High-Pressure Turbine Test Rig: Part 1 — Experimental Results","authors":"A. Krumme, Clemens Buske, Johannes R. Bachner, J. Dähnert, M. Tegeler, F. Ferraro, S. Gövert, F. Kocian, F. Mare, A. Pahs","doi":"10.1115/gt2019-90733","DOIUrl":"https://doi.org/10.1115/gt2019-90733","url":null,"abstract":"\u0000 Within the scope of European Commission FP7 project FACTOR, dedicated to combustor-turbine-interaction research, a clean-sheet design of a rotating turbine test rig featuring a non-reacting combustor simulator was created and built among the partners. German Aerospace Center DLR provided the operational facility NG-Turb to which the rig was adapted and was responsible for global rig integration and operation, also including aerodynamic probe measurements of the flow field.\u0000 The rig and experimental set-up is described and post-processed results from probe traverses in several measurement planes are presented and discussed. Special attention is paid to the comparison and influence of two combustor-NGV clocking positions on the periodic turbine flow field, made possible by rig adaptation during the campaign. The strongly distorted and nonuniform turbine inlet flow created by the combustor simulator proved challenging for the probe measurements, but at the same time set a realistic boundary condition enabling the analysis of ‘CTI’ by flow structures migrating through the blade rows.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"23 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126062947","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 effect of five arrangements of the double-slot injections on the leakage flow control is studied in a honeycomb-tip turbine cascade numerically. The honeycomb tip is covered with 67 intact honeycomb cavities, since the uneven tip is wearable and the cavity vortex could realize the aerodynamic sealing for the leakage flow. Then in the present study, a pair of injection slots is arranged blow each cavity, aiming to enhance the leakage flow suppression by modifying the cavity vortex. According to the orientation of the two slots, five designs of the double-slot injections are proposed. In detail, the two slots are opposite to each other or keep tangential to the original cavity vortex roughly. The three dimensional calculations were completed by using Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model in the commercial software ANSYS CFX. The estimation of these tip designs is mainly according to the tip leakage mass flow rate and the total pressure loss. Firstly, the injection structures induced by the slots can be divided into X- and T-types inside the cavity. The results show that the T-type structure is more effective in reducing the tip leakage mass flow rate, with the maximum reduction up to 48.2%. Then the effect on the flow field inside the gap and the secondary flow in the upper passage is analyzed. Compared with the flat tip, the span-wise position of the tip leakage vortex core drops within the cascade and the range of the affected loss region expands. At the cascade exit, the tip leakage vortex moves toward the passage vortex near the casing, while the latter’s core rises. The position changes of the secondary vortices eventually determine the total pressure loss contour downstream the cascade. Finally, the injection total pressure and the upper casing motion are investigated. Interestingly, the injection intensity (mass flow rate) increases with the injection total pressure but this value decreases as the casing speed increases. The tip leakage mass flow rate decreases linearly as increasing the injection total pressure or the casing speed. Yet the averaged total pressure loss downstream the cascade increases with the injection total pressure but appears a nonlinear distribution against the casing speed.
{"title":"Effect of the Double-Slot Injection on the Leakage Flow Control in a Honeycomb-Tip Turbine Cascade","authors":"Yabo Wang, Yan-ping Song, Jianyang Yu, Fu Chen","doi":"10.1115/gt2019-90589","DOIUrl":"https://doi.org/10.1115/gt2019-90589","url":null,"abstract":"\u0000 The effect of five arrangements of the double-slot injections on the leakage flow control is studied in a honeycomb-tip turbine cascade numerically. The honeycomb tip is covered with 67 intact honeycomb cavities, since the uneven tip is wearable and the cavity vortex could realize the aerodynamic sealing for the leakage flow. Then in the present study, a pair of injection slots is arranged blow each cavity, aiming to enhance the leakage flow suppression by modifying the cavity vortex. According to the orientation of the two slots, five designs of the double-slot injections are proposed. In detail, the two slots are opposite to each other or keep tangential to the original cavity vortex roughly. The three dimensional calculations were completed by using Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model in the commercial software ANSYS CFX. The estimation of these tip designs is mainly according to the tip leakage mass flow rate and the total pressure loss. Firstly, the injection structures induced by the slots can be divided into X- and T-types inside the cavity. The results show that the T-type structure is more effective in reducing the tip leakage mass flow rate, with the maximum reduction up to 48.2%. Then the effect on the flow field inside the gap and the secondary flow in the upper passage is analyzed. Compared with the flat tip, the span-wise position of the tip leakage vortex core drops within the cascade and the range of the affected loss region expands. At the cascade exit, the tip leakage vortex moves toward the passage vortex near the casing, while the latter’s core rises. The position changes of the secondary vortices eventually determine the total pressure loss contour downstream the cascade. Finally, the injection total pressure and the upper casing motion are investigated. Interestingly, the injection intensity (mass flow rate) increases with the injection total pressure but this value decreases as the casing speed increases. The tip leakage mass flow rate decreases linearly as increasing the injection total pressure or the casing speed. Yet the averaged total pressure loss downstream the cascade increases with the injection total pressure but appears a nonlinear distribution against the casing speed.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115369628","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}
K. Yonezawa, M. Takayasu, Genki Nakai, K. Sugiyama, Katsuhiko Sugita, S. Umezawa, Shuichi Ohmori
Nozzle guide vanes (NGVs) and rotor blades deteriorate due to erosion, and this may affect the aerodynamic characteristics of gas turbines. According to previous studies, the erosion of first-stage NGVs significantly affected the blade loading of the first-stage rotor. An increase in the tip gap also may significantly affect the gas turbine performance. In the present study, numerical investigations have been carried out using a real eroded nozzle and blade geometries for two purposes. One purpose was to clarify the influences underlying the deterioration of the nozzle and the rotor blade, such as the effects on the erosion of NGVs in the first stage and the effects of the tip gap on the gas turbine performance. The other was to develop a method to estimate the total gas turbine performance using a CFD simulation and a heat balance analysis. The results show that the erosion of NGV leads to an increased flow rate and affects the operating condition of the gas turbine cycle. This, in turn, can decrease the total thermal efficiency. The experimental results suggest that an increase in the tip gap width decreases rotor output almost linearly, and the numerical results showed the same tendency. The influence of the tip gap in the real gas turbine condition was also examined, revealing that an increase in the tip gap leads to an increase in the pressure loss in the nozzle downstream as well as around the rotor blade itself. Consequently, the total power output and the isentropic efficiency of the turbine decreased.
{"title":"An Impact Assessment of Erosion of Nozzle Guide Vanes and Rotor Blades on Aerodynamic Performance of a Gas Turbine by CFD","authors":"K. Yonezawa, M. Takayasu, Genki Nakai, K. Sugiyama, Katsuhiko Sugita, S. Umezawa, Shuichi Ohmori","doi":"10.1115/gt2019-90636","DOIUrl":"https://doi.org/10.1115/gt2019-90636","url":null,"abstract":"\u0000 Nozzle guide vanes (NGVs) and rotor blades deteriorate due to erosion, and this may affect the aerodynamic characteristics of gas turbines. According to previous studies, the erosion of first-stage NGVs significantly affected the blade loading of the first-stage rotor. An increase in the tip gap also may significantly affect the gas turbine performance. In the present study, numerical investigations have been carried out using a real eroded nozzle and blade geometries for two purposes. One purpose was to clarify the influences underlying the deterioration of the nozzle and the rotor blade, such as the effects on the erosion of NGVs in the first stage and the effects of the tip gap on the gas turbine performance. The other was to develop a method to estimate the total gas turbine performance using a CFD simulation and a heat balance analysis. The results show that the erosion of NGV leads to an increased flow rate and affects the operating condition of the gas turbine cycle. This, in turn, can decrease the total thermal efficiency. The experimental results suggest that an increase in the tip gap width decreases rotor output almost linearly, and the numerical results showed the same tendency. The influence of the tip gap in the real gas turbine condition was also examined, revealing that an increase in the tip gap leads to an increase in the pressure loss in the nozzle downstream as well as around the rotor blade itself. Consequently, the total power output and the isentropic efficiency of the turbine decreased.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116949703","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}
J. Uher, P. Milčák, Radek Škach, D. Fenderl, P. Zítek, Marek Klimko
Long-term efforts have been made to understand loss generation and its reduction in the field of axial turbomachines. The traditional approach to losses for an isolated blade row considers the profile and the secondary losses as a result of viscous flow. The additional kinds of losses in the stage are connected with the shear stress in the mixing process. These losses result from the mixing of the main stream flow with 1) the stator leakage injected through the root axial gap and 2) the return of the tip leakage over the bucket shroud. This article focuses on the first type of mixing losses. The leakage to the main stream flow ratio and the root reaction are the two key parameters investigated in this study. The primary data source for this study is the experiment. An experimental single stage air turbine was modified to set and precisely measure the stator leakage flow. Three configurations of the single-stage test rig with different reaction levels were tested. The second data source for this study is CFD computation. These computations are applied to different geometries and conditions from the experiment; they are derived from real steam turbine stages designed in DSPW. The computations simulate multistage configuration and real steam is considered as the working fluid. CFD computations were performed in the commercial software ANSYS CFX. Each configuration task was computed in three iterative steps. Each step takes the distribution of the flow parameters on the boundary domains from the previous iteration. The final results from this ‘repeating boundary conditions’ approach better correspond with the real expansion in a multistage configuration. The two data sources are not directly comparable. The experiment is used for validation of the trends. The computations provide the possibility of a multi-parametric study. The multi-parametric study is necessary to obtain a more general loss model which can be used during turbine design. The evaluation of the experimental and numerical parts focuses on a comparison of the overall stage performance. Stage efficiency and reaction are presented in relation to the ratio between leakage and main stream flow.
{"title":"Experimental and Numerical Evaluation of Losses From Turbine Hub Clearance Flow","authors":"J. Uher, P. Milčák, Radek Škach, D. Fenderl, P. Zítek, Marek Klimko","doi":"10.1115/gt2019-90726","DOIUrl":"https://doi.org/10.1115/gt2019-90726","url":null,"abstract":"\u0000 Long-term efforts have been made to understand loss generation and its reduction in the field of axial turbomachines. The traditional approach to losses for an isolated blade row considers the profile and the secondary losses as a result of viscous flow. The additional kinds of losses in the stage are connected with the shear stress in the mixing process. These losses result from the mixing of the main stream flow with 1) the stator leakage injected through the root axial gap and 2) the return of the tip leakage over the bucket shroud. This article focuses on the first type of mixing losses. The leakage to the main stream flow ratio and the root reaction are the two key parameters investigated in this study.\u0000 The primary data source for this study is the experiment. An experimental single stage air turbine was modified to set and precisely measure the stator leakage flow. Three configurations of the single-stage test rig with different reaction levels were tested.\u0000 The second data source for this study is CFD computation. These computations are applied to different geometries and conditions from the experiment; they are derived from real steam turbine stages designed in DSPW. The computations simulate multistage configuration and real steam is considered as the working fluid. CFD computations were performed in the commercial software ANSYS CFX. Each configuration task was computed in three iterative steps. Each step takes the distribution of the flow parameters on the boundary domains from the previous iteration. The final results from this ‘repeating boundary conditions’ approach better correspond with the real expansion in a multistage configuration.\u0000 The two data sources are not directly comparable. The experiment is used for validation of the trends. The computations provide the possibility of a multi-parametric study. The multi-parametric study is necessary to obtain a more general loss model which can be used during turbine design.\u0000 The evaluation of the experimental and numerical parts focuses on a comparison of the overall stage performance. Stage efficiency and reaction are presented in relation to the ratio between leakage and main stream flow.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114316383","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}
J. Eitenmüller, M. Wilhelm, L. Gresser, Tom Ostrowksi, Sebastian Leichtfuß, H. Schiffer, Christoph Lyko, S. Naik
High pressure turbines are nowadays designed to a point where most design enhancements only yield marginal efficiency improvements. This challenges research facilities to reliably resolve ever smaller differences in efficiency caused by individual design changes. In recent years, immense efforts towards such highly accurate delta-efficiency measurements have been undertaken at the Large Scale Turbine Rig (LSTR). This paper comprises an overview of the applied methodology and the achievements on the basis of various validation cases. By thoroughly controlling the operation point and accounting for all variables affecting the efficiency η, the rig can resolve efficiency-differences Δη of ±0.1 % for a single day measurement. Four benchmark cases are investigated to validate the rig’s capabilities. First, the influence of tip clearance is investigated for a squealer-type geometry for swirling inflow. It is found that for an increase in tip clearance of 1 %, η is decreased by 2.68 %. Then, it is shown that a winglet-type tip geometry may improve the efficiency by Δη 0.33% in comparison to the squealer tip. Third, it is shown that these trends are similar for plain inflow, however swirl decreases efficiency by up to 1.25 % in comparison to plain inflow. Finally, the clocking-position of the combustor-module relative to the nozzle guide vanes is varied leading to efficiency differences of up to 0.52 %.
{"title":"Highly Accurate Delta Efficiency Measurements at the Large Scale Turbine Rig","authors":"J. Eitenmüller, M. Wilhelm, L. Gresser, Tom Ostrowksi, Sebastian Leichtfuß, H. Schiffer, Christoph Lyko, S. Naik","doi":"10.1115/GT2019-90294","DOIUrl":"https://doi.org/10.1115/GT2019-90294","url":null,"abstract":"\u0000 High pressure turbines are nowadays designed to a point where most design enhancements only yield marginal efficiency improvements. This challenges research facilities to reliably resolve ever smaller differences in efficiency caused by individual design changes. In recent years, immense efforts towards such highly accurate delta-efficiency measurements have been undertaken at the Large Scale Turbine Rig (LSTR). This paper comprises an overview of the applied methodology and the achievements on the basis of various validation cases.\u0000 By thoroughly controlling the operation point and accounting for all variables affecting the efficiency η, the rig can resolve efficiency-differences Δη of ±0.1 % for a single day measurement. Four benchmark cases are investigated to validate the rig’s capabilities. First, the influence of tip clearance is investigated for a squealer-type geometry for swirling inflow. It is found that for an increase in tip clearance of 1 %, η is decreased by 2.68 %. Then, it is shown that a winglet-type tip geometry may improve the efficiency by Δη 0.33% in comparison to the squealer tip. Third, it is shown that these trends are similar for plain inflow, however swirl decreases efficiency by up to 1.25 % in comparison to plain inflow. Finally, the clocking-position of the combustor-module relative to the nozzle guide vanes is varied leading to efficiency differences of up to 0.52 %.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127175318","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}
D. Biliotti, Alberto Greco, F. Cangioli, G. Iurisci
The performance of radial inflow turbines, and specifically of turboexpanders for oil & gas applications, has been traditionally described in terms of efficiency versus velocity speed ratio (U/C) and discharge flow coefficient (Q/N). Especially in the testing phase, this latter parameter has been often preferred to the angle setting of moveable inlet guide vanes (IGV), which are standard equipment for most turboexpanders. In practice, the expander U/C has been often considered to give the performance backbone, while the Q/N ratio has been used for secondary corrections. Moreover, although the role of pressure ratio (PR) is recognized, its impact has been experimentally unexplored in those cases where testing facilities had capacity limitations. Eventually, in case of variable nozzles, the inlet flow capacity curve has been rarely included among the output performance variables, being the attention mainly focused on efficiency. In the present paper, beside an overview and an explanation of the physical meaning of traditional performance parameters, an alternative approach based on torque mapping versus U/C is introduced and discussed in detail. As a matter of fact, numerical and experimental data show smooth and regular trends when torque coefficient is used instead of adiabatic efficiency. Moreover, performance based on torque coefficient can be more conveniently extrapolated at extreme off-design conditions such as start-up (locked rotor condition) or full speed no load. The ease of extrapolation is particularly important for machine operability, which often requires accurate modeling of transient missions at very partial loads (as for instance during start-up or shut-down). Examples will be offered to show the advantages of torque coefficient representation and how sensitive this is to IGV setting and pressure.
{"title":"A New Approach to Performance Mapping of Radial Inflow Turbines","authors":"D. Biliotti, Alberto Greco, F. Cangioli, G. Iurisci","doi":"10.1115/gt2019-91856","DOIUrl":"https://doi.org/10.1115/gt2019-91856","url":null,"abstract":"\u0000 The performance of radial inflow turbines, and specifically of turboexpanders for oil & gas applications, has been traditionally described in terms of efficiency versus velocity speed ratio (U/C) and discharge flow coefficient (Q/N). Especially in the testing phase, this latter parameter has been often preferred to the angle setting of moveable inlet guide vanes (IGV), which are standard equipment for most turboexpanders. In practice, the expander U/C has been often considered to give the performance backbone, while the Q/N ratio has been used for secondary corrections. Moreover, although the role of pressure ratio (PR) is recognized, its impact has been experimentally unexplored in those cases where testing facilities had capacity limitations. Eventually, in case of variable nozzles, the inlet flow capacity curve has been rarely included among the output performance variables, being the attention mainly focused on efficiency.\u0000 In the present paper, beside an overview and an explanation of the physical meaning of traditional performance parameters, an alternative approach based on torque mapping versus U/C is introduced and discussed in detail. As a matter of fact, numerical and experimental data show smooth and regular trends when torque coefficient is used instead of adiabatic efficiency. Moreover, performance based on torque coefficient can be more conveniently extrapolated at extreme off-design conditions such as start-up (locked rotor condition) or full speed no load. The ease of extrapolation is particularly important for machine operability, which often requires accurate modeling of transient missions at very partial loads (as for instance during start-up or shut-down). Examples will be offered to show the advantages of torque coefficient representation and how sensitive this is to IGV setting and pressure.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134262261","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}
Matthias Abel, R. Martinez-Botas, Michael Wöhr, M. Müller, Johannes Leweux
This paper presents a detailed loss analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy duty engine turbocharger. The analysis is carried out in order to investigate the loss distribution in the stage. To quantify the impact of different loss types and locations, a detailed validated steady-state 3D CFD solution is employed. The local entropy production rate is calculated for two operating points (full load and part load), which are most relevant to the real world operation of the compressor in a truck application. Two methods are suggested as the procedure for the division of the whole fluid volume into sub-volumes, because this is key for the resulting loss distribution. The primary loss generating mechanisms are shown at main operating conditions to reveal the regions of improvement. A detailed grid study was conducted to enable the calculation of the entropy ratio. It was possible to capture around 78% (partial load) and 70% (full load) of the entropy production with a mesh with circa 100 million elements. Around half of the losses were due to the boundary layer friction, followed by losses associated with a boundary layer separation resulting from the back-flow at the shroud contour close to the impeller exit and back disk friction accounted for with 6–7% of the stage’s losses.
{"title":"3D Computational Loss Analysis of a Compressor for Heavy Duty Truck Engine Turbochargers","authors":"Matthias Abel, R. Martinez-Botas, Michael Wöhr, M. Müller, Johannes Leweux","doi":"10.1115/gt2019-90038","DOIUrl":"https://doi.org/10.1115/gt2019-90038","url":null,"abstract":"\u0000 This paper presents a detailed loss analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy duty engine turbocharger. The analysis is carried out in order to investigate the loss distribution in the stage. To quantify the impact of different loss types and locations, a detailed validated steady-state 3D CFD solution is employed. The local entropy production rate is calculated for two operating points (full load and part load), which are most relevant to the real world operation of the compressor in a truck application. Two methods are suggested as the procedure for the division of the whole fluid volume into sub-volumes, because this is key for the resulting loss distribution.\u0000 The primary loss generating mechanisms are shown at main operating conditions to reveal the regions of improvement. A detailed grid study was conducted to enable the calculation of the entropy ratio. It was possible to capture around 78% (partial load) and 70% (full load) of the entropy production with a mesh with circa 100 million elements. Around half of the losses were due to the boundary layer friction, followed by losses associated with a boundary layer separation resulting from the back-flow at the shroud contour close to the impeller exit and back disk friction accounted for with 6–7% of the stage’s losses.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125553407","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}
Blade loading on a single stage high pressure centrifugal compressor is limited due to separation that might occur on the suction side of the airfoil at mass flow rates lower than design point. A novel configuration of centrifugal compressor is designed and analyzed to overcome this issue by placing multiple rotors on the same hub with a stator vane in between similar to a multi-stage axial compressor blade arrangement. By having independent rotors, blade loading can be distributed more efficiently and higher pressure rise can be achieved through this design. As the blade chord length is reduced due to splitting of single impeller blade, the effective turning angle is divided through several stages thereby lowering the adverse pressure gradient reducing the chance of separation. Stator vanes are placed in between the rotors so that the successive rotor receives the flow at desired incidence angle. The attempt here is to apply the same principle of axial compressor multi-staging on a centrifugal compressor and compare the performance with single stage using low to high fidelity analysis framework developed in-house. A low fidelity 1D analysis tool CIMdes is used for evaluating blade angles and stage degree of reaction which are exported to T-blade3, in-house parametric geometry tool, for 3D blade generation. These blades are further analyzed using 3D CFD analysis using an in-house automated multifidelity framework. Loss quantification revealed that diffuser losses are higher in singlestage and the novel design increased the backsweep angle resulting in lower diffuser losses. Splitting the single rotor facilitated the increase in backsweep angle to a larger range as compared to single rotor impeller configurations. Two configurations with different shroud height for the single stage compressors are investigated and compared with the novel compressor with respective flowpaths at 100% speedline using a multi-fidelity design analysis suite. The flow capacity is extended near the stall with a penalty in efficiency for configuration-1. Configuration-2 showed an improvement in efficiency at design mass flow rate. The preliminary analysis demonstrates the advantages of the multi-staging on the same hub and extends the design space for performance range improvement with some trade-offs.
{"title":"High Pressure Novel Single Hub Multi-Rotor Centrifugal Compressor: Performance Prediction and Loss Analysis","authors":"Sai Muppana, K. Siddappaji, S. Abdallah","doi":"10.1115/gt2019-91967","DOIUrl":"https://doi.org/10.1115/gt2019-91967","url":null,"abstract":"\u0000 Blade loading on a single stage high pressure centrifugal compressor is limited due to separation that might occur on the suction side of the airfoil at mass flow rates lower than design point. A novel configuration of centrifugal compressor is designed and analyzed to overcome this issue by placing multiple rotors on the same hub with a stator vane in between similar to a multi-stage axial compressor blade arrangement. By having independent rotors, blade loading can be distributed more efficiently and higher pressure rise can be achieved through this design. As the blade chord length is reduced due to splitting of single impeller blade, the effective turning angle is divided through several stages thereby lowering the adverse pressure gradient reducing the chance of separation. Stator vanes are placed in between the rotors so that the successive rotor receives the flow at desired incidence angle. The attempt here is to apply the same principle of axial compressor multi-staging on a centrifugal compressor and compare the performance with single stage using low to high fidelity analysis framework developed in-house. A low fidelity 1D analysis tool CIMdes is used for evaluating blade angles and stage degree of reaction which are exported to T-blade3, in-house parametric geometry tool, for 3D blade generation. These blades are further analyzed using 3D CFD analysis using an in-house automated multifidelity framework. Loss quantification revealed that diffuser losses are higher in singlestage and the novel design increased the backsweep angle resulting in lower diffuser losses. Splitting the single rotor facilitated the increase in backsweep angle to a larger range as compared to single rotor impeller configurations. Two configurations with different shroud height for the single stage compressors are investigated and compared with the novel compressor with respective flowpaths at 100% speedline using a multi-fidelity design analysis suite. The flow capacity is extended near the stall with a penalty in efficiency for configuration-1. Configuration-2 showed an improvement in efficiency at design mass flow rate. The preliminary analysis demonstrates the advantages of the multi-staging on the same hub and extends the design space for performance range improvement with some trade-offs.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131733783","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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