An experimental and computational investigation has been undertaken into the effects of deterioration of the first stage rotor shroud knife-edge seal clearance in a two-stage turbine which has engine representative cavity geometries. Four values of deterioration were investigated which cover the new-condition to old-condition knife-edge seal clearance. Measurements within the first stage rotor shroud cavity show that whilst the leakage mass flow rate increases with deterioration, the angle at which the leakage flow approaches the downstream stator is essentially fixed and independent of the flow coefficient. This is in agreement with a simple over-tip leakage model. Because of the engine representative cavity geometry, the over-shroud leakage flow undergoes little mixing when it re-enters the mainstream and approaches the downstream stator at more than 60° negative incidence. Detailed measurements at the exit of the second stage stator identified two large positive vortices which were not consistent with the horseshoe vortex model for secondary flow. A computational investigation revealed that one vortex originates from the rolling-up within the stator passage of the streamwise vorticity sheet associated with the first stage rotor over-shroud leakage. This roll-up vortex cannot be eliminated. The second vortex is generated within the stator passage by the separation of the over-shroud leakage flow at the leading-edge due to the large negative incidence. It was hypothesised that this separation vortex might be eliminated by locally redesigning the stator. A new stator was designed, manufactured and tested. As predicted, the roll-up vortex was still present but the separation vortex was eliminated. For all the values of deterioration tested the entropy loss coefficient of the new stator and the unchanged second stage rotor were reduced. It is estimated that the new stator would improve the lifetime average efficiency by 0.5% compared to the original.
{"title":"A New Multi-Stage Turbine Stator Design for Improved Performance Retention","authors":"Heather K. Jameson, J. P. Longley","doi":"10.1115/GT2020-14407","DOIUrl":"https://doi.org/10.1115/GT2020-14407","url":null,"abstract":"\u0000 An experimental and computational investigation has been undertaken into the effects of deterioration of the first stage rotor shroud knife-edge seal clearance in a two-stage turbine which has engine representative cavity geometries. Four values of deterioration were investigated which cover the new-condition to old-condition knife-edge seal clearance.\u0000 Measurements within the first stage rotor shroud cavity show that whilst the leakage mass flow rate increases with deterioration, the angle at which the leakage flow approaches the downstream stator is essentially fixed and independent of the flow coefficient. This is in agreement with a simple over-tip leakage model. Because of the engine representative cavity geometry, the over-shroud leakage flow undergoes little mixing when it re-enters the mainstream and approaches the downstream stator at more than 60° negative incidence.\u0000 Detailed measurements at the exit of the second stage stator identified two large positive vortices which were not consistent with the horseshoe vortex model for secondary flow. A computational investigation revealed that one vortex originates from the rolling-up within the stator passage of the streamwise vorticity sheet associated with the first stage rotor over-shroud leakage. This roll-up vortex cannot be eliminated. The second vortex is generated within the stator passage by the separation of the over-shroud leakage flow at the leading-edge due to the large negative incidence. It was hypothesised that this separation vortex might be eliminated by locally redesigning the stator.\u0000 A new stator was designed, manufactured and tested. As predicted, the roll-up vortex was still present but the separation vortex was eliminated. For all the values of deterioration tested the entropy loss coefficient of the new stator and the unchanged second stage rotor were reduced. It is estimated that the new stator would improve the lifetime average efficiency by 0.5% compared to the original.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128681706","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. Simoni, D. Lengani, Daniele Petronio, F. Bertini
A Bayesian method has been used to identify the best model strategy to describe the profile losses of low pressure turbine (LPT) cascades operating under unsteady inflow. The model has been tuned with experimental data measured in a large scale cascade facility, equipped with a moving bar system. Tests have been carried out on two different cascades, investigating three different reduced frequencies, three mass flow coefficients and several Reynolds numbers (up to eight) per condition, accounting for an overall amount of 51 different combinations of these parameters for each cascade. The predictor functions included into the model have been varied starting from a classic polynomial formulation for each influencing parameter, and then with functional relationships mimicking physical constrains and loss tendencies. Different combinations of the predictors, also including different types and orders of the cross-terms, have been evaluated by means of a Bayesian model selection method searching for the maximum probability of the model in fitting the cloud of experimental data. In particular, the evaluation of the Model Evidence (ME) using the Bayesian Information Criterion approximation (BIC) has allowed obtaining sufficient accuracy and avoiding overfitting at the same time. The best model here identified will be shown to be able to well reproduce the loss surface of a third different cascade that does not participate to the model selection. Realistic profile loss evolutions outside of the design space tested are provided, thus also allowing for a generalization of the structure of the model for other applications and future works.
{"title":"A Bayesian Approach for the Identification of Cascade Loss Model Strategy","authors":"D. Simoni, D. Lengani, Daniele Petronio, F. Bertini","doi":"10.1115/GT2020-14625","DOIUrl":"https://doi.org/10.1115/GT2020-14625","url":null,"abstract":"\u0000 A Bayesian method has been used to identify the best model strategy to describe the profile losses of low pressure turbine (LPT) cascades operating under unsteady inflow. The model has been tuned with experimental data measured in a large scale cascade facility, equipped with a moving bar system. Tests have been carried out on two different cascades, investigating three different reduced frequencies, three mass flow coefficients and several Reynolds numbers (up to eight) per condition, accounting for an overall amount of 51 different combinations of these parameters for each cascade. The predictor functions included into the model have been varied starting from a classic polynomial formulation for each influencing parameter, and then with functional relationships mimicking physical constrains and loss tendencies.\u0000 Different combinations of the predictors, also including different types and orders of the cross-terms, have been evaluated by means of a Bayesian model selection method searching for the maximum probability of the model in fitting the cloud of experimental data. In particular, the evaluation of the Model Evidence (ME) using the Bayesian Information Criterion approximation (BIC) has allowed obtaining sufficient accuracy and avoiding overfitting at the same time.\u0000 The best model here identified will be shown to be able to well reproduce the loss surface of a third different cascade that does not participate to the model selection. Realistic profile loss evolutions outside of the design space tested are provided, thus also allowing for a generalization of the structure of the model for other applications and future works.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":" 21","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113948004","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. Granovskiy, I. Afanasiev, V. Kostege, E. Marchukov
Vanes of low-pressure turbines (LPT) run under inlet conditions generated by a preceding high-pressure turbine (HPT). HP stages are generally cooled and transonic as well due to the large pressure ratio necessary to reduce the gas temperature upstream of the downstream stages. Therefore radial distributions of inlet flow angle, total pressure and total temperature at the boundary upstream of the LPT are highly non–uniform. Such non-uniform inlet conditions can result in enhanced level of the total losses including the secondary losses. Moreover, vanes of LPT have meridional openings along inner and outer boundaries of the flow path, which causes intensification of the secondary flows leading to an increase in secondary losses. In this case the special meridional contouring of the vanes’ outer and inner surfaces allows a decrease in the flare angle namely meridional opening in the rear part of the vane. In this work, in order to compensate the negative effect of non-uniform inlet conditions, meridional opening and low aspect ratio, 3D profiling of the vane row is used as a way of reducing secondary losses. Some variants of LPT vanes with various complex 3D shapes are investigated. In particular, vane variants with a “reversed bow”, a “bowed” and a “lean” in the circumferential direction have been examined. Significant modification of the vane row is limited by cooling system design, which has to incorporate a deflector in the inner hollow of the vane to improve cooling effectiveness. A compromise between aerodynamic quality and cooling limitations has been achieved.
{"title":"Improving Characteristics of a Cooled Transonic Vane of Low Pressure Turbine Under Nonuniform Inlet Conditions","authors":"A. Granovskiy, I. Afanasiev, V. Kostege, E. Marchukov","doi":"10.1115/GT2020-15589","DOIUrl":"https://doi.org/10.1115/GT2020-15589","url":null,"abstract":"\u0000 Vanes of low-pressure turbines (LPT) run under inlet conditions generated by a preceding high-pressure turbine (HPT). HP stages are generally cooled and transonic as well due to the large pressure ratio necessary to reduce the gas temperature upstream of the downstream stages. Therefore radial distributions of inlet flow angle, total pressure and total temperature at the boundary upstream of the LPT are highly non–uniform. Such non-uniform inlet conditions can result in enhanced level of the total losses including the secondary losses. Moreover, vanes of LPT have meridional openings along inner and outer boundaries of the flow path, which causes intensification of the secondary flows leading to an increase in secondary losses. In this case the special meridional contouring of the vanes’ outer and inner surfaces allows a decrease in the flare angle namely meridional opening in the rear part of the vane. In this work, in order to compensate the negative effect of non-uniform inlet conditions, meridional opening and low aspect ratio, 3D profiling of the vane row is used as a way of reducing secondary losses. Some variants of LPT vanes with various complex 3D shapes are investigated. In particular, vane variants with a “reversed bow”, a “bowed” and a “lean” in the circumferential direction have been examined. Significant modification of the vane row is limited by cooling system design, which has to incorporate a deflector in the inner hollow of the vane to improve cooling effectiveness. A compromise between aerodynamic quality and cooling limitations has been achieved.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131159750","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}
Rossella Cinelli, G. Maggiani, S. Gabriele, A. Castorrini, G. Agati, F. Rispoli
The Gas Turbine (GT) Axial Compressor (AXCO) can absorb up to the 30% of the power produced by the GT, being the component with the largest impact over the performances. The axial compressor blades might undergo the fouling phenomena as a consequence of the unwanted material locally accumulating during the machine operations. The presence of such polluting substances reduces the aerodynamic efficiency as well as the air intake causing the drop of performances and the increase of the fuel consumption. To address the above-mentioned critical issues, several washing strategies have been implemented so far, among the most promising ones, High Flow On-Line Water Washing (HFOLWW) is worth to mention. Exploiting this technique, the performance levels are preserved, whereas the stops for maintenance should be reduced. Nevertheless, this comes at the cost of a long-term erosion exposure caused by the impact of water washing droplets. Hence, it was deemed necessary to carry out a finite element method (FEM) structural analysis of the first rotor stage of the compressor of an aeroderivative GT, integrated into the HFOLWW scheme, in order to evaluate the fatigue strength of the component subjected to the erosion; possibly along with its acceptability limits. The first step requires the determination of the blade areas affected by erosion, using computational fluid dynamics (CFD) simulations, followed by the creation and the 3D modelling of the damaged geometry. The final step consists in the evaluation of the static stress and the dynamic agents, to perform a fatigue analysis through the Goodman relation and carrying out a simulation of damage propagation exploiting the theory of fracture mechanics. This procedure has been extended to the damage-free baseline component to set-up a model suitable for comparison. The structural analysis confirms the design of the blade, moreover dynamic and static evaluation of the eroded profiles haven’t outlined any working, nor mechanical, issue. This entitles the structural choice of HFOLWW as a system which guarantees full performance levels of the compressor.
{"title":"Structural Analysis of a Gas Turbine Axial Compressor Blade Eroded by Online Water Washing","authors":"Rossella Cinelli, G. Maggiani, S. Gabriele, A. Castorrini, G. Agati, F. Rispoli","doi":"10.1115/GT2020-15942","DOIUrl":"https://doi.org/10.1115/GT2020-15942","url":null,"abstract":"\u0000 The Gas Turbine (GT) Axial Compressor (AXCO) can absorb up to the 30% of the power produced by the GT, being the component with the largest impact over the performances. The axial compressor blades might undergo the fouling phenomena as a consequence of the unwanted material locally accumulating during the machine operations. The presence of such polluting substances reduces the aerodynamic efficiency as well as the air intake causing the drop of performances and the increase of the fuel consumption. To address the above-mentioned critical issues, several washing strategies have been implemented so far, among the most promising ones, High Flow On-Line Water Washing (HFOLWW) is worth to mention. Exploiting this technique, the performance levels are preserved, whereas the stops for maintenance should be reduced. Nevertheless, this comes at the cost of a long-term erosion exposure caused by the impact of water washing droplets. Hence, it was deemed necessary to carry out a finite element method (FEM) structural analysis of the first rotor stage of the compressor of an aeroderivative GT, integrated into the HFOLWW scheme, in order to evaluate the fatigue strength of the component subjected to the erosion; possibly along with its acceptability limits. The first step requires the determination of the blade areas affected by erosion, using computational fluid dynamics (CFD) simulations, followed by the creation and the 3D modelling of the damaged geometry. The final step consists in the evaluation of the static stress and the dynamic agents, to perform a fatigue analysis through the Goodman relation and carrying out a simulation of damage propagation exploiting the theory of fracture mechanics. This procedure has been extended to the damage-free baseline component to set-up a model suitable for comparison. The structural analysis confirms the design of the blade, moreover dynamic and static evaluation of the eroded profiles haven’t outlined any working, nor mechanical, issue. This entitles the structural choice of HFOLWW as a system which guarantees full performance levels of the compressor.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127061785","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}
Zengyan Lian, Q. Du, Guang Liu, Ruonan Wang, Lei Xie
Hot gas ingestion into the wheel space can reduce the lifetime of vulnerable components in gas turbine like the turbine disk. Rim seal structure at the periphery of the wheel-space is designed to protect the turbine disk from hot gas. This paper describes the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) computation method with Shear Stress Transport (SST) turbulent model using commercial CFD code and the validation of grids. The RANS and URANS computation have been carried out in a one stage turbine model with different rim seal configurations: fish-mouth rim seal and double rim seal. A 10.91° sector computation model comprises one pitch in a row of stator vanes, and rotor blades is set up and simulated with different sealant flow rate. Results show that the fish-mouth rim seal can achieve higher sealing effectiveness with low sealant flow rate by installing the inner shell at high radius on the stator disk. The comparison between the steady and unsteady results indicates that the RANS computation underpredicts the level of the hot gas ingestion, especially in the double rim seal configuration. It can be found in the URANS computation results at different time steps that, when the rotating effect is considered, the interaction between the vane wake and the wave of the blade leading edge can lead to more serious pressure asymmetry, which worsens the hot gas ingestion. The counter-rotating vortex induced at outer wheel space and the Kelvin-Helmholtz-like vortices caused by velocity difference of mainstream and sealing flow can further aggravate the ingress.
{"title":"Numerical Investigation on Unsteady Characteristics in Different Rim Seal Geometries: Part B","authors":"Zengyan Lian, Q. Du, Guang Liu, Ruonan Wang, Lei Xie","doi":"10.1115/gt2020-15607","DOIUrl":"https://doi.org/10.1115/gt2020-15607","url":null,"abstract":"\u0000 Hot gas ingestion into the wheel space can reduce the lifetime of vulnerable components in gas turbine like the turbine disk. Rim seal structure at the periphery of the wheel-space is designed to protect the turbine disk from hot gas. This paper describes the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) computation method with Shear Stress Transport (SST) turbulent model using commercial CFD code and the validation of grids. The RANS and URANS computation have been carried out in a one stage turbine model with different rim seal configurations: fish-mouth rim seal and double rim seal. A 10.91° sector computation model comprises one pitch in a row of stator vanes, and rotor blades is set up and simulated with different sealant flow rate. Results show that the fish-mouth rim seal can achieve higher sealing effectiveness with low sealant flow rate by installing the inner shell at high radius on the stator disk. The comparison between the steady and unsteady results indicates that the RANS computation underpredicts the level of the hot gas ingestion, especially in the double rim seal configuration. It can be found in the URANS computation results at different time steps that, when the rotating effect is considered, the interaction between the vane wake and the wave of the blade leading edge can lead to more serious pressure asymmetry, which worsens the hot gas ingestion. The counter-rotating vortex induced at outer wheel space and the Kelvin-Helmholtz-like vortices caused by velocity difference of mainstream and sealing flow can further aggravate the ingress.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133605479","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}
Yun Zheng, Xiubo Jin, Hui Yang, Qingzhe Gao, K. Xu
The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.
{"title":"Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine","authors":"Yun Zheng, Xiubo Jin, Hui Yang, Qingzhe Gao, K. Xu","doi":"10.1115/GT2020-15295","DOIUrl":"https://doi.org/10.1115/GT2020-15295","url":null,"abstract":"\u0000 The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123351216","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, Junichi Sakamoto, K. Sugiyama, Shuichi Ohmori, S. Umezawa
Influences of age-related deterioration on the increase in rotor tip gap width are discussed numerically. In the gas turbine examined in the present study, there are two kinds of geometries around the rotor blade tip. In the first stage, there is clearance between the blade tip and the casing without any seal structures. On the other hand, there is a shroud and seal fin on the rotor blade tip. The blade geometries were measured using a 3-D scanner in a working power plant, and the tip clearances were varied by changing the casing contour. Steady-state CFD simulations were carried out. Tip gap widths were varied by shifting the casing wall. For simplicity, the blade geometries were not changed. The influence of tip clearance was examined by changing the geometries in each stage separately. Boundary conditions were determined using the previously developed hybrid method of heat balance analysis and CFD simulation, which can simulate the operating conditions of a working gas turbine. The results showed that the turbine performance degradation could spread to the following stage. Observation of entropy fields revealed that the increase in the tip leakage flow affected the flow in the following nozzle, and the loss increased.
{"title":"Numerical Study of Influence of Rotor Tip Gap Increase due to Age Deterioration in 3-Stage Gas Turbine","authors":"K. Yonezawa, Junichi Sakamoto, K. Sugiyama, Shuichi Ohmori, S. Umezawa","doi":"10.1115/GT2020-16270","DOIUrl":"https://doi.org/10.1115/GT2020-16270","url":null,"abstract":"\u0000 Influences of age-related deterioration on the increase in rotor tip gap width are discussed numerically. In the gas turbine examined in the present study, there are two kinds of geometries around the rotor blade tip. In the first stage, there is clearance between the blade tip and the casing without any seal structures. On the other hand, there is a shroud and seal fin on the rotor blade tip. The blade geometries were measured using a 3-D scanner in a working power plant, and the tip clearances were varied by changing the casing contour. Steady-state CFD simulations were carried out. Tip gap widths were varied by shifting the casing wall. For simplicity, the blade geometries were not changed. The influence of tip clearance was examined by changing the geometries in each stage separately. Boundary conditions were determined using the previously developed hybrid method of heat balance analysis and CFD simulation, which can simulate the operating conditions of a working gas turbine. The results showed that the turbine performance degradation could spread to the following stage. Observation of entropy fields revealed that the increase in the tip leakage flow affected the flow in the following nozzle, and the loss increased.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115308314","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}
Stefano Oliani, N. Casari, M. Pinelli, A. Suman, M. Carnevale
Particle ingestion is a major concern for the operation of gas turbines. In the case of an aircraft, particle dispersed in the air ingested by the engine can threaten flight safety. Swallowed particles can erode or stick to aerodynamic surfaces. Both the occurrences translate in a reduction of performance due to variation in shape and in roughness of the aerodynamic surfaces. This work is devoted to the analysis of fouling, i.e. the deposition of particles over time. By observing that the deposition pattern is strongly influenced by the flow field in the nearby of the walls, the central idea of this work is to employ Active Flow Control (AFC) to mitigate fouling when emergency conditions are met by the aircraft. The proposed system will inject air bled from compressor discharge in front of the critical locations where fouling is supposed to occur. The present work aspires to lay the foundations for the development of such an AFC device, by focusing on the modified aerodynamics consequent to the introduction of the transverse jet. The potential of this device is evaluated quantitatively using CFD simulations. An energy-based sticking model, coupled with a mesh-morphing solver, is used to track the airfoil deposition thickness evolution in time. The work is two-fold: first, the dynamics of the interaction between flow structures and particle transport is addressed. Second, the attention is posed on correlating fouling pattern variation to the modified aerodynamics of the vane consequent to the introduction of the device. Three design concepts are investigated on the 3D test case geometry of an HPT NGV cascade. The counter-rotating vortex pair (CVP) is detected as the main responsible for jet-particle interaction. Finally, the jet impact on aerodynamic performance is also assessed.
{"title":"Effect of Jets in Crossflow in Deposition Mitigation on Full 3D NGV With Endwall Features","authors":"Stefano Oliani, N. Casari, M. Pinelli, A. Suman, M. Carnevale","doi":"10.1115/GT2020-15367","DOIUrl":"https://doi.org/10.1115/GT2020-15367","url":null,"abstract":"\u0000 Particle ingestion is a major concern for the operation of gas turbines. In the case of an aircraft, particle dispersed in the air ingested by the engine can threaten flight safety. Swallowed particles can erode or stick to aerodynamic surfaces. Both the occurrences translate in a reduction of performance due to variation in shape and in roughness of the aerodynamic surfaces. This work is devoted to the analysis of fouling, i.e. the deposition of particles over time. By observing that the deposition pattern is strongly influenced by the flow field in the nearby of the walls, the central idea of this work is to employ Active Flow Control (AFC) to mitigate fouling when emergency conditions are met by the aircraft. The proposed system will inject air bled from compressor discharge in front of the critical locations where fouling is supposed to occur. The present work aspires to lay the foundations for the development of such an AFC device, by focusing on the modified aerodynamics consequent to the introduction of the transverse jet. The potential of this device is evaluated quantitatively using CFD simulations. An energy-based sticking model, coupled with a mesh-morphing solver, is used to track the airfoil deposition thickness evolution in time. The work is two-fold: first, the dynamics of the interaction between flow structures and particle transport is addressed. Second, the attention is posed on correlating fouling pattern variation to the modified aerodynamics of the vane consequent to the introduction of the device. Three design concepts are investigated on the 3D test case geometry of an HPT NGV cascade. The counter-rotating vortex pair (CVP) is detected as the main responsible for jet-particle interaction. Finally, the jet impact on aerodynamic performance is also assessed.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"158 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126595074","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}
Boundary layer ingestion has significant potential to reduce fuel burn in aircraft engines. However, designing a fan that can operate in an environment of continuous distortion without aeromechanical failure is a critical challenge. Capturing the requisite aeromechanical flow features in a high-fidelity computational setting is necessary in validating satisfactory designs as well as determining possible regions for overall improvement. In the current work, a three-dimensional, time-accurate, Reynolds-averaged Navier-Stokes computational fluid dynamic code is utilized to study a distortion-tolerant fan coupled to a boundary layer ingesting inlet. The comparison between this coupled inlet-fan and a previous fan-only simulation will provide insight into the changes in aeromechanic response of the fan blades. Additionally, comparisons to previous wind tunnel tests are made to provide validation of inlet distortion as seen by the distortion-tolerant fan. A resonant crossing was also investigated for the 85% speed operational line condition to compare resonant response between the inlet-fan, fan-only, and experiment. A decrease in maximum tip displacement is observed in the forced response of the coupled inlet-fan compared to the fan-only simulation. The predicted maximum tip displacement was still below the upper limit on the range observed in the wind tunnel tests but matched well with the average tip displacement value of 27.6 mils. A single mode was chosen at the 100% speed condition to provide insight into the effects that the inlet duct has on fan stability. Near stall and near choke conditions were also simulated to observe how the changes of progressing along the speed line affects flutter stability prediction. The analysis shows the fan has low levels of aerodynamic damping at all the conditions tested. However, the coupled inlet-fan shows a decrease in the level of aerodynamic damping over what was observed with the fan-only simulation. Some of the blades experienced single cycles of negative aerodamping which indicate a possibility of increased blade vibration amplitude but were followed by positive aerodamping cycles. Work is continuing to understand possible sources to account for the differences observed between the two simulation cases as well as with the experiment.
{"title":"Aeromechanic Response of a Coupled Inlet-Fan Boundary Layer Ingesting Distortion-Tolerant Fan","authors":"G. Heinlein, M. Bakhle, Jen‐Ping Chen","doi":"10.1115/gt2019-91866","DOIUrl":"https://doi.org/10.1115/gt2019-91866","url":null,"abstract":"\u0000 Boundary layer ingestion has significant potential to reduce fuel burn in aircraft engines. However, designing a fan that can operate in an environment of continuous distortion without aeromechanical failure is a critical challenge. Capturing the requisite aeromechanical flow features in a high-fidelity computational setting is necessary in validating satisfactory designs as well as determining possible regions for overall improvement. In the current work, a three-dimensional, time-accurate, Reynolds-averaged Navier-Stokes computational fluid dynamic code is utilized to study a distortion-tolerant fan coupled to a boundary layer ingesting inlet. The comparison between this coupled inlet-fan and a previous fan-only simulation will provide insight into the changes in aeromechanic response of the fan blades. Additionally, comparisons to previous wind tunnel tests are made to provide validation of inlet distortion as seen by the distortion-tolerant fan. A resonant crossing was also investigated for the 85% speed operational line condition to compare resonant response between the inlet-fan, fan-only, and experiment. A decrease in maximum tip displacement is observed in the forced response of the coupled inlet-fan compared to the fan-only simulation. The predicted maximum tip displacement was still below the upper limit on the range observed in the wind tunnel tests but matched well with the average tip displacement value of 27.6 mils. A single mode was chosen at the 100% speed condition to provide insight into the effects that the inlet duct has on fan stability. Near stall and near choke conditions were also simulated to observe how the changes of progressing along the speed line affects flutter stability prediction. The analysis shows the fan has low levels of aerodynamic damping at all the conditions tested. However, the coupled inlet-fan shows a decrease in the level of aerodynamic damping over what was observed with the fan-only simulation. Some of the blades experienced single cycles of negative aerodamping which indicate a possibility of increased blade vibration amplitude but were followed by positive aerodamping cycles. Work is continuing to understand possible sources to account for the differences observed between the two simulation cases as well as with the experiment.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"25 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":"116761355","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 development and verification of new turbulence models for RANS equations based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique is given. The presented time mean fields, as well as total turbulence data demonstrate with an average deviation of ΔTu < 0.4% and ΔC/Cref < 0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.
{"title":"A Comparison of Turbulence Levels From PIV and CTA Downstream of a Low-Pressure Turbine Cascade at High-Speed Flow Conditions","authors":"Silvio Chemnitz, R. Niehuis","doi":"10.1115/gt2019-90473","DOIUrl":"https://doi.org/10.1115/gt2019-90473","url":null,"abstract":"\u0000 The development and verification of new turbulence models for RANS equations based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique is given. The presented time mean fields, as well as total turbulence data demonstrate with an average deviation of ΔTu < 0.4% and ΔC/Cref < 0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.","PeriodicalId":388234,"journal":{"name":"Volume 2B: Turbomachinery","volume":"74 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":"114839633","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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