A. Bakhtiari, T. Sander, M. Straußwald, M. Pfitzner
In modern gas turbines, heat loads on thermal highly stressed components are reduced by film cooling, where a layer of cold gas is injected for the protection of these components. In order to optimize present cooling designs, experiments under realistic operating conditions have to be performed especially including the effect of turbulence intensity and turbulent length scale. In this work, an active turbulence grid was designed, built and tested in order to increase the turbulence conditions in a closed-loop, thermal wind tunnel facility for future film cooling investigations. The grid design, which is based on designs proposed in literature, and its implementation are described in detail. For the investigation of the resulting flow field without film cooling injection, the measurement techniques hotwire anemometry and high-speed PIV were used, which are described shortly. The measurements were carried out at different axial positions downstream of the turbulence grid, at different main flow velocities and various rotation rates of the grid. The results show that the turbulence intensity decays with increasing distance and stays constant at a distance of X/M = 14 downstream of the grid, which will be the position of film cooling flow injection in future investigations. For the investigated measurement points a decreasing rotation rate of the grid leads to an increase of the turbulence intensity. Increasing the main flow velocity significantly increases the turbulence intensity especially close to the grid. The calculated turbulent length scales for different axial positions downstream of the grid and three different main flow velocities stay within a narrow band between 10 mm and 30 mm, which is below the mesh size of the grid. Furthermore, the calculated data for different rotation rates and main flow velocities at X/M = 14 show a constant turbulent length scale of 20 mm for rotation rates higher than 1200 rpm, independently of the main flow velocity. However, for lower rotation rates a strong dependence of the turbulent length scale on rotation rate and on main flow velocity was seen. The results of both measurement techniques match very well, leading to the conclusion that the presented approach investigating turbulence intensity and turbulent length scale provides a reliable database for future investigations of film cooling configurations.
{"title":"Active Turbulence Generation for Film Cooling Investigations","authors":"A. Bakhtiari, T. Sander, M. Straußwald, M. Pfitzner","doi":"10.1115/GT2018-76451","DOIUrl":"https://doi.org/10.1115/GT2018-76451","url":null,"abstract":"In modern gas turbines, heat loads on thermal highly stressed components are reduced by film cooling, where a layer of cold gas is injected for the protection of these components. In order to optimize present cooling designs, experiments under realistic operating conditions have to be performed especially including the effect of turbulence intensity and turbulent length scale. In this work, an active turbulence grid was designed, built and tested in order to increase the turbulence conditions in a closed-loop, thermal wind tunnel facility for future film cooling investigations. The grid design, which is based on designs proposed in literature, and its implementation are described in detail. For the investigation of the resulting flow field without film cooling injection, the measurement techniques hotwire anemometry and high-speed PIV were used, which are described shortly. The measurements were carried out at different axial positions downstream of the turbulence grid, at different main flow velocities and various rotation rates of the grid. The results show that the turbulence intensity decays with increasing distance and stays constant at a distance of X/M = 14 downstream of the grid, which will be the position of film cooling flow injection in future investigations. For the investigated measurement points a decreasing rotation rate of the grid leads to an increase of the turbulence intensity. Increasing the main flow velocity significantly increases the turbulence intensity especially close to the grid. The calculated turbulent length scales for different axial positions downstream of the grid and three different main flow velocities stay within a narrow band between 10 mm and 30 mm, which is below the mesh size of the grid. Furthermore, the calculated data for different rotation rates and main flow velocities at X/M = 14 show a constant turbulent length scale of 20 mm for rotation rates higher than 1200 rpm, independently of the main flow velocity. However, for lower rotation rates a strong dependence of the turbulent length scale on rotation rate and on main flow velocity was seen. The results of both measurement techniques match very well, leading to the conclusion that the presented approach investigating turbulence intensity and turbulent length scale provides a reliable database for future investigations of film cooling configurations.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114281314","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. Bertini, L. Mazzei, S. Puggelli, A. Andreini, B. Facchini, L. Bellocci, A. Santoriello
Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation, however, involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. A reduced coolant mass flow rate in conjunction with higher compressor discharge temperature negatively affect the cooling potential thus requiring the exploitation of efficient schemes such as effusion cooling. This work describes the experimental and numerical final validation of an aeronautical effusion-cooled lean-burn combustor. Full annular tests were carried out to measure temperature profiles and metal temperature distributions at different operating conditions of the ICAO cycle. Such an outcome was obtained also with an in-house developed CHT methodology (THERM3D). RANS simulations with the Flamelet Generated Manifold combustion model were performed to estimate aerothermal field and heat loads, while the coupling with a thermal conduction solver returns the most updated wall temperature. The heat sink within the perforation is treated with a 0D correlative model that calculates the heat pickup and the temperature rise of coolant. The results highlight an overall good capability of the proposed approach to estimate the metal temperature distribution at different operating conditions. It is also shown how more advanced scale-resolving simulations could significantly improve the prediction of turbulent mixing and heat loads.
{"title":"Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Metal Temperature","authors":"D. Bertini, L. Mazzei, S. Puggelli, A. Andreini, B. Facchini, L. Bellocci, A. Santoriello","doi":"10.1115/GT2018-76779","DOIUrl":"https://doi.org/10.1115/GT2018-76779","url":null,"abstract":"Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation, however, involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. A reduced coolant mass flow rate in conjunction with higher compressor discharge temperature negatively affect the cooling potential thus requiring the exploitation of efficient schemes such as effusion cooling.\u0000 This work describes the experimental and numerical final validation of an aeronautical effusion-cooled lean-burn combustor. Full annular tests were carried out to measure temperature profiles and metal temperature distributions at different operating conditions of the ICAO cycle. Such an outcome was obtained also with an in-house developed CHT methodology (THERM3D). RANS simulations with the Flamelet Generated Manifold combustion model were performed to estimate aerothermal field and heat loads, while the coupling with a thermal conduction solver returns the most updated wall temperature. The heat sink within the perforation is treated with a 0D correlative model that calculates the heat pickup and the temperature rise of coolant. The results highlight an overall good capability of the proposed approach to estimate the metal temperature distribution at different operating conditions. It is also shown how more advanced scale-resolving simulations could significantly improve the prediction of turbulent mixing and heat loads.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128269406","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 complex flowfield in a gas turbine combustor makes cooling the liner walls a challenge. In particular, this paper is primarily focused on the region surrounding the dilution holes, which is especially challenging to cool due to the interaction between the effusion cooling jets and high-momentum dilution jets. This study presents overall effectiveness measurements for three different cooling hole patterns of a double-walled combustor liner. Only effusion hole patterns near the dilution holes were varied, which included: no effusion cooling; effusion holes pointed radially outward from the dilution hole; and effusion holes pointed radially inward toward the dilution hole. The double-walled liner contained both impingement and effusion plates as well as a row of dilution jets. Infrared thermography was used to measure the surface temperature of the combustor liners at multiple dilution jet momentum flux ratios and approaching freestream turbulence intensities of 0.5% and 13%. Results showed the outward and inward geometries were able to more effectively cool the region surrounding the dilution hole compared to the closed case. A significant amount of the cooling enhancement in the outward and inward cases came from in-hole convection. Downstream of the dilution hole, the interactions between the inward effusion holes and the dilution jet led to lower levels of effectiveness compared to the other two geometries. High freestream turbulence caused a small decrease in overall effectiveness over the entire liner and was most impactful in the first three rows of effusion holes.
{"title":"Effects of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner: Part 1 — Overall Effectiveness Measurements","authors":"Adam C. Shrager, K. Thole, Dominic Mongillo","doi":"10.1115/gt2018-77288","DOIUrl":"https://doi.org/10.1115/gt2018-77288","url":null,"abstract":"The complex flowfield in a gas turbine combustor makes cooling the liner walls a challenge. In particular, this paper is primarily focused on the region surrounding the dilution holes, which is especially challenging to cool due to the interaction between the effusion cooling jets and high-momentum dilution jets. This study presents overall effectiveness measurements for three different cooling hole patterns of a double-walled combustor liner. Only effusion hole patterns near the dilution holes were varied, which included: no effusion cooling; effusion holes pointed radially outward from the dilution hole; and effusion holes pointed radially inward toward the dilution hole. The double-walled liner contained both impingement and effusion plates as well as a row of dilution jets. Infrared thermography was used to measure the surface temperature of the combustor liners at multiple dilution jet momentum flux ratios and approaching freestream turbulence intensities of 0.5% and 13%.\u0000 Results showed the outward and inward geometries were able to more effectively cool the region surrounding the dilution hole compared to the closed case. A significant amount of the cooling enhancement in the outward and inward cases came from in-hole convection. Downstream of the dilution hole, the interactions between the inward effusion holes and the dilution jet led to lower levels of effectiveness compared to the other two geometries. High freestream turbulence caused a small decrease in overall effectiveness over the entire liner and was most impactful in the first three rows of effusion holes.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122067151","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}
C. Salpingidou, D. Misirlis, Z. Vlahostergios, M. Flouros, F. Donus, K. Yakinthos
The present work is focused on the optimization of the performance characteristics of a recuperator specifically designed for aero engine applications, targeting the reduction of specific fuel consumption and taking into consideration aero engine geometrical constraints and limitations. The recuperator design was based on the elliptically profiled tubular heat exchanger which was developed and invented by MTU Aero Engines AG. For the specific fuel consumption investigations the Intercooled Recuperated Aero engine cycle, combining both intercooling and recuperation, was considered. The optimization was performed with the development of a recuperator surrogate model, capable to incorporate major recuperator geometrical features. A large number of recuperator design scenarios was assessed, in which additional design criteria and constraints were applied. Thus, a significantly large recuperator design space was covered resulting to the identification of feasible recuperator designs providing beneficial effect on the Intercooled Recuperated Aero engine leading to reduced specific fuel consumption and weight.
{"title":"Design Optimization of Heat Exchangers for Aero Engines With the Use of a Surrogate Model Incorporating Performance Characteristics and Geometrical Constraints","authors":"C. Salpingidou, D. Misirlis, Z. Vlahostergios, M. Flouros, F. Donus, K. Yakinthos","doi":"10.1115/GT2018-76097","DOIUrl":"https://doi.org/10.1115/GT2018-76097","url":null,"abstract":"The present work is focused on the optimization of the performance characteristics of a recuperator specifically designed for aero engine applications, targeting the reduction of specific fuel consumption and taking into consideration aero engine geometrical constraints and limitations. The recuperator design was based on the elliptically profiled tubular heat exchanger which was developed and invented by MTU Aero Engines AG. For the specific fuel consumption investigations the Intercooled Recuperated Aero engine cycle, combining both intercooling and recuperation, was considered.\u0000 The optimization was performed with the development of a recuperator surrogate model, capable to incorporate major recuperator geometrical features. A large number of recuperator design scenarios was assessed, in which additional design criteria and constraints were applied. Thus, a significantly large recuperator design space was covered resulting to the identification of feasible recuperator designs providing beneficial effect on the Intercooled Recuperated Aero engine leading to reduced specific fuel consumption and weight.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133716684","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}
Unsteady effects impact the aerothermal performance of the turbine blade rows, originating noise, mechanical and thermal fatigue. Blade row interactions are due to the relative motion between nearby rows of airfoils, the periodic occurrence of flow distortions generated by the airfoil rows or combustors. The detailed characterization of the thermal boundary layer under periodic fluctuations is vital to improve the performance of cooled turbine airfoils. In the present contribution, we performed series of Unsteady Reynolds Averaged Navier-Stokes simulations to investigate the wall heat flux response to periodic flow velocity fluctuations, on a flat plate of 0.5 m. We investigated the boundary layer response to sudden flow acceleration and periodic flow perturbations, caused by inlet total pressure variations. Because of the flow acceleration the boundary layer is first stretched, resulting in an increase of the wall shear stress. Later on, due to the viscous diffusion, the low momentum flow adjusts to the new free stream conditions. The behavior of the boundary layer at low frequency is similar to the response to an individual deceleration followed by one acceleration. However, at higher frequencies the mean flow topology is completely altered. One would expect that higher acceleration rates would cause a further stretching of the boundary layer that should cause even greater wall shear stresses and heat fluxes. However, we observed the opposite; instead, the amplitude of the skin friction coefficient is abated, while the peak level is one order of magnitude smaller than at low frequency. Two counteracting effects influence the response of both the momentum and the thermal boundary layer. In one hand, the stagnant flow quantities propagate at characteristic velocities guiding the establishment of the mean flow conditions. On the other hand, the diffusion across the boundary layer leads the final response of the near wall region. However, the dynamic pressure gradients imposed in the mean flow modulate the viscous properties of the boundary layer through local flow acceleration, transforming the expected pattern.
{"title":"Thermal Boundary Layer Response to Periodic Fluctuations","authors":"J. Saavedra, G. Paniagua, O. Chazot","doi":"10.1115/GT2018-76896","DOIUrl":"https://doi.org/10.1115/GT2018-76896","url":null,"abstract":"Unsteady effects impact the aerothermal performance of the turbine blade rows, originating noise, mechanical and thermal fatigue. Blade row interactions are due to the relative motion between nearby rows of airfoils, the periodic occurrence of flow distortions generated by the airfoil rows or combustors. The detailed characterization of the thermal boundary layer under periodic fluctuations is vital to improve the performance of cooled turbine airfoils. In the present contribution, we performed series of Unsteady Reynolds Averaged Navier-Stokes simulations to investigate the wall heat flux response to periodic flow velocity fluctuations, on a flat plate of 0.5 m. We investigated the boundary layer response to sudden flow acceleration and periodic flow perturbations, caused by inlet total pressure variations. Because of the flow acceleration the boundary layer is first stretched, resulting in an increase of the wall shear stress. Later on, due to the viscous diffusion, the low momentum flow adjusts to the new free stream conditions. The behavior of the boundary layer at low frequency is similar to the response to an individual deceleration followed by one acceleration. However, at higher frequencies the mean flow topology is completely altered. One would expect that higher acceleration rates would cause a further stretching of the boundary layer that should cause even greater wall shear stresses and heat fluxes. However, we observed the opposite; instead, the amplitude of the skin friction coefficient is abated, while the peak level is one order of magnitude smaller than at low frequency. Two counteracting effects influence the response of both the momentum and the thermal boundary layer. In one hand, the stagnant flow quantities propagate at characteristic velocities guiding the establishment of the mean flow conditions. On the other hand, the diffusion across the boundary layer leads the final response of the near wall region. However, the dynamic pressure gradients imposed in the mean flow modulate the viscous properties of the boundary layer through local flow acceleration, transforming the expected pattern.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"10 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131539896","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}
Recent studies have demonstrated that cylindrical hole with backward injection arrangement, of which the jets are injected reverse to the mainstream flow direction, outperforms its forward injection counterpart, of which the jets are injected along the flow direction, at high blowing ratio, since the jet starts to lift off typically for forward injection when blowing ratio is greater than 1.0. However, the backward injection configuration features a large separation and induces high heat transfer near the hole. Relative few studies have been conducted to mitigated the drawbacks of backward injection arrangements. The present study investigated several flat plate trenched hole arrangements with backward injection. Experiments were conducted in a low speed suction type wind tunnel. The trench width was varied from 2d to 4d for the backward arrangements with fixed trench depth of 0.75d. Besides, a simple backward and a trenched hole with forward injection, whose width is 2d and depth is 0.75d, were also studied as references. Transient thermal measurements were carried out for all the arrangements with IR camera. Detailed distributions of heat transfer coefficient were obtained. For each case, blowing ratio was varied from 0.25 to 4.0, while the density ratio was almost unity. Effects of injection angle, trench width and blowing ratio on the surface heat transfer distributions were obtained, and the results are presented and explained in this investigation.
{"title":"High Resolution Heat Transfer Measurements of Cylindrical Holes Embedded in a Trench With Backward Injection","authors":"Bo Shi, Xueying Li, Jing Ren, Hongde Jiang","doi":"10.1115/GT2018-76676","DOIUrl":"https://doi.org/10.1115/GT2018-76676","url":null,"abstract":"Recent studies have demonstrated that cylindrical hole with backward injection arrangement, of which the jets are injected reverse to the mainstream flow direction, outperforms its forward injection counterpart, of which the jets are injected along the flow direction, at high blowing ratio, since the jet starts to lift off typically for forward injection when blowing ratio is greater than 1.0. However, the backward injection configuration features a large separation and induces high heat transfer near the hole. Relative few studies have been conducted to mitigated the drawbacks of backward injection arrangements. The present study investigated several flat plate trenched hole arrangements with backward injection. Experiments were conducted in a low speed suction type wind tunnel. The trench width was varied from 2d to 4d for the backward arrangements with fixed trench depth of 0.75d. Besides, a simple backward and a trenched hole with forward injection, whose width is 2d and depth is 0.75d, were also studied as references. Transient thermal measurements were carried out for all the arrangements with IR camera. Detailed distributions of heat transfer coefficient were obtained. For each case, blowing ratio was varied from 0.25 to 4.0, while the density ratio was almost unity. Effects of injection angle, trench width and blowing ratio on the surface heat transfer distributions were obtained, and the results are presented and explained in this investigation.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125097897","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}
F. Wagner, A. Kühhorn, T. Janetzke, U. Gerstberger
Due to the increasing turbine inlet temperature and in order to improve the overall efficiency it is necessary to optimize the cooling design of the hot gas components of an aero engine. The current paper discusses the strategy of optimizing a rotor blade cooling configuration of a small civil aero engine, comprising of films and internal turbulators (ribs). An insight into the parametrization is given including the location of the films and ribs as well as the number of the films and ribs. The parameter reduction results in 18 input parameters for the optimizations to limit the number of parameters to an acceptable level. Two optimizations are carried out with the primary objectives of non-dimensional mass flow and overall cooling effectiveness. Different optimization algorithms are used, namely AMGA and NSGA-II, and compared afterwards. A further optimization is carried out with direct objectives of mass flow and mean surface temperature using the AMGA algorithm. The outputs from the optimizations are presented as a pareto-front. These plots are used for a comparison of the optimization algorithms and formulations respectively. Finally, the differences are discussed and the advantages and disadvantages of the algorithms used are highlighted.
{"title":"Multi-Objective Optimization of the Cooling Configuration of a High Pressure Turbine Blade","authors":"F. Wagner, A. Kühhorn, T. Janetzke, U. Gerstberger","doi":"10.1115/GT2018-75616","DOIUrl":"https://doi.org/10.1115/GT2018-75616","url":null,"abstract":"Due to the increasing turbine inlet temperature and in order to improve the overall efficiency it is necessary to optimize the cooling design of the hot gas components of an aero engine.\u0000 The current paper discusses the strategy of optimizing a rotor blade cooling configuration of a small civil aero engine, comprising of films and internal turbulators (ribs). An insight into the parametrization is given including the location of the films and ribs as well as the number of the films and ribs. The parameter reduction results in 18 input parameters for the optimizations to limit the number of parameters to an acceptable level.\u0000 Two optimizations are carried out with the primary objectives of non-dimensional mass flow and overall cooling effectiveness. Different optimization algorithms are used, namely AMGA and NSGA-II, and compared afterwards. A further optimization is carried out with direct objectives of mass flow and mean surface temperature using the AMGA algorithm.\u0000 The outputs from the optimizations are presented as a pareto-front. These plots are used for a comparison of the optimization algorithms and formulations respectively. Finally, the differences are discussed and the advantages and disadvantages of the algorithms used are highlighted.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126628211","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}
Jeongju Kim, W. Seo, Minho Bang, Seon Ho Kim, S. Choi, H. Cho
Film cooling effectiveness and heat transfer were measured in squealer tip configurations on the blade tip surface. Three different shelf squealer tip geometries were studied: conventional, vertical, and inclined. The experiment was carried out in a wind tunnel with an inlet mainstream Reynolds number, based on the axial chord length of the blade, of 140,000. The experiments were conducted in five blades in linear cascade with an averaged turbulence intensity of 8.5%. The film cooling effectiveness and heat transfer coefficient on the tip surface were obtained using the transient IR thermography technique. For the pressure side film cooling holes, averaging blowing ratios (M) of 1.0 and 2.0 were set. The results showed the film cooling effectiveness distributions on the tip surface. Owing to the mainstream, the cooling effect appeared after x/Cx = 0.15 and the film cooling effectiveness tended to increase toward downstream of the trailing edge. Additionally, the heat transfer distributions were investigated regarding the film cooling holes. In the presence of film cooling holes, the heat transfer distribution had more uniformity than without them on the pressure side. As the blowing ratio increased from 1 to 2, the heat transfer was decreased on the tip surface. The heat transfer ratio represented the change of heat transfer distribution with and without film cooling holes. Those of results were compared in three squealer tip geometries. The overall area-averaged net heat flux reduction (NHFR) levels on the tip surface were enhanced as the blowing ratio increased. The NHFR of the shelf squealer tip configurations was better than that with the conventional squealer tip.
{"title":"Effect of Shelf Squealer Tip Configurations on Film Cooling Effectiveness","authors":"Jeongju Kim, W. Seo, Minho Bang, Seon Ho Kim, S. Choi, H. Cho","doi":"10.1115/GT2018-75377","DOIUrl":"https://doi.org/10.1115/GT2018-75377","url":null,"abstract":"Film cooling effectiveness and heat transfer were measured in squealer tip configurations on the blade tip surface. Three different shelf squealer tip geometries were studied: conventional, vertical, and inclined. The experiment was carried out in a wind tunnel with an inlet mainstream Reynolds number, based on the axial chord length of the blade, of 140,000. The experiments were conducted in five blades in linear cascade with an averaged turbulence intensity of 8.5%. The film cooling effectiveness and heat transfer coefficient on the tip surface were obtained using the transient IR thermography technique. For the pressure side film cooling holes, averaging blowing ratios (M) of 1.0 and 2.0 were set. The results showed the film cooling effectiveness distributions on the tip surface. Owing to the mainstream, the cooling effect appeared after x/Cx = 0.15 and the film cooling effectiveness tended to increase toward downstream of the trailing edge. Additionally, the heat transfer distributions were investigated regarding the film cooling holes. In the presence of film cooling holes, the heat transfer distribution had more uniformity than without them on the pressure side. As the blowing ratio increased from 1 to 2, the heat transfer was decreased on the tip surface. The heat transfer ratio represented the change of heat transfer distribution with and without film cooling holes. Those of results were compared in three squealer tip geometries. The overall area-averaged net heat flux reduction (NHFR) levels on the tip surface were enhanced as the blowing ratio increased. The NHFR of the shelf squealer tip configurations was better than that with the conventional squealer tip.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130141167","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 numerical description of combustion provides a good understanding of the thermal boundary conditions of a combustor already in the early design phase. With an accurate simulation, the thermal load on the combustor wall as well as the turbine inlet profile can be estimated and potentially tailored to the structural requirements. At MTU Aero Engines AG, the authors set up a multi-physics solver in OpenFOAM to support the development process for combustors. This article shows the activities for a redesign of a commercial engine combustor and the successful numerical description of all related physical aspects. The comparison of combustor liner temperatures predicted via Conjugate Heat Transfer (CHT) with thermal paint results show excellent agreement. The numerical results allow the evaluation of different redesign options with respect to maximum liner temperatures and impact on turbine inlet temperature profiles. The application of a multi-physics solver to real engine combustor designs is limited to the availability of computational power and acceptable running time. The applicability of the presented approach to complex engine designs is not only shown by the successful simulation results. The choice of an open source code allows the usage of massive parallelization. A parallelization up to 1024 CPUs was tested to evaluate the potential of speeding up the simulations. The results are encouraging and show that complex meshes with ∼15 million cells can be simulated within acceptable calculation time.
{"title":"Multi-Physics Simulations With OpenFOAM in the Re-Design of a Commercial Combustor","authors":"M. Konle, Ludovic de Guillebon, Christopher Beebe","doi":"10.1115/GT2018-76578","DOIUrl":"https://doi.org/10.1115/GT2018-76578","url":null,"abstract":"The numerical description of combustion provides a good understanding of the thermal boundary conditions of a combustor already in the early design phase. With an accurate simulation, the thermal load on the combustor wall as well as the turbine inlet profile can be estimated and potentially tailored to the structural requirements.\u0000 At MTU Aero Engines AG, the authors set up a multi-physics solver in OpenFOAM to support the development process for combustors. This article shows the activities for a redesign of a commercial engine combustor and the successful numerical description of all related physical aspects. The comparison of combustor liner temperatures predicted via Conjugate Heat Transfer (CHT) with thermal paint results show excellent agreement. The numerical results allow the evaluation of different redesign options with respect to maximum liner temperatures and impact on turbine inlet temperature profiles.\u0000 The application of a multi-physics solver to real engine combustor designs is limited to the availability of computational power and acceptable running time. The applicability of the presented approach to complex engine designs is not only shown by the successful simulation results. The choice of an open source code allows the usage of massive parallelization. A parallelization up to 1024 CPUs was tested to evaluate the potential of speeding up the simulations. The results are encouraging and show that complex meshes with ∼15 million cells can be simulated within acceptable calculation time.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132027814","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}
Craig Fernandes, J. Hodges, E. Fernandez, J. Kapat
The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially-resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 degrees to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work. Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the u’rms line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level (u’rms), and length scales profiles.
{"title":"Flow Statistics and Visualization of Multi-Row Film Cooling Boundary Layers Emanating From Cylindrical and Diffuser Shaped Holes","authors":"Craig Fernandes, J. Hodges, E. Fernandez, J. Kapat","doi":"10.1115/GT2018-76964","DOIUrl":"https://doi.org/10.1115/GT2018-76964","url":null,"abstract":"The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially-resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 degrees to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work.\u0000 Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the u’rms line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level (u’rms), and length scales profiles.","PeriodicalId":239866,"journal":{"name":"Volume 5C: Heat Transfer","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132186299","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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