Turbulence intensity impacts the performance of turbine stages and it is an important inlet boundary condition for CFD computations; the knowledge of its value at the turbine inlet is then of paramount importance. In combustor–turbine interaction experimental studies, combustor simulators replace real combustors and allow for the introduction of flow perturbation at the turbine inlet. Therefore, the turbulence intensity of a combustor simulator used in a wide experimental campaign at Politecnico di Milano is characterized using a hot-wire probe in a blow-down wind tunnel, and the results are compared to URANS CFD computations. This combustor simulator can generate a combination of a swirl profile with a steady/unsteady temperature disturbance. In the cold unsteady disturbance case, hot-wire measurements are phase-averaged at the frequency of the injected perturbation. The combustor simulator turbulence intensity is measured at two different axial positions to understand its evolution.
{"title":"Turbulence measurements downstream of a combustor simulator designed for studies on the combustor-turbine interaction","authors":"A. Notaristefano, G. Persico, Paolo Gaetani","doi":"10.29008/etc2023-323","DOIUrl":"https://doi.org/10.29008/etc2023-323","url":null,"abstract":"Turbulence intensity impacts the performance of turbine stages and it is an important inlet boundary condition for CFD computations; the knowledge of its value at the turbine inlet is then of paramount importance. In combustor–turbine interaction experimental studies, combustor simulators replace real combustors and allow for the introduction of flow perturbation at the turbine inlet. Therefore, the turbulence intensity of a combustor simulator used in a wide experimental campaign at Politecnico di Milano is characterized using a hot-wire probe in a blow-down wind tunnel, and the results are compared to URANS CFD computations. This combustor simulator can generate a combination of a swirl profile with a steady/unsteady temperature disturbance. In the cold unsteady disturbance case, hot-wire measurements are phase-averaged at the frequency of the injected perturbation. The combustor simulator turbulence intensity is measured at two different axial positions to understand its evolution.","PeriodicalId":445987,"journal":{"name":"European Conference on Turbomachinery Fluid Dynamics and Thermodynamics","volume":"70 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139440729","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 maximum power of single-flow steam turbines is determined by the amount of steam that can be passed through its last stage. With a fixed length of the blades of this stage, the passage of steam into the condenser can be increased by increasing the number of steam flows. Structurally, this problem is solved by using double-flow low-pressure cylinders (LPC) and increasing the number of LPCs. It is this path that is currently being intensively used in the world turbomachinery industry. As a result, over the past decades, the blade lengths of the last stages of condensing steam turbines have increased from 1200 mm to 1500 mm. The presented materials consider an alternative solution based on the Bauman stage. This method was used in steam turbines until the middle of the twentieth century and was rejected due to the very low efficiency of such LPCs. It is shown that such a decision was made without a proper analysis of the reasons for the low efficiency of cylinders with Bauman stages. Elimination of these reasons will allow creating a low-pressure cylinder with one and a half exhaust steam, the efficiency of which may be higher than the efficiency of a modern low-pressure cylinder made on the basis of the last stage rotor blades with a length of 1400-1500 mm. When developing a new low-pressure cylinder with one and a half steam exhaust, two-tier stages were considered as stages made on the basis of two-tier fork blades, which made it possible to sharply reduce losses from the fan, and nozzle diaphragm of these stages were equipped with upstream distribution grids, which ensured a uniform distribution of steam flow rates over all sections of the two-tier stages.
{"title":"Development and research of efficiency of a new low-pressure turbine with one and a half exhaust based on forked two-tier blades","authors":"A. Zaryankin, V. Krutitskii","doi":"10.29008/etc2021-473","DOIUrl":"https://doi.org/10.29008/etc2021-473","url":null,"abstract":"The maximum power of single-flow steam turbines is determined by the amount of steam that can be passed through its last stage. With a fixed length of the blades of this stage, the passage of steam into the condenser can be increased by increasing the number of steam flows. Structurally, this problem is solved by using double-flow low-pressure cylinders (LPC) and increasing the number of LPCs. It is this path that is currently being intensively used in the world turbomachinery industry. As a result, over the past decades, the blade lengths of the last stages of condensing steam turbines have increased from 1200 mm to 1500 mm. The presented materials consider an alternative solution based on the Bauman stage. This method was used in steam turbines until the middle of the twentieth century and was rejected due to the very low efficiency of such LPCs. It is shown that such a decision was made without a proper analysis of the reasons for the low efficiency of cylinders with Bauman stages. Elimination of these reasons will allow creating a low-pressure cylinder with one and a half exhaust steam, the efficiency of which may be higher than the efficiency of a modern low-pressure cylinder made on the basis of the last stage rotor blades with a length of 1400-1500 mm. When developing a new low-pressure cylinder with one and a half steam exhaust, two-tier stages were considered as stages made on the basis of two-tier fork blades, which made it possible to sharply reduce losses from the fan, and nozzle diaphragm of these stages were equipped with upstream distribution grids, which ensured a uniform distribution of steam flow rates over all sections of the two-tier stages.","PeriodicalId":445987,"journal":{"name":"European Conference on Turbomachinery Fluid Dynamics and Thermodynamics","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122376414","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}
S. Kubacki, D. Simoni, D. Lengani, M. Dellacasagrande, E. Dick
A constitutive law for the Reynolds stresses during boundary layer laminar-to-turbulent transition, constructed in previous work by elastic-net regression on an experimental data base, has been incorporated in an algebraic intermittency model. The objective is prediction improvement of transition in a separated layer under an elevated free-stream turbulence level. The modelling for such cases functions through additional production terms in the transport equations of turbulent kinetic energy and specific dissipation rate of a k-ω turbulence model. A sensor detects the front part of a separated layer and activates the production terms. These express the effect of Klebanoff streaks generated upstream of separation on the Kelvin-Helmholtz instability rolls in the separated part of the layer. By the Klebanoff streaks, the breakdown is faster and the speed of breakdown increases by the combined effects of a large adverse pressure gradient and an elevated free-stream turbulence level.
{"title":"Further development of an algebraic intermittency model for separation-induced transition under elevated free-stream turbulence","authors":"S. Kubacki, D. Simoni, D. Lengani, M. Dellacasagrande, E. Dick","doi":"10.29008/etc2021-512","DOIUrl":"https://doi.org/10.29008/etc2021-512","url":null,"abstract":"A constitutive law for the Reynolds stresses during boundary layer laminar-to-turbulent transition, constructed in previous work by elastic-net regression on an experimental data base, has been incorporated in an algebraic intermittency model. The objective is prediction improvement of transition in a separated layer under an elevated free-stream turbulence level. The modelling for such cases functions through additional production terms in the transport equations of turbulent kinetic energy and specific dissipation rate of a k-ω turbulence model. A sensor detects the front part of a separated layer and activates the production terms. These express the effect of Klebanoff streaks generated upstream of separation on the Kelvin-Helmholtz instability rolls in the separated part of the layer. By the Klebanoff streaks, the breakdown is faster and the speed of breakdown increases by the combined effects of a large adverse pressure gradient and an elevated free-stream turbulence level.","PeriodicalId":445987,"journal":{"name":"European Conference on Turbomachinery Fluid Dynamics and Thermodynamics","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133413571","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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