Abstract In this paper, the predictions of an analytical model for seal flutter have been compared with the experimental data of a rotating multi-cavity labyrinth seal test rig. The experiments were conducted to assess the flutter inception in a large set of operating conditions by varying the rotational speed and the total pressure ratio across the seal. The analytical model derived by Corral et al. (2022, “Effective Clearance and Differential Gapping Impact on Seal Flutter Modelling and Validation,” ASME J. Turbomach., 144 (7), p. 071010) has been previously validated by using a frequency domain linearized Navier–Stokes solver retaining the effect of the effective gaps and the kinetic energy carried over to the downstream fin. A set of 3D steady RANS simulations has been carried out to reduce the uncertainty in the steady characteristics of the seal that are used to inform the flutter model. The simulations consider the static deformation due to the pressure and the centrifugal force through a set of numerical models with geometrical gap differences. The stability has been investigated in a large range of operating conditions. It is concluded that the analytical model can be used to quickly predict the modes susceptible to flutter, provided that the steady flow field and the effective running clearances of the seal are well predicted.
本文将密封颤振分析模型的预测结果与旋转多腔迷宫密封试验台的实验数据进行了比较。通过改变密封的转速和总压比，进行了试验，以评估在一组大的操作条件下颤振的开始。Corral等人(2022，“有效间隙和差异间隙对密封颤振建模和验证的影响”，ASME J. Turbomach。之前已经通过使用频域线性化的Navier-Stokes解算器进行了验证，该解算器保留了有效间隙和传递到下游鳍片的动能的影响。为了减少用于颤振模型的密封稳定特性的不确定性，已经进行了一组3D稳态RANS模拟。通过一组具有几何间隙差的数值模型，模拟考虑了压力和离心力引起的静态变形。在大范围的操作条件下，对其稳定性进行了研究。结果表明，只要能准确预测密封的稳定流场和有效运行间隙，该解析模型可以快速预测易受颤振影响的模态。
{"title":"EXPERIMENTAL VALIDATION OF A SEAL FLUTTER MODEL","authors":"Roque Corral, Michele Greco","doi":"10.1115/1.4063514","DOIUrl":"https://doi.org/10.1115/1.4063514","url":null,"abstract":"Abstract In this paper, the predictions of an analytical model for seal flutter have been compared with the experimental data of a rotating multi-cavity labyrinth seal test rig. The experiments were conducted to assess the flutter inception in a large set of operating conditions by varying the rotational speed and the total pressure ratio across the seal. The analytical model derived by Corral et al. (2022, “Effective Clearance and Differential Gapping Impact on Seal Flutter Modelling and Validation,” ASME J. Turbomach., 144 (7), p. 071010) has been previously validated by using a frequency domain linearized Navier–Stokes solver retaining the effect of the effective gaps and the kinetic energy carried over to the downstream fin. A set of 3D steady RANS simulations has been carried out to reduce the uncertainty in the steady characteristics of the seal that are used to inform the flutter model. The simulations consider the static deformation due to the pressure and the centrifugal force through a set of numerical models with geometrical gap differences. The stability has been investigated in a large range of operating conditions. It is concluded that the analytical model can be used to quickly predict the modes susceptible to flutter, provided that the steady flow field and the effective running clearances of the seal are well predicted.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jannik Petermann, Kevin Schulz, Bernd Becker, Volker Gümmer
Abstract The aerodynamic impact of hub gap leakage on the performance characteristics of an axial compressor rotor in conventional design (no blisk) with a high hub-to-tip ratio has been investigated using three-dimensional steady-state Reynolds-averaged Navier–Stokes simulations. The inclusion of circumferential hub gaps in front of the leading edge and after the trailing edge, as well as inter-platform leakage, reduced the total pressure ratio and the polytropic efficiency of the rotor by as much as 3.74% and 3.97%, respectively, compared to a design case with clean endwalls. Potential design recommendations in terms of improved aerodynamic robustness against leakage effects were derived from the separate sealing of each hub gap. Six geometry modifications were assessed, which based on these results. In a throttled operating condition, large edge radii in the front gap on the disk and platform partially recovered the initial losses of both the total pressure ratio (17.7%) and polytropic efficiency (19.6%). A circular lateral platform shape with the opening pointing toward the blade’s pressure side showed superior loss recovery capabilities at a dethrottled operating point. The combination of both features did not reduce the losses further. However, the circular lateral platform shape combined with smaller front gap chamfers proved more beneficial in a throttled state.
{"title":"ATTENUATION OF DETRIMENTAL HUB LEAKAGE EFFECTS IN AN AXIAL COMPRESSOR ROTOR BY CUSTOMIZED GEOMETRICAL DESIGN FEATURES","authors":"Jannik Petermann, Kevin Schulz, Bernd Becker, Volker Gümmer","doi":"10.1115/1.4063508","DOIUrl":"https://doi.org/10.1115/1.4063508","url":null,"abstract":"Abstract The aerodynamic impact of hub gap leakage on the performance characteristics of an axial compressor rotor in conventional design (no blisk) with a high hub-to-tip ratio has been investigated using three-dimensional steady-state Reynolds-averaged Navier–Stokes simulations. The inclusion of circumferential hub gaps in front of the leading edge and after the trailing edge, as well as inter-platform leakage, reduced the total pressure ratio and the polytropic efficiency of the rotor by as much as 3.74% and 3.97%, respectively, compared to a design case with clean endwalls. Potential design recommendations in terms of improved aerodynamic robustness against leakage effects were derived from the separate sealing of each hub gap. Six geometry modifications were assessed, which based on these results. In a throttled operating condition, large edge radii in the front gap on the disk and platform partially recovered the initial losses of both the total pressure ratio (17.7%) and polytropic efficiency (19.6%). A circular lateral platform shape with the opening pointing toward the blade’s pressure side showed superior loss recovery capabilities at a dethrottled operating point. The combination of both features did not reduce the losses further. However, the circular lateral platform shape combined with smaller front gap chamfers proved more beneficial in a throttled state.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This paper presents a detailed numerical investigation of a transonic centrifugal compressor to understand the mechanism causing its pressure rise characteristic rollover, which fundamentally impacts compressor stability. Distinct characteristic rollover behaviors at different compressor speeds are predicted and studied. It is found that the impeller characteristic rollover occurs at high blade tip Mach number (>1) conditions. It is the result of a combination of the inducer and exducer performance. The inducer is found to stall early, while the exducer is mostly a stable part maintaining the overall impeller stability. The overall impeller characteristic rolls over when the exducer’s performance deteriorates significantly, which happens at higher flow conditions toward high speed. This is due to the flow compressibility effect (density change). It shows that the flow density across the impeller increases with the blade tip Mach number. The increased density leads to a reduced exducer exit flow coefficient with higher workload and aerodynamic losses. Detailed analysis is carried out to understand the 1D and 3D flow mechanisms governing the inducer and exducer, hence the impeller characteristic.
{"title":"PRESSURE CHARACTERISTIC ROLLOVER OF A TRANSONIC CENTRIFUGAL IMPELLER","authors":"Teng Cao, Yoshihiro Hayashi, Isao Tomita","doi":"10.1115/1.4063517","DOIUrl":"https://doi.org/10.1115/1.4063517","url":null,"abstract":"Abstract This paper presents a detailed numerical investigation of a transonic centrifugal compressor to understand the mechanism causing its pressure rise characteristic rollover, which fundamentally impacts compressor stability. Distinct characteristic rollover behaviors at different compressor speeds are predicted and studied. It is found that the impeller characteristic rollover occurs at high blade tip Mach number (>1) conditions. It is the result of a combination of the inducer and exducer performance. The inducer is found to stall early, while the exducer is mostly a stable part maintaining the overall impeller stability. The overall impeller characteristic rolls over when the exducer’s performance deteriorates significantly, which happens at higher flow conditions toward high speed. This is due to the flow compressibility effect (density change). It shows that the flow density across the impeller increases with the blade tip Mach number. The increased density leads to a reduced exducer exit flow coefficient with higher workload and aerodynamic losses. Detailed analysis is carried out to understand the 1D and 3D flow mechanisms governing the inducer and exducer, hence the impeller characteristic.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The design of film-cooled engine components requires an understanding of the expected temperature distributions while in service, thus requiring accurate predictions through low-temperature testing. Overall effectiveness, ϕ, is the integrated indicator of overall cooling performance. An experiment to measure ϕ at low temperature requires appropriate scaling through careful selection of not only the coolant and freestream gases but also the model material itself. Matching ϕ requires that the experiment has matched values of the adiabatic effectiveness, Biot number, coolant warming factor, and ratio of external to internal heat transfer coefficient. Previous research has shown the requirements to match each of those four parameters individually. However, matching all those parameters simultaneously presents an overconstrained problem, and no comprehensive recommendations exist for the practical experimentalist who wishes to conduct an appropriately scaled, low-temperature experiment truly suitable for determining ϕ. Four fluidic parameters are identified, which in an experiment must be as close as possible to their values at engine conditions. A normalized root-mean-square difference (NRMSD) of the residuals of those parameters is proposed to quantify how well a proposed wind tunnel experiment is likely to yield engine-relevant ϕ values. We show that this process may be used by any experimentalist to identify the appropriate fluids, conditions, and materials for a matched ϕ experiment. Several case studies were performed using computational fluid dynamics (CFD) to show the utility of this process. Of the common experimental techniques examined here, a matched Biot number experiment with 500 K freestream air and 250 K coolant appears to be particularly adept at simulating engine conditions, even better than experiments that make use of CO2 coolant.
{"title":"SCALING OVERALL EFFECTIVENESS IN LOW TEMPERATURE EXPERIMENTS","authors":"Carol Bryant, James L. Rutledge","doi":"10.1115/1.4063412","DOIUrl":"https://doi.org/10.1115/1.4063412","url":null,"abstract":"Abstract The design of film-cooled engine components requires an understanding of the expected temperature distributions while in service, thus requiring accurate predictions through low-temperature testing. Overall effectiveness, ϕ, is the integrated indicator of overall cooling performance. An experiment to measure ϕ at low temperature requires appropriate scaling through careful selection of not only the coolant and freestream gases but also the model material itself. Matching ϕ requires that the experiment has matched values of the adiabatic effectiveness, Biot number, coolant warming factor, and ratio of external to internal heat transfer coefficient. Previous research has shown the requirements to match each of those four parameters individually. However, matching all those parameters simultaneously presents an overconstrained problem, and no comprehensive recommendations exist for the practical experimentalist who wishes to conduct an appropriately scaled, low-temperature experiment truly suitable for determining ϕ. Four fluidic parameters are identified, which in an experiment must be as close as possible to their values at engine conditions. A normalized root-mean-square difference (NRMSD) of the residuals of those parameters is proposed to quantify how well a proposed wind tunnel experiment is likely to yield engine-relevant ϕ values. We show that this process may be used by any experimentalist to identify the appropriate fluids, conditions, and materials for a matched ϕ experiment. Several case studies were performed using computational fluid dynamics (CFD) to show the utility of this process. Of the common experimental techniques examined here, a matched Biot number experiment with 500 K freestream air and 250 K coolant appears to be particularly adept at simulating engine conditions, even better than experiments that make use of CO2 coolant.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Experiments were conducted to validate the building blocks of a fluidically controlled variable area turbine concept that uses injected high-pressure air to effectively reduce the choke area of the turbine inlet. Preliminary results from a simple quasi-1D converging-diverging nozzle, with an injection flow slot upstream of the throat, showed a 2.2:1 ratio between throttled mass flowrate and injected mass flowrate at a constant nozzle pressure ratio. The penetration of the injection flow and corresponding reduction in the primary flow streamtube were successfully visualized using a shadowgraph technique. Building on this success, a representative single passage nozzle guide vane transonic flowpath was constructed to demonstrate feasibility beyond the quasi-1D converging-diverging nozzle. Both secondary slot blowing from the vane pressure surface and vane suction surface just upstream of the passage throat again successfully reduced primary flow. In addition, fluidic vortex generators were used on the adjacent suction surface to reduce total pressure loss and further throttle the primary flow. Implications for the application of this active flow control technology to a variable area turbine are considered.
{"title":"Active Fluidic Control of a Nozzle Guide Vane Throat","authors":"Alexander Spens, Jeffrey Bons","doi":"10.1115/1.4063677","DOIUrl":"https://doi.org/10.1115/1.4063677","url":null,"abstract":"Abstract Experiments were conducted to validate the building blocks of a fluidically controlled variable area turbine concept that uses injected high-pressure air to effectively reduce the choke area of the turbine inlet. Preliminary results from a simple quasi-1D converging-diverging nozzle, with an injection flow slot upstream of the throat, showed a 2.2:1 ratio between throttled mass flowrate and injected mass flowrate at a constant nozzle pressure ratio. The penetration of the injection flow and corresponding reduction in the primary flow streamtube were successfully visualized using a shadowgraph technique. Building on this success, a representative single passage nozzle guide vane transonic flowpath was constructed to demonstrate feasibility beyond the quasi-1D converging-diverging nozzle. Both secondary slot blowing from the vane pressure surface and vane suction surface just upstream of the passage throat again successfully reduced primary flow. In addition, fluidic vortex generators were used on the adjacent suction surface to reduce total pressure loss and further throttle the primary flow. Implications for the application of this active flow control technology to a variable area turbine are considered.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135666577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Particle deposition is a common phenomenon in a turbine cascade. It can change the surface condition, which influences the flow and heat transfer. It is very important to accurately predict the particle deposition and surface condition changes. In this study, a combined particle deposition algorithm is proposed based on the critical viscosity deposition model and roughness height prediction. It couples the influence of surface roughness into the particle deposition. The combined model newly developed is employed for the particle deposition. Its effects in a turbine cascade with the combine model is discussed. The results show the deposition is mainly concentrated on the leading edge of the cascade and the pressure side. Small diameter particles are mainly deposited on the suction side and the large are mainly deposited on the pressure side due to inertial effect. The deposition number increases with the particle diameter. As time goes by, more particles deposit on the wall, which builds roughness height and shows a spreading characteristic. Heat transfer is enhanced by the surface roughness and flow characteristics including separation vortex and leakage vortex, in which flow pattern may dominate the effect. In addition, the separation vortex and leakage vortex have a significant effect on the deposition distribution, especially for smaller diameter particles
{"title":"A method proposed to predict particle deposition based on critical viscosity model and roughness height prediction in a turbine cascade","authors":"Hong Wang, Peilin He, Jialong Li, Huawei Lu","doi":"10.1115/1.4063752","DOIUrl":"https://doi.org/10.1115/1.4063752","url":null,"abstract":"Abstract Particle deposition is a common phenomenon in a turbine cascade. It can change the surface condition, which influences the flow and heat transfer. It is very important to accurately predict the particle deposition and surface condition changes. In this study, a combined particle deposition algorithm is proposed based on the critical viscosity deposition model and roughness height prediction. It couples the influence of surface roughness into the particle deposition. The combined model newly developed is employed for the particle deposition. Its effects in a turbine cascade with the combine model is discussed. The results show the deposition is mainly concentrated on the leading edge of the cascade and the pressure side. Small diameter particles are mainly deposited on the suction side and the large are mainly deposited on the pressure side due to inertial effect. The deposition number increases with the particle diameter. As time goes by, more particles deposit on the wall, which builds roughness height and shows a spreading characteristic. Heat transfer is enhanced by the surface roughness and flow characteristics including separation vortex and leakage vortex, in which flow pattern may dominate the effect. In addition, the separation vortex and leakage vortex have a significant effect on the deposition distribution, especially for smaller diameter particles","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135970128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jannik Eckel, Lukas Reisinger, Philipp von Jeinsen, Volker Gümmer
Abstract In [1], Eckel et al. proposed using a convex-profiled pressure side region close to the tip, known as belly, as an effective method of extending the operating range of low-speed axial compressor rotors. In the literature, circumferential grooves are another well-described technique for improving the stable working range of a compressor rotor. No research has been conducted to date to determine which modification is more effective and how they interact when used together. This paper numerically investigates the influence of circumferential casing grooves and near tip modifications on the flow field in the tip region of a highly-loaded, low-speed axial compressor rotor. The simulated rotor consists of a hybrid blade configuration with a tandem profile in the mid-span region and single blade profiles near the endwalls. The aim of the numerical analysis is to explain the interaction of the secondary flow phenomena when applying the circumferential grooves and the belly geometries. It is shown that a circumferential groove can further increase the operating range for all belly configurations when positioned axially correctly. In this respect, equalization of the near-casing deceleration in the circumferential direction leads to an extension of the stall margin with both modifications. In general, the groove and belly should be positioned where the tip leakage vortex meets the pressure side of the adjacent blade. If using only one modification, the belly appears better suited for ensuring an extension of the operating range while maintaining high efficiencies.
{"title":"NUMERICAL INVESTIGATION OF THE INTERACTION OF A CIRCUMFERENTIAL GROOVE CASING TREATMENT AND NEAR-TIP MODIFICATIONS FOR A HIGHLY-LOADED LOW-SPEED ROTOR UNDER THE INFLUENCE OF DOUBLE LEAKAGE","authors":"Jannik Eckel, Lukas Reisinger, Philipp von Jeinsen, Volker Gümmer","doi":"10.1115/1.4063756","DOIUrl":"https://doi.org/10.1115/1.4063756","url":null,"abstract":"Abstract In [1], Eckel et al. proposed using a convex-profiled pressure side region close to the tip, known as belly, as an effective method of extending the operating range of low-speed axial compressor rotors. In the literature, circumferential grooves are another well-described technique for improving the stable working range of a compressor rotor. No research has been conducted to date to determine which modification is more effective and how they interact when used together. This paper numerically investigates the influence of circumferential casing grooves and near tip modifications on the flow field in the tip region of a highly-loaded, low-speed axial compressor rotor. The simulated rotor consists of a hybrid blade configuration with a tandem profile in the mid-span region and single blade profiles near the endwalls. The aim of the numerical analysis is to explain the interaction of the secondary flow phenomena when applying the circumferential grooves and the belly geometries. It is shown that a circumferential groove can further increase the operating range for all belly configurations when positioned axially correctly. In this respect, equalization of the near-casing deceleration in the circumferential direction leads to an extension of the stall margin with both modifications. In general, the groove and belly should be positioned where the tip leakage vortex meets the pressure side of the adjacent blade. If using only one modification, the belly appears better suited for ensuring an extension of the operating range while maintaining high efficiencies.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135969762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Massimiliano Nardini, Melissa Kozul, Thomas Jelly, Richard Sandberg
Abstract High-fidelity simulation of transitional and turbulent flows over multi-scale surface roughness presents several challenges. For instance, the complex and irregular geometrical nature of surface roughness makes it impractical to employ conforming structured grids, commonly adopted in large-scale numerical simulations due to their high computational efficiency. One possible solution to overcome this problem is offered by immersed boundary methods, which allow wall boundary conditions to be enforced on grids that do not conform to the geometry of the solid boundary. To this end, a three-dimensional, second-order accurate Boundary Data Immersion Method (BDIM) is adopted. The new framework is validated by performing a Direct Numerical Simulation (DNS) of fully-developed turbulent channel flow over sinusoidal egg-carton roughness in a minimal span domain. General guidelines on the BDIM resolution requirements for multi-scale roughness simulation are given. Momentum and energy balance methods are used to validate the calculation of the overall skin friction and heat transfer at the wall. The BDIM is then employed to investigate the effect of irregular homogeneous surface roughness on the performance of an LS89 high-pressure turbine blade at engine-relevant conditions using DNS. This is the first application of the BDIM to realize multi-scale roughness for transitional flow in transonic conditions in the context of high-pressure turbines. The methodology adopted to generate the desired roughness distribution and to apply it to the reference blade geometry is introduced. The results are compared to the case of an equivalent smooth blade.
{"title":"Direct Numerical Simulation of transitional and turbulent flows over multi-scale surface roughness - Part I: methodology and challenges","authors":"Massimiliano Nardini, Melissa Kozul, Thomas Jelly, Richard Sandberg","doi":"10.1115/1.4063753","DOIUrl":"https://doi.org/10.1115/1.4063753","url":null,"abstract":"Abstract High-fidelity simulation of transitional and turbulent flows over multi-scale surface roughness presents several challenges. For instance, the complex and irregular geometrical nature of surface roughness makes it impractical to employ conforming structured grids, commonly adopted in large-scale numerical simulations due to their high computational efficiency. One possible solution to overcome this problem is offered by immersed boundary methods, which allow wall boundary conditions to be enforced on grids that do not conform to the geometry of the solid boundary. To this end, a three-dimensional, second-order accurate Boundary Data Immersion Method (BDIM) is adopted. The new framework is validated by performing a Direct Numerical Simulation (DNS) of fully-developed turbulent channel flow over sinusoidal egg-carton roughness in a minimal span domain. General guidelines on the BDIM resolution requirements for multi-scale roughness simulation are given. Momentum and energy balance methods are used to validate the calculation of the overall skin friction and heat transfer at the wall. The BDIM is then employed to investigate the effect of irregular homogeneous surface roughness on the performance of an LS89 high-pressure turbine blade at engine-relevant conditions using DNS. This is the first application of the BDIM to realize multi-scale roughness for transitional flow in transonic conditions in the context of high-pressure turbines. The methodology adopted to generate the desired roughness distribution and to apply it to the reference blade geometry is introduced. The results are compared to the case of an equivalent smooth blade.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135969949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lorenzo Orsini, Alessio Picchi, Bruno Facchini, Alessio Bonini, Luca Innocenti
Abstract The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modelling of rim seal flows still represent an open question. Fundamental test cases have been used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration of a foreign gas on the stator surface used to seed the purge flow. Consequently, the results are usually single point measurements, unsteady effects are inevitably neglected, the intrusiveness of the approach must be carefully checked and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the PSP technique to the study of hot gas ingestion phenomena on a single stage rotating cold rig. The 2D distributions of partial pressure of oxygen collected through the wide optical accesses present in the rig were then related to the seal effectiveness. The proposed methodology was firstly validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique. The analysis of the results highlighted the capabilities of the PSP to fast collect data on both stator and rotor side, including the tip of the seal tooth where non uniform efficiency distributions in the circumferential direction have been detected.
{"title":"ON THE USE OF PSP TO DETERMINE THE RIM SEALING EFFECTIVENESS","authors":"Lorenzo Orsini, Alessio Picchi, Bruno Facchini, Alessio Bonini, Luca Innocenti","doi":"10.1115/1.4063754","DOIUrl":"https://doi.org/10.1115/1.4063754","url":null,"abstract":"Abstract The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modelling of rim seal flows still represent an open question. Fundamental test cases have been used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration of a foreign gas on the stator surface used to seed the purge flow. Consequently, the results are usually single point measurements, unsteady effects are inevitably neglected, the intrusiveness of the approach must be carefully checked and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the PSP technique to the study of hot gas ingestion phenomena on a single stage rotating cold rig. The 2D distributions of partial pressure of oxygen collected through the wide optical accesses present in the rig were then related to the seal effectiveness. The proposed methodology was firstly validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique. The analysis of the results highlighted the capabilities of the PSP to fast collect data on both stator and rotor side, including the tip of the seal tooth where non uniform efficiency distributions in the circumferential direction have been detected.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135923415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper we study the relationship between overall cooling effectiveness (or so-called metal effectiveness) and mainstream-to-coolant total temperature ratio (TR), for typical high-pressure nozzle guide vane (HPNGV) cooling systems. The temperature ratio range studied is that between typical experimental conditions (TR ≅ 1.2) and typical engine conditions (TR ≅ 2.0). The purpose is twofold: firstly, to quantify the difference in overall cooling effectiveness between experimental and engine conditions of temperature ratio; and—secondly—to understand the physical bases for the difference, separated in terms of changes in five local surface boundary conditions. We do this using a bespoke conjugate thermal model which includes models of both the internal cooling and the external film cooling layer. Three typical cooling architectures are studied. The results allow comparison and scaling between situations at different conditions of temperature ratio.
{"title":"FUNDAMENTALS OF SCALING OF OVERALL COOLING EFFECTIVENESS WITH TEMPERATURE RATIO","authors":"James Cartlidge, Thomas Povey","doi":"10.1115/1.4063730","DOIUrl":"https://doi.org/10.1115/1.4063730","url":null,"abstract":"Abstract In this paper we study the relationship between overall cooling effectiveness (or so-called metal effectiveness) and mainstream-to-coolant total temperature ratio (TR), for typical high-pressure nozzle guide vane (HPNGV) cooling systems. The temperature ratio range studied is that between typical experimental conditions (TR ≅ 1.2) and typical engine conditions (TR ≅ 2.0). The purpose is twofold: firstly, to quantify the difference in overall cooling effectiveness between experimental and engine conditions of temperature ratio; and—secondly—to understand the physical bases for the difference, separated in terms of changes in five local surface boundary conditions. We do this using a bespoke conjugate thermal model which includes models of both the internal cooling and the external film cooling layer. Three typical cooling architectures are studied. The results allow comparison and scaling between situations at different conditions of temperature ratio.","PeriodicalId":49966,"journal":{"name":"Journal of Turbomachinery-Transactions of the Asme","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136295952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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