Marco Beghini, Tommaso Grossi, G. Macoretta, B. Monelli, Ivan Senegaglia, Paolo del Turco, Andrea Fardelli, Francesco Morante
Thanks to the increasingly widespread additive manufacturing technology and promising properties, the use of Lattice Structures (LS) is becoming increasingly frequent. LS allows the components to be designed with tunable stiffness, which can unlock the control of natural frequencies. However, crucial challenges must be faced to integrate LS into the typical design process. In the present work, an experimental and numerical study of LS-enabled tuning of natural frequencies in mechanical components is proposed. In a first step, the difficulties arising with the large amount of FEM nodes, that are required to predict LS complex shapes in detail, are overcome by modeling LS with an elastic metamaterial whose stiffness properties are determined through ad hoc finite element analyses. After that, a simplified investigation can be conducted on the modal properties of components with fixed external shape and variable internal LS filling, based on Triply Periodic Minimal Surfaces (TPMS) lattices. In those conditions, the parameters of the LS core can be tuned to control and optimize the global modal frequencies of the entire geometry. In addition, the admissible range of frequencies can be estimated. Optimized plates results are validated through an experimental test campaign on additively manufactured specimens made with Laser Powder Bed Fusion (L-PBF) technology. The samples are hammer-tested with various boundary conditions while laser sensors measure the oscillation data of selected points. Finally, estimated and identified natural frequencies were compared. The described model is suitable to be implemented in an automated tool for designers.
由于增材制造技术的日益普及和良好的性能，晶格结构（LS）的使用越来越频繁。LS 允许设计具有可调刚度的部件，从而实现对固有频率的控制。然而，要将 LS 整合到典型的设计流程中，必须面对关键的挑战。在本研究中，我们提出了一项关于利用 LS 调节机械部件固有频率的实验和数值研究。首先，通过对弹性超材料进行建模，克服了预测 LS 复杂形状所需的大量有限元节点带来的困难，而弹性超材料的刚度特性是通过特别有限元分析确定的。之后，可以基于三周期最小面（TPMS）晶格，对具有固定外部形状和可变内部 LS 填充物的组件的模态特性进行简化研究。在这些条件下，可以调整 LS 内核的参数，以控制和优化整个几何体的全局模态频率。此外，还可以估算出允许的频率范围。通过对采用激光粉末床融合（L-PBF）技术制造的快速成型试样进行实验测试，验证了优化板的结果。样品在各种边界条件下进行锤击测试，同时激光传感器测量选定点的振荡数据。最后，对估计的自然频率和确定的自然频率进行了比较。所描述的模型适合用于设计人员的自动化工具中。
{"title":"Tuning Modal Behavior Of Additively Manufactured Lattice Structures","authors":"Marco Beghini, Tommaso Grossi, G. Macoretta, B. Monelli, Ivan Senegaglia, Paolo del Turco, Andrea Fardelli, Francesco Morante","doi":"10.1115/1.4064264","DOIUrl":"https://doi.org/10.1115/1.4064264","url":null,"abstract":"Thanks to the increasingly widespread additive manufacturing technology and promising properties, the use of Lattice Structures (LS) is becoming increasingly frequent. LS allows the components to be designed with tunable stiffness, which can unlock the control of natural frequencies. However, crucial challenges must be faced to integrate LS into the typical design process. In the present work, an experimental and numerical study of LS-enabled tuning of natural frequencies in mechanical components is proposed. In a first step, the difficulties arising with the large amount of FEM nodes, that are required to predict LS complex shapes in detail, are overcome by modeling LS with an elastic metamaterial whose stiffness properties are determined through ad hoc finite element analyses. After that, a simplified investigation can be conducted on the modal properties of components with fixed external shape and variable internal LS filling, based on Triply Periodic Minimal Surfaces (TPMS) lattices. In those conditions, the parameters of the LS core can be tuned to control and optimize the global modal frequencies of the entire geometry. In addition, the admissible range of frequencies can be estimated. Optimized plates results are validated through an experimental test campaign on additively manufactured specimens made with Laser Powder Bed Fusion (L-PBF) technology. The samples are hammer-tested with various boundary conditions while laser sensors measure the oscillation data of selected points. Finally, estimated and identified natural frequencies were compared. The described model is suitable to be implemented in an automated tool for designers.","PeriodicalId":508252,"journal":{"name":"Journal of Engineering for Gas Turbines and Power","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139182803","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}
Zhaoming Mai, Yingtao Wu, Chenglong Tang, Wei Wang, Zuohua Huang
Adding high reactivity fuel in the binary mixtures generally exhibits nonlinear promoting effect on the ignition. To understand the effect of n-heptane (NC7H16) addition on the auto-ignition of methane (CH4) at low to intermediate temperatures, the ignition delay times (IDTs) of stoichiometric CH4/NC7H16 blends with varying NC7H16 concentrations were measured at temperatures from 600 to 1000 K, pressures of 20 and 40 bar. Detailed chemical kinetic mechanisms were validated against the newly measured IDTs. Adding NC7H16 in the binary mixture shows a nonlinear promoting effect on the IDTs: micro addition of NC7H16 can significantly reduce the IDTs of the binary mixture when the NC7H16 is lower than 20%. However, the decrease of the IDTs becomes much slower when further increasing the NC7H16 addition. Affected by the negative temperature coefficient behavior (NTC) of NC7H16, this nonlinear effect is particularly notable at around 795 K, the low boundary of the NTC region. To reveal the nonlinear reactivity promoting effect of NC7H16 addition on the binary mixture, reaction flux, ignition sensitivity, rate of production of the key radicals along with heat production analyses were conducted. Apart from contributing more ȮH production through the low-temperature chain-branching reaction pathways of NC7H16, adding NC7H16 also promotes the pre-ignition heat release of the binary mixture. The heat release raises the system temperature and further promotes the mixture ignition, enhancing the nonlinear effect at low temperatures.
{"title":"Understanding the Nonlinear Reactivity Promoting Effect of n-heptane Addition On the Binary Mixture From Low to Intermediate Temperature: A Case of Methane/n-heptane Mixtures","authors":"Zhaoming Mai, Yingtao Wu, Chenglong Tang, Wei Wang, Zuohua Huang","doi":"10.1115/1.4064148","DOIUrl":"https://doi.org/10.1115/1.4064148","url":null,"abstract":"Adding high reactivity fuel in the binary mixtures generally exhibits nonlinear promoting effect on the ignition. To understand the effect of n-heptane (NC7H16) addition on the auto-ignition of methane (CH4) at low to intermediate temperatures, the ignition delay times (IDTs) of stoichiometric CH4/NC7H16 blends with varying NC7H16 concentrations were measured at temperatures from 600 to 1000 K, pressures of 20 and 40 bar. Detailed chemical kinetic mechanisms were validated against the newly measured IDTs. Adding NC7H16 in the binary mixture shows a nonlinear promoting effect on the IDTs: micro addition of NC7H16 can significantly reduce the IDTs of the binary mixture when the NC7H16 is lower than 20%. However, the decrease of the IDTs becomes much slower when further increasing the NC7H16 addition. Affected by the negative temperature coefficient behavior (NTC) of NC7H16, this nonlinear effect is particularly notable at around 795 K, the low boundary of the NTC region. To reveal the nonlinear reactivity promoting effect of NC7H16 addition on the binary mixture, reaction flux, ignition sensitivity, rate of production of the key radicals along with heat production analyses were conducted. Apart from contributing more ȮH production through the low-temperature chain-branching reaction pathways of NC7H16, adding NC7H16 also promotes the pre-ignition heat release of the binary mixture. The heat release raises the system temperature and further promotes the mixture ignition, enhancing the nonlinear effect at low temperatures.","PeriodicalId":508252,"journal":{"name":"Journal of Engineering for Gas Turbines and Power","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139209687","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}
One of the main causes of damage to gas turbine nozzle guide vanes (NGVs) is creep, which threatens the safety and reliability of gas turbines. Although creep life prediction has been applied to design and maintenance, creep damage is still frequently observed. Inadequate knowledge of the spatial-temporal evolution of creep damage makes it difficult to evaluate and accurately protect NGVs against abnormal creep damage. An integrated aero-thermal-structural simulation method based on conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element method (FEM) is proposed to predict the spatial-temporal evolution of creep damage in the NGVs with internal cooling structures. In the temporal dimension, creep life is calculated by Larson-Miller parameters. In the spatial dimension, creep damage is characterized by a parametric modeling and CHT mesh generation procedure. The predicted results show that creep damage forms a groove or crack along the span at the leading edge of the suction side where the stress concentrates, which is similar to the frequently observed damage on the actual NGVs. The interactions between creep damage, flow, and heat transfer are discussed. The increase in turbine inlet temperature significantly shortens the time required for creep formation and evolution. It is suggested that creep damage through the NGV wall could radically alter the heat transfer and flow, resulting in a 30K increase in average leading edge temperature. As a result, the evolution of creep damage is self-promotingly accelerated.
{"title":"Multidisciplinary Prediction of Spatial-Temporal Evolution of Creep Damage on an Internally Cooled Turbine Vane","authors":"Qingfu He, Zhongran Chi, S. Zang","doi":"10.1115/1.4064129","DOIUrl":"https://doi.org/10.1115/1.4064129","url":null,"abstract":"One of the main causes of damage to gas turbine nozzle guide vanes (NGVs) is creep, which threatens the safety and reliability of gas turbines. Although creep life prediction has been applied to design and maintenance, creep damage is still frequently observed. Inadequate knowledge of the spatial-temporal evolution of creep damage makes it difficult to evaluate and accurately protect NGVs against abnormal creep damage. An integrated aero-thermal-structural simulation method based on conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element method (FEM) is proposed to predict the spatial-temporal evolution of creep damage in the NGVs with internal cooling structures. In the temporal dimension, creep life is calculated by Larson-Miller parameters. In the spatial dimension, creep damage is characterized by a parametric modeling and CHT mesh generation procedure. The predicted results show that creep damage forms a groove or crack along the span at the leading edge of the suction side where the stress concentrates, which is similar to the frequently observed damage on the actual NGVs. The interactions between creep damage, flow, and heat transfer are discussed. The increase in turbine inlet temperature significantly shortens the time required for creep formation and evolution. It is suggested that creep damage through the NGV wall could radically alter the heat transfer and flow, resulting in a 30K increase in average leading edge temperature. As a result, the evolution of creep damage is self-promotingly accelerated.","PeriodicalId":508252,"journal":{"name":"Journal of Engineering for Gas Turbines and Power","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139244317","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}
Giuseppe Tilocca, David Sánchez, Miguel Torres García, Antonio Escamilla Perejon, Simon Minett
Micro gas turbines are an on-site power and heat generation technology with a small footprint, low gaseous (NOx) and acoustic emissions, low maintenance and high-grade heat. They entered the market at the dawn of the twentieth century; nevertheless, they achieved minimal success and a marginal role in the microgeneration market. Reciprocating internal combustion engines raised considerable barriers hindering their market deployment, and Fuel Cells are also set to compete in this segment. In this scenario, this work presents an analysis of competitiveness grounded in the Theory of Constraints. To this end, a specific Key Performance Indicator has been produced, which combines technical, economic, and operational factors according to the end-user requirement. This indicator is a function of several penalty factors representing technology and market barriers, which aims to yield a unique insight into the most competitive technology for a given application, accounting for the uncertainty deriving from technical and economic elements. This novel methodology is applied to a new potential niche market: Power-to-Hydrogen-to-Power for remote applications. The methodology is applied to an independent rural community in South Wales, for which a backup power system is assessed. Four technologies are considered in the analysis: reciprocating engines, fuel cells and two different microturbines layouts. Finally, this work provides an overview of the possible R&D&I paths necessary to increase the competitiveness of micro gas turbines in certain markets.
{"title":"A Holistic Methodology to Quantify Product Competitiveness and Define Innovation Requirements for Micro Gas Turbine Systems in Hydrogen-Based Energy Storage Applications","authors":"Giuseppe Tilocca, David Sánchez, Miguel Torres García, Antonio Escamilla Perejon, Simon Minett","doi":"10.1115/1.4064061","DOIUrl":"https://doi.org/10.1115/1.4064061","url":null,"abstract":"Micro gas turbines are an on-site power and heat generation technology with a small footprint, low gaseous (NOx) and acoustic emissions, low maintenance and high-grade heat. They entered the market at the dawn of the twentieth century; nevertheless, they achieved minimal success and a marginal role in the microgeneration market. Reciprocating internal combustion engines raised considerable barriers hindering their market deployment, and Fuel Cells are also set to compete in this segment. In this scenario, this work presents an analysis of competitiveness grounded in the Theory of Constraints. To this end, a specific Key Performance Indicator has been produced, which combines technical, economic, and operational factors according to the end-user requirement. This indicator is a function of several penalty factors representing technology and market barriers, which aims to yield a unique insight into the most competitive technology for a given application, accounting for the uncertainty deriving from technical and economic elements. This novel methodology is applied to a new potential niche market: Power-to-Hydrogen-to-Power for remote applications. The methodology is applied to an independent rural community in South Wales, for which a backup power system is assessed. Four technologies are considered in the analysis: reciprocating engines, fuel cells and two different microturbines layouts. Finally, this work provides an overview of the possible R&D&I paths necessary to increase the competitiveness of micro gas turbines in certain markets.","PeriodicalId":508252,"journal":{"name":"Journal of Engineering for Gas Turbines and Power","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139262442","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}
Solid particle erosion of dusty energy recovery turbine blades has a great impact on the operating economics and safety of the unit. To mitigate the erosion of blade and improve the aerodynamic performance of the turbine, a multiobjective optimization method for turbine cascade based on the experimental design method, genetic algorithm and CFD multiphase flow simulation was developed. The optimization results show that the number of stator and rotor blades and the trailing edge angle at 50% blade span are the main parameters affecting the efficiency and blade erosion of the dusty turbine. By reducing the number of stator blades and the circumferential bending angle of the stator trailing edge, the impingement velocity and impingement probability of particles impinging on the stator trailing edge decrease by 7.5%~16.8% and 8.9%~46.2%, respectively. Additionally, compared with the original design, the flow separation loss and secondary flow intensity of the rotor cascade are suppressed by adjusting the load distribution and inlet attack angle of the rotor; thus, the turbine efficiency effectively improves by 2.28%. Meanwhile, the optimized blade reduces the particle impingement velocity and probability on the rotor leading edge, and the erosion condition of the rotor leading edge decreases by 70%.
{"title":"Multiobjective Optimization Study On the Aerodynamic Performance and Anti-Erosion Characteristics of a Single-Stage Dusty Flue Gas Turbine","authors":"Liuxi Cai, Yao He, Jiawei Yao, Yanfang Hou, Shun-sen Wang, Zhenping Feng","doi":"10.1115/1.4064060","DOIUrl":"https://doi.org/10.1115/1.4064060","url":null,"abstract":"Solid particle erosion of dusty energy recovery turbine blades has a great impact on the operating economics and safety of the unit. To mitigate the erosion of blade and improve the aerodynamic performance of the turbine, a multiobjective optimization method for turbine cascade based on the experimental design method, genetic algorithm and CFD multiphase flow simulation was developed. The optimization results show that the number of stator and rotor blades and the trailing edge angle at 50% blade span are the main parameters affecting the efficiency and blade erosion of the dusty turbine. By reducing the number of stator blades and the circumferential bending angle of the stator trailing edge, the impingement velocity and impingement probability of particles impinging on the stator trailing edge decrease by 7.5%~16.8% and 8.9%~46.2%, respectively. Additionally, compared with the original design, the flow separation loss and secondary flow intensity of the rotor cascade are suppressed by adjusting the load distribution and inlet attack angle of the rotor; thus, the turbine efficiency effectively improves by 2.28%. Meanwhile, the optimized blade reduces the particle impingement velocity and probability on the rotor leading edge, and the erosion condition of the rotor leading edge decreases by 70%.","PeriodicalId":508252,"journal":{"name":"Journal of Engineering for Gas Turbines and Power","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139260963","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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