This paper investigates the possibility of identifying and monitoring the modal shapes of a turbine blade by means of continuous optical fiber sensors based on Optical Backscatter Reflectometry (OBR). The advantage of this approach would be the possibility of embedding the sensors in future carbon fiber blades, in order to make this modal analysis approach available also for the blade operating conditions, since no modifications in the blade fluid-structure interaction occur. The paper describes the proposed method and provides some experimental results obtained on a 3D printed model of an existing steam turbine blade.
{"title":"Modal Analysis of Turbine Blades by Means of Distributed Optical Fiber Sensors","authors":"P. Pennacchi, G. Cazzulani, Alejandro Silva","doi":"10.1115/GT2020-15390","DOIUrl":"https://doi.org/10.1115/GT2020-15390","url":null,"abstract":"\u0000 This paper investigates the possibility of identifying and monitoring the modal shapes of a turbine blade by means of continuous optical fiber sensors based on Optical Backscatter Reflectometry (OBR). The advantage of this approach would be the possibility of embedding the sensors in future carbon fiber blades, in order to make this modal analysis approach available also for the blade operating conditions, since no modifications in the blade fluid-structure interaction occur. The paper describes the proposed method and provides some experimental results obtained on a 3D printed model of an existing steam turbine blade.","PeriodicalId":186943,"journal":{"name":"Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124445542","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}
Pub Date : 2020-09-21DOI: 10.1299/JSMEDMC.2018.432
R. Umehara, H. Shiraishi, Tetsuya Shimmyo, N. Onozato, Hiroki Kitada, Tomohiro Akaki
Turbine blades are now being used under increasingly severe conditions in order to increase the thermal efficiency of gas turbines. Friction dampers are often used to reduce the vibration of the blade and improve the plant reliability. This is a general study dealing with resonance passing where the natural frequency of the turbine blade coincides with the frequency of specific harmonic excitation forces while increasing the turbine rotation speed. Asynchronous components of excitation forces are also considered in addition to the synchronous components caused by specific harmonic excitation forces. In this study, a new method for predicting the characteristics of nonlinear vibration under excitation force including both synchronous and asynchronous force components is developed. In order to investigate the effect of additional asynchronous loading, time history response analyses considering nonlinear vibration using simulated turbine blades were conducted. Results showed that friction damper slip can be induced by the presence of the additional asynchronous excitation force components even for low values of synchronous excitation force. It is shown that it is possible to use a calibration factor to predict vibration characteristics considering friction slipping by estimating the ratio of the total excitation force to the single harmonic excitation force. To verify the effect of asynchronous excitation force and the validity of the proposed correction method, verification tests were conducted experimentally. The experimental results show that friction slipping occurred under small harmonic excitation force when there was asynchronous excitation force and show good agreement with the numerical results. Moreover, the validity of the proposed method which corrects the dynamic characteristics obtained using of the first order harmonic balance method is confirmed.
{"title":"Nonlinear Vibration by Asynchronous Excitation Force in Friction Damper of Turbine Blade","authors":"R. Umehara, H. Shiraishi, Tetsuya Shimmyo, N. Onozato, Hiroki Kitada, Tomohiro Akaki","doi":"10.1299/JSMEDMC.2018.432","DOIUrl":"https://doi.org/10.1299/JSMEDMC.2018.432","url":null,"abstract":"\u0000 Turbine blades are now being used under increasingly severe conditions in order to increase the thermal efficiency of gas turbines. Friction dampers are often used to reduce the vibration of the blade and improve the plant reliability. This is a general study dealing with resonance passing where the natural frequency of the turbine blade coincides with the frequency of specific harmonic excitation forces while increasing the turbine rotation speed. Asynchronous components of excitation forces are also considered in addition to the synchronous components caused by specific harmonic excitation forces. In this study, a new method for predicting the characteristics of nonlinear vibration under excitation force including both synchronous and asynchronous force components is developed. In order to investigate the effect of additional asynchronous loading, time history response analyses considering nonlinear vibration using simulated turbine blades were conducted. Results showed that friction damper slip can be induced by the presence of the additional asynchronous excitation force components even for low values of synchronous excitation force. It is shown that it is possible to use a calibration factor to predict vibration characteristics considering friction slipping by estimating the ratio of the total excitation force to the single harmonic excitation force. To verify the effect of asynchronous excitation force and the validity of the proposed correction method, verification tests were conducted experimentally. The experimental results show that friction slipping occurred under small harmonic excitation force when there was asynchronous excitation force and show good agreement with the numerical results. Moreover, the validity of the proposed method which corrects the dynamic characteristics obtained using of the first order harmonic balance method is confirmed.","PeriodicalId":186943,"journal":{"name":"Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128521584","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}
Akshay Khadse, Andres Curbelo, L. Vesely, J. Kapat
The first stage of turbine in a Brayton cycle faces the maximum temperature in the cycle. This maximum temperature may exceed creep temperature limit or even melting temperature of the blade material. Therefore, it becomes an absolute necessity to implement blade cooling to prevent them from structural damage. Turbine inlet temperatures for oxy-combustion supercritical CO2 (sCO2) are promised to reach blade material limit in near future foreseeing need of turbine blade cooling. Properties of sCO2 and the cycle parameters can make Reynolds number external to blade and external heat transfer coefficient to be significantly higher than those typically experience in regular gas turbines. This necessitates evaluation and rethinking of the internal cooling techniques to be adopted. The purpose of this paper is to investigate conjugate heat transfer effects within a first stage vane cascade of a sCO2 turbine. This study can help understand cooling requirements which include mass flow rate of leakage coolant sCO2 and geometry of cooling channels. Estimations can also be made if the cooling channels alone are enough for blade cooling or there is need for more cooling techniques such as film cooling, impingement cooling and trailing edge cooling. The conjugate heat transfer and aerodynamic analysis of a turbine cascade is carried out using STAR CCM+. The turbine inlet temperature of 1350K and 1775 K is considered for the study considering future potential needs. Thermo-physical properties of this mixture are given as input to the code in form of tables using REFPROP database. The blade material considered is Inconel 718.
{"title":"A Numerical Study on Conjugate Heat Transfer for Supercritical CO2 Turbine Blade With Cooling Channels","authors":"Akshay Khadse, Andres Curbelo, L. Vesely, J. Kapat","doi":"10.1115/GT2020-14679","DOIUrl":"https://doi.org/10.1115/GT2020-14679","url":null,"abstract":"\u0000 The first stage of turbine in a Brayton cycle faces the maximum temperature in the cycle. This maximum temperature may exceed creep temperature limit or even melting temperature of the blade material. Therefore, it becomes an absolute necessity to implement blade cooling to prevent them from structural damage. Turbine inlet temperatures for oxy-combustion supercritical CO2 (sCO2) are promised to reach blade material limit in near future foreseeing need of turbine blade cooling. Properties of sCO2 and the cycle parameters can make Reynolds number external to blade and external heat transfer coefficient to be significantly higher than those typically experience in regular gas turbines. This necessitates evaluation and rethinking of the internal cooling techniques to be adopted.\u0000 The purpose of this paper is to investigate conjugate heat transfer effects within a first stage vane cascade of a sCO2 turbine. This study can help understand cooling requirements which include mass flow rate of leakage coolant sCO2 and geometry of cooling channels. Estimations can also be made if the cooling channels alone are enough for blade cooling or there is need for more cooling techniques such as film cooling, impingement cooling and trailing edge cooling. The conjugate heat transfer and aerodynamic analysis of a turbine cascade is carried out using STAR CCM+. The turbine inlet temperature of 1350K and 1775 K is considered for the study considering future potential needs. Thermo-physical properties of this mixture are given as input to the code in form of tables using REFPROP database. The blade material considered is Inconel 718.","PeriodicalId":186943,"journal":{"name":"Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2","volume":"382 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129237550","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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