Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines最新文献

{"title":"Detached-Eddy Simulation Applied to the Tip-Clearance Flow in a Last Stage Steam Turbine Blade","authors":"T. Sun, P. Petrie-Repar, D. Vogt","doi":"10.1115/GT2018-75943","DOIUrl":"https://doi.org/10.1115/GT2018-75943","url":null,"abstract":"Prediction of the aerodynamic stability of rotor blades at the last stage of steam turbines is of great importance and widely studied. Considering the large span and low natural frequency of these blades, flow at the tip region has a remarkable effect on blade flutter characteristics. However, the transonic tip-clearance flow in these blades has a complex structure of vortices. To obtain a deep understanding of the transonic tip-clearance flow structure in steam turbines, the Detached-Eddy Simulation (DES) is applied in this paper. DES is a hybrid LES/RANS method that activates LES in specified flow regions and applies URANS in other regions of the flow field. As far as we are aware, the tip-clearance flow structure of real-scale last stage steam turbine by high-fidelity numerical method had not been much analyzed in open literature. In this paper, the transonic tip-clearance flow structure in modern last stage of steam turbines is analyzed by both URANS and DES approaches. The open steam turbine model designed by Durham University is chosen as the research model. The flow solver applied is the commercial software ANSYS CFX. From the DES result, the tip leakage vortex and the induced vortices are presented. Based on the comparison between tip-clearance flow structure captured by the two approaches, the URANS method is not able to resolve all induced vortices. Therefore, the distribution of aerodynamic loading on the blade surface is different between URANS and DES results. The present study serves as a basis for investigating the influence of the tip-clearance flow structure on blade aeroelasticity.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"43 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":"127696976","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}

{"title":"Effects of Inlet Chamber Structure of the Control Stage on the Unsteady Aerodynamic Force","authors":"Gao Keke, Wang Chongyu, Yonghui Xie, Di Zhang","doi":"10.1115/GT2018-76632","DOIUrl":"https://doi.org/10.1115/GT2018-76632","url":null,"abstract":"Blade fatigue fracture is the main factor affecting the safe operation of the turbine and the aerodynamic exciting force caused by partial admission accelerates the fatigue failure of the control stage blade. In this paper, based on the three-dimensional unsteady flow research of 300MW control stage, a new type of inlet chamber structure is proposed, which can reduce the local aerodynamic exciting force effectively. The performance of original structure and new structure is compared at 0.7 partial admission operation condition in details. Firstly, the paper gives the overall performance of the control stage under the two structures. It is proved that the new inlet chamber structure proposed in this paper only has a slight influence on the overall performance, which is shown as mass flow, power and efficiency. Secondly, distributions of flow parameters such as pressure, static entropy and axial velocity at the stator inlet and rotor inlet are given in the paper. The new structure is found to alleviate the sudden change of flow parameters such as pressure at the inlet steam chamber transition region. Finally, five key points of axial aerodynamic force and seven key points of tangential aerodynamic force are captured to illustrate the influence of partial admission on instantaneous aerodynamic exciting force. Further, the mechanism of new inlet chamber structure on local aerodynamic exciting forces is explained. The result shows that the new inlet chamber structure can reduce the local axial aerodynamic exciting force up to 13% and reduce the local tangential aerodynamic exciting force up to 29.7%, which is beneficial to improve the safety and reliability of the turbine operation.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"21 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":"134539686","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}

{"title":"Performance of the Automotive Turbocharger Compressor With Various CO2-Air Mixtures","authors":"Tomasz Duda, C. Copeland","doi":"10.1115/GT2018-75747","DOIUrl":"https://doi.org/10.1115/GT2018-75747","url":null,"abstract":"The automotive low pressure exhaust gas recirculation or closed-cycle gas turbine engines are among applications where an alternative fluids to air are used. This paper analyses compressor performance measured while operating with substitute gas. Several compressor performance maps were generated and compared on a steady-state turbocharger test facility run in a closed-loop mode. The automotive centrifugal compressor was mapped with pure air, CO2-air mixtures (3%, 5%, 10% CO2 by mass) and pure CO2. The analysis of the obtained data has indicated that the use of reduced speed parameter and reduced mass flow parameter formulas worked well in the process of the compressor map correction for the CO2-air mixtures. The corrected (with reduced mass flow and speed parameters) compressor performance map generated for the case of pure CO2 has shown a shift in both choke and surge lines and changes in measured pressure ratio and efficiency. Further efficiency and pressure ratio corrections based on the method proposed by Roberts and Sjolander [1] have shown no match between the predicted and measured values of efficiency for CO2. The series of adiabatic 3D CFD simulations indicated that this was likely caused by the heat transfer between the uninsulated turbomachinery components.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"23 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":"115783277","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}

{"title":"Influence of Wet Steam on the Five-Stage Steam Turbine Efficiency","authors":"M. Hoznedl, M. Kolovratník, L. Tajč, Andreas Weiß, Lukáš Mrózek","doi":"10.1115/GT2018-75049","DOIUrl":"https://doi.org/10.1115/GT2018-75049","url":null,"abstract":"In the paper the behaviour of the five-stage experimental steam turbine 10 MW is described during the expansion transition from superheated steam to wet steam as well as the influence of wet steam on the flow path efficiency. The influence of wet steam occurrence on one to four last stages is given by setting the inlet steam parameters. The wetness of steam behind the last stage is calculated using two methods, first by enthalpy drop with the output measured by water brake and second by an optical probe. The results of both methods are compared. The impact of steam wetness increasing on a decrease in turbine efficiency is observed. In the paper the influence of steam wetness on the individual stage efficiency is also described and wetness loss coefficient is determined. Using the optical probe, assessment of poly-disperse structure of fine droplets is carried out, which is presented here by Sauter mean diameter. A pneumatic probe is used to define the distribution of velocities and pressures along the blade length after the last stage.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"613 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":"116454077","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}

{"title":"On Possibilities of Using Relative Shaft Vibration Signals for Rotating Blades Monitoring","authors":"J. Liška, V. Vašíček, J. Jakl","doi":"10.1115/GT2018-76565","DOIUrl":"https://doi.org/10.1115/GT2018-76565","url":null,"abstract":"Ensuring the reliability of the steam turbine is the key for its long life. For this purpose monitoring systems are standardly used. Early detection of any failure can avoid possible economical and material losses. A monitoring of rotating blades vibration belongs to the very important tasks of the turbomachinery state assessment. Especially in terms of the last stages of low-pressure part, where the longest blades are vibrating at most. Commonly used methods for blade vibration monitoring are based on contact measurement using strain gauges or non-contact approach based on blade tip timing measurement.\u0000 Rising demand for low-cost monitoring systems has initiated development of a new approach in blade vibration monitoring task. The presented approach is based on usage of relative rotor vibration signals. Its advantage is in using of standardly installed sensors making this approach economically interesting for the turbine operators compared to the traditionally used methods, mentioned above.\u0000 This paper summarizes the symptoms of blade vibration phenomenon in relative shaft vibration signals, the impact of operating conditions on the blade vibration amplitude and its comparison to blade tip-timing measurement results. In addition of several examples, the article also describes an evaluation of proposed method in operation of steam turbine with power of 170MW.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","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":"129406685","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}

{"title":"Utilization of a Thermo-Mechanical Model Coupled With Multi-Objective Optimization to Enhance the Start-Up Process of Solar Steam Turbines","authors":"Monika Topel, A. Vitrano, Björn Laumert","doi":"10.1115/GT2018-75829","DOIUrl":"https://doi.org/10.1115/GT2018-75829","url":null,"abstract":"The need to mitigate the climate change has brought in the last years to a fast rise of renewable technologies. The inherent fluctuations of the solar resource make concentrating solar power technologies an application that demands full flexibility of the steam turbine component. A key aspect of this sought steam turbine flexibility is the capability for fast starts, in order to harvest the solar energy as soon as it is available. However, turbine start-up time is constrained by the risk of low cycle fatigue damage due to thermal stress, which may bring the machine to failure. Given that the thermal limitations related to fatigue are temperature dependent, a transient thermal analysis of the steam turbine during start process is thus necessary in order to improve the start-up operation.\u0000 This work focuses on the calculation of turbine thermo-mechanical properties and the optimization of different start-up cases in order to identify the best solution in terms of guaranteeing reliable and fast start-ups. In order to achieve this, a finite element thermal model of a turbine installed in a concentrating solar power plant was developed and validated against measured data. Results showed relative errors of temperature evolutions below 2%, making valid the assumptions and simplifications made. Since there is trade-off between start-up speed and turbine lifetime consumption, the model was then implemented within a multi-objective optimization scheme in order to test and design faster start-ups while ensuring safe operation of the machine. Significant improvements came up in terms of start-up time reduction up to 30% less than the standard start-up process.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"48 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":"130418455","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}

{"title":"Methodology for Evaluating Efficiency Benefits of Hydrophobic Coatings in Steam Turbine Applications","authors":"Mauro Melas, R. Sigg, Stefan Bühlmann, Daniela Limacher, Thomas Manyoky","doi":"10.1115/GT2018-76854","DOIUrl":"https://doi.org/10.1115/GT2018-76854","url":null,"abstract":"Performance of steam turbines operating under wet steam is known to worsen proportionally to the increase in wetness at turbine exhaust. Numerous strategies have been attempted in the past to minimize the efficiency loss and mechanical damage associated with liquid phase formation, mostly with limited success and poor commercial viability due to increased complexity.\u0000 The application of hydrophobic coatings is a simple economically favorable strategy and is expected to partially inhibit the formation of water films on blade surfaces and associated consequences.\u0000 This paper addresses a need of turbine manufacturers: the development of a methodology to test, rapidly and economically, performance impact and endurance of coatings to allow a systematic selection. The resulting methodology employs specialized equipment to measure the fog rejection effectiveness of coatings and to generate droplet impingement and thermal loads comparable to real applications, all under laboratory conditions. Measurement results indicated that different materials cause different wetness losses and turbine efficiency can be improved with the coating of blades. Transfer functions used to generate the correspondence between laboratory and representative turbine conditions enabled the coating selection for turbine application. Finally, tests in a model turbine allowed validating the prediction of efficiency improvement, confirming the suitability of the developed methodology.\u0000 This work demonstrates that this technology delivers an important improvement in turbine efficiency.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"109 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":"129623728","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}

{"title":"An Integrated Design Approach for Turbocharger Turbines Based on the Performance Optimization in Transitory Conditions","authors":"M. Checcucci, Michele Becciani, J. Bellucci, A. Bianchini, G. Ferrara, A. Arnone, Francesco Cencherle, Michele De Luca, L. Marmorini, Stéphane Montesino, N. Pini","doi":"10.1115/GT2018-76719","DOIUrl":"https://doi.org/10.1115/GT2018-76719","url":null,"abstract":"Turbocharged engines are setting themselves as the present standard in case of high-performance engines for sport applications. The coupling of a turbomachine with an internal combustion engine poses, however, some serious challenges, especially regarding the time lags and the transitory flow conditions. In particular, focus is presently being paid to the acceleration phase of these sport vehicles, where the mass flow is much lower than that attended at maximum efficiency condition and the transitory response of the turbocharger becomes pivotal to provide promptly high compression ratios to the engine. In this view, the global optimization process of new turbochargers must be oriented not only at maximizing the aerodynamic efficiency at the best design point but also at providing good efficiency at low mass flow rates, combined with a reduced inertia to enable fast acceleration.\u0000 In the study, a multi-objective methodological approach is presented aimed at designing the turbine of a high-performance turbocharged engine based on the following requirements: 1) high efficiency at the design point; 2) good efficiency at low mass flow rates, typical of the acceleration phase; 3) reduced inertia; 4) overall aerodynamic design adaptable with constructive constraints. In doing so, some design considerations are also provided, pointing out the different design choices that can be made in a design strategy focused either on maximum efficiency or on the minimization of the system inertia. The aerodynamic optimization has been carried out with an in-house CFD 3D code, while the turbine coupling with the engine has been obtained by embedding the aerodynamic maps into the 1D engine model.\u0000 The analysis showed that the new focus on the transitory response modified substantially the conventional design of the turbine, leading to new geometries able to improve notably the overall performance of the turbocharger.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"19 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":"116991371","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}

{"title":"Laboratory Method to Evaluate Fog Rejection Effectiveness of Hydrophobic Coatings for Steam Turbine Applications","authors":"Stefan Bühlmann, Daniela Limacher, Thomas Manyoky, Mauro Melas","doi":"10.1115/GT2018-77296","DOIUrl":"https://doi.org/10.1115/GT2018-77296","url":null,"abstract":"The application of hydrophobic coatings in steam turbines is expected to partially inhibit the formation of water films on blade surfaces, and consequently reduce the associated efficiency loss and mechanical damage.\u0000 Since testing coatings in real steam turbines is impractical, a method is presented to assess, under laboratory conditions, the tendency of materials to reject rather than collect water droplets impinging on them.\u0000 This behavior was demonstrated to poorly correlate with wetting angle measurements which proved the necessity to use a more complex approach.\u0000 A test rig was therefore used which allows evaluating fog-rejection effectiveness, by placing coated specimens on a rotor and exposing them to a flow of saturated steam carrying micron size droplets. Steam condition, impact angle, droplet size and velocity are kept close to what is expected in low pressure steam turbines.\u0000 While rotating, the formed water film is centrifuged and captured in tanks within the supports holding the coated specimens. The mass of their content is measured upon experiment completion. Having tanks in 4 different locations along a specimen’s edge gives an additional insight about variations in collection location and film flow direction.\u0000 Repeatability and parameter variation tests have shown that the collection is reasonably insensitive to the changes in operation conditions, yet the scatter in the data remained high. Nevertheless, statistical analysis showed that the method is able to clearly detect differences in collection behavior, thus enabling the industrial partner to select coatings that provide enduring steam turbine efficiency increase.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","volume":"149 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":"133344911","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}

{"title":"Analysis of Steam Turbine Blade Tip Excitation Forces by Means of Computational Fluid Dynamics and Experimental Cascade Results","authors":"S. Wiesche, Maximilian Passmann","doi":"10.1115/GT2018-75179","DOIUrl":"https://doi.org/10.1115/GT2018-75179","url":null,"abstract":"A semi-empirical steam excitation force model is presented for freestanding unshrouded blades. The model is resting on a superposition of the classical Thomas-Alford cross forces and additional fluid derived forces. The additional fluid derived forces are caused by static pressure modifications in the blade tip region and large-scale redistributions of the inflow velocity caused by the varying tip gap width due to eccentricity. The empirical model parameters are obtained by means of computational fluid dynamics (CFD) and experimental turbine cascade results. The Thomas-Alford cross force contribution is formulated by means of an analytical relation for the effective discharge coefficient. It is found, that the Thomas-Alford coefficient for the excitation cross-force increases if the blade tip gap decreases. That effect is caused by taking viscous flow effects into account, and it is in good agreement with available literature data. The direct force contribution results mainly from local pressure variation in the blade tip region, and it depends also on the mean tip gap width. A further effect is caused by an upstream redistribution of the velocity due to the varying tip gap width. This effect was discovered by Song and Martinez-Sanchez first, and it is confirmed experimentally by cascade measurements in the present paper.","PeriodicalId":105494,"journal":{"name":"Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines","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":"115076967","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}