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Статті в журналах з теми "Steam Turbine Condensation Droplets Efficiency Two-Phase CFD"
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Guha, A. "Computation, analysis and theory of two-phase flows." Aeronautical Journal 102, no. 1012 (February 1998): 71–82. http://dx.doi.org/10.1017/s0001924000065556.
Повний текст джерелаАнотація:
AbstractThe non-equilibrium fluid mechanics and thermodynamics of two-phase vapour-droplet and gas-particle flow are considered. The formation of the droplets as well as their subsequent interaction with the vapour are discussed. Five topics have been given particular attention: (i) CFD application to unsteady condensation waves, (ii) CFD application to shock waves moving through a vapour-droplet mixture, (iii) a new theory of nucleation of water droplets in steam turbines based on Monte Carlo simulation (steam turbines are responsible for 80% of global electricity production and the presence of moisture significantly reduces the turbine efficiency costing £50m per annum in the UK alone), (iv) a unified theory for the interpretation of total pressure and total temperature in two-phase flows and, (v) a unified theory of particle transport in a turbulent flowfield.
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Ma, Ziyue, Xiaofang Wang, Jinguang Yang, Wei Wang, Wenyang Shao, and Xiaowu Jiang. "Acid Corrosion Analysis in the Initial Condensation Zone of a H2O/CO2 Turbine." Energies 14, no. 11 (June 5, 2021): 3323. http://dx.doi.org/10.3390/en14113323.
Повний текст джерелаАнотація:
A supercritical H2O/CO2 turbine is a key piece of equipment for the coal gasification in the supercritical water (CGSW) cycle to achieve conversion of heat into power. Compared with a traditional steam turbine, the working medium of an H2O/CO2 turbine has a relatively high CO2 concentration. In the initial condensation zone (ICZ), steam condenses into droplets on the turbine blades and the droplets combine with CO2 to form carbonic acid, which corrodes the turbine blades. In order to research the characteristics of acid corrosion in the ICZ of a H2O/CO2 turbine, the acid corrosion rate of the blades in the ICZ of the H2O/CO2 turbine was calculated and analyzed based on the three-dimensional CFD (3D CFD) method and a one-dimensional numerical model of CO2 corrosion. The results suggest that acid corrosion rates decrease stage by stage in the ICZ due to the reduction in temperature and pressure. Rotor blades in the first stage in the ICZ suffer the worst and form a corrosion zone at the trailing edge of the blade and on the pressure surface. The decline of efficiency caused by corrosion settles down to a relatively steady value of 0.6% for a 10 year service time. Moreover, the corrosion area for the last two stages shrinks with the service time due to the rearward movement of the ICZ.
Дисертації з теми "Steam Turbine Condensation Droplets Efficiency Two-Phase CFD"
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Maceli, Nicola. "Towards the advanced modelling of the low pressure stages of the steam turbines." Doctoral thesis, 2021. http://hdl.handle.net/2158/1238857.
Повний текст джерелаАнотація:
La tesi affronta il problema dell'accuratezza della previsione delle prestazioni per gli stadi di bassa pressione delle turbine a vapore, e ne propone una soluzione accoppiando ad un codice CFD commerciale una serie di modelli numerici per includere le perdite dovute alla condensazione del vapore durante l'espansione. La metodologia è stata validata utilizzando considerando varie configurazioni di comlessità crescente, fino ad arrivare allo studio di una turbina di bassa pressiore per la quale sono disponibile numerosi dati sperimentali. La tesi dimostra che la metodologia sviluppata migliora l'accuratezza nella stima dell'efficienza rispetto a metodi più tradizionalmente utilizzati nell'industria e che tale metodologia si pone come valido strumento per la riduzione dei costi di sviluppo di nuove sezioni di bassa pressione di turbine a vapore.
Тези доповідей конференцій з теми "Steam Turbine Condensation Droplets Efficiency Two-Phase CFD"
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Chandler, Kane, Mauro Melas, and Teresa Jorge. "A Study of Spontaneous Condensation in an LP Test Turbine." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42458.
Повний текст джерелаАнотація:
Recent advances in computational fluid dynamics (CFD) offer the possibility to predict condensing flows in 3D LP steam turbine geometries. Correct analysis of wetness losses, droplet deposition and other two-phase effects in LP steam turbines requires accurate prediction of the non-equilibrium flow field and droplet sizes. The paper compares numerical results from a 3D, polydispersed, condensing flow CFD code to experimental data measured in a scaled model LP turbine for a range of operating conditions. In order to compare the computed efficiencies with the measured values, a method for averaging non-equilibrium flow fields has been developed. Comparisons are made between computational and experimental results for a series of inlet temperature variation tests where the inlet and exit pressures were kept constant. The steady calculations accurately predict the temperature that the primary nucleation zone moves to an upstream row. Furthermore, the mechanism of condensation as nucleation changes rows is explored and it is shown that initially a significant degree of subcooling is maintained in the inter-blade section and, as a result, nucleation occurs at a relatively low rate in a zone that extends far downstream of the blade’s trailing edge. This produces relatively large droplets compared to when nucleation occurs predominantly within the blade passage and is clearly visible in the measured module efficiencies and local flow angles, static pressures and light extinction. The measured variation of efficiency and specific work with inlet temperature is predicted accurately by the computations. It is concluded that steady condensing flow wet-steam calculations are able to predict the location of nucleation and the variation of flow dynamics and performance with inlet temperature accurately. A description of the condensation process as nucleation moves between rows has been given and is consistent with the numerical and experimental results.
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Patel, Yogini, Giteshkumar Patel, and Teemu Turunen-Saaresti. "Influence of Turbulence Modelling to Condensing Steam Flow in the 3D Low-Pressure Steam Turbine Stage." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57590.
Повний текст джерелаАнотація:
With the tremendous role played by steam turbines in power generation cycle, it is essential to understand the flow field of condensing steam flow in a steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The turbulence has a leading role in condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of turbulence modelling on non-equilibrium condensing steam flows in a LP steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of turbulence modelling on the wet-steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of condensing steam flow requires the turbulence to be modelled accurately.
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Kim, Changhyun, JaeHyeon Park, DongIl Kim, and Jehyun Baek. "Numerical Analysis on Non-Equilibrium Steam Condensing Flow in Rotating Machinery." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7588.
Повний текст джерелаАнотація:
Flow of steam, different from other gas flows, involves droplet generation in flow expansion process. This phase transition affects not only the flow fields, but also machine performance including efficiency. In addition, it is totally harmful for machine structures as blades and casing. Therefore, prevention or preparation of droplet generation in steam flows is dreadfully important in stable machine operation. Nowadays, Computational Fluid Dynamics (CFD) is widely used in machine design and optimization process. Thus, simulation with CFD should consider this droplet generation phenomena to predict internal flows precisely. Many studies that analyze steam condensing flow in nozzles, cascades and steam turbines were carried out. Though, the flows of wet-steam which include non-equilibrium phase-transition phenomena are still difficult to predict, especially in the 3D rotating cases as steam turbines. Therefore, more studies are required to get comparable results with experiment. In this study, non-equilibrium wet-steam model was implemented on T-Flow to simulate realistic non-equilibrium steam condensing flow. In the cases of White cascade, characteristics of wet-steam flow were studied and pressure distributions were compared with experimental results for model validation. To use implemented wet-steam model for calculating flows in rotation, especially in steam turbines, a study of steam condensing flow in single stage steam turbine was conducted. Interaction between the stator and rotor using frozen rotor or mixing plane method in steady calculations were compared in order to find the effects of used interface on flow fields and steam condensation. As a result, condensing flows were predicted well even in the rotating cases by using non-equilibrium wet-steam model. The wet-steam parameters (nucleation, droplet size, wetness) are differed throughout the spans due to 3D effects and influenced by selection of interface as expected. In addition, droplet generation enhances entropy rise throughout the domain. The case using mixing plane seems to be overestimate the size of high wetness zone and it is recommended to use frozen rotor in multi-phase calculations. However, to apply this model in general cases, comparison with experimental data from real steam turbines should be conducted in further studies.
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Mahpeykar, M. R., E. Amirirad, and E. Lakzian. "The Effects of Water Injections in Wet Steam Flow in Different Regions of a Mini Laval Nozzle." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62252.
Повний текст джерелаАнотація:
Progress in the development of the steam turbines brings about a renewal of interest in wetness associated problems. In turbine steam expansion, the vapour first supercools and then condenses spontaneously to become a two phase mixture. The flow initially is single phase but after Wilson point water droplets are developed and there is a non equilibrium two phase flow. The formation and behavior of the liquid create problems that lower the performance of the turbine wet stage and the mechanisms underlying this are insufficiently understood. This growing droplets release their latent heat to the flow and this heat addition to the supersonic flow cause a pressure rise called condensation shock. Because of irreversible heat transfer in this region the entropy will increase tremendously. Removal of condensates from wet steam flow in the last stage of steam turbines significantly promotes stage efficiency and prevents erosion of rotors. The following study investigates the spraying water droplets at inlet and at throat of mini Laval nozzle and their effects on nucleation rate and condensation shock. According to the results, the nucleation rate is considerably suppressed and therefore the condensation shock nearly disappeared. In other words the injecting droplets would decrease the thermodynamic losses or improve the turbine efficiency.
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Maceli, Nicola, Lorenzo Arcangeli, and Andrea Arnone. "Two Phase Flow CFD Modeling to Enhance Steam Turbines LP Stages Performance Predictability: Comparison With Data and Correlations." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16312.
Повний текст джерелаАнотація:
Abstract The whole energy market, from production plants to end-users, is marked by a strong impulse towards a sustainable use of raw materials and resources, and a reduction of its carbon foot-print. Increasing the split of energy produced with renewables, improving the efficiency of the power plants and reducing the waste of energy appear to be mandatory steps to reach the goal of sustainability. The steam turbines are present in the power generation market with different roles: they are used in fossil, combined cycles, geothermal and concentrated solar plants, but also in waste-to-energy and heat recovery applications. Therefore, they still play a primary role in the energy production market. There are many chances for efficiency improvement in steam turbines, and from a rational point of view, it is important to consider that the LP section contributes to the overall power delivered by the turbine typically by around 40% in industrial power generation. Therefore, the industry is more than ever interested in developing methodologies capable of providing a reliable estimate of the LP stages efficiency, while reducing development costs and time. This paper presents the results obtained using a CFD commercial code with a set of user defined subroutines to model the effects of non-equilibrium steam evolution, droplets nucleation and growth. The numerical results have been compared to well-known test cases available in literature, to show the effects of different modeling hypotheses. The paper then focuses on a test case relevant to a cascade configuration, to show the code capability in terms of bladerow efficiency prediction. Finally, a comprehensive view of the obtained results is done through comparison with existing correlations.
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Sasao, Yasuhiro, Kiyoshi Segawa, Takeshi Kudo, Ryo Takata, Masaki Osako, and Satoru Yamamoto. "Wetness Measurement and Droplet Transport Analysis in Actual Steam Test on a Scaled Low Pressure Turbine." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-16117.
Повний текст джерелаАнотація:
Abstract Understanding the phenomenon and quantitative prediction of wet loss, quantitative prediction of erosion are still challenges in ST development. The aim of the actual steam test reported in this paper was to verify the performance of a newly developed ST. Still a comprehensive understanding of the wetness phenomenon is also a significant issue. Therefore, in connection with the actual steam test, efforts were made to develop a method for analyzing the three-dimensional causes of wetness loss and erosion. As the first report on the wet phenomenon analysis performed in this actual steam test, this paper reports wet measurement results and analysis results. In the actual steam testing of a 0.33 scaled steam turbine, wetness measurements were carried out at the third stage (L-1) and the final stage (L-0), and its characteristic wetness distribution was analyzed using our original CFD-code MHPS-NT. This 0.33 scaled steam turbine consists of the final three stages (LP-end) and the inlet steam conditioning stage (total of four stages), and wetness distributions in the blade height-wise were measured using two different wetness probes under several operating conditions. Wetness distribution did not change linearly with changes in ST inlet temperature, but dynamic changes in peak position and shape were observed. From the ST inlet to the exhaust chamber, the generation of fine droplets, the capturing of droplets by the wall surfaces, and the behavior of water films and coarse droplets were comprehensively analyzed using a three-dimensional (3-D) unsteady Eulerian-Lagrangian coupling solver that takes into account non-equilibrium condensation. This CFD code (MHPS-NT) is an improved version of Original-NT developed by Tohoku University. By considering the relative position and structure of the wet probe and blade cascade in CFD, it was found that the wetness is formed remarkable circumferential distribution by the moisture separation of the upstream blade rows and end-walls. The circumferential distribution of wetness can be a factor that makes it difficult to grasp the liquid phase distribution inside the steam turbine as an error factor independent of the accuracy of the optical measurement device. Due to the effects of water droplet capturing, the LP-end outlet wetness at the design point may be underestimated by 21% relative. It is also reported that because the wetness has a distribution in the meridian direction, wetness measurements by the wet probe may contain measurement errors independent of the measurement accuracy.
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Senoo, Shigeki, and Yoshio Shikano. "Non-Equilibrium Homogeneously Condensing Flow Analyses as Design Tools for Steam Turbines." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31191.
Повний текст джерелаАнотація:
In order to get the details of flow fields in steam turbines, three-dimensional turbulent flow calculations are useful. However in a design procedure, three-dimensional flow calculations are only possible in the last design stage, because they need in-depth boundary conditions of both geometries and flows. At such a late time in the procedure, it is difficult to go back and change main design parameters, such as flow area and stage load. Both three-dimensional flow patterns and non-equilibrium condensation caused by rapid expansions of steam have important roles with respect to steam turbine performance particularly in low-pressure sections. The steam turbine internal efficiency can be improved by taking account of these effects in the early design stage, especially in flow pattern design. This paper describes a multi-stage through-flow calculation technique including both three-dimensional flow efffects and phase changes from vapour to small droplets. To compute the high-speed two phase steam flow, a flux-splitting procedure including non-equilibrium homogeneously condensation is introduced. Three-dimensional blade forces are calculated by using angles of both blade camber and radial lean. The blade camber lines can be decided without in-depth blade geometries. Therefore this computational technique is applicable in the flow pattern design. The calculation results agree well with fully three-dimensional flow calculation and the calculation can predict supersaturating states and Wilson lines which are defined as the maximum supercooling.
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Narabayashi, Tadashi, Yoichiro Shimazu, Toshihiko Murase, Masatoshi Nagai, Michitsugu Mori, and Shuichi Ohmori. "Development of Technologies on Innovative Simplified Nuclear Power Plant Using High-Efficiency Steam Injectors: Part 10—Application to a Small District-Heating Reactor." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89753.
Повний текст джерелаАнотація:
A steam injector (SI) is a simple, compact and passive pump and also acts as a high-performance direct-contact compact heater. This provides SI with capability to use as a passive ECCS pump and also as a direct-contact feedwater heater that heats up feedwater by using extracted steam from the turbine. In order to develop a high reliability passive ECCS pump and a compact feedwater heater, it is necessary to quantify the characteristics between physical properties of the flow field. We carried out experiments to observe the internal behavior of the water jet as well as measure the velocity of steam jet using a laser Doppler velocimetry. Its performance depends on the phenomena of steam condensation onto the water jet surface and heat transfer in the water jet due to turbulence on to the phase-interface. The analysis was also conducted by using a CFD code with the separate two-phase flow models. With regard to the simplified feed-water system, size of four-stage SI system is almost the same as the model SI that had done the steam and water test that pressures were same as that of current ABWR. The authors also conducted the hot water supply system test in the snow for a district heating. With regard to the SI core cooling system, the performance tests results showed that the low-pressure SI core cooling system will decrease the PCT to almost the same as the saturation temperature of the steam pressure in a pressure vessel. As it is compact equipment, SI is expected to bring about great simplification and materials-saving effects, while its simple structure ensures high reliability of its operation, thereby greatly contributing to the simplification of the power plant for not only an ABWR power plant but also a small PWR/ BWR for district heating system.
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Zhuk, Yuri. "Nanostructured CVD W/WC Coating Protects Steam and Gas Turbine Blades Against Water Droplet Erosion." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-80263.
Повний текст джерелаАнотація:
Abstract Gas turbine compressor blades operating with air inlet fogging can suffer from Water Droplet Erosion (WDE). WDE can also affect the last rows of steam turbines where expanding steam produces water condensation, especially under start-up and low load conditions. WDE damages the blades’ leading and sometimes trailing edges, increasing turbine rotation drag, reducing efficiency and leading to costly maintenance. This paper reports the testing of Hardide® nano-structured W/WC metal matrix composite coating as a protection against WDE. The Chemical Vapor Deposition (CVD) technology crystallizes the coating atom-by-atom from the gas phase and produces a uniform pore-free coating on complex shaped parts like turbine blades, vanes and pump impellers, including non-line-of-sight areas. Two variants of CVD W/WC coatings were tested: “A” type is 50–100 microns thick and has a hardness range of 800–1200 Hv and “T” type is 35–65 microns thick with a higher hardness of 1100–1600 Hv. Both coating types are made of Tungsten Carbide nanoparticles dispersed in metal Tungsten matrix. This composition and structure produce a combination of enhanced fracture toughness with high hardness and enables the deposition of exceptionally thick hard CVD coatings to provide durable protection against WDE and solid particle erosion. The coatings are pore-free thus also provide an effective barrier against corrosion. The coatings were tested for WDE resistance by the UK National Physics Laboratory (NPL) using 350 μm water droplets at 300 m/sec velocity. Uncoated 410 SS control samples suffered from a major loss of material after just 7-hours of exposure to WDE, forming a 200 μm deep scar across the whole tested area. After a much longer exposure of 90 hours, the coating samples showed negligible WDE damage, only measurable on the samples’ edges. The coating also outperformed Stellite, which is widely used as WDE protection in the form of welded overlay or plates brazed to the blade’s leading edge. The thicker and less hard type “A” CVD coating showed better performance when compared to the thinner, harder type “T”. The effects of the coatings’ thickness, hardness, and residual stresses on the WDE resistance are discussed. The rig testing showed that the CVD WC/W coating can protect steam and gas turbine blades against WDE thus increasing the service life of equipment and maintaining its optimal performance for longer, reducing CO2 emissions and cutting the life-cycle costs. Hardide coatings are used by major oil service companies, pump and valve producers to improve durability in abrasive and corrosive environments. Airbus has approved Hardide-A coating as a REACH-compliant replacement for Hard Chrome plating on aircraft components. Other customers include BAE Systems, EDF Energy, Leonardo Helicopters and Lockheed Martin. The Hardide coating service is provided from state-of-the-art coating facilities near Oxford (UK) and in Virginia (US). Production and quality control are accredited to ISO9001, AS9100 and NADCAP standards.