This study concerns the use of counter based laser Doppler anemometry in a wet steam flow of variable wetness fraction. Velocity measurements across the flow were made under different steam conditions. Comparison was made with a theoretical profile based upon a simple flow analysis. A small radial turbocharger was used as a means of extracting enthalpy homogeneously from a dry superheated flow of steam using the compressor as a brake. The wetness fraction of the exhaust was estimated using measured values of the thermodynamic properties. A laser extinction method was used to determine the number concentration and mean radius of the water droplets acting as natural scatterers in the wet steam. A laser anemometer was designed which made use of the properties of a propagating gaussian beam to produce a small probe volume. This was required to reduce the number of water droplets likely to be present simultaneously in the measuring volume. Good Doppler signals were obtained and these have been presented for a range of wet steam conditions. A computer model was developed to predict the scattering of laser light through wet steam. Results have shown that this can be accurately modelled using a particle size distribution function. The program written to perform the simulation takes into account both single and multiple scattering events. The parameters used for the distribution function required a knowledge of the wetness fraction and so provided a useful means of checking the estimate based upon the thermodynamic measurements. It has been demonstrated that the ability to obtain Doppler signals from the wet steam can be predicted by computation of the signal-to-noise ratio for the medium. Good results were obtained for the wet steam conditions under investigation.

The design of last stage low pressure steam (LP) turbines has become increasingly complicated as turbine manufacturers have pushed for larger and more efficient turbines. The tip sections of these LP turbines encounter condensing wet steam at high velocities resulting in increased losses. These losses are difficult to predict with computational fluid dynamic models. To study these losses and improve the design of LP turbines a study was commissioned to determine the feasibility and cost of a steam cascade facility for measuring low pressure turbine blade tip section aerodynamic and thermodynamic performance. This study focused on two objectives: 1) design a steam production facility capable of simulating actual LP turbine operating conditions, and 2) design an instrumentation system to measure blade performance in wet steam. The steam production facility was designed to allow the test section size to be selected later. A computer code was developed to model the facility cycle and provide equipment requirements. Equipment to meet these requirements, vendors to provide it, and costs were found for a range of test section sizes. A method to control the test section conditions was also developed. To design the instrumentation system two methods of measuring blade losses through entropy generation were proposed. The first method uses existing total pressure probe techniques. The second method uses advanced particle imaging velocimetry techniques possibly for the first time in wet steam. A new method is then proposed to modify the two techniques to take measurements at non-equilibrium states. Finally accuracy issues are discussed and the challenges associated with achieving periodic flow in this facility are investigated. / Master of Science

The work deals with the design of a system of orifices for high pressure difference. The task of this work is to design a device for controlled discharge of steam-gas mixture from a volume compensator with an overpressure of 12,27 MPa to a tank with an overpressure of 0,02 MPa at a constant mass flow of 40 kg/h. The first part of the thesis contains the theory and also the basic principles of calculations. In the next part of the work, the theoretical properties of flow, such as the speed of sound in wet steam, are determined. This knowledge then serves the main goal of the work, namely to design a system of orifices to release steam-gas mixture from the volume compensator.

This thesis is concerned on the simulation of wet steam flow using discontinuous Galerkin method. Wet steam flow equations consist of Naviere-Stokes equations for compressible flow and Hill's equations for condensation of water vapor. The first part of this thesis describes the mathematical formulation of wet steam model and the derivation of Hill's equations. The model equations are discretized with the aid of discontinuous Galerkin method and backward difference formula which leads to implicit scheme represented by nonlinear algebraic system. This system is solved using Newton-like method. The derived scheme was implemented in program ADGFEM which is used for solving non-stationary convective-diffusive problems. The numerical results are presented in the last part of this thesis. 1

This Master’s thesis deals with a pre-calculation of a steam condensation turbine on a blading mid diameter. The governing stage is solved as a A-turbine wheel, impulse blading. Multistage blading is solved as a reacion stage by ca/u method. Further, detailed calculation of last stage with a twisted blade is made. Thesis contains comparision of obtained results with a results provided by contracting company. Final part of thesis deals with a design of sectional shape of a turbine blade.

Le bon fonctionnement et les performances des turbines à vapeur sont liés à l’état de la vapeur et notamment au taux d’humidité qu’elle contient. EDF souhaite pouvoir maîtriser les phénomènes spécifiques à ces problématiques afin d’améliorer l’utilisation et l’évolution de ses turbines. Le sujet de recherche concerne la modélisation de la formation de l’humidité dans un corps de turbine et l’étude des couplages entre la phase liquide et les instationnarités. Dans ce contexte, la démarche adoptée est la suivante : la présence d’humidité est prise en compte à l’aide d’un modèle homogène, couplé à des modèles de condensation permettant de prendre en compte les phénomènes hors-équilibre thermodynamique : le grossissement et la nucléation des gouttes d’eau dans la vapeur. Pour mener à bien les calculs, des méthodes numériques adaptées aux gaz réels ont été utilisées et testées à l’aide d’un code monodimensionnel avant d’être intégrées dans le code 3D elsA. Deux types de modèles de condensation ont été mis en œuvre, considérant ou non la polydispersion des gouttes dans la vapeur. Les couplages instationnaires entre la condensation et l’écoulement principal ont été étudiés à différents niveaux d’observations (1D, 1D − 3D, 3D). Il a été montré que la méthode des moments apporte une richesse supplémentaire par rapport à un modèle mono-dispersé, et permet de mieux capter les couplages instationnaires entre l’humidité et le champ principal. / In addition to conventional turbomachinery problems, both the behavior and performances of steam turbines are highly dependent on the vapour thermodynamic state and the presence of a liquid phase. EDF, the main French electricity producer, is interested in further developing its’ modelling capabilities and expertise in this area to allow for operational studies and long-term planning. This PhD thesis explores the modelling of wetness formation and growth in a steam turbine and an analysis of the coupling between the liquid phase and the main flow unsteadiness. To this end, the work in this thesis took the following approach. Wetness was accounted for using a homogeneous model coupled with transport equations to take into account the effects of non-equilibrium phenomena, such as the growth of the liquid phase and nucleation. The real gas attributes of the problem demanded adapted numerical methods. Before their implementation in the 3D elsA solver, the accuracy of the chosen models was tested using a developed one-dimensional nozzle code. In this manner, various condensation models were considered, including both polydispersed and monodispersed behaviours of the steam. Finally, unsteady coupling effects were observed from several perspectives (1D, 1D − 3D, 3D), demonstrating the ability of the method of moments to sustain unsteady phenomena which were not apparent in a simple monodispersed model.