CFD driven optimization of hydraulic turbine draft tubes using surrogate models

The efficiency of a hydraulic reaction turbine is significantly affected by the performance of its draft tube. The shape and velocity distribution at the inlet are, in next turn, two main factors that affects the performance of the draft tube. Traditionally, the design of this component has been based on simplified analytic methods, experimental rules of thumb and model tests. In the last decade or two, the usage of computational fluid dynamics (CFD) has dramatically increased in the design process and will continue to grow due to is flexibility and cost-effectiveness. A CFD-based design search can further be aided with a robust and userfriendly optimization framework. Numerical prediction of the draft tube flow are, on the other hand, challenging and time consuming, caused by its complex flow features, e.g. unsteadiness, turbulence, separation, streamline curvature, secondary flow, swirl, and vortex breakdown. Hence, there is a great need of developing both accurate and reliable CFD models, together with efficient and effective optimization frameworks. In this work, a surrogate-based optimization (SBO) framework has been employed, in order to develop and implement a computer tractable approach to optimize the shape of hydraulic turbine draft tubes. By this methodology, one can replace the expensive CFD model with a surrogate model in the optimizations phase, in order to provide a faster and more effective exploration of the design and solution space. In addition, one gets a better insight into the true relationship between design variables and objective functions. Furthermore, this study has surveyed to enhance the quality and trust of non-trivial draft tube flow simulations. Mainly, since the initial CFD predictions were found to be in poor agreement with model tests, whereby the work has been split into two major parts, one concerning the SBO analysis and the other concerning the validity of the obtained CFD calculations. The outcome of this research, demonstrates the potential and benefits of using surrogate models in the design phase of hydraulic turbines draft tubes. For example, is the computational burden with a SBO framework drastically reduced, compared to solely utilizing a standard optimization framework. It is also preferable to test multiple surrogate models, since the prediction capabilities of it is highly problem dependent and the time cost of doing it is relatively low. The optimization results show moreover similar trends as model tests, illustrating the reliability of the approach. Some quantitative discrepancies are, however, found and it is recommended to further enhance the CFD simulations, by for instance include the runner geometry and/or use more advanced turbulence models in the calculations.Godkänd; 2006; 20061116 (pafi)</p

CFD driven optimering av vattenvägarna i ett vattenkraftverk med hjälp av surrogatmodeller

Godkänd; 2007; 20070905 (ysko)</p

Pressning av SMC : numeriska tryckfältsberäkningar med hjälp av inversmodellering

Godkänd; 2007; 20070905 (ysko

Comparison of three turbulence models in the modeling of kiln aerodynamics

Godkänd; 2014; 20140821 (soflar)Fastelaboratoriet - VINNEX

PIV analysis of merging flow in a simplified model of a rotary kiln

Godkänd; 2012; 20140821 (soflar)Fastelaboratoriet - VINNEX

Simulation driven processing function development, offering and operation

In today’s industry, functional provision is becoming more and more important, necessitating increased simulation support. In this paper, the objective is to present a modeling and simulation approach for simulation-driven design (SDD) to support function development. The scope of this paper is simulation support for developing hardware equipment used in processing industry. The research is founded on industrial needs identified through two parallel interview-based studies in the Swedish process industry. Both companies explore doing business with functional products rather than hardware, in scenarios where the responsibility for and availability of the functions may remain with the service provider. One as-is and one future (to-be) scenario are presented. A decomposition of a general processing function (applicable to both companies) describes how the companies transfer machine input to output specifications. The decomposition includes customer and provider value and the paper demonstrates, as part of the results and based on the SDD approach, how that value may be increased through evaluation and prioritization. Additionally, the SDD approach shows that it is possible to identify a set of solutions which meet the specified requirements, supporting evaluation and prioritization of business offers and activities.Godkänd; 2012; 20130117 (ysko)Fastelaboratoriet - VINNEX

The Effect of Reynolds Number on Jet in Asymmetric Co-Flows: A CFD Study

In rotary kilns in grate-kiln systems for iron ore pelletizing, a long and stable jet flame is needed to ensure a high quality of the pellets. The primary jet issuing from the nozzle interacts with two asymmetric co-flows creating a very complex flow. In order to better understand and eventually model this flow with quality and trust, simplified cases need to be studied. In this work, a simplified and virtual model is built based on a down-scaled kiln model established in a previous experimental work. The aim is to numerically study the jet development as a function of position and Reynolds number (Re). The numerical simulations are carried out with the standard k-ε model, and quite accurate velocity profiles are obtained while the centerline decays and spreading of the passive scalars are over predicted. The model is capable of predicting a Re dependency of the jet development. With increasing Re, the jet is longer while it generally decays and spreads faster resulting from the stronger shear between the jet and co-flows and the stronger entrainment from the recirculation zone. This recirculation found in the simulations restrain the momentum spreading in the spanwise direction, leading to a slower velocity spreading with higher Re. For further validation and understanding, more measurements in the shear layer and simulations with more advanced turbulence models are necessary

Grate aerodynamic : Model strategies for gas flow through a 2D iron ore pellet bed

Godkänd; 2014; 20140923 (andbra