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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Wind energy is the fastest growing alternate source of energy in the world since its purely economic potential is complemented by its great positive environmental impact. The wind turbine, whether it may be a Horizontal-Axis Wind Turbine (HAWT) or a Vertical-Axis Wind Turbine (VAWT), offers a practical way to convert the wind energy into electrical or mechanical energy. Although this book focuses on the aerodynamic design and performance of VAWTs based on the Darrieus concept, it also discusses the comparison between HAWTs and VAWTs, future trends in design and the inherent socio-economic and environmental friendly aspects of wind energy as an alternate source of energy.

Wind turbine design with emphasis on Darrieus concept Ion Paraschivoiu

Wind energy, together with other renewable energy sources, are expected to grow substantially in the coming decades and play a key role in mitigating climate change and achieving energy sustainability. One of the main challenges in optimizing the design, operation, control, and grid integration of wind farms is the prediction of their performance, owing to the complex multiscale two-way interactions between wind farms and the turbulent atmospheric boundary layer (ABL). From a fluid mechanical perspective, these interactions are complicated by the high Reynolds number of the ABL flow, its inherent unsteadiness due to the diurnal cycle and synoptic-forcing variability, the ubiquitous nature of thermal effects, and the heterogeneity of the terrain. Particularly important is the effect of ABL turbulence on wind-turbine wake flows and their superposition, as they are responsible for considerable turbine power losses and fatigue loads in wind farms. These flow interactions affect, in turn, the structure of the ABL and the turbulent fluxes of momentum and scalars. This review summarizes recent experimental, computational, and theoretical research efforts that have contributed to improving our understanding and ability to predict the interactions of ABL flow with wind turbines and wind farms.

https://link.springer.com/content/pdf/10.1007/s10546-019-00473-0.pdf

Wind-Turbine and Wind-Farm Flows: A Review

The cumulative global capacity of organic Rankine cycle (ORC) power systems for the conversion of renewable and waste thermal energy is undergoing a rapid growth and is estimated to be approx. 2000 MWe considering only installations that went into operation after 1995. The potential for the conversion of the thermal power coming from liquid-dominated geothermal reservoirs, waste heat from primary engines or industrial processes, biomass combustion, and concentrated solar radiation into electricity is arguably enormous. ORC technology is possibly the most flexible in terms of capacity and temperature level and is currently often the only applicable technology for the conversion of external thermal energy sources. In addition, ORC power systems are suitable for the cogeneration of heating and/or cooling, another advantage in the framework of distributed power generation. Related research and development is therefore very lively. These considerations motivated the effort documented in this article, aimed at providing consistent information about the evolution, state, and future of this power conversion technology. First, basic theoretical elements on the thermodynamic cycle, working fluid, and design aspects are illustrated, together with an evaluation of the advantages and disadvantages in comparison to competing technologies. An overview of the long history of the development of ORC power systems follows, in order to place the more recent evolution into perspective. Then, a compendium of the many aspects of the state of the art is illustrated: the solutions currently adopted in commercial plants and the main-stream applications, including information about exemplary installations. A classification and terminology for ORC power plants are proposed. An outlook on the many research and development activities is provided, whereby information on new high-impact applications, such as automotive heat recovery is included. Possible directions of future developments are highlighted, ranging from efforts targeting volume-produced stationary and mobile mini-ORC systems with a power output of few kWe, up to large MWe base-load ORC plants.

/pdf/organic-rankine-cycle-power-systems-from-the-concept-to-10dpkniszb.pdf

Organic Rankine Cycle Power Systems: From the Concept to Current Technology, Applications, and an Outlook to the Future

An important problem that arises in the design and the performance of axial flow turbines is the understanding, analysis, prediction and control of secondary flows. Sieverding1 has given a review of secondary flow literature, covering up to 1985. In this paper a brief review of pre-1985 work is given, and then a survey of open literature secondary flow investigations since the Sieverding review is presented. Most of the studies reviewed deal with plane or annular cascade flows. Tip clearance effects are not covered. The basic secondary flow picture for a turbine cascade, as measured and verified by a number of investigators is described. Recent work that shows refined secondary flow vortex structures is examined. A flow parameter based on inlet boundary layer properties used to predict horseshoe vortex swirl is presented. Work on secondary flow loss reduction, involving airfoil geometry, endwall fences and endwall contouring is briefly reviewed. A new leading edge bulb geometry that has demonstrated impressive loss reduction is considered. It is concluded that accurate routine prediction of secondary flow losses has not yet been achieved, and must await either a better turbulence model or more experiments to reveal new endwall loss production mechanisms. Lastly, loss is examined from the standpoint of entropy generation.

Secondary Flows in Axial Turbines—A Review

In order to investigate in detail the performance of steam turbine stages the Low Speed Test Rig at Politecnico di Milano has been adapted. The setup consists of a one and an half turbine stage with an inlet guide vane. Two kind of experimental approaches are planned in the project: the first, denominated “performance”, has been carried out by the OGTL department of GE OilG this large amount of data will be used to validate the results of the CFD simulation carried out in the design stage. In this paper the preliminary findings of the steady flow-field will be presented as the basis for further analysis.© 2015 ASME

Flow Evolution in a One and a Half Axial Steam Turbine Stage Under Different Operating Conditions

On testing the aerodynamics of film-cooled blades

https://re.public.polimi.it/bitstream/11311/1031203/1/87-GPPF17-32.pdf

Investigation of the Flow Field in a Gas Turbine Exhaust Diffuser at Design and Part Load Conditions

The paper describes the results of a numerical and experimental research program addressing the aerodynamic investigation on the performance of blade profiles specifically developed for application in highly loaded impulse type turbine stages. The industrial requirements driving toward the adoption of highly loaded stage solutions are presented, along with an estimation of the profiles operating parameters. Two stator vanes and one rotor blade profile have been developed and extensively tested by means of flow field measurements and schlieren visualization in a transonic blow-down wind tunnel for linear cascades. Experimental results for the relevant operating conditions are presented, providing validation data for the CFD model used for blade design and evidencing that the main goals of the design optimization procedure have been achieved.

/pdf/experimental-and-numerical-analysis-of-supersonic-blade-194agx1bff.pdf

Vincenzo Dossena

Papers

Flow Evolution in a One and a Half Axial Steam Turbine Stage Under Different Operating Conditions

On testing the aerodynamics of film-cooled blades

Investigation of the Flow Field in a Gas Turbine Exhaust Diffuser at Design and Part Load Conditions

Experimental and numerical analysis of supersonic blade profiles developed for highly loaded impulse type steam turbine stages

Simulation of R718 flash boiling flow inside motive nozzle of ejector.