Wind turbines with a rated power of 5 to 6 MW are now being designed and installed, mostly for offshore operation. Within the EU supported UpWind research project, the barriers for a further increase of size, up to 20 MW, are considered. These wind turbines are expected to have a rotor diameter up to 250 m and a hub height of more than 150 m. Initially, the theoretical implications of upscaling to such sizes on the weight and loads of the wind turbines are examined, where it is shown that unfavourable increases in weight and load will have to be addressed. Following that, empirical models of the increase in weight cost and loads as a function of scale are derived, based on historical trends. These include the effects of both scale and technology advancements, resulting in more favourable scaling laws, indicating that technology breakthroughs are prerequisites for further upscaling in a cost-efficient way. Finally, a theoretical framework for optimal design of large wind turbines is developed. This is based on a life cycle cost approach, with the introduction of generic models for the costs, as functions of the design parameters and using basic upscaling laws adjusted for technology improvement effects. The optimal concept or concepts is obtained as the one that minimizes the total expected costs per megawatt hour (levelized production costs).

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This paper describes an effort to model the performance maps of compressors and turbines (i.e., the relation between mass ow, pressure ratio, and ef ciency), using analytical functions. Analytical functions are tted to the available experimental data using a least-squares-type approach for determining the parameters of the tting function. The success of using a particular function for an application is assessed through a suitably de ned mean error of the model. Apart from presenting the method for setting up these analytical representations, applications to performance modeling and fault diagnosis are discussed. The change in model parameters is used to characterize changes of the engine condition and possibly diagnose occurring faults. The impact of introducing analytical component models into overall engine computer models, replacing a tabulated form of the component maps, is also discussed. NomenclatureF f = ow function, Eq. (18) h t = total enthalpy m Ç = mass ow N = rotational speed, rpm n = nondimensional rotational speed P f = power function, Eq. (18) P t = total pressure T t = total temperature X, Y = transformed values of the map variables x, y = raw values of the map variables ai = parameters of the analytical functions D h t = enthalpy drop in the turbine d = P t /Pt-REF hc = compressor adiabatic ef ciency, total -total hT = turbine adiabatic ef ciency, total -total u = T t /T t-REF i = corrected mass ow, m Ç ? /d u Ï P = compressor pressure ratio Subscripts REF = value at a reference point sl = value at the surge line

Rain ingestion can significantly affect the performance and operability of gas turbine aero-engines. In order to study and understand rain ingestion phenomena at engine level, a performance model is required that integrates component models capable of simulating the physics of rain ingestion. The current work provides, for the first time in the open literature, information about the setup of a mixed-fidelity engine model suitable for rain ingestion simulation and corresponding overall engine performance results. Such a model can initially support an analysis of rain ingestion during the predesign phase of engine development. Once components and engine models are validated and calibrated versus experimental data, they can then be used to support certification tests, the extrapolation of ground test results to altitude conditions, the evaluation of control or engine hardware improvements and eventually the investigation of in-flight events. In the present paper, component models of various levels of fidelity are first described. These models account for the scoop effect at engine inlet, the fan effect and the effects of water presence in the operation and performance of the compressors and the combustor. Phenomena such as velocity slip between the liquid and gaseous phases, droplet breakup, droplet–surface interaction, droplet and film evaporation as well as compressor stages rematching due to evaporation are included in the calculations. Water ingestion influences the operation of the components and their matching, so in order to simulate rain ingestion at engine level, a suitable multifidelity engine model has been developed in the Proosis simulation platform. The engine model's architecture is discussed, and a generic high bypass turbofan is selected as a demonstration test case engine. The analysis of rain ingestion effects on engine performance and operability is performed for the worst case scenario, with respect to the water quantity entering the engine. The results indicate that rain ingestion has a strong negative effect on high-pressure compressor surge margin, fuel consumption, and combustor efficiency, while more than half of the water entering the core is expected to remain unevaporated and reach the combustor in the form of film.

An EERA (European Energy Research Alliance) consortium started an ambitious EU FP7 project AVATAR (AdVanced Aerodynamic Tools of lArge Rotors) in November 2013. The project lasts 4 years and is carried out in a consortium with 11 research institutes and two industry partners. The motivation for the AVATAR project lies in the fact that future 10 to 20 MW turbine design model analysis will importantly violate known validity limits of today's aerodynamic and aero-elastic models in aspects like compressibility and Reynolds number effects, laminar/turbulent transition and separation effects, all in combination with a much more complex fluid-structure interaction. Further complications enter by the possible use of active or passive flow devices. AVATAR's main aim is then to develop enhancements for aerodynamic and aero-elastic models suitable for large (10MW+) wind turbines analysis. The turbine modelling improvements will be demonstrated on a new 10MW reference turbine design model description. The first results from the AVATAR project are presented in this paper.