Arezki Smaili

On the Rotor Effects upon Nacelle Anemometry for Wind Turbines

The objective of this paper is to study the typical atmospheric turbulent flow around the rotor and nacelle of a HAWT, in order to (i) investigate the impact of the turbines rotating blades on the flow field over the nacelle, i.e. the rotor-nacelle interaction; (ii) assess the appropriate anemometer location on the nacelle, and therefore (iii) establish the relationship between wind speed measured near the nacelle and free stream wind speed. The paper presents a numerical method for investigating the effects of rotating rotor blades on the nacelle anemometry of a horizontal axis wind turbine (HAWT). The flow field around the turbine and nacelle is described by the Reynolds averaged Navier-Stokes equations. The k – ε model has been chosen for the closure of time-averaged turbulent flow equations. The rotor is modelled using the actuator-disk concept. The simulation results were performed using a commercial wind turbine rated at 750kW. In general, good qualitative agreements have been found, supporting the validity of the proposed method. However, quantitatively, the accuracy of the simulation results should be confirmed before any use is made in power performance testing.

Numerical Study of Thermal Behavior of a Wind Turbine Nacelle Operating in a Nordic Climate

This article presents a numerical method for investigating the thermal behavior of a wind turbine nacelle operating in a Nordic climate. External air flow around the nacelle and rotor as well as internal air flow through the nacelle are described using the Reynolds-averaged Navier-Stokes equations. The energy equation is used to account for heat transfer effects. The standard k − ε model is chosen for the closure of time-averaged turbulent flow equations. The rotor is modeled using the actuator-disk concept. An unstructured control-volume finite-element method is employed to solve the resulting governing equations. This article focuses on the effects of external air temperature, wind velocity, and the heat rate released by an electrical generator on the spatial distribution of the temperature inside the nacelle. It is found that, to maintain an acceptable temperature level within the nacelle during summer, the amount of air mass rate flowing through the nacelle should be adjusted properly as a function of wind velocity and external temperature. During winter, the nacelle should be well insulated and the air should be well stirred to obtain nearly uniform temperature distribution within the nacelle.

Experimental Study of a Multilayer Active Magnetic Regenerator Refrigerator-Demonstrator

This work presents an experimental investigation on a reciprocating active magnetic regenerator (AMR) refrigerator-demonstrator operating near room temperature. La(Fe, Co)13−x Si x is used as a refrigerant material in the form of multilayer and water as heat transfer fluid to release and absorb heat at the hot and cold sources, respectively. Experimental tests using the multilayer regenerator with an applied magnetic field of 1.45 T have produced a temperature span of 15.6 K, without cooling load. The effects of the following cycle parameters, namely, utilisations, frequencies and mass flow rates, on the AMR cycle performance are presented and discussed. A parametric study was conducted on the behaviour of the temperature span to define the optimum demonstrator parameters to improve performance and validate the concept of multilayer and provide useful data for magnetic refrigerator design.

Numerical Investigations of Nacelle Anemometry for Horizontal Axis Wind Turbines

This paper presents a numerical method for investigating nacelle anemometry of an horizontal axis wind turbine. The flowfield around the turbine and nacelle is described by the Reynolds averaged Navier-Stokes equations. The k–e model has been chosen for the closure of time-averaged turbulent flow equations. The turbine is modeled using the actuator disk concept. Most of the nacelle region is represented by it real geometrical shape as wall boundary, except for the cooling system (radiator) of the electric generator which is modeled as a permeable surface with some prescribed pressure jump. The main purpose of this paper is to establish the relationship between the nacelle wind speed and free stream wind speed for an isolated turbine, in order to assess the impacts of the variation of some operational parameters (e.g. blade pitch angle changes), as well as atmospheric turbulence, on this relationship. The simulation results have been compared with the experimental data (from a typical stall-controlled wind turbine rated more than 600kW and comercially available). In general, good qualitative agreements have been found proving the validity of the proposed method. However, the level of accuracy is still insufficient for use in power performance testing. On the other hand, the numerical method might be a useful tool for locating nacelle anemometers.Copyright

Composite material based on LaFe(Co, Si) for active magnetic regenerator operating near room temperature

The aim of this paper is to propose a composite material based on compounds of LaFeCoSi operated in temperature range 275-315K. The composite material was designed according to the optimum composite fractions, which were determined numerically. A force of approximately 100 kN was applied to the assemblies of the composite elements to obtain a homogeneous disk. A direct measurement of the adiabatic temperature change under magnetic field of 2T has been carried out by the test bench built at Heig-VD. The comparison results between the numerical prediction and experimental of the magnetocaloric effect has been presented and discussed to validate the proposed model.