Author: Aubryn Murray Cooperman Publisher: ISBN: 9781267967886 Category : Languages : en Pages :
Book Description
Increases in wind turbine size have made controlling loads on the blades an important consideration for future turbine designs. One approach that could reduce extreme loads and minimize load variation is to incorporate active control devices into the blades that are able to change the aerodynamic forces acting on the turbine. A wind tunnel model has been constructed to allow testing of different active aerodynamic load control devices. Two such devices have been tested in the UC Davis Aeronautical Wind Tunnel: microtabs and microjets. Microtabs are small surfaces oriented perpendicular to an airfoil surface that can be deployed and retracted to alter the lift coefficient of the airfoil. Microjets produce similar effects using air blown perpendicular to the airfoil surface. Results are presented here for both static and dynamic performance of the two devices. Microtabs, located at 95% chord on the lower surface and 90% chord on the upper surface, with a height of 1% chord, produce a change in the lift coefficient of 0.18, increasing lift when deployed on the lower surface and decreasing lift when deployed on the upper surface. Microjets with a momentum coefficient of 0.006 at the same locations produce a change in the lift coefficient of 0.19. The activation time for both devices is less than 0.3 s, which is rapid compared to typical gust rise times.The potential of active device to mitigate changes in loads was tested using simulated gusts. The gusts were produced in the wind tunnel by accelerating the test section air speed at rates of up to 7 ft/s2. Open-loop control of microtabs was tested in two modes: simultaneous and sequential tab deployment. Activating all tabs along the model span simultaneously was found to produce a change in the loads that occurred more rapidly than a gust. Sequential tab deployment more closely matched the rates of change due to gusts and tab deployment. A closed-loop control system was developed for the microtabs using a simple feedback control based on lift measurements from a six-component balance. An alternative input to the control system that would be easier to implement on a turbine was also investigated: the lift force was estimated using the difference in surface pressure at 15% chord. Both control system approaches were found to decrease lift deviations by around 50% during rapid changes in the free stream air speed.
Author: Myra Louise Blaylock Publisher: ISBN: 9781267967572 Category : Languages : en Pages :
Book Description
A fast, efficient way to control loads on industrial scale turbines is important for the growth of the wind industry. Active Aerodynamic Load Control (AALC) is one area which addresses this need. In particular, microjets, which are pneumatic jets located at the trailing edge of a wind turbine blade and blow perpendicular to the blade surface, are a possible AALC candidate. First, the Computational Fluid Dynamics (CFD) solver OVERFLOW is used to explore the effects of a microjet on lift, drag, and pitching moment. Then the interaction between an aerodynamic disturbance and an airfoil equipped with a microjet is modeled. The object of this dissertation is to investigate microtabs as viable AALC devices by presenting their aerodynamic properties and testing whether a proportional-integral (PI) controlled jets can alleviate loads caused by wind gusts. The use of CFD to simulate a microjet is validated by comparing the results to both previous experiments found in the literature as well as wind tunnel tests completed at UC Davis. The aerodynamic effectiveness of the jet is investigated as a function of various parameters such as Reynolds number, angle of attack, and the momentum coefficient of the jet. The effects of the microjet are found to be very similar to another AALC device, the microtab. An aerodynamic disturbance is simulated, and a control algorithm which is incorporated into the OVERFLOW code is used to activate the microjet, thus reducing the change of the blade load due to the gust. Finally, a more realistic model is made by adding both a linear and a torsional spring and damper to represent the blade movement. This two-degree of freedom system shows that during a gust the vertical blade movement is reduced when the microjets are activated. Microjets are found to work well to alleviate the changes in aerodynamic loads felt by the airfoil, and are therefore a good candidate for a practical AALC device. However, further investigation is needed in the areas of aeroacoustics, system energy requirements, and logistics of implementation.
Author: Matthew Stephen Brunner Publisher: ISBN: 9781267758477 Category : Languages : en Pages :
Book Description
A pneumatic "microjets" Active Aerodynamic Load Control (AALC) system was designed, built and tested in the wind tunnel to actively control the aerodynamics of a wind turbine test blade. The microjets system blows air at a high flow rate, perpendicular to the surface of the blade, out of thin (0.56% of chord) spanwise slots near the trailing edge on the upper (suction) and lower (pressure) surfaces of a blade. The flow manipulates the circulation about the airfoil, effectively changing the Kutta condition and thus changing the generated lift. To test the microjets concept in the wind tunnel, a ducting and plenum system was designed with 3D solid modeling and printed with a rapid prototyping machine to fit inside the existing geometry of an aluminum test blade. An air supply was sourced and a hose network was designed to feed the plenums with the high flow rate air supply. A one-to-six hose connector was also designed and printed which evenly fed the six microjet slots per side of the test blade. The plenum design was robust, leak-free, and simple to install. The system successfully distributed air evenly to the microjets slots, both on the bench and in wind tunnel testing. The air supply, however, could not output the desired volumetric flow rate through the system. In the wind tunnel, the system measurably decreased the lift when blown on the suction side, but did not have sufficient flow rate to measurably increase the lift when blown on the pressure side. Further testing, with a more powerful air supply and eventually a controllable valve, can use this system to test dynamic responses to wind gusts to implement pneumatic AALC.
Author: Owen Francisco Hurley Publisher: ISBN: 9781321806397 Category : Languages : en Pages :
Book Description
A computational investigation was performed analyzing the potential for reduction in wind turbine fatigue utilizing microjets for active aerodynamic load control. Increasing size of wind turbine rotors requires methods for reduction of critical fatigue and extreme loads. Active Aerodynamic Load Control provides local control of aerodynamic properties utilizing active flow control devices to alter loads along the wind turbine span to reduce total loading. These devices respond quickly allowing for on demand control of aerodynamic loading. Microjets have shown promising aerodynamic characteristics but require pneumatic input to operate which poses as a potentially difficult to overcome obstacle to implementation in wind turbine applications where Cost of Energy (COE) is critical. This thesis explores systems with both passive and active driven pneumatic systems comparing the energy input to the potential for fatigue reduction. Analysis of a wide range of potential configurations of microjets along the NREL Baseline Offshore 5-MW Reference Wind Turbine is conducted. A program developed to calculate flow potential at each configuration is integrated with WT-Perf, a BEM horizontal wind turbine performance simulation tool that is used to calculate the reduction in steady state flapwise root bending moment. Reduction in steady state flapwise root bending moment across the wind turbine's operating range is the primary metric for comparing the success of each microjet system configuration. Passive systems in which no externally driven pneumatic devices, such as blowers, are considered along with active systems which include external means of driving flow through the microjet. The findings in this thesis indicate that the optimum location for a microjet system on the NREL 5-MW begins approximately halfway down the span of the wind turbine blade extending a length of approximate one quarter of the total blade length. With a passive system, maximum reduction in flapwise root bending moment at rated wind speed was approximately 4.5% of the total flapwise moment which increases to 6% with the addition of a 5kPa blower.
Author: Alan Pope Publisher: Wiley-Interscience ISBN: Category : Science Languages : en Pages : 562
Book Description
Good,No Highlights,No Markup,all pages are intact, Slight Shelfwear,may have the corners slightly dented, may have slight color changes/slightly damaged spine.
Author: Charlotte Bay Hasager Publisher: MDPI ISBN: 3038979422 Category : Technology & Engineering Languages : en Pages : 290
Book Description
This Special Issue “Atmospheric Conditions for Wind Energy Applications” hosts papers on aspects of remote sensing for atmospheric conditions for wind energy applications. Wind lidar technology is presented from a theoretical view on the coherent focused Doppler lidar principles. Furthermore, wind lidar for applied use for wind turbine control, wind farm wake, and gust characterizations is presented, as well as methods to reduce uncertainty when using lidar in complex terrain. Wind lidar observations are used to validate numerical model results. Wind Doppler lidar mounted on aircraft used for observing winds in hurricane conditions and Doppler radar on the ground used for very short-term wind forecasting are presented. For the offshore environment, floating lidar data processing is presented as well as an experiment with wind-profiling lidar on a ferry for model validation. Assessments of wind resources in the coastal zone using wind-profiling lidar and global wind maps using satellite data are presented.
Author: Wen Zhong Shen Publisher: MDPI ISBN: 3039215248 Category : Technology & Engineering Languages : en Pages : 410
Book Description
Wind turbine aerodynamics is one of the central subjects of wind turbine technology. To reduce the levelized cost of energy (LCOE), the size of a single wind turbine has been increased to 12 MW at present, with further increases expected in the near future. Big wind turbines and their associated wind farms have many advantages but also challenges. The typical effects are mainly related to the increase in Reynolds number and blade flexibility. This Special Issue is a collection of 21 important research works addressing the aerodynamic challenges appearing in such developments. The 21 research papers cover a wide range of problems related to wind turbine aerodynamics, which includes atmospheric turbulent flow modeling, wind turbine flow modeling, wind turbine design, wind turbine control, wind farm flow modeling in complex terrain, wind turbine noise modeling, vertical axis wind turbine, and offshore wind energy. Readers from all over the globe are expected to greatly benefit from this Special Issue collection regarding their own work and the goal of enabling the technological development of new environmentally friendly and cost-effective wind energy systems in order to reach the target of 100% energy use from renewable sources, worldwide, by 2050
Author: Gijs van Kuik Publisher: Springer ISBN: 3319469193 Category : Technology & Engineering Languages : en Pages : 111
Book Description
This book presents the view of European wind energy experts on the long-term research challenges to be solved in order to develop wind energy beyond the applications of today and tomorrow. By this book, the European Academy of Wind Energy (eawe), representing universities and institutes with a significant wind energy programme in 14 countries, wants to: identify current technological and scientific barriers and to stimulate new creative ideas to overcome these barriers define priorities for future scientific research rethink our scientific view of wind energy stimulate the cooperation among researchers in fundamental and applied sciences towards wind energy research The eawe has discussed these long-term research with an explicit focus on a longer-term perspective, in contrast to research agendas addressing short- to medium-term research activities. In other words, this long-term research agenda is driven by problems and curiosity, addressing basic research and fundamental knowledge in 11 research areas, ranging from physics and design to environmental and societal aspects. Because of the very nature of this initiative, this document does not intend to be permanent or complete. It shows the vision of the experts of the European Academy of Wind Energy, but other views may be possible. The eawe sincerely hopes that it will spur an even more intensive discussion worldwide within the wind energy community.
Author: Aubryn Murray Cooperman
Author: Myra Louise Blaylock
Author: Matthew Stephen Brunner
Author: Owen Francisco Hurley
Author: Athanasion Konstantinou Barlas
Author: Alan Pope
Author: Alena Berit Bach
Author: Charlotte Bay Hasager
Author: Wen Zhong Shen
Author: Gijs van Kuik