Browse Topic: Wind power

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Study on the Influence of Mass Flow Rate over a National Advisory Committee for Aeronautics 6321 Airfoil Using Improved Blowing and Suction System for Effective Boundary Layer Control01-14-02-00118/6/2021
The numerical analysis of the three-dimensional (3D) flow over a National Advisory Committee for Aeronautics (NACA) 6321 airfoil to evaluate the mass flow rate by using a novel method Improved Blowing and Suction System (IBSS) to control the boundary layer is presented in this study. Analysis is performed based on 3D Reynolds-Averaged Navier-Stokes (RANS) equation with a K-omega SST solver. The aerodynamic performance of the NACA 6321 is analyzed at a Mach number of 0.10 with three different mass flow rates, namely, 0.08 kg/s, 0.10 kg/s, and 0.12 kg/s. From the study, it is seen that when the mass flow rate decreased, the aerodynamics performance also reduced, and the aerodynamic performance improved with the increase in mass flow rate. Results also show that a mass flow rate of 0.10 kg/s improved the stalling angle of attack (AoA) by 60% and coefficient of lift (CL) by 50%, enabling optimum efficiency of the aircraft wing in all aspects compared to the baseline airfoil model. The mass flow for optimum efficiency is computed based on the velocity at the separation point on the airfoil.
Karuppiah, Balaji, Wessley, Jims John
Shape Sensing Innovations Dramatically Improve Structural Design ToolsTBMG-357931/1/2020
Advances in fiber optic shape sensing developed at NASA's Armstrong Flight Research Center are enabling the development of next-generation flexible aircraft wings that maximize structural efficiency and reduce weight, improving fuel efficiency. These same advances will help engineers design stronger bridges, buildings, ocean vessels, and more.
Adaptive Spatial Resolution Enables Focused Fiber Optic SensingTBMG-3572512/1/2019
This advanced fiber optic sensing innovation developed at NASA’s Armstrong Flight Research Center offers a unique combination of high-resolution processing and flexibility. The algorithm was originally developed to enhance Armstrong’s multi-patented Fiber Optic Sensing System (FOSS). With over 2,000 sensors per fiber, FOSS enables thousands of high-resolution measurements at once including strain, shape, temperature, pressure, and more.
Wind Event Warning SystemTBMG-3545411/1/2019
NASA Langley Research Center developed a wind event warning technology that provides a practical early warning system (5-10 minutes) for a severe change in the wind vector. Events such as gusts, shear, microbursts, or thunderstorm outflows can be detected in time to prevent damage to wind turbines or help airports prevent damage to aircraft. Further, an alternative power source could be ramped up or down as needed to accommodate the power draw in the electrical grid.
Optimal Sizing and Energy Management of a Microgrid Using Single and Multi-Objective Particle Swarm Optimization under Autonomous and Grid Connected Mode2019-28-015810/11/2019
The conventional energy sources are getting depleted while at the same time the energy demand keeps growing. Hence, it is important to consider non-conventional energy sources to meet future energy demands. The renewable energy based microgrid system is one of the promising solutions to meet this increasing energy demand. The major parameters under consideration in a micro-grid system are cost-effectiveness, quality of service and energy management. This work concentrates on the energy management of the Photovoltaic/Wind based microgrid system connected to the fuel cell, microturbine and battery under Islanding (or) Autonomous mode and Grid-Connected Mode. The current model of PV, Wind and Battery systems are employed. The Wind, PV and Battery types are chosen from i-HOGA. The optimal combination of these sources with the aim of minimizing the operating cost, pollutant treatment cost and maximizing reliability using both single and multi-objective particle swarm optimization (PSO) has been considered. This microgrid has also been analyzed under three different strategies for both grids connected and islanded mode and the best energy management strategy is obtained after analysis. In addition to this, the type and number of PV, Wind, and Battery to meet the forecasted demand are determined under islanding mode using Multi-Objective Particle Swarm Optimization (MOPSO). A solitary best-accepted solution is attained from Fuzzy membership function. The algorithm proposed decides the optimal number of units and types of units selected to achieve the optimal cost. The simulation has been performed in MATLAB environment.
Dayalan, Suchitra, Rathinam, Rajarajeswari, Valliappan, Subramaniyan
Demand Side Load Management by Using Priority Based Load Shedding Algorithm with and without Renewable Energy Generation2019-28-007310/11/2019
Demand side load management (DSLM) emphasizes control of the power demanded, by reducing the peak load and control of energy utilization of the system. DSLM is introduced to improve the flexibility of the grid power usage and also to aid the utilization of Renewable Energy Generation (REG) which is intermittent. In this work, implementation of load shedding (LS) algorithm for the residential load is performed with the limit of power as constraint, considering REG and grid in three different modes of operation. Solar and Wind power are the REG considered in this work. Priority Based Load Shedding (PBLS) is performed to limit the power consumption of equipment during peak hours with the implementation of varying pricing signal. In order to implement PBLS, three residential user load data for 24 hours is considered. The users are categorized as low, medium and high priority user. The priority of the user is based on the load consumption for 24 hours. The proposed LS scheme is performed, depending on the power requirements of Home Electric Devices (HEDs) and the priority of consumer. The main objective of cost reduction (power consumption) along with minimization of user discomfort is achieved by using the PBLS algorithm. Simulation results for REG islanded mode, grid connect mode and REG aided grid mode is performed. The further cost comparison is made with and without a load schedule. The scheduling of load curve is performed using Genetic Algorithm (GA) optimization.
Rathinam, Rajarajeswari, Dayalan, Suchitra
Structure Deformation Calculation Program for Structural Shape MonitoringTBMG-3528910/1/2019
Researchers at NASA’s Armstrong Flight Research Center are pioneering shape-sensing technologies that seek to maximize structural integrity and efficiency. A new and versatile computer program offers critical shape-monitoring capabilities and has applications for a wide variety of structures.
New Airplane Wing Assembled from Tiny Identical PiecesTBMG-3527710/1/2019
A radically new kind of airplane wing, assembled from hundreds of tiny identical pieces, can change shape to control the plane’s flight, and could provide a significant boost in aircraft production, flight, and maintenance efficiency. The new approach to wing construction could afford greater flexibility in the design and manufacturing of future aircraft.
Schlieren System Captures Brilliant Shockwave ImagesTBMG-3525410/1/2019
Supersonic flight over land is generally prohibited because sonic booms created by shockwaves disturb people on the ground and can damage property. Armstrong innovators are working to solve this problem with a novel system for capturing images of shockwaves created by supersonic aircraft. The Background Oriented Schlieren Using Celestial Objects (BOSCO) technology uses a celestial object, such as the Sun, as a background to secure unique, measurable shockwave images of full-scale aircraft. The patented image-processing technology captures hundreds of observations with each shockwave, benefitting NASA engineers in their efforts to develop a supersonic aircraft that will produce a soft “thump” in place of a disruptive sonic boom.
Basic Composite Repair Technician Certification StandardARP6262A (Current)9/10/2019
It is recognized that the structural integrity of repaired composite structures depends upon the capabilities of the individuals who are responsible for performing the repairs. This document is intended to address repairs of composite structure regardless of the type of structure such as marine, wind turbine, automotive, aircraft, or other applications. This certification standard establishes the minimum requirements for training, examining, and certifying composite structure repair personnel. It establishes criteria for the certification of personnel requiring appropriate knowledge of the technical principles underlying the composite structural repairs they perform. Persons certified under this document may be eligible for licensing or certification/ qualification by an appropriate authority, in addition to this industry accepted basic composite repair technician certification. Persons who successfully complete the requirements of this certification standard are considered to be able to perform basic composite repairs to composite structures in compliance with the manufacturers’ repair documentation or other acceptable repair methods. This document is not intended to include structure specific repairs that are in manufacturer’s maintenance or repair manuals. Additional specific training may be required by the maintenance organization.
AMS CACRC Commercial Aircraft Composite Repair Committee
A Parametric Study on the Thermodynamic Characteristics of DBD Plasma Actuation and Its Potential for Wind Turbine Icing Mitigation2019-01-20316/10/2019
Wind turbine icing represents the most significant threat to the integrity of wind turbines in cold weather. Ice formation on wind turbine blades was found to cause significant aerodynamic performance degradation, resulting in a substantial drop in energy production. Recently developed Dielectric barrier discharge (DBD) plasma-based anti-/de-icing systems showed very promising effects for aircraft icing mitigation. In this present study, DBD plasma-based anti-/de-icing systems were employed for wind turbine icing mitigation. First, a comprehensive parametric study is conducted to investigate the effects of various DBD plasma actuation parameters on its thermodynamic characteristics. An infrared (IR) thermal imaging system is used to quantitatively measure the temperature distributions over the test plate under various test conditions. DBD plasma actuators are embedded over the surface of a DU91-W2-250 wind turbine blade model, and a series of experiments were conducted by using the Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to evaluate the anti-/de-icing performance of the system for wind turbine icing mitigation. Dynamic anti-icing process was recorded by a high-speed imaging system, and an IR thermal camera was used to map the temperature distributions over the surface of the wind turbine blade model during the anti-/de-icing processes.
Kolbakir, Cem, Gao, Linyue, Liu, Yang, Hu, Hui
Quantification of 3D Ice Structures Accreted on a Wind Turbine Airfoil Model2019-01-20306/10/2019
Accurate quantification of 3D shapes of the complex ice structures accreted on wind turbine blades is highly desirable to develop ice prediction models for more accurate prediction of the aerodynamic performance degradation and power reduction due to the ice accretion on wind turbine blades. In the present study, an experimental investigation was conducted to quantitatively characterize the 3D shapes of the ice structures accreted over a DU91-W2-250 wind turbine airfoil model in the Icing Research Tunnel available at Iowa State University (ISU-IRT). A glaze icing condition and a rime icing condition that wind turbines usually experience in winter were duplicated by using ISU-IRT. A high-resolution non-intrusive 3D scanning system was used to make detailed 3D-shape measurements to quantify the complicated ice structures accreted on the wind turbine airfoil model as a function of the ice accretion time. The measurements results show that the complex 3D shapes of the ice structures accreted over the surfaces of the airfoil model under both glaze icing and rime icing conditions were well captured. It is found that the glaze ice accretion has stronger 3D features, in comparison to the rime ice accretion case, due to its wet nature. The measured 3D shapes of the complex ice structures at different ice accretion moments were also provided to demonstrate the progressive shape changes of the ice structures during the dynamic ice accretion process.
Gao, Linyue, Veerakumar, Ramsankar, Liu, Yang, Hu, Hui
A Novel Heating-Coating Hybrid Strategy for Wind Turbine Icing Mitigation2019-01-20296/10/2019
The electro-thermal method is most commonly used for wind turbine anti-/de-icing. The upmost drawback of such systems is the high power consumption. In the present study, we proposed to use a durable slippery liquid-infused porous surface (SLIPS) to effectively reduce the power requirement of the heating element during the anti-/de-icing process. The explorative study was conducted in the Icing Research Tunnel at Iowa State University (ISU-IRT) with a DU91-W2-250 wind turbine blade model exposed under severe icing conditions. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion process, an infrared (IR) thermal imaging system was also utilized to achieve the simultaneous surface temperature measurements over the test model. In comparison to the traditional electrical heating strategies to brutally heat massive area of entire turbine blades, a novel heating-coating hybrid strategy, i.e., combining a leading-edge (LE) heating element to cover the first 30% of the chord length (C) along with using SLIPS to coat entire blade surface, was found to be able to keep the entire blade surface completely free of ice, but with only an approximately 30% of the required energy consumption. The readily bouncing of the water droplets upon impinging onto the durable SLIPS and the much lower ice adhesion strength/capillary force over the SLIPS coated surface are believed to be the reasons to lead the better anti-/de-icing performance of the heating-coating hybrid strategy to prevent ice accretion/formation over the surfaces of the wind turbine blades.
Gao, Linyue, Ma, Liqun, Liu, Yang, Hu, Hui
A Smart Icing Detection System for Any Location on the Outer Aircraft Surface2019-01-19316/10/2019
Given approximately one million small and light aircraft in operation worldwide, icing detection and icing quantification of in-flight icing are still an open research topic. Despite technical means are available to de-ice on ground, there is a lack of a suitable control system based on sensor data to de-ice while the aircraft is airborne. Most often, it is still task of the pilot to visually inspect the icing status of the airfoil and/or other critical parts of the aircraft such as engine air intakes, which distracts the flight crew from flying the aircraft especially in IMC conditions. Based on preliminary simulation and tests in 2014 in a collaborative research project lasting from 2015 until 2018, the technology of energy self-sustaining, wireless, self-adhesive smart sensors for industrial sensing in an aerodynamically critical environment (i.e. wind turbines) was further investigated to fulfil general aviation requirements. Prototype hardware setups have been designed and built for application on aircraft. In test flights carried out in Scotland in late 2017, the functionality of the system could be demonstrated. It could be shown that a wireless, energy self-sustaining detection system for early icing can be implemented based on currently available technologies and components. Additionally, it could be shown that detection sensitivity is sufficient to detect ice at very thin layers.
Schlegl, Thomas, Moser, Michael, Loss, Theresa, Unger, Thomas
An Experimental Investigation of a Wind-Driven Water Droplet over the Slippery Liquid Infused Porous Surface2019-01-19516/10/2019
The promising anti-icing performance of the slippery liquid infused porous surface (SLIPS) has been recently demonstrated for various engineering applications. The runback icing for aircraft and wind turbines could be effectively mitigated considering the timely removal of water droplet by the wind shearing force due to the low adhesion on the SLIPS. In this study, the flow field both inside and around the wind-driven droplet over the SLIPS was experimentally investigated by using Particle Image Velocimetry (PIV) technique. Previous studies majorly focus on the internal flow pattern before the droplet incipient motion. In this study, the flow field inside a moving droplet was firstly investigated. As a result of the low surface adhesion of the SLIPS, droplet oscillations were eliminated and the droplet internal flow field could be corrected from the optical distortion. Besides the discussion on the wind speed, the droplet viscosity was also studied by varying the water concentration of the glycerin-water solution. It was found that the internal circulation was highly related with the droplet viscosity. The inner circulations within the water droplet would be reduced, or eliminated, when the droplet viscosity was increased, which would change the droplet motion from sliding into rolling. It was suggested that the internal flow should be considered when theoretically modeling the wind-driven droplet movement over the SLIPS. This study could provide experimental evidence for a broader application of the SLIPS in the icing-related industrial world.
Ma, Liqun, Hu, Hui
Rotary Electrical ContactTBMG-346206/1/2019
Researchers have developed a fundamentally new type of rotary electrical contact that addresses the two limitations of conventional brush/slip ring technology: 1) short operating lifetime due to sliding-contact wear, and 2) electrical arcing associated with contact bounce.
Fine Tuning the SST k − ω Turbulence Model Closure Coefficients for Improved NASCAR Cup Racecar Aerodynamic Predictions2019-01-06414/2/2019
Faster turn-around times and cost-effectiveness make the Reynolds Averaged Navier-Stokes (RANS) simulation approach still a widely utilized tool in racecar aerodynamic development, an industry where a large volume of simulations and short development cycles are constantly demanded. However, a well-known flaw of the RANS methodology is its inability to properly characterize the separated and wake flow associated with complex automotive geometries using the existing turbulence models. Experience suggests that this limitation cannot be overcome by simply refining the meshing schemes alone. Some earlier researches have shown that the closure coefficients involved in the RANS turbulence modeling transport equations most times influence the simulation prediction results. The current study explores the possibility of improving the performance of the SST k − ω turbulence model, one of the most popular turbulence models in motorsports aerodynamic applications, by re-evaluating the values of certain model closure constants. A detailed full-scale current generation NASCAR Cup racecar was used for the investigation. The simulations were run using a commercial CFD package STAR-CCM+ (version 13.04.010). Five different closure coefficients in the SST k − ω model, σk1, σk2, σω1, σω2 and β∗, were examined. The investigation suggests the influence of each closure coefficient on the simulation prediction results are significantly different. β∗ appeared to be the most sensitive closure coefficient whereas both σk1 and σk2 had almost no effect on the NASCAR Cup racecar aerodynamic predictions. This study proposes a new set of SST k − ω turbulence model closure coefficients which has the potential of providing better-correlated aerodynamic predictions of a NASCAR Cup racecar under a range of different operating conditions.
Fu, Chen, Bounds, Charles, Uddin, Mesbah, Selent, Christian
The Review of Present and Future Energy Structure in China2019-01-06124/2/2019
Both the economy and energy demand increase rapidly in China. The government is facing severe problems from energy security, carbon emissions and environmental issues. The past trends and future plans of energy will have great influence on the transportation, construction and industry development. This paper summarizes the present and future energy structure in China. Conventional fossil energy, nuclear energy and renewable energy are all included. Electricity will account for more proportion in total energy consumption in the future, and the structure of electricity will be cleaner. That will promote the development of electric vehicles and the transformation of China’s automotive industry. The optimization of energy structure will accelerate the low-carbon development in China. China’s energy development will enter a new stage from the expansion of total quantity to the upgrading of quality and efficiency. In order to realize the Paris Climate Agreement, China must steadily control the total energy consumption. The energy consumption in China will be in a period of slow growth. Constantly optimizing the energy structure and promoting renewable energy will both ease the energy crisis and ensure that China’s goal of reducing CO2 emissions can be achieved. China will further strengthen international cooperation in energy projects in the future. Through the cooperation, the energy structure in China will be further optimized. The efficient technology research & development and infrastructure construction of energy storage and remote power transfer will be vital to energy development. It will have influence on the future promotion of various renewable energy resources. The government will propel the reform of the oil and gas industry, and gradually open the market to the social capital. This measure will emphasize the role of the market in the energy development.
Liu, Feiqi, Zhao, Fuquan, Hao, Han, Liu, Zongwei
Plasma Generator Using Spiral ConductorsTBMG-337032/1/2019
NASA's Langley Research Center has developed a patented SansEC sensor technology for use in many different areas, including tall structures and wind turbines. The SansEC technology is a proven wireless sensing platform capable of measuring the electrical impedance of physical matter in proximity to the sensor based on a change in its resonance response. The SansEC sensor also exhibits a unique characteristic to disperse the lightning strike current to help mitigate lightning damage. In a turbine blade application, an array of SansEC sensors will cover the surface area of the composite blade, providing both lightning mitigation and damage sensing. NASA Langley is seeking industrial partners/licensees to commercialize this technology. The research team at NASA Langley is available to assist with further development.
Material Removes Ice Buildup Without Power or ChemicalsTBMG-336802/1/2019
From airplane wings, to overhead power lines, to the giant blades of wind turbines, a buildup of ice can cause problems ranging from impaired performance all the way to catastrophic failure. Preventing that buildup usually requires energy-intensive heating systems or chemical sprays that are environmentally harmful.
Facility Focus: Ames LaboratoryTBMG-3340812/1/2018
Ames Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, IA. For more than 70 years, Ames Laboratory has successfully partnered with Iowa State University and is unique among the DOE laboratories in that it is physically located on the campus of a major research university.
Synthesis and Development of Polyurethane Coatings Containing Fluorine Groups for Adhesive ApplicationsTBMG-3322911/1/2018
Accumulation of insect strikes on the leading edge of airplane wings is a more serious problem than one might realize. Depending on the magnitude, such accumulation changes the aerodynamic characteristics of the wing, causing a change from laminar to turbulent flow and resulting in decreased lift and increased drag. Overall, this also results in decreased fuel efficiency. Proposed solutions include elastic surfaces, coatings, soluble films, and fluid covers. Coatings offer an advantage over other strategies due to ease of application, potentially negligible weight penalty, reduced environmental concerns, better economics, and continual function throughout the flight profile.
Numerical and Experimental Second Law Analysis of a Low Thickness High Chamber Wing Profile2018-01-195510/30/2018
This paper presents a coupled numerical and experimental study of an unconventional wing profile such as cp-180-050-gn (Cambered plate C = 18% T = 5% R = 0.78). This wing profile deals with low speeds. It is not currently used on any aircraft model. Otherwise, it presents interesting performances that can be exploited for the design of low-speed STOL or VTOL aircraft by mean of the very high lift that it can generate and can fit with different uses such as VAWT, cyclorotors drones, which are designed explicitly for low-speed operations. After a preliminary CFD assessment of the wing a complete experimental characterisation also at high angles of attack has been performed. The excellent agreement between CFD and experiments has allowed producing a complete analysis of the behaviour of the wing profile both before and after stall conditions. This study has the objective of analysing the viability of such an unconventional wing in traditional or over-stalling conditions. A complete modelling of the specific wing is produced with the definition of its potential deployment into unconventional aircraft architectures and both Darreius and Savonius wind turbines.
Trancossi, Michele, Sharma, Shivesh
Water-Based Battery Stores Solar and Wind EnergyTBMG-324768/1/2018
Wind and solar energy generation creates challenges, since the Sun only shines by day, and sometimes the wind doesn't blow. Another variability is surges of demand on the grid. On a hot day when air conditioning is in use, utilities must have load-balancing strategies to meet peak demand. A water-based battery was developed that could provide a cheap way to store wind or solar energy generated when the Sun is shining and wind is blowing so it can be fed back into the electric grid and be redistributed when demand is high.
Mobile Power Distribution SystemTBMG-296907/1/2018
Mobile or transportable power supply and distribution systems are needed for various types of work that require electrical power in a field or outdoor environment — such as construction and environmental remediation projects — to power tools, lights, and other devices. For many projects, this need is met by either running a power line from the nearest available power source (referred to as shore power) or through use of a generator. While generators provide a source of electrical power in a field environment, the limited number and type of electrical outlets on the generator and the preset configuration of a given generator may be insufficient for the operation.
Nano-Sized Actuator Lifts Many Times its WeightTBMG-290376/1/2018
Actuators are used in a wide variety of electromechanical systems and in robotics, in applications such as steerable catheters, aircraft wings that adapt to changing conditions, and wind turbines that reduce drag.
“Intelligent” Rotor Blades React Quickly to Changing ConditionsTBMG-290056/1/2018
The giant rotor blades are one central part of a wind turbine. Researchers developed a rotor blade that makes more efficient use of large fluctuations in wind strength using a passive bend-twist coupling (BTC) that adapts continuously to the wind forces acting on the rotor blade. When the wind loads become too high, the coupling reduces the forces affecting the structure.
Wind Turbine Blade Testing System Using Base ExcitationTBMG-281741/1/2018
Wind turbine designers are working to provide blade designs that allow a turbine connected to the blades or rotor to effectively convert wind into electricity. The blades must also be designed properly to withstand inertial forces, aerodynamic forces, and structural forces to provide a relatively long service life and safe operation. Like all rotating machines, wind turbines are generators of fatigue, and every revolution of their components, including the turbine blades, produces a load or fatigue cycle, with each of these cycles causing a small, finite amount of damage that eventually may lead to fatigue cracks or other failures.
Fluorinated Alkyl Ether Epoxy Resin Compositions and Applications ThereofTBMG-281681/1/2018
NASA Langley Research Center has developed fluorinated alkyl ether-containing epoxies designed as an anti-insect coating. The robust and durable coating was developed to improve aircraft efficiency, but the coating could be useful in a variety of applications where reduction of insect residue adherence is desirable, such as in automotive and wind energy industries.
Data Optimization Technology Helps Wind Farm Operator Examine CostsTBMG-271907/1/2017
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External Aircraft Noise Reduction LinersTBMG-272047/1/2017
NASA Langley Research Center, in collaboration with Boeing and Lockheed Martin, has developed a new external acoustic liner for aircraft noise reduction. While the acoustic liner can be placed on any external aircraft surface, one attractive application is for open-rotor noise reduction. Airframe manufacturers are considering open rotor engines for future aircraft designs as they provide significant fuel savings. However, open rotor engines have no nacelle and thus, do not allow the use of conventional nacelle liners for noise abatement. This technology strategically places acoustic liners on the external surface of the aircraft to reduce such engine noise.
Gear Repair for Helicopters and Wind Turbines via Isotropic SuperfinishingF-0073-2017-121405/9/2017
ABSTRACT The wind turbine, aerospace, and helicopter gear industries recognize the importance of surface finish and surface texture for maximizing component and system performance. Optimizing surface finish and surface texture has been shown to reduce failure rates and increase operating safety margins. Isotropic superfinishing in the form of chemically accelerated vibratory finishing has been utilized to increase the performance of new wind turbine, aerospace, and helicopter gears for many years. The wind turbine gearbox industry has also used isotropic superfinishing as a method of repairing damaged gears for over a decade. The aerospace and helicopter gear industries have only minimally employed this technology as a repair technique. As the aerospace and helicopter industries scrap many gears due to only minor surface damage, further consideration of isotropic superfinishing as a repair tool is warranted. This paper will summarize the technical capabilities, recent advancements, and economic benefits of using isotropic superfinishing to repair wind turbine, aerospace, and helicopter gears. With this information, the aerospace and helicopter gear industries will be better positioned to evaluate isotropic superfinishing's potential to recover otherwise scrap gears and thereby reduce sustainment costs.
Cline, Vincent, Michaud, Justin, Winkelmann, Lane
Aeroelastic Optimization of Composite Wind Turbine Blades using Variable Stiffness LaminatesF-0073-2017-121415/9/2017
ABSTRACT A variable stiffness composite optimization framework for wind turbine rotor blades is presented. The framework consists of a multi-fidelity approach for wind turbine rotor analysis, where both structural and aerodynamic constraints are considered during the optimization. The potential of twist coupled blades to regulate the power on stall controlled wind turbines is investigated by exploiting the characteristic of unbalanced laminates to induce twist coupling. A complete stiffness variation along the blade span is considered during the optimization, while using the cost of energy as the objective function. Results show that unbalanced laminates provide a greater capabilitiy (compared to balanced laminates) to reduce the cost of energy of stall controlled wind turbines by exploiting extention-twist and bend-twist coupling of composite blades.
Ferede, Etana, Abdalla, Mostafa, Dillinger, Johannes, Gandhi, Farhan, Bussel, Gerard
CFD Analysis of the Effect of Atmospheric Boundary Layer on Wind Turbine WakeF-0073-2017-121395/9/2017
ABSTRACT The wake behind a wind turbine in an atmospheric boundary layer (ABL) is investigated using a numerical simulation method. From the viewpoint of cost effectiveness, collective installations (wind farms) are desired because they can reduce the total length of the power-transmission lines and labor costs for maintenance. However, a wake from an upwind turbine may significantly reduce power production downstream and cause large load variations on the blades. Numerical methods based on computational fluid dynamics (CFD) are efficient for investigating the structures and characteristics of wind-turbine wakes. This study mainly discusses the effect of wind shear of ABL on a wind turbine wake by focusing on the behavior of tip vortices and recovery process of velocity deficits. It is found that the wind shear mainly influence on near-wake structure and the effect on far-wake is relatively weak.
Kimura, Keita, Tanabe, Yasutada, Arakawa, Chuichi, Iida, Makoto, Aoyama, Takashi, Matsuo, Yuichi
Residual Mode FiltersTBMG-253189/1/2016
NASA has developed a unique control algorithm and synthesis method that uses a system’s output to modify control inputs to cause the system to track a reference model or a fixed value in the presence of unmodeled system dynamics, varying operating environments, and unpredictable disturbances. The unique feature of this algorithm is the ability to instantaneously adapt the system according to its output, rejecting persistent disturbances, and ultimately improving the system’s performance. This makes the controller ideally suited for applications where there are unknown modeling parameters or uncertain operating environments. Many aerospace systems must function in unknown or highly variable environments. This technology allows the system to achieve its objectives in these types of unpredictable environments. In comparison to current adaptive controller technologies, the addition of residual mode filters allows operation when flexible modes are present that could inhibit the controller. This is especially useful for systems where initial modeling is costly, or the fidelity of existing system models is low.
An Overset Adaptive High-Order Approach for Blade-Resolved Wind Energy ApplicationsF-0072-2016-115865/17/2016
An overset dual-mesh, dual-solver for computational fluid dynamics (CFD) is presented for wind energy applications. The dual-mesh paradigm is implemented in a near-body/off-body mesh system utilizing an unstructured mesh for the near-body and a Cartesian mesh for the off-body. The dual-solver paradigm uses variable-order, mixed-discretization solvers optimized for the respective near-body/off-body grids. Preliminary results of a computational study of the National Renewable Energy Laboratory (NREL) Phase VI wind turbine are presented. Results for uniform axial inflow velocities (7, 10, and 15 m/s) compare computed and measured results, including total power and thrust, sectional pressure coefficient, and a down-stream wake deficit profile for a uniform axial inflow velocity of 10 m/s. Qualitative results are presented for a dynamically mesh adaptive off-body solver in the dual-mesh, dual-solver paradigm. Preliminary results using a statically refined mesh indicate the power and thrust curves are over predicted and the pressure coefficient results indicate good agreement for the pressure side of the rotor blade but over prediction the suction side.
Kirby, Andrew, Sitaraman, Jay, Mavriplis, Dimitri, Brazell, Michael
Wind Farm Performance Improvement by Using Wake TransportF-0072-2016-115835/17/2016
Wake shielding on wind farms substantially reduces the efficiency of downstream wind turbines due to the interaction with the energy-depleted wakes from upwind turbines. This research considers a method to mitigate the wake shielding effect by tilting the turbine axes upward producing a download that causes streamwise vorticity so that the energy depleted wakes transport upward alleviating shielding, and pumping more energetic fluid into downstream turbines. The wake steering effect for tipped turbines is verified and the degree of effectiveness is assessed. The simulations utilize a specially developed free-wake method, appropriate for wind turbines, that utilizes constant circulation contours with a large degree of downwind vorticity diffusion. This approach has been implemented to capture the natural behavior of multi-filament multi-blade complex turbine wakes, with relatively short simulation time. Detailed turbine wake structure is studied to obtain insights into how to strengthen the steering effect. Besides a single rotor tilted turbine, two unconventional turbine configurations, each consisting of two overlapping counter-rotating rotors, have been studied to assess their potential to increase the upward transport of their wakes. The three turbine configurations are compared along with a discussion of potential advantages and challenges, and additional research goals going forward. Initial promising results from preliminary wind tunnel studies of the wake of a single tipped turbine are briefly described.
Su, Keye, Bliss, Donald
Numerical Simulation of Multiple Interacting Wind Turbines on a Complex TerrainF-0072-2016-115825/17/2016
Modern wind farms are subjected to significant aerodynamic interference due to unsteady wakes of individual turbines as well as the complex terrains on which they are erected. The present study uses a new mixed basis formulation of the Navier-Stokes equations for accurate numerical simulation of convection-dominated flows on a complex terrain. The turbines are modeled using a distribution of momentum sources and the incompressible, turbulent flow-field is solved using the Reynolds Averaged Navier-Stokes (RANS) equations. A finite-volume procedure is used on body fitted grids and the SIMPLER algorithm is used to obtain the flow-field. Three different turbulence models including the standard, RNG, and realizable K - ε are implemented and compared. Results validating the ability of the numerical procedure to simulate flows over complex terrains and wind turbines are presented. Applications providing insights into the performance and loading on wind turbines subjected to turbine-terrain interference are studied. The evolution and interaction of the turbine wake with the complex terrain are also analyzed.
Murali, Avinaash, Rajagopalan, R.
A Study of Individual Pitch Control of a Horizontal Axis Wind Turbine in Atmospheric Boundary LayerF-0072-2016-115855/17/2016
An Individual Pitch Control (IPC) system to reduce the yawing and tilting moments on the hub of Horizontal Axis Wind Turbines (HAWTs) in Atmospheric Boundary Layer (ABL) is constructed and a trim routine is numerically simulated to check the effectiveness of the system. With 1/rev cyclic pitch control, it is found that for a three-bladed turbine, the averages can be trimmed to nearly zero while the 3/rev fluctuations cannot be effectively reduced . However, for a two-bladed turbine, the averaged moments can be reduced to nearly zero, and furthermore, the load fluctuations on rotor hub can also be significantly reduced. For both type of HAWTs, the oscillations of flapwise bending moment on the blade root can be remarkably reduced when IPC is applied.
Tanabe, Yasutada, Oe, Harutaka, Aoyama, Takashi, Sugiura, Masahiko, Yamamoto, Makoto
Rigid Actuation Of The Wind TurbineF-0072-2016-115845/17/2016
The possibility of a wind turbine entering vortex ring state during pitching oscillations is explored in this paper. The work first validated the employed CFD method, and continued with computations at fixed yaw of the NREL Phase VI wind turbine. The aerodynamic performance of the rotor was computed using the Helicopter Multi-Block flow solver. This code solves the Navier-Stokes equations in integral form using the arbitrary Lagrangian-Eulerian formulation for time-dependent domains with moving boundaries. With confidence on the established method, yawing and pitching oscillations were performed suggesting partial vortex ring state during pitching motion. The results also show the strong effect of the frequency and amplitude of oscillations on the wind turbine performance.
Leble, Vladimir, Barakos, George
A Possible Adaptive Wing Apparatus for New UAV Configurations2015-01-24639/15/2015
The problem of wing shape modification under loads in order to enhance the aircraft performance and control is continuously improving by researchers. This requirement is in contrast to the airworthiness regulations that constraint stiffness and stress of the structure in order to maintain structural integrity under operative flight conditions. The lifting surface modification is more stringent in those cases, such as UAV configurations, where the installed power is limited but the variety of operative scenario is wider than in conventional aircraft. A possible solution for adaptive wing configuration can be found in the VENTURAS Project idea. The VENTURAS Project is a funded project with the aim of improve the wind turbine efficiency by means of introducing a twisting capability for the blade sections according to the best situation in any wind condition. The blade structure is composed by two parts: 1) internal supporting element, 2) external deformable envelope. The internal structure is dimensioned in order to support the shear-bending-torsion resultant loads due to wind condition, the external deformable part is capable of supporting aerodynamic pressure, transferring the surface loads to internal specific ribs that rotate in order to reach the optimal blade configuration in twist. The VENTURAS items will be presented with the major results for the structural point of view. The evaluation of the extension of such an idea to UAV wing structure will be presented and discussed.
Frulla, Giacomo, Cestino, Enrico, Gili, Piero, Visone, Michele, Scozzola, Domenico
Flow Simulation and Theoretical Investigation on Aerodynamics of NACA-2415 Aerofoil at Low Reynolds Number2015-01-25769/15/2015
The Aerofoil theory along with its design has integrated itself into the vast areas of applications ranging from Automobile, Aeronautical, Wind Turbine, Micro-Vehicles, UAVs applications. In this paper, knowing the intricacy of the airfoil's applications, A MATLAB Code for NACA-2415 Airfoil is developed and a Model with dimensions c=180mm, w=126mm, tmax=27mm is generated. The model is then subjected to Flow Simulation with various input parameters: Reynolds Numbers taken are- (REN-1) 105 and (REN-2) 2×105 [Laminar External Flow], Angles of attack taken are-0°, 4°, 8°, 12°. The pressure and velocity distribution along the airfoil sketch curve are graphed qualitatively, emphasizing on the flow separation leading to the transition from laminar to turbulent flow. The various aerodynamics characteristic curves for coefficient of pressure, coefficient of lift and coefficient of drag are plotted against different angle of attacks for REN-1 and REN-2. The results were found in good harmony with the established experimental data. Also, the maximum percentage error for maximum coefficient of pressure between the two studies was obtained.
Kumar, Vasu, Tomar, Vishvendra, Kumar, Naveen, Jain, Samarth
New Tracking Technology Enables Robots to Carry Out New Tasks on Composite Parts and its Molds2015-01-25989/15/2015
Composites are becoming a common material for aero structures; that means new manufacturing processes with new problems and new challenges have to be solved. Our engineering team (EiNA) has recently developed and patented a new end effector for Robots that is able to track any kind of surface (even if the surface is moving, swinging, bending….which usually happens when working with big composite parts.) and carry out the required task. This new feature has enabled robots to automate manual tasks that hadn't been automated jet like sanding, cleaning, polishing, applying solvents, applying release and cleaning agents not only on aero structures but also on its molds. The solution is based on a set of sensors, a postprocessor which runs a software and a mechanical compensation gadget. As a result, we can keep all the parameters of a process fully under control even if the part we are working on is not stable and it moves swings and bends.
Lasierra Ferrer, Gustavo
Getting it RIGHT with composites15MEIP09_049/1/2015
With composites now a mainstay in most new aircraft designs, the engineering emphasis has switched from understanding if they work to thinking through the most efficient way to manufacture them, such as using design-for-manufacturing software. “Composite design and analysis is a highly integrated activity,” said Chris Gear, Chief Technology Officer & Senior Technical Fellow for GKN Aerospace. He noted that how composite material is placed, how it moves, how it cures, and the quality and conformance of the product are all inter-related. All of these factors are considered in the final release of the data for manufacturing, he said, aided by design-for-manufacturing (DFM). Complicating manufacturing optimization is the very nature of advanced composites, requiring a unique design process, unlike isotropic, homogenous metal. Controlling fiber orientation and number of layers of fiber embedded in a plastic matrix is vital for its performance. Initial CAD definitions that specify the outer and/or inner mold lines of the part require further definition of material type, fiber orientation, stack-up order, balance, symmetry, drop-offs, splices, and darts.
Morey, Bruce
SPH Simulation of Rivulet Dynamics on Surfaces with Various Wettabilities2015-01-90059/1/2015
Rivulet dynamics is involved in different scientific problems and industrial applications from production of microchips, to rain flow on structural systems such as wind turbine blades and aircraft wings. In the latter case for example, rivulet flow leads to accumulation of ice on airfoil surface that may affect the aircraft performance. Hence, understanding the dynamics of rivulets is important in solving various scientific problems. In this paper the results of a numerical simulation based on smoothed particle hydrodynamic (SPH) method will be reported on dynamics of rivulets under the effect of various air shear speeds and different surface morphologies. The simulation results will be compared and validated with experiments to shed more lights in understanding the mechanism of shear driven rivulet flow on solid substrates.
Moghtadernejad, Sara, Jadidi, Mehdi, Dolatabadi, Ali, Esmail, Nabil
Developing a Novel Ice Protection System for Wind Turbine Blades Using Vibrations of Both Short and Long Wavelengths2015-01-20816/15/2015
Icing conditions in cold regions of the world may cause problems for wind turbine operations, since accreted ice can reduce the efficiency of power generation and create concerns regarding ice-shedding. This paper covers modelling studies and some experimental development for an ongoing ice protection system that provides both deicing and anti-icing actions for wind turbine blades. The modelling process contained two main sections. The first part involved simulation of vibrations with very short wavelength or ultrasonic guided waves (UGW) on the blade to determine optimal excitation frequency and transducer configuration. This excitation creates horizontal shear stress at the interface between ice and blade and focuses energy at the leading edge for de-bonding ice layers. The second modelling approach simulated the effects of vibrations with very long wavelength along with estimation of fatigue life due to harmonic forces to characterise the best parameters for shaker (s) mounted on blades. In parallel with this study, an empirical array of novel resonating shear transducers has been developed using a Design of Experiments (DoE) approach to demonstrate the practicability of inducing shear horizontal waves at the leading edge of wind turbine blades. This experimental verification also makes it possible to investigate the many parameters influencing ice-removal. In addition, piezo-electric and macro-fibre composite actuators have been investigated in place of conventional electro-magnetic shakers, in order to save weight and simplify integration of the deicing system components. The ongoing research is intended to provide an active solution for icing prevention and deicing, enabling safe and reliable operation of wind turbines in adverse weather conditions.
Habibi, Hossein, Edwards, Graham, Cheng, Liang, Zheng, Haitao, Marks, Adam, Kappatos, Vassilios, Selcuk, Cem, Gan, Tat-Hean
Getting It Right with Composites15AERP06_026/1/2015
With composites now a mainstay in most new aircraft designs, the engineering emphasis has switched from understanding if they work to thinking through the most efficient way to manufacture them, such as using design-for-manufacturing software. “Composite design and analysis is a highly integrated activity,” said Chris Gear, Chief Technology Officer & Senior Technical Fellow for GKN Aerospace. He noted that how composite material is placed, how it moves, how it cures, and the quality and conformance of the product are all interrelated. All of these factors are considered in the final release of the data for manufacturing, according to him, aided by design-for-manufacturing (DFM). Complicating manufacturing optimization is the very nature of advanced composites, requiring a unique design process, unlike isotropic, homogenous metal. Controlling fiber orientation and number of layers of fiber embedded in a plastic matrix is vital for its performance. Initial CAD definitions that specify the outer and/or inner mold lines of the part require further definition of material type, fiber orientation, stack-up order, balance, symmetry, drop-offs, splices, and darts.
Morey, Bruce
Getting It Right with CompositesTBMG-222956/1/2015
"Composite design and analysis is a highly integrated activity,” said Chris Gear, Chief Technology Officer & Senior Technical Fellow for GKN Aerospace. He noted that how composite material is placed, how it moves, how it cures, and the quality and conformance of the product are all interrelated. All of these factors are considered in the final release of the data for manufacturing, according to him, aided by design-for-manufacturing (DFM).
Experimental and Computational Investigation of a Small-Scale Vertical Axis Wind Turbine with Dynamic Blade PitchingF-0071-2015-103005/5/2015
ABSTRACT This paper describes the systematic performance measurements and computational (CFD) studies conducted to investigate the performance of a small-scale dynamic-pitch vertical axis wind turbine (VAWT). The VAWT prototype was built and tested in a wind tunnel to understand the role of blade-pitch kinematics and flow curvature effects on turbine aerodynamic efficiency. The three parameters investigated in the experimental study were blade pitching amplitude (symmetric pitching), asymmetry in pitch kinematics between frontal and rear halves, and blade chord (or chord/radius ratio). Even though the optimal pitch amplitude is dependent on the tip speed ratio (TSR), moderate pitch amplitudes (± 20° ) had the highest overall efficiency for the symmetric pitch cases. The tip speed ratio corresponding to the maximum CP decreased with increasing pitch amplitudes. The TSR corresponding to maximum CP for 20° pitch amplitude was around 1.4, while the optimal TSR for the 40° case was around 0.7. Because of the differences in the flow velocities in the front and rear halves, for maximizing power extraction, the pitch angles required in the front is significantly higher than that in the rear. The optimal performance of the turbine occurred at a phasing of 0°. However, the performance was observed to be forgiving for small changes in phasing (<10°) in the positive direction (phase-lead), however, not in the negative direction. Increasing the chord/radius from 0.19 to 0.25 caused significant improvements in turbine efficiency especially at higher pitch amplitudes because of the flow curvature effects. A CFD model was developed and extensively validated with the present experimental data. The validated CFD model was used to understand the effect of the different parameters on turbine performance by analyzing the blade aerodynamics at various azimuthal locations. CFD analysis showed that the blade extracts most of the power in the frontal half of its circular trajectory and in some cases even lose power in the rear half. This study clearly indicates the potential for major improvements in VAWT performance with novel blade kinematics, optimal chord/radius ratio, and using cambered blades.
Benedict, Moble, Lakshminarayan, Vinod, Garber, Jeremy, Chopra, Inderjit
Coupled NS/SPH Analysis of Off-Shore Wind TurbineF-0071-2015-103035/5/2015
ABSTRACT This paper presents results of numerical computations for floating off-shore wind turbines (FOWTs) using, as an example, a machine of 10-MW rated power. The aerodynamic loads on the rotor are computed by the Helicopter Multi-Block (HMB2) flow solver developed at University of Liverpool. HMB2 solves the Navier-Stokes equations in integral form using the arbitrary Lagrangian-Eulerian formulation for time-dependent domains with moving boundaries. Hydrodynamic loads on the support platform are computed using the Smoothed Particle Hydrodynamics (SPH) method, which is mesh-free and represents the water and floating structures by a set of discrete elements, referred to as particles. The motion of the FOWT is predicted using a multi-body dynamic model (MBDM) of rigid bodies and frictionless joints. Mooring cables are modelled as a set of springs and dampers. All solvers were validated separately before coupling, and the results are presented in this work. The importance of coupling is assessed and information about coupling algorithms is presented. The loosely coupled algorithm used in present work is described in details alongside the obtained results.
Leble, Vladimir, Barakos, George
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