Performance enhancement of PowerWindow, a linear cascade wind turbine, for application in urban environments

Urban environments have many attractions and difficulties when it comes to the development of wind energy harvesting systems. Critical issues of using these systems in urban environments include noise, aesthetics, integration into architectural systems, and efficient use of the available wind resource. Wind in urban areas tend to be more turbulent and multi-directional. The presence of buildings increases the turbulence of the wind and also deflects the direction of the wind from a horizontal free stream. Aesthetics is also a concern as many people find conventional wind turbines unattractive. There are also environmental concerns, such as the consideration of bird safety. Conventional horizontal and vertical axis wind turbines cannot easily be integrated with architectural designs due to their configuration and accommodation requirements. These systems need to be properly integrated with the architecture of urban environments. This research project aims to enhance the performance and application of a new wind turbine referred to as PowerWindow. PowerWindow is a type of Linear Cascade Wind Turbine (LCWT) that has recently been developed based on a modular approach and is flexible for integration with the architecture of urban environments. Furthermore, PowerWindow is capable of generating power in low wind velocity conditions with very low operation speed, which makes it an effective and safe wind turbine for application in urban environments. Hence PowerWindow is potentially an alternative to the conventional wind turbines for the application in urban environments

Analysis of the effect of large fuel tanks on aerodynamic performances of heavy trucks and large aircraft

Nowadays, 90% of the worldwide vehicles work with fossil fuels. Use of fossil fuels contributes to the greenhouse effect and, to increase the pollution worldwide. Hydrogen has been suggested as a possible alternative to fossil fuels. However, the use of hydrogen as fuel implies using, different fuel tanks. Due to its lower energy density, hydrogen requires fuel tanks with larger volume than conventional fuels, for an equivalent amount of energy released. The larger tanks modify the external geometry of the vehicle and therefore the aerodynamics are also different. The aim of this project is to carry out an experimental and Computational Fluid Dynamics (CFD) analysis of an Airbus A320 and a tanker truck for which the geometries have been modified accounting for the larger hydrogen fuel tanks needed. Then, the aerodynamic performances of the modified vehicles are compared with the reference conventional A320 and tanker truck. The software used in this analysis is ANSYS Fluent. As in other CFD analysis, the procedure we followed consisted of these steps: generation of the geometry, meshing, definition of the boundary conditions and the physics of the problem, solving, processing of the results. Firstly, the A320 and tanker truck fuel tank modelling have been done in order to stock up the same quantity of fuel as before and to keep an equivalent energy. The modelling process has been performed thinking about the worst possible aerodynamics case. Furthermore, the control volume dimensions have been chosen, that is, the fluid field domain around the target body. Dimensions of the control volume have to be sufficiently big in order to not disrupt the simulation. ANSYS Meshing allowed us to do the mesh. We have tried that cells were refined as much as possible into the interest zones. The mesh quality parameters have been considered to ensure that the simulation is reliable. For the Airbus A320 study, two simulations have been carried out, the first one without any modification and the second one considering the implementation of hydrogen as fuel. For the tanker truck study, three simulations have been carried out, the first one without any modification, the second one considering that is constituted by one single hydrogen tank and the last one considering that is constituted by two hydrogen tanks in order to improve the manoeuvrability. The idea is to compare the simulations to better understand what is happening in each vehicle. It has been seen that the modified A320 presents an increase on drag and lift forces. To be able to overcome this increase on drag, extra fuel will be burnt. Furthermore, because of the implementation of the hydrogen tank, the aircrafts structure weights more than before. However, as hydrogen is now the fuel and it weighs less than Jet A, the total weight of the aircraft is reduced. In this way, we do not need to fly with any AOA higher than the actual one because the current lift is able to compensate the weight of the aircraft. Pitifully, hydrogen is so expensive at present day, and its implementation would be very expensive for airlines. Regarding the tanker truck modifications, the tanker truck constituted by two hydrogen tanks presents the higher increase on drag. However, is not too much larger than the one single hydrogen tank tanker truck. Because of the higher manoeuvrability, it is thought that it would be the best option. We printed 3D models of the A320 studied geometries and tested them in a wind tunnel to measure experimentally the aerodynamic performances and compare them with the results of the CFD simulations. From this analysis, appears that there are many external factors that affect the experiment. However, it has been seen that the modified aircraft presents more drag because of the new fuel tank and the efficiency also diminishes

Aerodynamic Optimization and Wind Load Evaluation Framework for Tall Buildings

Wind is the governing load case for majority of tall buildings, thus requiring a wind responsive design approach to control and assess wind-induced loads and responses. The building shape is one of the main parameters that affects the aerodynamics that creates a unique opportunity to control the wind load and consequently building cost without affecting the structural elements. Therefore, aerodynamic mitigation has triggered many researchers to investigate various building shapes that can be categorized into local (e.g. corners) and global mitigations (e.g. twisting). Majority of the previous studies compare different types of mitigations based on a single set of dimensions for each mitigation types. However, each mitigation can produce a wide range of aerodynamic performances by changing the dimensions. Thus, the first millstone of this thesis is developing an aerodynamic optimization procedure (AOP) to reduce the wind load by coupling Genetic Algorithm, Computational Fluid Dynamics (CFD) and an Artificial Neural Network surrogate model. The proposed procedure is adopted to optimize building corners (i.e. local) using three-dimensional CFD simulations of a two-dimensional turbulent flow. The AOP is then extended to examine global mitigations (i.e. twisting and opening) by conducting CFD simulations of three dimensional turbulent wind flow. The procedure is examined in single- and multi-objective optimization problems by comparing the aerodynamic performance of optimal shapes to less optimal ones. The second milestone is to develop accurate numerical wind load evaluation model to validate the performance of the optimized shapes. This is primary achieved through the development of a robust inflow generation technique, called the Consistent Discrete Random Flow Generation (CDRFG). The technique is capable of generating a flow field that matches the target velocity and turbulence profiles in addition to, maintaining the coherency and the continuity of the flow. The technique is validated for a standalone building and for a building located at a city center by comparing the wind pressure distributions and building responses with experimental results (wind tunnel tests). In general, the research accomplished in this thesis provides an advancement in numerical climate responsive design techniques, which enhances the resiliency and sustainability of the urban built environment

Design and Analysis of a 2kW Wind Turbine with a Flange Type Velocity Booster for Low Wind Speeds

Demand for the energy is raising with the population growth and technological advancement. There is a global trend to invest in renewable sources of energy to fulfil that demand due to increasing environmental effects which fossil fuels cause on earth. Other than this, renewable energy sources are ideal for places where there is no reliable electrical access. Similar situation occurred in Sri Lankan dairy industry, where small scale dairy farmers need a reliable source of power for their milk cooling systems, wind-PV hybrid system was proposed to fulfil their energy needs. This study is focused on designing a wind turbine for above project. Region where this wind turbine is to be installed is subjected to low wind conditions. Thus, wind speed augment device is also needed, and designed. First NREL pulse VI turbine was modelled and analyzed in Star CCM+ which is a finite volume based commercial CFD code. Then the available experimental data was used to compare numerical results. Comparison indicates satisfactory similarity. Thus, numerical code can be considered as valid and later used for wind turbine analysis of this project. Then, a 2 kW horizontal axis wind turbine was designed using NACA 634421 and FX 76 MP 140 air foils according to Blade Element Momentum theory. Then the performance characteristics of the turbine was evaluated using star CCM+. Power output of the turbine at designed wind velocity 7.5 m/s and TSR 7.5 was 2273.4 W. Power coefficient is 0.48 at this point which indicates the success of design. Next, four flanged type velocity booster models were designed with size constrains considering manufacturing and handling easiness. Flow behavior through these booster models were numerically analyzed. Scaled down models of 2 of these boosters were tested in a wind tunnel and numerical data were validated against those experimental results. Finally previous turbine was again analyzed numerically for its performances with each of four booster models. All four models indicated significant improvement in performances of the turbine. Turbines with booster model 1 and booster model 3 indicated similar behavior and improve the power output by a factor of 2 compared to the stand-alone turbine, while turbine with booster model 2 indicated slightly lower performance with power output increase by a factor of 1.98. Booster model 4 indicated even lower performances, but still increased the power output by a factor of 1.7. Both booster model 1 and 3 are recommended to use for smaller turbines considering their higher performance. Booster model 4 is also suitable, despite its comparatively lower performance due to its compact design. Considering the power requirement and size of this turbine, booster model 4 was selected due to its size and performance. Required power output was achieved using scaled down turbine and booster by 25% of its original design size. This was an additional advantage which leads to lower structural loads and lower material usage.List of figures iv List of tables viii Abstract x Nomenclature xii Abbreviations. xiv 1. Introduction 1 1.1. Background 1 1.2. Generation of wind 2 1.3. Classification of wind turbines 3 1.3.1. Rotor size and scale 3 1.3.2. Drag and lift wind machines 3 1.3.3. Horizontal and vertical axis wind turbines 4 1.4. Wind turbines with velocity augment devices 8 1.5. Purpose of the research 11 2. Theory behind wind turbine design 12 2.1. Introduction 12 2.2. Actuator Disc Model 12 2.3. Angular Momentum 15 2.4. Blade Element Theory 17 2.4.1. Tip Losses 19 2.5. Blade Element Momentum (BEM) Theory 20 3. Design of 2kW wind turbine and flange type velocity boosters 22 3.1. Determining the design wind speed 22 3.2. Calculating the Rotor Diameter and Rated Rotational Speed 23 3.3. Tip loss correction 23 3.4. Flow induction factors 24 3.5. Air foil selection 26 3.6. Chord length calculations 31 3.7. Twist angle calculations 32 3.8. Optimized blade parameters 34 3.9. Flange type velocity booster designs 36 4. CFD analysis 42 4.1. Computational fluid dynamics 42 4.1.1. Introduction 42 4.1.2. Governing equations 42 4.1.3. Creating the geometry 43 4.1.4. Defining the simulation settings and boundary conditions 43 4.1.5. Mesh generation 44 4.1.6. Solving the simulation 45 4.1.7. Post processing 46 4.2. NREL Phase VI Turbine analysis 46 4.3. 2 kW wind turbine analysis 53 4.4. Flange type velocity booster analysis 58 4.5. 2 kW wind turbine analysis with flange type velocity boosters 62 5. Results and Discussion 72 5.1. NREL Phase VI turbine 72 5.2. 2 kW turbine 76 5.3. Flange type velocity booster models 82 5.4. Wind tunnel experiment 87 5.5. 2 kW turbine with different flange type velocity booster models 98 5.6. Scaled down turbine-booster system 108 6. Conclusions 110 Acknowledgement 112 References 113Maste

On the turbulent flow models in modelling of omni-flow wind turbine

Yong Chen, Pei Ying, Yigeng Xu, Yuan Tian, 'On the turbulent flow models in modelling of omni-flow wind turbine', paper presented at The International Conference on Next Generation Wind Energy (ICNGWE2014), the Universidad Europa de Madrid, Madrid, Spain, 7th-10th October 2014.The computational fluid dynamics (CFD) has a wide application in the wind energy industry. In CFD simulations, a turbulence model plays a significantly important role in accuracy and resource cost. In this paper, a novel wind turbine, omni-flow wind turbine, was investigated with different turbulence models. Four turbulence models, standard k-ε, realizable k-ε, standard k-ω and SST k-ω models, were employed for this wind turbine in order to assess the best numerical configuration. The performance of these four turbulence models was validated with wind tunnel tests. It is evident that the realizable k-ε turbulence model is most suitable to simulate this novel wind turbine

Analysis and Optimisation of a Novel Wind Turbine

The technologies of urban wind turbines have been rapidly developed in recent years, but urban wind turbines have not found a wide application due to the limitations of their designs. The power output of urban wind turbine is significantly affected by urban terrain, which can cause low speed flow with frequent change of its direction. Thus, there is a need for a new wind turbine to meet the requirements of an urban wind turbine. In this study, a novel wind turbine for urban areas was designed and developed. The investigations of the novel urban wind turbine were carried out by using computational fluid dynamic (CFD) simulations and wind tunnel tests. The results from the investigation have shown that the novel wind turbine has a great potential to harvest wind energy in urban areas. A detailed study of effects of each parameter on wind energy concentration of the novel wind turbine was carried out with CFD simulations. According to the simulation results, the shroud structure of the novel wind turbine was modified and the dimensions of the final structure were identified. It was determined that the capability of wind energy concentration of the novel wind turbine shroud has been significantly improved through the structure optimisations. Furthermore, guide vane and impulse turbine were implemented in the novel wind turbine. The flow characteristics through the guide vane was studied and discussed. It was found that the wind flow characteristics can be properly modified by implementing guide vane and the structure of impulse turbine was suitable to be implemented in the novel wind turbine due to the flow characteristic through the guide vane

Review on Diffuser Augmented Wind Turbine (DAWT)

Wind energy technology is one of the fastest growing alternative energy technologies. However, conventional turbines commercially available in some countries are designed to operate at relatively high speeds to be appropriately efficient, limiting the use of wind turbines in areas with low wind speeds, such as urban areas. Therefore, a technique to enhance the possibility of wind energy use within the range of low speeds is needed. The techniques of augmenting wind by the concept of Diffuser Augmented Wind Turbine (DAWT) have been used to improve the efficiency of the wind turbines by increasing the wind speed upstream of the turbine. In this paper, a comprehensive review of previous studies on improving or augmentation power of Horizontal Axis Wind Turbines (HAWT) have been reviewed in two categories, first related with relative improvement of energy by improving the aerodynamic forces that affecting on HAWT in some different modifications for blades. Second, reviews different techniques to the augment the largest possible amount of power from HAWT focusing on DAWTs to gather information,helping researchers understand the research efforts undertaken so far and identify knowledge gaps in this area. DAWTs are studied in terms of diffuser shape design, sizing of investigation and geometry features which involved diffuser length, diffuser angle, and flange height. The conclusions in this work show that the use of DAWT achieves a quantum leap in increasing the production of wind power, especially in small turbines in urban areas if it properly designed. On the other hand, shrouding the wind turbine by the diffuser reduces the noise and protects the rotor blades from possible damage

Application of Computational Fluid Dynamics to the Study of Designed Green Features for Sustainable Buildings

2009-2010 > Academic research: refereed > Chapter in an edited book (author)published_fina

Experimental Aerothermal Performance of Turbofan Bypass Flow Heat Exchangers

The path to future aero-engines with more efficient engine architectures requires advanced thermal management technologies to handle the demand of refrigeration and lubrication. Oil systems, holding a double function as lubricant and coolant circuits, require supplemental cooling sources to the conventional fuel based cooling systems as the current oil thermal capacity becomes saturated with future engine developments. The present research focuses on air/oil coolers, which geometrical characteristics and location are designed to minimize aerodynamic effects while maximizing the thermal exchange. The heat exchangers composed of parallel fins are integrated at the inner wall of the secondary duct of a turbofan. The analysis of the interaction between the three-dimensional high velocity bypass flow and the heat exchangers is essential to evaluate and optimize the aero-thermodynamic performances, and to provide data for engine modeling. The objectives of this research are the development of engine testing methods alternative to flight testing, and the characterization of the aerothermal behavior of different finned heat exchanger configurations. A new blow-down wind tunnel test facility was specifically designed to replicate the engine bypass flow in the region of the splitter. The annular sector type test section consists on a complex 3D geometry, as a result of three dimensional numerical flow simulations. The flow evolves over the splitter duplicated at real scale, guided by helicoidally shaped lateral walls. The development of measurement techniques for the present application involved the design of instrumentation, testing procedures and data reduction methods. Detailed studies were focused on multi-hole and fine wire thermocouple probes. Two types of test campaigns were performed dedicated to: flow measurements along the test section for different test configurations, i.e. in the absence of heat exchangers and in the presence of different heat exchanger geometries, and heat transfer measurements on the heat exchanger. As a result contours of flow velocity, angular distributions, total and static pressures, temperatures and turbulence intensities, at different bypass duct axial positions, as well as wall pressures along the test section, were obtained. The analysis of the flow development along the test section allowed the understanding of the different flow behaviors for each test configuration. Comparison of flow variables at each measurement plane permitted quantifying and contrasting the different flow disturbances. Detailed analyses of the flow downstream of the heat exchangers were assessed to characterize the flow in the fins¿ wake region. The aerodynamic performance of each heat exchanger configuration was evaluated in terms of non dimensional pressure losses. Fins convective heat transfer characteristics were derived from the infrared fin surface temperature measurements through a new methodology based on inverse heat transfer methods coupled with conductive heat flux models. The experimental characterization permitted to evaluate the cooling capacity of the investigated type of heat exchangers for the design operational conditions. Finally, the thermal efficiency of the heat exchanger at different points of the flight envelope during a typical commercial mission was estimated by extrapolating the convective properties of the flow to flight conditions.Villafañe Roca, L. (2013). Experimental Aerothermal Performance of Turbofan Bypass Flow Heat Exchangers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34774TESI

Euromech Colloquium 509: Vehicle Aerodynamics. External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars - Proceedings

During the 509th Colloquium of the Euromech society, held from March 24th & 25th at TU Berlin, fifty leading researchers from all over europe discussed various topics affecting both road vehicle as well as railway vehicle aerodynamics, especially drag reduction (with road vehicles), cross wind stability (with trains) and wake analysis (with both). With the increasing service speed of modern high-speed railway traffic, aerodynamic aspects are gaining importance. The aerodynamic research topics comprise both pure performance improvements, such as the continuous lowering of aerodynamic drag for energy efficiency, as well as safety relevant topics, such as cross-wind stability. The latter topic was most recently brought to attention when a swiss narrow-gauge train overturned during the severe storm Kyrill in january 2007. The shape of the train head usually has largest influence on cross wind stability. Slipstream effects of passing trains cause aerodynamic loads on objects and passengers waiting at platforms. The strength of the slipstream is determined by both the boundary layer development along the length of the train and the wake developing behind the tail of the train. Since high-speed trains can be considered to be as smooth as technically possible, attention is drawn to the wake region. The wake of the train again is also one important factor for the total drag of a train. Due to the fact that trains are bidirectional, optimisation of the leading car of a train with respect to drag and cross wind performance while simultaneously minimising the wake of the train for drag and slipstream performance is a great challenge. Modern optimisation tools are used to aid this multi-parameter multi-constraint design optimisation in conjunction with both CFD and wind tunnel investigations. Since many of the aerodynamic effects in the railway sector are of similar importance to road vehicles, the aim of the colloquium is to bridge the application of shape optimisation principles between rail- and road vehicles. Particular topics to be addressed in the colloquium are: Drag, Energy consumption and emissions: Due to increase in energy cost, drag reduction has gained focus in the past years and attention will grow in the future. Pressure induced drag is of common importance for both rail- and road vehicles. The optimisation of head- and tail shape for road vehicles as well as for bi-directional vehicles (trains) is in the focus. Interference drag between adjacent components shall also be treated. Slipstream Effects: Are a safety issue for high-train operation (Prams sucked into track due to train-induced draught flows) when trains passing platforms at high speeds. For Road vehicles, the ride stability of overtaking cars is influenced by the wake of the leading trucks and busses. Common interest is the minimisation of wake effects for both rail and road vehicles. Cross-Wind Safety, Ride stability under strong winds: Both are safety issues for rail- and road vehicles. Aerodynamic forces shall be minimised (roll moment for trains and also yaw moment for road vehicles). Strategies for Vehicle shape optimisation (head, tail and roof shape) in order to minimise aerodynamic moments. Possibilities of Flow control. Optimisation strategies: Parametrisation, analyses (CFD), Optimisation tools and methods, Application to Drag, Cross-Wind, Ride stability and Snow issue