Power Augmentation Research Articles

A New Approach Toward Power Output Enhancement Using Multirotor Systems With Shrouded Wind Turbines

A multirotor system (MRS) is defined as containing more than one rotor in a single structure. MRSs have a great potential as a wind turbine system, saving mass and cost, and showing scale ability. The shrouded wind turbine with brimmed diffuser-augmented wind turbines (B-DAWT) has demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 2–5 compared with a bare wind turbine. In the present research, B-DAWTs are used in a multirotor system. The power output performance of MRSs using two and three B-DAWTs in a variety of configurations has been investigated in the previous works. In the present study, the aerodynamics of an MRS with five B-DAWTs, spaced in close vicinity in the same vertical plane normal to a uniform flow, has been analyzed. Power output increases of up to 21% in average for a five-rotor MRS configuration are achieved in comparison to that for the stand-alone configuration. Thus, when B-DAWTs are employed as the unit of a MRS, the total power output is remarkably increased. As the number of units for an MRS is increased from two to five, the increase in power output becomes larger and larger. This is because that the gap flows between B-DAWTs in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, a MRS with more B-DAWTs can draw more wind into turbines showing higher power output.

Is modeling stents still an important issue?

Numerical models of cardiovascular devices have always appeared in literature studies few years after their use in clinical practice. As example, FDA approval of Palmaz-Schatz stent was in 1994, while the first numerical studies on a similar stent model appeared after 1999. The same temporal delay can be observed for degradable stents, transcatheter valves or more recently for devices like the stent retrievers. This observation does not necessarily mean that numerical modeling had not been used in the design of the stents or cardiovascular devices. Companies might have used numerical tools but not published the results. Was the publication activity committed mainly to the academic world? Or was the numerical modeling an exclusive academic activity until a few years ago? Modeling has intrinsic errors, while prototyping looks immune, as it is the natural design process for a company. The real world has always attracted more attention than the virtual world. Models are useful and the gap between the industrial production and numerical tools in the designing of devices is being reduced recently. Nowadays advances in medical images and augmentation of computer power allow to think of building real-time simulations as well as patient-specific models to be used to predict the device behavior; this is a plus that numerical modeling has over the traditional design process of cardiovascular devices. Furthermore, as in the past, the identification of new unknown problems/failures will always make the usage of numerical modeling a useful tool to explain the reasons of failure. The future in modeling stents is envisioned in their use for in silico trials and in the link between biology, engineering, and science.

Segment Repetition Based on High Amplitude to Enhance a Speech Emotion Recognition

Speech Emotion Recognition (SER) is a technology developed on a computer to realize a Human-Computer Interaction (HCI). It is a challenging task since the lack of data. Some data augmentation methods have been created to increase the data variation, but they do not significantly improve accuracy. Therefore, a new additional data augmentation method called Segment Repetition based on High Amplitude (SRHA) is proposed to solve this problem. This method makes some repetitions on the segments that have the highest amplitude. An experiment of 10 times data augmentation, using five standard augmentations and the additional SRHA with a Long Short-Term Memory (LSTM) as the classifier, shows that the proposed SRHA significantly increases the SER accuracy from 95.88% to 98.16%. Other experiments for 20 and 40 times data augmentations also show that the SRHA outperforms the five standard augmentations. These indicate that the SRHA is a powerful data augmentation method for SER.

Parametric study of a diffuser for horizontal axis wind turbine power augmentation

For a wider dissemination and implementation of small wind turbines for rural electrification in developing countries, the cost of the system must be reduced. When searching for systems that are efficient and economical, Diffuser Augmented Wind turbine seems to have a potential role by increasing the power output and reducing the cost of the system most importantly at low speeds. In this paper, a detailed study has been done on Diffuser Augmented Wind Turbines to find a parametric relationship for power augmentation for horizontal axis wind turbines. A suitable diffuser was selected and its parameters were identified and their relationships were formulated based on Computational Fluid Dynamics. The result has been validated using experimental analysis. Based on the result, the power output and performance of a wind turbine is improved while using diffuser. The result shows the velocity peaks at a location immediately after the diffuser inlet. The velocity, then, levels off and further decreases as the flow continues to the diffuser outlet and exits it. This suggests a possible location of a wind turbine at the vicinity of the inlet. Based on the result, the length of the diffuser and the flange height were the major parameters to be considered. Maximum velocity ratios up to 1.5 were obtained with potential power increase of more than 2 times. It has also been observed that velocity ratios of up to 1.3 can be achieved with more compact diffusers potentially reducing the cost of the diffuser and the whole system. The mathematical relations obtained for the major parameters and the velocity ratio can be used in the performance prediction and optimization of a diffuser. Finally, possible directions for further research are recommended considering that this work shows a good agreement with previous works and predictions.

Numerical study for the flow field and power augmentation in a horizontal axis wind turbine

The flow field around a horizontal-axis wind turbine is analyzed numerically by solving the flow governing equations namely Reynolds’s Averaged Navier-Stokes (RANS). The effect of wind velocity on the flow field and the wall static pressure coefficient was examined. The numerical results were compared with the available experimental measurements from the open literature to verify model predictions which showed reasonable agreement. Then, the numerical model was used to investigate the effect of wind turbine shroud on the flow field and the generated power from the wind turbine. A parametric study was performed to examine the effect of different shroud geometries on the flow and the velocity at wind turbine rotor. The flow field around wind turbine rotor was calculated for the proper geometry of the shroud, and the developed torque was obtained and consequently the generated power. The performance of the shrouded wind turbine was compared to that of the un-shrouded wind turbine, and it was found that a considerable increase in the generated power was obtained using the shroud.

Effects of upstream buildings on the performance of a synergistic roof-and-diffuser augmentation system for cross flow wind turbines

In a previous work we investigated the effectiveness of combining the concentration effects generated by a dual-pitched roof and a convergent-divergent semi-diffuser placed over a cross flow turbine (CFT), which is rooftop mounted with horizontal shaft running close to the roof ridge. By means of 2D CFD we now assess the effects of the upstream buildings on the performance of this concentration system. Three different urban layouts are simulated via a challenging fully-resolved URANS approach that gives unprecedented insight into the complex interactions of the flow around buildings, diffuser and turbine's blades. A promising power augmentation of 40% with respect to the case without diffuser are obtained and the mechanism behind this performance enhancement are analysed. The beneficial effect of the diffuser on the torque fluctuations damping (∼60%) is also discussed. Important remarks on the load control strategy for diffuser-augmented CFT are finally presented.

Optimization of wet compression effect on the performance of V94.2 gas turbine

Wet compression has been widely used in recent years for power augmentation and gas turbine efficiency improvement. In order to explore this issue, the paper first focuses on the effects of wet compression, an analytical method based on droplet evaporation. Matching compressor-turbine or typically matching component has been added to this model for the compatibility of mass flow, rotational speed and power. Since this essay advances the idea of optimization, one of the metaheuristic algorithms Cuckoo Search (CS) has been considered. Three variables including droplet diameter, amount of overspray and droplet size have been taken into account. The objective function is turbine output work where compressor will work out of surge and choke domain. The numerical results indicate degradation in compressor inlet air temperature and noticeable power increments.

Optimization of the Power Output of a Bare Wind Turbine by the Use of a Plain Conical Diffuser

A plain conical diffuser is optimized to augment the wind speed at the throat of the diffuser. The diffuser is used in the construction of a diffuser augmented wind turbine (DAWT) to augment the power output of a bare wind turbine (BWT). Experiments with empty conical diffusers were done to determine optimum geometrical parameters for the diffuser to achieve maximum wind speed augmentation. Using the obtained optimum geometrical parameters, an optimized plain conical DAWT was designed, constructed, and field tested. A twin decentralized wind energy system which comprised a BWT and the optimized plain conical DAWT was erected. The electrical power output from these systems was measured and compared. The optimized plain conical DAWT reduced the cut-in wind speed of a BWT from 2.5 m/s to 1.6 m/s. The power output was increased by a factor of 2.5. This power output is comparable to that of flanged diffusers. However, flanged-DAWTs are more inert due to the addition of the flange. Its response to wind speed and direction is slow as compared to plain conical DAWT. Thus, it cannot fully exploit the potential of the wind. Also, the addition of the flange increases its production cost. Therefore, plain conical DAWT can replace flanged-DAWT in wind power augmentation.

Effects of Tip Vanes on Aerodynamic Performance of H-Type VAWT

In order to investigate the effect of the tip vanes on the aerodynamic performance of H-type vertical axis wind turbines (H-VAWTs), adopting the method of the CFD numerical simulation to analysis blade surface pressure distribution, tip vortex and power coefficient of H-VAWTs that are installed two different kinds of tip vanes on both ends of the blade and not installed. The result showed that the tip vanes can weaken the tip vortex, increase the blade surface pressure difference and improve the power coefficient of the H-VAWT. In addition, the power coefficient of the rotor with V type tip vane was greater than that of the rotor with S type tip vane. The maximum improvement achieved was a 37.5 percent increase in power coefficient with V type tip vane and a 33 percent increase in power coefficient with S type tip vane, the tip vanes made the power augmentation of the H-VAWT.

Investigation on the Effect of Surface Wettability on a Two-Phase Flow in a Compressor Cascade

In recent years overspray fogging has become a powerful means for power augmentation of industrial gas turbines. Despite the positive thermodynamic effect on the cycle droplets entering the compressor increase the risk of water droplet erosion. Further deposited water leads to a higher sensitivity toward fouling due to an increased stickiness of the blades. Therefore, erosion resistant hydrophobic coatings are applied to the first stages of compressors. Although some patents claim the use of such coatings the aerodynamic impact of a different wettability is not regarded so far. This issue was addressed in the field of aerodynamic efficiency of wings in heavy rain showing higher penalty for hydrophobic coatings. In this study, the issue of a different blade surface wettability in a linear transonic compressor cascade is addressed. Different coatings are applied resulting in contact angles of 51–95 deg. The inflow Mach number was fixed at design inflow Mach number, and the inflow angle was varied over a broad range. The effect on the water film pattern is analyzed in terms of position of film breakup, rivulet width, and totally wetted surface. The performance of the cascade under two-phase flow was analyzed using laser Doppler anemometry/phase Doppler anemometry measurement technique in terms of loss coefficient based on wake momentum thickness and flow turning. It is shown that the wettability of the surface has significant effects on the film structure leading to a lower fraction of wetted surface with increasing contact angle. The influence on performance is limited to effects in the proximity of the surface and is dependent on operation point. While in design conditions hydrophilic coating show lower losses, the trend is vice-versa for off-design conditions. The data represent first experimental work on the influence of surface wettability in a droplet-laden flow supporting positive features for hydrophobic coatings in gas turbine compressors.

An Analysis of an Advanced Compressed Air Energy System (CAES) Using Turbomachinery for Energy Storage and Recovery and for Continuous On-Site Power Augmentation as an Air Brayton Cycle

Abstract A thermodynamic analysis of an advanced CAES for Distributed Power Generation (DPG) is presented that utilizes turbomachinery for energy recovery, but also gives continuous power generation to augment on-site power. The advanced CAES uses renewable energy such as wind power and solar PV in the power range of 1500 to 2500 kW plus recuperation of waste heat from the existing on-site prime mover to improve the utility of the energy storage system. The proposed system also utilizes battery storage to maintain high energy density storage, preferably without the need for costly electrical rectifying and inversion systems to improve the stabilization of power generation. This proposed system may be thought of as a “cross-over” system that combines CAES technology with electric battery storage technology, particularly if the stored electric power is used directly as D.C. power at an industrial facility. The direct use of stored energy from a battery as heat input to the proposed “cross-over” system also may be considered in some limited applications. The ideal application of the proposed system is for isolated DPG systems perhaps in remote sites utilizing “power islands” of renewable energy augmented with on-site fossil fuel prime mover, power generation systems. The proposed “cross-over” system enables higher reliability, faster response to transient power loads, and the efficient use of renewable energy, as well as heat recovery from conventional prime mover systems that are on site.

Novel soft bending actuator-based power augmentation hand exoskeleton controlled by human intention

This article presents the development of a soft material power augmentation wearable robot using novel bending soft artificial muscles. This soft exoskeleton was developed as a human hand power augmentation system for healthy or partially hand disabled individuals. The proposed prototype serves healthy manual workers by decreasing the muscular effort needed for grasping objects. Furthermore, it is a power augmentation wearable robot for partially hand disabled or post-stroke patients, supporting and augmenting the fingers’ grasping force with minimum muscular effort in most everyday activities. This wearable robot can fit any adult hand size without the need for any mechanical system changes or calibration. Novel bending soft actuators are developed to actuate this power augmentation device. The performance of these actuators has been experimentally assessed. A geometrical kinematic analysis and mathematical output force model have been developed for the novel actuators. The performance of this mathematical model has been proven experimentally with promising results. The control system of this exoskeleton is created by hybridization between cascaded position and force closed-loop intelligent controllers. The cascaded position controller is designed for the bending actuators to follow the fingers in their bending movements. The force controller is developed to control the grasping force augmentation. The operation of the control system with the exoskeleton has been experimentally validated. EMG signals were monitored during the experiments to determine that the proposed exoskeleton system decreased the muscular efforts of the wearer.

Ultrasound-assisted synthesis of N235-impregnated resins for vanadium (V) adsorption.

N235-impregnated resins were prepared using XAD-16HP macroporous adsorption resins as support with and without ultrasonic irradiation to evaluate the effects of ultrasound impregnation (UI) on the preparation and adsorption characteristics of the resins. The results show that the impregnation ratio of the solvent-impregnated resins (SIRs) prepared by ultrasound impregnation method (SIRs-UI) increases obviously but their adsorption capacity for V(V) just slightly increases and the utilization rate of the extractant decreases with the augmentation of ultrasound power. This may be caused by the fact that more extractant can enter into the deeper pores of the resins under high ultrasound intensity, but these extractants cannot effectively react with V(V). The impregnation equilibrium time of SIRs-UI can be obviously shortened in comparison to that of the SIRs prepared by conventional impregnation method (SIRs-CI) (3 min versus 240 min) due to the cavitation effect evoked by ultrasound. Ultrasonic irradiation may cause more N235 desorbed from the pores of the resin at low N235 content, resulting in lower adsorption capacity for V(V) than that of SIRs-CI, but the adsorption capacity is inverse at higher N235 content. N235 may be distributed more homogeneously in the pores of XAD-16HP with ultrasonic irradiation, thus, SIRs-UI presents higher adsorption capacity and stronger stability than SIRs-CI. This study manifests that ultrasound-assistant impregnation method may be a potential and promising technique for the preparation of SIRs.

Potential of on-board energy recovery systems to reduce the costs of diesel–electric mine truck haulage

ABSTRACTOn-board energy recovery systems (ERSs) are expected to reduce fuel consumption of open-pit mine haul trucks. However, the additional mass of an ERS would reduce the truck’s payload, hence reducing productivity, effectively increasing other haul-related costs. Using a simulation program incorporating appropriate models for a diesel-electric mine haul truck, capital costs, operating costs and four energy recovery technologies, this paper investigates how various ERS technologies would affect overall haulage cost. Two energy re-use strategies are considered. The power augmentation strategy, which aims to reduce cycle times, promises greater savings than the fuel replacement strategy, which reduces engine power using recovered power. The ERS technologies found to be best suited to the application are fast charging LiFePO4 batteries, and electro-mechanical flywheels. Using the power augmentation strategy, the potential cost reduction for both technologies under ideal conditions is 7%. Restrictions on exploiting the full potential of ERS systems are highlighted and discussed.

Experimental study to assess effects of ballooning and fuel relocation on the coolability of fuel rod bundle

For a large break loss-of-coolant accident (LB LOCA) in a pressurized water reactor, the clad temperature increases until the reflood phase. This causes ballooned fuel rods and fuel relocation, thereby reducing the flow passage area of the subchannels and redistributing the flow and heat transfer in the subchannels. The fuel relocation induces augmentation of power and temperature at the ballooned region simultaneously. In this light, research on the coolability of the deformed fuel and fuel relocation is very important for preventing and mitigating severe accidents. In the present study, reflood experiments were performed to investigate the coolability in the ballooned fuel rod geometry and fuel relocation condition under a LB LOCA for a Korean nuclear power plant, APR1400. The coolability experiments were carried out using three kinds of test sections. The first experiments using a 6 × 6 intact rod bundle were performed as a reference case. The second experiments simulated the deformed fuel using a 5 × 5 ballooned rod bundle. The last experiments were performed using another ballooned 5 × 5 rod bundle with a local power increase to simulate fuel relocation. The reflood phenomena were scrutinized for these three rod bundles. While there were not substantial differences in the peak cladding temperature between the intact and ballooned cases, the fuel relocated bundle showed high peak cladding temperatures.

Minimization of Real Power Loss and Augmentation of Static Voltage Stability Margin by Enhanced Algorithm

This paper presents a new Enhanced African Wild Dog Algorithm (EAWDA) for solving the multi-objective reactive power dispatch problem.Inspired by Basic African wild dog algorithm (AWDA), this paper progresses by adding rounding up behaviours of wild dog, The proposed (EAWDA) algorithm has been tested on standard IEEE 30 bus test system and simulation results shows clearly about the noble performance of the projected algorithm.

Pushing Nonlinear Optical Oxides into the Mid-Infrared Spectral Region Beyond 10 μm: Design, Synthesis, and Characterization of La3SnGa5O14.

Mid-infrared (mid-IR) coherent light is crucial for several applications in science as well as daily life, and its development especially in powerful augmentation is constrained by the availability of nonlinear optical (NLO) materials. The development of useful mid-IR NLO materials is limited by the requirements of a wide mid-IR transparent window, high laser damaged threshold (LDT), and strong NLO effect. It is common knowledge that oxides are not suitable mid-IR NLO materials, as their IR absorption cutoff wavelengths are usually <6 μm; however, their LDTs and NLO effects can be large. Herein, we focused on langasite oxides and built structure-composition-property maps that describe the NLO properties in these materials by combining computational property prediction and experimental characterization. Accordingly, rational molecular design was performed, a new member of the langasite family, La3SnGa5O14 (LGSn), was synthesized, and single crystals were grown. The produced material exhibits the widest transparent region (0.27-11.0 μm) among available oxides, the largest LDT (846 MW/cm2) among materials that are transparent to 10 μm, and the strongest SHG effect among langasites. The discovery of LGSn facilitates the application of oxides as NLO crystals in the mid-IR spectral region beyond 10 μm. More generally, the developed strategy could be used to guide and accelerate the systematic discovery of functional materials through understanding the key structure-composition-property relationships using the predictive power of computational tools.

Experimental and simulation investigation into the effects of a flat plate deflector on vertical axis wind turbine

Power augmentation features have been proven as one of the wind turbine performance enhancement methods particularly for vertical axis wind turbines (VAWTs). Researches showed that with the aid of a deflector, shroud or a single plate, the power output of a VAWT can be increased remarkably. In this paper, lab tests and simulations were performed to investigate the aerodynamic effects and the flow field around a flat plate deflector as a power augmentation device which is placed at the lower upstream of a micro H-rotor VAWT. From the study, the deflector is able to induce a high velocity wind at the near-wake region which was about 25% higher compared to the oncoming wind velocity. The deflected wind flows improve the performance significantly as well as reduce the self-start velocity of the turbine. Nonetheless, it is highly dependent on the positioning of the flat plate deflector. Both experiment and simulation showed a notable observation on the position effect of the flat plate deflector. From the lab test, with the deflector at the optimal position, the maximum coefficient of power (CP) achieved was 7.4% increment compared to the bare turbine. Also, from the simulation, the optimal position showed an improvement of averaged CP up to 33% compared to the bare turbine. The flat plate deflector is simple, low cost, and can be easily retrofitted to existing stand-alone VAWT systems to improve the efficiency making them suitable for on-site power generation in urban and isolated places.

Application of ultrasound treatment for improving the physicochemical, functional and rheological properties of myofibrillar proteins

The aim of this study was to evaluate the impact of duration (10, 20 and 30min) and power (100 and 300W) of high-intensity ultrasound (20kHz) on physicochemical properties of beef myofibrillar proteins in order to investigate novel process for modification of its functional characteristics. Results showed that augmentation of duration and power of ultrasound led to enhance pH. Also, the water holding capacity and gel strength were improved by increasing pH. The highest value in pH, reactive sulfhydryl content, water holding capacity and gel strength was obtained in sample subjected to 30min of ultrasound at 300W. The particle size distribution of the proteins was decreased after ultrasound treatment because of the cavitation force of ultrasound waves. In this circumstance, an improvement of emulsifying properties can be obtained. Ultrasonic waves had significant effects on the rheological properties of myofibrillar proteins. Treated samples were more elastic and stiffer than control, although the inverse trend was observed after 30min treatment at each power. Finally, a reducing trend in viscosity was observed by increasing time and power of sonication. Ultrasonic treatment could successfully improve functional properties with effect on physicochemical properties of myofibrillar proteins.

Diffuser Augmented Wind Turbine (DAWT) Technologies: A Review

Diffuser Augmented Wind Turbines (DAWT) are an optimised class of wind turbines that use the theory of a Diffuser to accelerate and direct air flow onto a wind turbine rotor to drive it for higher rotations-per-minute and power output. This power output is typically measured and rated in terms of the power augmentation. Diffuser theory was pioneered in the 1970’s and has re-emerged in recent years with a range of new technological approaches to achieving laminar wind profiles, low exit pressures, improved pressure recovery, reduced blade tip losses, improved torque generation and adaptability to wind directional and speed changes. Research has been pivotal in the advancement of design and performance of DAWT’s with CFD remaining a critical analysis tool. Power augmentations have been realistically achieved within the range of 2-3 for small-medium scale turbines. In this review, ground-based Diffuser technologies have been presented primarily according to rotor type. Large-scale on-shore and off-shore concepts have been presented along with airborne technologies. Building-integrated DAWT’s are then presented with a description of some of the influential economic and technical factors that currently affect and will continue to affect the development of the DAWT industry. DAWT’s prove to have a realisable significant potential even when considered in applications across the wind turbine sector. The current DAWT industry is mostly research-based with very little commercialisation as the majority of technologies presented here are in their early developmental stages. It is expected that subsequent research and innovation in this field will be able to advance this issue to allow DAWT’s a credible chance as a key player in the wind technology sector.