scholarly journals Calculation of the power output loss based on thermographic measurement of the leading edge condition

2018 ◽  
Vol 1037 ◽  
pp. 052011
Author(s):  
C Dollinger ◽  
N Balaresque ◽  
N Gaudern ◽  
M Sorg ◽  
A Fischer
Keyword(s):  
Power Output ◽  
Leading Edge ◽  
Edge Condition ◽  
Output Loss ◽  
Thermographic Measurement

scholarly journals Inlet Air Fogging of Marine Gas Turbine in Power Output Loss Compensation

2015 ◽  
Vol 22 (4) ◽  
pp. 53-58 ◽  
Author(s):  
Zygfryd Domachowski ◽  
Marek Dzida
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Gas Turbines ◽  
Evaporative Cooling ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Output Loss ◽  
Direct Evaporative Cooling ◽  
Loss Compensation ◽  
The World

Abstract The use of inlet air fogging installation to boost the power for gas turbine engines is widely applied in the power generation sector. The application of fogging to mechanical drive is rarely considered in literature [1]. This paper will cover some considerations relating to its application for gas turbines in ship drive. There is an important evaporative cooling potential throughout the world, when the dynamic data is evaluated, based on an analysis of coincident wet and dry bulb information. This data will allow ships’ gas turbine operators to make an assessment of the economics of evaporative fogging. The paper represents an introduction to the methodology and data analysis to derive the direct evaporative cooling potential to be used in marine gas turbine power output loss compensation.

The Effect of the Configuration of the Amplification Device on the Power Output of a Piezoelectric Strip

2012 ◽  
Author(s):  
Jesse M. McCarthy ◽  
Arvind Deivasigamani ◽  
Sabu J. John ◽  
Simon Watkins ◽  
Floreana Coman
Keyword(s):  
Aspect Ratio ◽  
Power Output ◽  
Polyvinylidene Fluoride ◽  
Leading Edge ◽  
Wind Speeds ◽  
Start Up ◽  
Piezoelectric Strip ◽  
Power Measurements ◽  
System 1 ◽  
Leaf Parameters

We investigated the behaviour of a polyvinylidene-fluoride piezoelectric strip (‘stalk’) clamped at the leading edge, and hinged to an amplification device (‘leaf’) at the trailing edge. Flutter of this cantilevered system was induced within smooth, parallel flow, and an AC voltage was generated from the PVDF strip. A polypropylene, triangle comprised the leaf. Two leaf parameters were varied so as to quantify their effect on the power output of the system: 1) the area, and 2) the aspect ratio. It was found that the highest power output was realised with the 2nd-largest leaf across a range of wind speeds, but the variation in power measurements was large. Thus, the 3rd-largest leaf was found to give the highest power output with the lowest power variation. This leaf area was then fixed and the aspect ratio varied. It was found that the largest aspect ratio-leaf rendered the highest power output, but had a relatively high start-up wind speed.

Performance of a High Tip Speed Ratio H-Darrieus in the Skewed Flow on a Roof

2003 ◽  
Author(s):  
Sander Mertens ◽  
Gijs van Kuik ◽  
Gerard van Bussel
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Energy Demand ◽  
Leading Edge ◽  
Spatial Dimension ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Blade Element Theory ◽  
Excess Power ◽  
Flat Roof

Small wind turbines sited on a flat roof have good opportunities to become widespread. They operate in the accelerated wind above the roof and deliver the power where it is needed. Since the power produced offsets that which would otherwise be bought from the utility, they reduce energy demand and bills from the utility. Furthermore excess power can be sold back to the utility, thus producing income as well. Flow over a building separates at the roof leading edge at a certain angle. Wind turbines sited well above the roof thus operate in skewed flow. H-Darrieus operating at (flat) roofs just recently start to be at public interest, operation of an H-Darrieus in skewed flow is thus not discussed in literature until now. To examine this, a model of an H-Darrieus with high Tip Speed Ratio (λ) in skewed flow is developed. The model is based on multiple stream-tube theory: a combination of axial momentum and blade element theory on an actuator plate representation of the rotor, which is divided into multiple stream-tubes. The model shows that, for an H-Darrieus designed for skewed flow, the optimal power output in skewed flow can be up to two times the power output in normal - perpendicular to the H-Darrieus axis- flow. The spatial dimension of the H-Darrieus is responsible for this.

Observation and Discussion of Leading Edge Vortex Shedding From Laboratory-Scaled Cross-Flow Hydrokinetic Turbines in Counter-Rotating Configurations

2021 ◽  
Author(s):  
Minh Doan ◽  
Yuriko Kai ◽  
Takuya Kawata ◽  
Ivan Alayeto ◽  
Shinnosuke Obi
Keyword(s):  
Vortex Shedding ◽  
Power Output ◽  
Turbine Blades ◽  
Cross Flow ◽  
Leading Edge ◽  
Vertical Axis ◽  
Freestream Velocity ◽  
Leading Edge Vortex ◽  
Hydrokinetic Turbines ◽  
Edge Vortex

Abstract In 2011, John Dabiri proposed the use of counter-rotating vertical-axis wind turbines to achieve enhanced power output per unit area of a wind farm. Since then, various studies in the wind energy and marine hydrokinetic (MHK) literature have been dedicated to pairs of vertical axis turbines in both co-rotating and counter-rotating configurations, in terms of their power production, wake characterization, and optimal array design. Previous experimental works suggest an enhancement of up to 27.9% in the system power coefficient of pair configurations compared to a single turbine. Additionally, previous numerical studies have indicated that the increased power output is correlated with higher torque on the turbine blades which correspondingly produces a stronger leading edge vortex. This paper presents an extended investigation into a pair of laboratory scaled cross-flow hydrokinetic turbines in counter-rotating configurations. Experiments were conducted to observe, compare, and discuss the leading edge vortex shedding from the turbine blades during their positive torque phase. The turbines operated in a small water flume at the diameter-based Reynolds number of 22,000 with a 0.316 m/s freestream velocity and 4% turbulent intensity. Using a monoscopic particle image velocimetry setup, multiple realizations of the water flow around each blade at their positive torque phase were recorded and phase-averaged. Results show consistent leading vortex shedding at these turbine angles while a correlation between the turbine power performance and the vortex size and strength was observed.

The aerodynamics of hovering insect flight. VI. Lift and power requirements

1984 ◽  
Vol 305 (1122) ◽  
pp. 145-181 ◽  
Keyword(s):  
Vortex Shedding ◽  
Power Output ◽  
Flight Muscle ◽  
Insect Flight ◽  
Separation Bubble ◽  
Leading Edge ◽  
Mechanical Power ◽  
Mechanical Power Output ◽  
Edge Vortex ◽  
Edge Separation

The lift and power requirements for hovering insect flight are estimated by combining the morphological and kinematic data from papers II and III with the aerodynamic analyses of papers IV and V. The lift calculations are used to evaluate the importance in hovering of two distinct types of aerodynamic mechanisms: (i) the usual quasi-steady mechanism, where the circulation for lift is primarily determined by translation of the wing, and (ii) rotational mechanisms, where the circulation is largely governed by wing rotation at either end of the wingbeat. Power estimates are compared with the available measurements of metabolic rate during hovering to investigate the role of elastic energy storage, the maximum mechanical power output of the flight muscles, and the muscle efficiency. The quasi-steady mechanism proves inadequate for the lift requirements of hover-flies using an inclined stroke plane, and for a ladybird beetle and a crane-fly hovering with a horizontal stroke plane. Observed angles of attack rule out lift enhancement by unsteady modifications to the quasi-steady mechanism, such as delayed stall, but the rotational lift mechanisms proposed in paper IV seem consistent with the kinematics. The rotational mechanisms rely on concentrated vortex shedding from the leading edge during rotation, with attachment of that vorticity as a leading edge separation bubble during the subsequent half-stroke. Strong leading edge vortex shedding should result from delayed pronation for the hover-fly, a near fling and partial fling for the ladybird, and profile flexion for the crane-fly (the flex mechanism). The kinematics for the other insects hovering with a horizontal stroke plane are basically the same as for the anomalous crane-fly, and the quasi-steady mechanism cannot be accepted for them while rejecting it for the crane-fly. All of these insects flex their wings in a similar manner during rotation, and could use the flex mechanism for lift generation. The implication is that most, if not all, hovering animals do not rely on quasi-steady aerodynamics, but use rotational lift mechanisms instead. It is not possible to reconcile the power estimates with the commonly accepted values of both the mechanochemical efficiency of insect flight muscle (about 25%) and its maximum mechanical power output (about 20 W N -1 of muscle). Maximum efficiencies of 12-29% could be obtained only if there is no elastic storage of the kinetic energy of the flapping wings, but this would require more than twice the accepted value for maximum mechanical power output. The available evidence suggests that substantial elastic storage does occur, and that the maximum mechanical power output is close to the accepted value. If so, then the efficiency of both fibrillar and non-fibrillar flight muscle is likely to be only 5-9%.

Study of Aerodynamic Performance and Power Output for Residential-Scale Wind Turbines

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Alaa S. Hasan ◽  
Mohammed Abousabae ◽  
Abdel Rahman Salem ◽  
Ryoichi S. Amano
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Speed Ratio ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine ◽  
Layer Transition ◽  
Baseline Design ◽  
Wind Speeds

Abstract This study presents the rotor blade airfoil analysis of residential-scale wind turbines. On this track, four new airfoils (GOE 447, GOE 446, NACA 6412, and NACA 64(3)-618) characterized by their high lift-to-drag ratios (161.3, 148.7, 142.7, and 136.3, respectively). These new airfoils are used to generate an entire 7 m long blades for three-bladed rotor horizontal axis wind turbine models tested numerically at low, medium, and rated wind speeds of 7.5, 10, and 12.5 m/s, respectively, with a design tip speed ratio of 7. The criterion to judge each model’s performance is power output. Thus, the blades of the model that produce the highest power are selected to undergo a tip modification (winglet) and leading-edge modification (tubercles), seeking power improvement. It is found that the GOE 447 airfoil outperformed the other three airfoils at all tested wind speeds. Thus, it is opted for adding winglets and tubercles. At 12.5 m/s, winglet design produced 5% more power, while tubercles produced 5.5% more power than the GOE 447 baseline design. Furthermore, the computational domain is divided into two regions: rotating (the disc that encloses the rotor) and stationary (the rest of the flow domain). Meanwhile, the numerical model is validated against the experimental velocity measurements. Since Reynolds-averaged Navier–Stokes with k–ω shear stress transport turbulence model can capture the laminar-to-turbulent boundary layer transition, it is used in the 18 simulations of the current work. However, large eddy simulation (LES) can deal successfully with the various scale eddies resulting from the rotor blades and its interactions with the surrounding flow. Thus, the LES was used in the six simulations done at the rated wind speed. LES power output calculation is 7.9% to 11.9% higher than the RANS power output calculation.

A Numerical Study on the Performance Improvement for a Vertical-Axis Wind Turbine at Low Tip-Speed-Ratios

2017 ◽  
Author(s):  
Zhenyu Wang ◽  
Mei Zhuang
Keyword(s):  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbines ◽  
Flow Separation ◽  
Power Output ◽  
Numerical Study ◽  
Leading Edge ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Energy Extraction

Vertical-axis wind turbines (VAWTs) are a promising solution for the use of renewable energy in residential areas. Compared to traditional horizontal-axis wind turbines (HAWTs), VAWTs are usually smaller, quieter, and insensitive to the wind direction and can be installed in a wide range of urban, suburban and rural places such as top of buildings, backyard, etc. In addition, VAWTs require a lower wind speed to self-start which increases the capability of wind energy extraction in the areas with low wind speed. However, VAWTs are less efficient and the power output of VAWTs is substantially affected by the phenomenon of dynamic stall induced by the variations of angle of attack of rotating blades, especially at low tip speed ratios (λTSR<4). When the dynamic stall vortices, formed near the leading-edge, are transported downstream, it creates large and sudden fluctuations in torques. At low values of the tip speed ratio and relatively low Reynolds number (Re<105), dynamic stall occurs periodically throughout the rotation of the blades. This results a sharp drop in lift coefficient and therefore rotor torque and power output are substantially reduced. The purpose of the present study is to investigate the prospects for improving the flow performances of small VAWTs using serrated leading-edge configurations on straight blades in a conventional H-type VAWT design to control dynamic flow separation. A numerical study is carried out to obtain the detailed flow fields for analysis and visualization. The results show that the turbine blade with the serration profiles of h = 0.025c (amplitude) and λs = 0.33c (wavelength) not only increased the power generation at low TSRs, but also enhanced the capability of wind energy extraction at the optimum TSR in comparison to the baseline model. The dynamic stall was suppressed significantly in the range of the azimuth angle from 80° to 160°. The flow separation induced by large angles of attack was essentially alleviated in the modified turbine model due to the serrated configuration implemented on the blade leading-edge.

scholarly journals An Experimental Investigation on Photovoltaic Array Power Output Affected by the Different Partial Shading Conditions

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2344
Author(s):  
Ghoname Abdullah ◽  
Hidekazu Nishimura ◽  
Toshio Fujita
Keyword(s):  
Experimental Investigation ◽  
Power Output ◽  
Maximum Power ◽  
Photovoltaic Module ◽  
Partial Shading ◽  
Output Loss ◽  
Array Configuration ◽  
Photovoltaic Array ◽  
Pv Array ◽  
Current Maximum

This paper presents an experimental investigation on photovoltaic array (PV array) power output affected by partial shading conditions (PSCs). An experiment setup of a PV array with a series configuration using 2 × 4 photovoltaic modules (PV modules) was built. The power output loss due to the shading effect on the first photovoltaic cells (PV cell) connected with bypass diodes of each photovoltaic module, installed in the PV array in the horizontal direction, was evaluated. Depending on the direction of the sun relative to the PV array configuration, the shading percentage was measured during the test and recorded the current and voltage of the PV array. The performance evaluation of the PV array configurations is referred to with respect to the values of maximum power voltage, the maximum power current, maximum power output, power output losses and fill factor (FF). The experimental results show that 44% shading of the first PV cells affects PV array power output loss by more than 80%.

On the Aerodynamic Design of Slender Wings

1959 ◽  
Vol 63 (588) ◽  
pp. 709-721 ◽  
Author(s):  
E. C. Maskell ◽  
J. Weber
Keyword(s):  
Leading Edge ◽  
Velocity Fields ◽  
Rational Approach ◽  
Edge Condition ◽  
Aerodynamic Design ◽  
Trailing Edge ◽  
High Lift ◽  
Boundary Layer Development ◽  
Doubly Curved ◽  
Layer Development

Summary:—Since flow separation occurs readily from a highly swept leading edge, but gives rise in general to a steady flow, it is proposed that the rational approach to the aerodynamic design of slender wings is to attempt to control, rather than to suppress, these separations. This leads to the suggestion that the leading edges should be sharp, and that the wing should be shaped so as to make them attachment lines at one attitude (the design attitude) at which classical wing theory can be applied. It is argued, further, that if the leading edge separations are to develop regularly with change of attitude of the wing, separation must occur only from the trailing edge at the design attitude; and the velocity field favourable to boundary layer development without separation forward of the trailing edge is discussed. Subject to the restrictions thus imposed on the design, low drag is sought at the design attitude. This leads to the consideration of a particular class of doubly curved mean surfaces satisfying the leading edge condition, onto which thickness distributions are superposed so as to provide favourable velocity fields together with low drag. A number of examples are considered, using slender thin wing theory for flexibility, to illustrate the manner in which plan form and thickness distributions affect the pressure distribution, and to indicate the relatively high lift/drag ratios which seem feasible. Some consideration is given to the limitations of the theory used and to the further developments which seem desirable.

scholarly journals Numerical Study of the Dynamic Stall Effect on a Pair of Cross-Flow Hydrokinetic Turbines and Associated Torque Enhancement due to Flow Blockage

2021 ◽  
Vol 9 (8) ◽  
pp. 829
Author(s):  
Minh N. Doan ◽  
Shinnosuke Obi
Keyword(s):  
Power Output ◽  
Numerical Study ◽  
Cross Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Hydrokinetic Turbines ◽  
Hydrokinetic Turbine ◽  
Direction Of Movement

An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could either produce higher torque or create more energy loss. For both of the scenarios where a blade interacted with the channel wall or another blade, the key behind torque enhancement was forcing the flow through its suction side and manipulating the LEV.

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