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The hydrokinetic energy conversion system has capabilities to supply inevitable and secured power which is obtained from free stream like ocean, river, and man-made channel etc. So far, researchers have done different work on resource availability, design parameter, electricity generation cost, reactivity of plant, its impact on environmental separately. In this paper an attempt is made to review the technology, performance, design optimization, reliability, techno-economic analysis and environmental impact of the hydrokinetic energy conversion systems altogether to establish the relationship between the above said aspects towards the viability of power project. After conducting these reviews it has become clear that in order to avoid cavitation, coefficient of pressure should be less than cavitation coefficient especially at leading edge of hydrokinetic turbine blade. Moreover, to avoid stall and separation, angle of attack should be kept as less as possible. By implementing hydrofoil blade profile, performance of the hydrokinetic turbine can be improved. Sometimes, implementation of double blade hydrofoil may be beneficial and increase the coefficient of lift more than that of the single blade hydrofoil. Apart from the above considerations it is to be noted that deployment of turbine near bed level should be avoided as it brings down available power, increase hydrodynamic loading, turbulence level, and fouling by sediments. Moreover to increase the performance arm and end plate can be incorporated in hydrokinetic turbine design. It is also observed that hybrid conversion system is also viable in order to reduce power generation cost. This paper will help researchers to identify areas of design parameter of hydrokinetic turbine that need to improve and encourage the project developer, funding and financial institution, policy maker or government officials, and local community, to provide knowledge about hydrokinetic energy conversion system for executing the project and compete with the existing market. [ABSTRACT FROM AUTHOR]

In order to achieve high aerodynamic efficiency of a turbine stage, it is crucial to identify the source of aerodynamic losses and understand the associated loss generation mechanisms. This helps a turbine designer to maximize the peiformance of the turbine stage. It is well known that aerodynamic losses include profile, endwall, cooling!mixing loss, leakage, and trailing edge loss components. However, it is not a trivial task to separate one from the others because different loss sources occur concurrently and they interact with each other in a machine. Consequently, designers tend to rely on various empirical correlations to get an approximate estimate of each aerodynamic loss contribution. In this study, a systematic loss audit of an uncooled turbine stage has been undertaken by conducting a series of numerical experiments. By comparing entropy growth across the turbine stage, aerodynamic losses are broken down within the stator, rotor, and interblade row gap. Furthermore, losses across each blade row are broken down into profile, leakage, endwall, and trailing edge losses. The effect of unsteady interaction due to the relative motion of the stator and the rotor was also identified. For the examined turbine stage, trailing edge losses of the rotor were dominated, contributing to more than a third of the total aerodynamic loss. The profile loss across the stator and the rotor, unsteady loss between the stator and the rotor, and the stator endwall loss were also identified to be the significant loss sources for this turbine stage. The design implications of the findings are discussed. [ABSTRACT FROM AUTHOR]

Vortex identification techniques are used to analyse the wake of a 4 × 3 array of model wind turbines. The Q-criterion, Δ-criterion, and λ2-criterion are applied to particle image velocimetry data gathered fore and aft of the last row centerline turbine. The Q-criterion and λ2-criterion provide a clear indication of regions where vortical activity exists, while the Δ-criterion is not successful. Galilean decomposition, Reynolds decomposition, vorticity, and swirling strength are used to further understand the location and behaviour of the vortices. The techniques identify and display the high-magnitude vortices in high-shear zones resulting from the blade tips. Using Galilean and Reynolds decomposition, swirling motions are shown encapsuling vortex regions in agreement with the identification criteria. The Galilean decompositions selected are 20% and 50% of a convective velocity of 7 m/s. As the vortices convect downstream, the strength of the vortices decreases in magnitude, particularly in the far wake of the array, to approximately 25% of those present in the near wake. A high level of vortex activity is visualised as a result of the top tip of the wind turbine blade -- the location where the highest vertical entrainment is present. Analysing the full frame set, the Q-criterion, λ2-criterion, and swirling strength prove comparable, while the Δ-criterion under-performs in regions of high turbulence activity, namely in the back of the turbine. Entraining flow into the turbine canopy interacting with the turbine generates high-magnitude vortices concentrated at the blade tips. The count of vortices decreases when moving from the top tip down to the wall, as well as their strength for each Galilean technique when a non-zero threshold is applied. Vortex sizes in the near wake are found comparable to turbine blade, hub, and mast dimensions. In the far wake, the resulting size of the vortices is approximately 30% of those in the near wake. These vortices increase in velocity as they convect downstream, following the mean velocity behaviour. The lowest magnitude vortices reside at the hub height in the near-wake region, where they convect at nearly half the speed of those at the blade tips. [ABSTRACT FROM PUBLISHER]

The current prevailing idea of tidal energy conversion is that it is presumed uneconomical to extract power from tidal flows of less than 2 m/s. As a result, there are a limited number of locations where energy from tidal flows can be exploited worldwide. Increasing the operating range of tidal energy devices to enable the extraction of useful power from low-velocity tidal flows would make tidal energy conversion possible in many more places around the world and greatly increase the potential global generating capacity. This paper presents a novel approach in extracting power from low tidal flows using vertical arrays of reduced diameter turbines. This has the effect of reducing the cut-in speed, increasing the operating range of the tidal energy device as well as the advantage of a lower cost, modular design, which addresses the issue of economical extraction at low flow rates. An assessment of the tidal energy resource around Hong Kong has been conducted for the preliminary stages of an ongoing tidal energy research project. The gathered data have been used to demonstrate the effectiveness of the presented concept in the Hong Kong region and other areas of low-velocity tidal flows. It has been demonstrated that a power increase of 40% is attainable from a vertical array of reduced diameter turbines when compared to a single, large-diameter device with the same frontal area. With the additional advantages of reduced cost of fabrication, installation, and maintenance from using smaller-diameter, modular tidal turbines, the concept is highly important to the advancement of global tidal power generation. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The motion of a fluid around a body of any shape. This phenomenon occurs when there is an area along the contour of the body has a tendency to increase pressure. This effect is felt when rotating turbine rotor. [ABSTRACT FROM AUTHOR]

Sealing air is used in gas turbines to reduce the amount of hot gas that is ingested through the rim seals into the wheel-space between the turbine disk and its adjacent stationary casing. The sealing air attaches itself to the rotor, creating a buffering effect that reduces the amount of ingested fluid that can reach the suiface of the rotor. In this paper, a theoretical model is developed, and this shows that the maximum buffering effect occurs at a critical flow rate of seating air, the value of which depends on the seal geometry. The model, which requires two empirical constants, is validated using experimental data, obtained from infrared (IR) temperature measurements, which are presented in a separate paper. There is good agreement between the adiabatic effectiveness of the rotor estimated from the mode1 and that obtained from the IR measurements. Of particular interest to designers is that significant ingress can enter the wheel-space before its effect is sensed by the rotor. [ABSTRACT FROM AUTHOR]

Cavitation produces undesirable effects within turbines, such as noise, decreases in efficiency, and structural degradation of the device. Two microhydro turbines incorporating Archimedean spiral blade geometries were investigated numerically for cavitation effects using computational fluid dynamics (CFD). Separate blade geometries, one with a uniform blade pitch angle and the other with a 1.5 power pitch, were modeled using the Schnerr-Sauer cavitation model. The method used to determine where cavitation occurs along the blade and within the flow involved vaiying inlet flow rates and the rotation rate of the blade. Cavitation analysis was conducted locally as well as globally, using both cavitation number and Thoma number. The cavitation number was used to correlate the single-phase to the multiphase results for rotation rates o f250 and 500 rpm, allowing for the single-phase simulations to be used to determine where the onset of cavitation occurs. It was determined that cavitation occurred at the exit of the blade at a flow coefficient of approximately 0.33 for the 1.5 pitch blade geometry, while the uniform blade geometry had a value of 1.35. When the rotation rate was reduced to 250 rpm, cavitation occurred at a flow coefficient of 0.72. From the simulations at both rotation rates, it was determined that both geometry and rotation rate have a significant effect on the onset of cavitation and water vapor inception within the flow field. As the rotation rate of the turbine decreases, the onset of cavitation will be prolonged to larger flow coefficients. As the flow coefficient increased beyond the value at which the onset of cavitation occurs, the intensity of cavitation increases and efficiency drops of up to 20% were experienced by the turbines. Based on the net positive suction head required in the system and the available head in the system, the cavitation results were validated. It was determined that the inception cavitation number, Cax, where the onset of cavitation occurs is approximately -1.51. [ABSTRACT FROM AUTHOR]

A comparative experimental and numerical analysis is carried out to assess the aerodynamic performance of a novel partial shroud in a straight turbine cascade. This partial shroud is designed as a combination of winglet and shroud. A plain tip is employed as a baseline case. A pure winglet tip is also studied for comparison. Both experiments and predictions demonstrate that this novel partial shroud configuration has aerodynamic advantages over the pure winglet arrangement. Predicted results show that, relative to the baseline blade with a plain tip, using the partial shroud can lead to a reduction o f20.89% in the mass-averaged total pressure coefficient on the upper half-span of a plane downstream of the cascade trailing edge and 16.53% in the tip leakage mass flow rate, whereas the pure winglet only decreases these two performance parameters by 11.36% and 1.32%, respectively. The flow physics is explored in detail to explain these results via topological analyses. The use of this new partial shroud significantly affects the topological structures and total pressure loss coefficients on various axial cross sections, particularly at the rear part of the blade passage. The partial shroud not only weakens the tip leakage vortex (TLV) but also reduces the strength of passage vortex near the casing (PVC) endwall. Furthermore, three partial shrouds with width-to-pitch ratios of 3%, 5%, and 7% are considered. With an increase in the width of the winglet part, improvements in aerodynamics and the tip leakage mass flow rate are limited. [ABSTRACT FROM AUTHOR]

The turbocharger is the key enabler for energy conservation in Internal Combustion Engine (ICE). A turbine of a turbocharger is fed by highly pulsating flow due to the reciprocating engine, resulting in different behavior from that at steady conditions. This paper investigates the behavior of a mix-flow turbine under pulsating conditions via an analytical model and an in-house developed 1-D unsteady code ONDAS . Firstly, an analytical model of the ‘unsteadiness’ based on the mass flow imbalance is built and the mechanism of the unsteady behavior is discussed in details. Next, a 1-D unsteady model of the turbine under pulsating conditions is established and validated by experimental results. Finally, influence of the frequency, the magnitude and their product on unsteady behavior of the turbine is investigated by the reduced order model for further exploration of the analytical model. The investigation clearly demonstrates the impact of pulsating flow on the unsteady performance and unveils the mechanism of the ‘unsteadiness’ of turbine under pulsating conditions. [ABSTRACT FROM AUTHOR]

Vented attic is a design technique that provides a better solution to reduce solar heat gains trapped in a roof attic. However, its application in the tropical climate is very rare if not, ignored, especially in Malaysian houses. This paper seeks to identify, and compare the performance of attic ventilation by a single hybrid turbine ventilator for a specific volume under both unvented and vented conditions. The study was done in an actual roof attic (10 m3) located in Universiti Sains Malaysia. The results indicate that the reduction of the attic air temperature was 6.4°C, while stabilising the level of relative humidity to about 40–50% which is higher than that for an unvented attic by 10%. Furthermore, the findings reveal that by incorporating a 50 W poly-crystalline solar panel with a turbine ventilator of Ø 45 cm, the peak value of the attic air velocity had exceeded 1.3 m/s when the solar radiation was observed to be around 800 W/m2. [ABSTRACT FROM PUBLISHER]

Well knowing a good-running hydraulic turbine has important operational and financial benefits to those who operate a plant. Fatigue damage is the most fundamental failure type of hydraulic turbines. Existing flaws due to fatigue and their risk limit the operating time of a unit. Some plants have been temporarily shut down for up to a month and sometimes longer to repair these fatigue-induced damage, which has resulted in enormous economic losses. Fatigue problems must be solved or effectively prevented to ensure that turbine units run safely and steadily within their design life. This paper reviews loading features and some key issues (e.g. different load operations, start-up, emergency shut-down, load rejections, and runaway) on the fatigue damage, and provides the latest information about different prediction approaches. At last, it also attempts to present an overview of the complete failure modes, therefore other types of failure including cavitation, erosion and ingested bodies are introduced briefly. [ABSTRACT FROM AUTHOR]

The proliferation of renewable energies in the last decade coupled with their low processing capacity on the grid is bringing old power storage methods back into consideration, as is the case with pumped hydro power plants. In our case, we have taken as a reference an existing dam from which water will be pumped to the reservoir to be constructed, using surplus or off-peak power generated by a nearby wind farm, taking advantage of the potential energy acquired in order to run the turbines at peak times. We therefore want to determine the optimal location of the upper reservoir for it to comply with a number of construction and economic criteria that would make its construction viable. For this, multicriteria analysis methods will be used, assisted by the versatility of geographical information systems. The results obtained have been validated via on site verification based on the authors engineering experience, as well as on their extensive knowledge of the area studied, so that the methodology applied in this study can be extrapolated to other geographic areas, making it a valuable tool. [ABSTRACT FROM AUTHOR]

Large arrays of tidal turbines are critical to realise the potential of tidal current power. This study is a systematic exploration of large tidal array optimisation in channels with numerically modelled array layouts in 2-D. Crucially, flow along channels is driven by head loss leading to significantly more realistic results than previous models which assume constant velocity. The 2-D adaptive mesh approach bridges the gap between large- and small-scale array models. Hundreds of layouts and turbine tunings have been simulated using LES of turbulent flow in tidally reversing currents to explore channel-scale optimisation and tuning of large arrays. Simulations show that total power capture increases as rows are added to the array although there are diminishing returns on additional turbines. Each turbine in 1 (7), optimally blocked row in a small channel captures 2.5 × ( 0.5 × ) the power of an isolated turbine. There is an optimum blockage for maximum power per turbine which decreases linearly from 1.0 as the number of rows increases. As array size increases individual turbine wakes become less important than stepped head loss across each row. Free-stream velocity reduces linearly with total power capture, with the gradient increasing with channel size. [ABSTRACT FROM AUTHOR]

The present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied. [ABSTRACT FROM AUTHOR]

A series of experiments were completed to investigate the interactions between relatively large-scale sediment dunes and axial flow hydrokinetic turbines. Baseline experiments were completed under clear water conditions to assess local scour impacts of single and two-turbine installations. Spatio-temporal measurements of bed elevation were obtained simultaneously with turbine voltage output, from which a measure of the instantaneous rotor angular velocity was used as a proxy for turbine response to unsteady loads. These experiments were completed in a mobile bed of 1.8 mm coarse sand with migrating bedforms. A bedform tracking routine was used to analyze streamwise bed elevation profiles to estimate bedform geometric characteristics and their corresponding impact on turbine performance. Cross-correlation analysis was also performed, investigating critical relationships between approaching bedform crest location, height and the corresponding turbine voltage output. In parallel with the analysis on bedform effects on turbine performance, an extended region downstream of the rotor location was analyzed to investigate how bedform geometric characteristics changed along the channel after turbine deployment. [ABSTRACT FROM AUTHOR]

Turbine components are usually designed onto safe-life approach, where the low-cycle fatigue analysis is based on design life curves with suitable probabilistic life margins. However, in order to design for a given reliability, the definition of the design curve should not only include the life variability but also the scatter of applied load. Unfortunately, in the literature there are few indications which only refer to safety factors under HCF, without any specific discussion for the case of components subjected to LCF. In this paper, we firstly propose a log-normal format for calculating reliability for an assessment point ( ∊ ̂ , N ^ ) based on a first order approximation. The validity of the approach is then proved for two different materials with a series of Monte Carlo simulations, where the material cyclic response is coupled to its ∊ - N diagram. The format is then used for estimating failure probability and for defining the design point which corresponds to a target failure probability. A safety factor is then proposed and its application to a series of steels for power generation is shown. [ABSTRACT FROM AUTHOR]

Our work presents the original mathematical model, which can be determined on the basis of the actual profits from electricity production in pumped storage hydropower plants (PSHP). The derived relationship was obtained by the dimensional analysis of the relevant physical parameters describing the production of energy. The main purpose of this paper is to prove whether a dimensional analysis can be a useful tool to describe the economic aspect of the phenomenon, as proved by its worth when examining technical phenomena. The mathematical model has been derived for PSHP Ružín in Slovakia, but its validity, based on the similarity theory, can be extended to any pumping power plant that works with the influx of water into the upper storage reservoir, and/or without the feed, respectively. The article discusses the effects of various parameters on the operating profit for the turbine operations and the costs associated with the pumping operation. [ABSTRACT FROM AUTHOR]

Automotive turbocharger turbines usually work under pulsating flow because of the sequential nature of engine breathing. However, existing turbine models are typically based on quasi-steady assumptions. In this paper a model where the volute is calculated in a quasi-2D scheme is presented. The objective of this work is to quantify and analyse the effect of the numerical resolution scheme used in the volute model. The conditions imposed upstream are isentropic pressure pulsations with different amplitude and frequency. The volute is computed using a finite volume approach considering the tangential and radial velocity components. The stator and rotor are assumed to be quasi-steady. In this paper, different integration and spatial reconstruction schemes are explored. The spatial reconstruction is based on the MUSCL method with different slope limiters fulfilling the TVD criterion. The model results are assessed against 3D U-RANS calculations. The results show that under low frequency pressure pulses all the schemes lead to similar solutions. But, for high frequency pulsation the results can be very different depending upon the selected scheme. This may have an impact in noise emission predictions. [ABSTRACT FROM AUTHOR]

Welding residual stress relaxation and migration behavior in the welded turbine rotor was studied by using thermal elastic–plastic finite element method under the fatigue and creep loadings. The effect of solid-state phase transformation on the generation of residual stress during welding process was involved. Results reveal that the increase of welding pass number will reduce the peak of residual stress and the width of heat affected zone (HAZ). Under the repeated loadings, the welding residual stress is largely released after the first cycle of start-up and shut-down with a residence time. In addition, such a relaxation mainly depends on the temperature, the initial level of residual stress and the residence time of steady operation. Compared to the contribution of alternating load induced during the start-up and shut-down operation, the relaxation of residual stress is mainly ascribed to the creep mechanism. [ABSTRACT FROM AUTHOR]

This paper presents a study of low-profile vortex generators flow control on the effect of casing boundary layer separation in an aggressive inter-turbine duct. Counter-rotating and co-rotating vortex generators configurations were tested parametrically to obtain the optimum low-profile vortex generators’ setup within the aggressive inter-turbine duct, in terms of the axial location, height, angle of attack and streamwise vortices per swirl vane pitch. Surface oil flow visualization was used to qualitatively examine the low-profile vortex generators eliminating the casing separation and subsequently the detailed seven-hole probe measurements were carried out to evaluate the loss reduction quantitatively. The inter-turbine duct examined for this study was more aggressive compared with the geometries found in the most current modern engine designs. Measurements were made inside the aggressive inter-turbine duct annulus at Reynolds number of 150,000. The flow structures within the aggressive inter-turbine duct were found to be dominated by counter-rotating vortices evolved by the swirl vanes and boundary layer separation in both casing and hub regions. A massive casing boundary layer separation extending from the duct first bend to the second bend was found within the aggressive inter-turbine duct. The primary source of pressure loss in the aggressive inter-turbine ducts was the result of the extensive casing boundary layer separation. Flow control by utilizing the low-profile vortex generators installed on the casing was conducted to eliminate the casing separation. Regardless of the vortex generator mitigating the casing separation associated with consequential loss reduction, a pair of casing counter-rotating vortices was always evident at the duct second bend in all cases. Among the tested low-profile vortex generator configurations, two of the most effective low-profile vortex generator configurations, one counter-rotating and one co-rotating low-profile vortex generator configurations, were acquired as a result of successfully eliminating the casing separation. Despite that the inter-turbine duct is aggressively designed, it is concluded that this duct associated with proper flow control techniques is considered as a potential candidate for weight saving in a high bypass ratio engine. [ABSTRACT FROM AUTHOR]

A centrifugal prototype turbine used in a supercritical CO2-based solar Rankine cycle system (SRCS) is proposed and investigated by both experimental and analytical methods. The basic operation of the turbine is checked, and its performance is also systematically analyzed based on the CO2 mass flow rate and temperature at the outlet of turbine, its rotational speed, and output torque. In addition, the choking phenomenon of the flow in the nozzle is also investigated when the inner diameter of nozzle in the turbine is increased from 0.5 to 1.0 mm. The results show that the choked flow does not occur, and the CO2 flow can go smoothly in the nozzle when the inner diameter is bigger than 0.7 mm. It is also found that the turbine output torques related with electric power generation increase with the increase of inner diameter of nozzle. Present study reveals that current turbine provides a well performance for this SRCS and is helpful for the further development of solar thermal-energy technologies. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Two-dimensional thermal profiles were experimentally measured downstream of a single row of film cooling holes on both an adiabatic and a matched Biot number model turbine vane. The measurements were taken as a comparison to computational simulations of the same model and flow conditions. Previously, adiabatic and overall effectiveness comparisons have been made between experimental and computational data. To improve computational models of the evolution of a film cooling jet as it propagates downstream, the thermal field above the vane, not just the footprint on the vane surface, must be analyzed. This study expands these data to include 2D thermal fields above the vane at 0, 5, and 10 hole diameters downstream of the film cooling holes. Four blowing ratios were tested, M = 0.28, 0.65, 1.11, and 2.41. In each case, the computational jets remained colder than the experimental jets because they did not diffuse into the mainstream as quickly. In addition, the computational results for the higher two blowing ratios exhibited the effects of the kidney vortex commonly studied in film cooling, but the experimental thermal fields were not dominated by this vortex. Finally, in comparing results above adiabatic and matched Biot number models, these thermal fields allow for an accurate analysis of whether or not the adiabatic wall temperature was a reasonable estimate of the driving temperature for heat transfer. [ABSTRACT FROM AUTHOR]

There have been numerous studies of the behavior of shaped film cooling holes for turbine applications. It is known that the introduction of coolant is an unsteady process, and a handful of studies have described and characterized the unsteadiness. To the best of our knowledge, there are no studies in which unsteady acoustic effects have been actively exploited such that they have led to novel designs with improved cooling performance. This paper discusses the fundamental mechanism of pressure wave propagation through cooling holes and describes systems in which holes which have been acoustically shaped have led to a direct improvement in film cooling hole performance. The mechanism relies on sequential pressure wave reflection within an acoustically shaped hole and is therefore applicable in regions where the external surface is subject to large pressure wave fluctuations at high frequency. The principle is developed analytically, and then demonstrated with a number of computational fluid dynamics (CFD) simulations. We demonstrate that a desired temporal mass flow rate profile can be achieved by appropriate acoustic shaping of the cooling hole. The purpose of this paper is to describe the fundamental design considerations relevant to acoustic shaping. The discussion is developed with reference to a film cooling system for the over-tip region of an unshrouded rotor. The performance benefit of the system in terms of modulation of unsteady mass flux and ingestion characteristics is quantified. It is believed that this is the first time this significant effect has been exploited in film cooling design. [ABSTRACT FROM AUTHOR]

This paper proposes a new auxiliary turbine torsional oscillation damping controller (TTODC) for static var compensator (SVC) to dampen out subsynchronous oscillations in power systems containing series compensated transmission lines. A new TTODC algorithm on the basis of synchronized pliasor measurements received from phasor measurement units (PMUs) is presented. The idea of using remote signals obtained from PMU to dampen subsynchronous resonance (SSR) presented, too. An auxiliary TTODC is proposed for a SVC, using the generator rotor speed deviation signal as the stabilizing and remote signal to dampen subsynchronous oscillations. The performance of the controller is verified in a detailed nonlinear system considering eigenvalue analysis and transient simulations. Sturdiness of the controller is examined by applying the disturbances in the system that causes significant changes in generator's operating point. The IEEE second benchmark (SBM) model is used for the analysis and the SVC is simulated using the power system blockset (PSB) in the matlabIsimulink environment. [ABSTRACT FROM AUTHOR]

The performance of horizontal axis tidal current turbines (HATCT) strongly depends on their geometry. According to this fact, the optimum performance will be achieved by optimized geometry. In this research study, the multi objective optimization of the HATCT is carried out by using four different multi objective optimization algorithms and their performance is evaluated in combination with blade element momentum theory (BEM). The second version of non-dominated sorting genetic algorithm (NSGA-II), multi objective particle swarm optimization algorithm (MOPSO), multi objective cuckoo search algorithm (MOCS) and multi objective flower pollination algorithm (MOFPA) are the selected algorithms. The power coefficient and the produced torque on stationary blade are selected as objective functions and chord and twist distributions along the blade span are selected as decision variables. These algorithms are combined with the blade element momentum (BEM) theory for the purpose of achieving the best Pareto front. The obtained Pareto fronts are compared with each other. Different sets of experiments are carried out by considering different numbers of iterations, population size and tip speed ratios. The Pareto fronts which are achieved by MOFPA and NSGA-II have better quality in comparison to MOCS and MOPSO, but on the other hand a detail comparison between the first fronts of MOFPA and NSGA-II indicated that MOFPA algorithm can obtain the best Pareto front and can maximize the power coefficient up to 4.3% and the produced torque on stationary blade up to 57.9%. The geometries of the first and last members of the Pareto front of MOFPA are compared to each other. These members which produce the maximum power coefficient and the maximum produced torque on stationary blade have hyperbolic and constant chord distributions, respectively. [ABSTRACT FROM AUTHOR]

MPC is a computer based technique that requires the process model to anticipate the future outputs of that process. An optimal control action is taken by MPC based on this prediction. The MPC is so popular since its control performance has been reported to be best among other conventional techniques to control the multivariable dynamical plants with various inputs and outputs constraints. In the present work the control of boiler turbine process with three manipulated variables namely fuel flow valve position, steam control valve position and feed water flow valve position and three controlled variables namely drum pressure, output power and drum water level deviation has been attempted using MPC technique. Boiler turbine process is very complex and nonlinear multivariable process. A linearized model obtained using Taylor series expansion around operating point has been used. [ABSTRACT FROM AUTHOR]

To study accurately the influence of the deformation, stress, and strain of turbine blisk on the performance of aeroengine, the comprehensive reliability analysis of turbine blisk with multiple disciplines and multiple objects was performed based on multiple response surface method (MRSM) and fluid-thermal-solid coupling technique. Firstly, the basic thought of MRSM was introduced. And then the mathematical model of MRSM was established with quadratic polynomial. Finally, the multiple reliability analyses of deformation, stress, and strain of turbine blisk were completed under multiphysical field coupling by the MRSM, and the comprehensive performance of turbine blisk was evaluated. From the reliability analysis, it is demonstrated that the reliability degrees of the deformation, stress, and strain for turbine blisk are 0.9942, 0.9935, 0.9954, and 0.9919, respectively, when the allowable deformation, stress, and strain are 3.7 × 10−3 m, 1.07 × 109 Pa, and 1.12 × 10−2 m/m, respectively; besides, the comprehensive reliability degree of turbine blisk is 0.9919, which basically satisfies the engineering requirement of aeroengine. The efforts of this paper provide a promising approach method for multidiscipline multiobject reliability analysis. [ABSTRACT FROM AUTHOR]

A variant of the combination of an NPP with a continually operating low-capacity additional steam turbine is proposed and analyzed. In the event of an accident with total blackout, the proposed setup makes it possible to supply electricity to first- and second-category consumers and circulation pumps. In addition, the residual heat released is used to maintain the require power of the additional turbine. A probabilistic safety evaluation of an NPP combined with an additional continually operating steam turbine is presented. The proposed setup makes it possible to increase considerably the reliability of the electricity supply in emergency situations associated with a blackout and reduce the probability of accidents in which the core is damaged. [ABSTRACT FROM AUTHOR]

The performance-enhancing effects of closely packing tidal turbines in single row arrays (tidal fences) are evaluated in this computational study. Infinitely long tidal fences are simulated with a range of lateral rotor spacings using a blade element momentum method embedded in a Reynolds averaged Navier–Stokes solver (RANS-BEM). First, a rotor design tool is applied to determine a hydrodynamically optimal rotor design for each lateral spacing. In the RANS-BEM method, the effect of blockage (the ratio of rotor swept area to channel cross-sectional area) on rotor optimization is accounted for. Increased blockage is found to result in increased optimal solidity and decreased optimal pitch. Next, each rotor design is simulated in its design spacing as well as several off-design spacings. The resulting power coefficient is largest when the rotor optimized for the highest blockage case operates in the array with the closest lateral spacing. Further, although a rotor's performance is improved through operation at a blockage higher than its design point, it still exhibits inferior performance relative to a rotor designed for that higher blockage. The results indicate that blockage must be considered in the rotor design process if the optimal rotor efficiency for a given spacing is to be achieved. [ABSTRACT FROM AUTHOR]

This paper is the second part of a two-part paper reporting on the increase in efficiency of a 1.5 stage axial test rig turbine with the use of nonaxisymmetric endwalls and 3D airfoil design. Contoured endwalls were developed for the inlet guide vane separately, as well as in combination with a bowed radial profile stacking. In addition, a contour endwall was applied to the hub of the unshrouded rotor. In Part I, the design of the profiled endwalls and 3D airfoils is presented, as well as a detailed analysis of the steady and unsteady computational fluid dynamics (CFD) results. Part II reports on the experimental validation of the numerical results. A distinct increase in mechanical efficiency for both new configurations in good agreement with the numerical results is observed. Additionally, performance map measurements demonstrate that the new designs are also beneficial under off-design conditions. Five- and three-hole-probes as well as fast-response total pressure probes are used to investigate the new designs. The main effect is the homogenization of the yaw angle behind the first stator. [ABSTRACT FROM AUTHOR]

This paper presents the results of the analysis of different 3D designs for the first stator and the rotor of a 1.5-stage turbine test rig. A tangential endwall contouring for the hub and the shroud, a bowed profile stacking, and a combination of those have been designed for the first stator. In addition, a tangential endwall contouring has been designed for the hub of the unshrouded rotor. Part I of this two-part paper deals with the design process and the numerical analysis of the results. All designs have been optimized using the stage efficiency as target function. For the design of the 3D stator vanes, the optimization led to an unexpected result: The secondary flow vortex strength increased. However, the secondary flow pattern is rearranged by the 3D-designing, leading to a smoother radial exit flow angle distribution. A subsequent reduction of the rotor losses overcompensates the higher stator losses. In order to understand how the 3D vanes affect the stator secondary flow pattern, a detailed analysis of vortex stretching and vortex dissipation is presented in this paper. With this approach, the various impacts of the 3D designs on the secondary flow vortices' strength can be quantified. In addition, the potential theory effect of the self-induced velocity is introduced here in order to explain the effects of a tangential endwall contouring on the trajectory of the pressure side leg of the horseshoe vortex (HVps). To the best of our knowledge, both approaches are new for the analysis of turbine secondary flows. The impact of the stronger but rearranged stator secondaiy flow on the rotor secondaiy loss development is analyzed by means of unsteady simulations. The results show that the rotor secondary flow can be effectively reduced through a proper stator secondaiy flow pattern. In Part II of this paper, the analysis of extensive experimental results validates and supplements the numerical analysis. [ABSTRACT FROM AUTHOR]

The article focuses on the use of natural gas for electric power generation as well as needed research and development to further improve existing natural gas combustion turbine technology. Topics discussed include the demand for natural gas-based electricity in 2013 according to the U.S. Energy Information Administration, factors that will influence the use of natural gas for electric power generation and the state of natural gas turbine technology in 2015.

Delaying a stall improves the performance of any turbomachinery system. TC (tip clearance), which is used in a bi-directional flow Wells turbine of an ocean wave energy device, changes the flow pattern on the turbine blade suction surface, while changing or modifying the TC zone can help obtaining a delayed stall. In the present work, a new tip grooving scheme is introduced and the performance is compared for different tip groove depths and TCs of a Wells turbine. The performance is defined in terms of wider operating range or stall delay, power production and efficiency. The problem was solved by a numerical analysis technique. A multi-block meshing scheme was employed to generate structured and hexahedral elements in the computational domain and the flow was solved in ANSYS CFX ® v14.5 by solving Reynolds-averaged Navier Stokes equations. It was found that the grooves improve the turbine operating range and power production as compared to those of the turbine without a groove. The groove depth of 3% of the chord length produced highest power and widest operating range. Using the circumferential groove, 26% increase in turbine power output for a particular operating point is achieved. [ABSTRACT FROM AUTHOR]

This work presents an efficient methodology for the Reliability Based Design Optimization (RBDO) of the tripod sub-structure of offshore wind turbines considering dynamic response requirements. The cost of supporting structure of offshore wind turbines is so high that optimization in the design stage is a basic requirement. Traditional design optimization methodology for offshore structures uses deterministic modeling. However, the existence of uncertainties, such as manufacturing tolerances, material properties, and environmental loads, requires a probabilistic optimization technique. Uncertainties in the offshore wind turbines design process may have a strong effect on its dynamic responses but very little researches have been conducted to incorporate the uncertainty property into design optimization of the supporting structures. In this study, a framework of a dynamic reliability based design optimization for tripod sub-structures was proposed. Firstly, a Finite Element (FE) model of a tripod sub-structure of the NERL 5 MW wind turbine was constructed for dynamic response analysis in time domain and generating several accurate sampling points. Secondly, an efficient approximate model was built utilizing these sampling points to replace the original time consuming dynamic response analysis of FE model. At last, this approximate model was used during the optimum iterative procedure with a global optimization algorithm to gain the final best design point considering uncertainties. In this optimization methodology, some sizes of structural components, applied loads, and some material properties are considered as random variables. The structural stress and natural frequency are considered as constraints and the weight of the structure is considered as the objective function. The reliability of the structure is finally determined through Monte Carlo simulations. The results show that the proposed methodology can obtain a reliable design with better dynamic performance and less weight. Compared with the deterministic optimization, the presented dynamic Reliability Based Design Optimization of tripod sub-structure of offshore wind turbines is more rational and practical and this efficient methodology can be applied in the design of other similar offshore structures. [ABSTRACT FROM AUTHOR]

A multistage vaneless counter-rotating turbine (MVCRT) eliminates vanes between rotors, which reduces the weight and size of the turbine and avoids viscous losses associated with vanes pronouncedly. An aircraft engine employing such a turbine would have greater thrust to weight ratio and smaller specific fuel consumption. This paper presents the aerodynamic design philosophy and performance analysis of the MVCRTs for gas turbine engines by a case study. The case is about a 1/2*4 turbine, which consists of a rotating frame and four rotors without any vanes between them. The first rotor and the third rotor are connected by a shaft to drive a compressor with a pressure ratio of 11.8, and the second rotor and the fourth rotor are connected by the rotating frame to deliver a total shaft power of around 2 MW. The stage loading of each rotor and flow axial acceleration of each duct are controlled to provide sufficient inlet swirls for their subsequent rotors. The stage work coefficients of each rotor are 0.95, 2.9, 1.4, and 1.0, respectively. Nonuniform radial circulation distributions are also used to maximize the turbine power output. Centrifuged forces in the outer rotor of the turbine are captured by carrying out a finite element analysis (FEA) to validate the aerodynamic design results. Threedimensional viscous numerical results show that an adiabatic total-to-total efficiency of 91.47% with a pressure ratio of 9.8 at design condition is obtained and achieves the initial design objective very well. Entropy creation associated with the tip leakage and secondary flow is also illustrated for understanding the origins and effects of losses in the turbine. Pressure ratios and efficiency at the speed combinations of the 80% to 100% inner and outer rotor design speeds are discussed to reveal the turbine characteristics at off-design conditions. [ABSTRACT FROM AUTHOR]

Cooling of turbine components that come in contact with the hot gases strongly affects the turbine's efficiency and service life. Designing effective and efficient cooling configurations requires detailed understanding on how geometry and operating conditions affect the way coolant cools the turbine materials. Experimental measurements that can reveal such information are difficult and costly to obtain because gas turbines operate at high temperatures (up to 2000 K), high pressures (30+ bar), and the dimensions of many key features in the cooling configurations are small (millimeters or smaller). This paper presents a method that enables experiments to be conducted at near room temperatures, near atmospheric pressures, and using scaled-up geometries to reveal the temperature and heat-flux distributions within turbine materials as if the experiments were conducted under engine operating conditions. The method is demonstrated by performing conjugate computational fluid dynamics (CFD) analyses on two test problems. Both problems involve a thermal barrier coating (TBC)-coated flat plate exposed to a hot-gas environment on one side and coolant flow on the other. In one problem, the heat transfer on the coolant side is enhanced by inclined ribs. In the other, it is enhanced by an array of pin fins. This conjugate CFD study is based on 3D steady Reynolds-averaged Navier-Stokes (RANS) closed by the shear-stress-transport turbulence model for the fluid phase and the Fourier law for the solid phase. Results obtained show that, of the dimensionless parameters that are important to this problem, it is the Biot number that dominates. This study also shows that for two geometrically similar configurations, if the Biot number distributions on the corresponding hot-gas and coolant sides are nearly matched, then the magnitude and contours of the nondimensional temperature and heat-flux distributions in the material will be nearly the same for the two configurations--even though the operating temperatures and pressures differ considerably. Thus, experimental measurements of temperature and heat-flux distributions within turbine materials that are obtained under "laboratory" conditions could be scaled up to provide meaningful results under "engine" relevant conditions. [ABSTRACT FROM AUTHOR]

The article discusses two issues relating to the clocking phenomenon in turbines, which are the physical course of stator wake deformation in rotor passages and its further interaction with downstream stator blades, and turbine geometry parameters which are believed to be most favourable for clocking. In both cases, the results presented in the article have made it possible to verify and reformulate the previously accepted opinions. [ABSTRACT FROM AUTHOR]

This work proposes the optimum gamma ray shield thickness around the HPLWR high pressure turbine for different occupancy periods in the turbine building. Monte Carlo method was employed in the design process and only radioactive nitrogen-16 was considered as the source of radiation. Five grades of concrete (ordinary, magnetite, heavy magnetite, steel magnetite and barite) were used as shielding materials. The isotope source term in the high pressure turbine was estimated by modeling the HPLWR three pass core in MCNP and tracking the inventory using a simple algorithm. The high pressure turbine was thereafter modeled in MCNP with a concrete shield arrayed in layers around it. The surface flux tally and ICRP74 dose conversion coefficients were employed to estimate the dose profile across the shield. For some shielding materials, exponential functions were fitted on the calculated data to extrapolate dose values beyond the model thickness. The optimum shield thickness was determined by comparing the calculated dose profiles with dose limit proposals in the IAEA standard (NS-G-1.13) on radiation protection considerations during nuclear power plant design. It was observed that with a 120 cm thick heavy concrete shield, the turbine building would be safe for most occupancy periods. However for ordinary concrete the shield would require some extension to guarantee safety. For very long occupancy (more than 10 person hours per week), magnetite shield may also require slight extension. It can therefore be concluded that the shield thickness recommended for BWR turbines (which operate on a direct cycle like HPLWR) could be sufficient for HPLWR if high density concretes are used. [ABSTRACT FROM AUTHOR]

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular, understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a three-dimensional (3D) airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed Reynolds-Averaged Navier-Stokes (RANS) solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane (NGV) row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by vaiying the mass flow through the turbine: measurements at the design point (ReCax = 7.2 x 105) and at a reduced mass flow rate (ReCax = 5.2 x 105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage. [ABSTRACT FROM AUTHOR]

A novel modular pumped-storage scheme is investigated that uses elevated water storage towers and cement pools as the upper and lower reservoirs. The scheme serves a second purpose as part of the wastewater treatment process, providing multiple benefits besides energy storage. A small pumped-storage scheme has been shown to be a competitive energy storage solution for micro renewable energy grids; however, pumped-storage schemes have not been implemented on scales smaller than megawatts. Off-the-shelf runner designs are not available for modular pumped-storage schemes, so a custom runner design is sought. A preliminary hydraulic design for a pump-turbine runner is examined and optimized for increased pumping hydraulic efficiency using a response surface optimization methodology. The hydraulic pumping efficiency was found to have improved by 1.06% at the best efficiency point, while turbine hydraulic efficiency decreased by 0.70% at the turbine best efficiency point. The round-trip efficiency for the system was estimated to be about 78%, which is comparable to larger pumped-storage schemes currently in operation. [ABSTRACT FROM AUTHOR]

New turbine engine designs requiring secondary flow compression often look to dual flow-path integrally bladed rotors (DFIBRs) since these stages have the ability to perform work on the secondary, or bypassed, flow-field. While analogous to traditional integrally bladed rotor stages, DFIBR designs have many differences that result in unique dynamic response characteristics that must be understood to avoid fatigue. This work investigates these characteristics using reduced-order models (ROMs) that incorporate mistuning through perturbations to blade frequencies. This work provides an alternative to computationally intensive geometric-mistuning approaches for DFIBRs by utilizing tuned blade mode reductions and substructure coupling in cyclic coordinates. Free and forced response results are compared to full finite element model (FEM) solutions to determine if any errors are related to the reduced-order model formulation reduction methods. It is shown that DFIBRs have many more frequency veering regions than their single flow-path integrally blade rotor (IBR) counterparts. Modal families are shown to transition between system, inner-blade, and outer-blade motion. Furthermore, findings illustrate that while mode localization of traditional IBRs is limited to a single or small subset of blades, DFIBRs can have modal energy localized to either an inner- or outer-blade set resulting in many blades responding above tuned levels. Lastly, ROM forced response predictions compare well to full FEM predictions for the two test cases shown. [ABSTRACT FROM AUTHOR]

There are two popular practical models of synchronous generators used in power system simulation, both based on Park equations, defined as assumedAand assumedBrespectively, according to the different assumptions. To study the influence of the different models on the first swing stability calculation precision, the physical essence of the two assumptions are revealed in theory, and it is obtained that assumedAtakes account of the mutual leakage flux linkage between field and damping windings and neglects the self-leakage flux linkage of damping winding, the opposite of assumedB. Taking a 300-MW turbine generator as an example, first swing stability limits calculated by two practical models are compared; simulation results are verified by the time-step finite-element model. The influence of line reactance and excitation system on first swing stability limits is studied. Results show that the first swing stability limit calculated by the practical model with assumedAis closer to the result of the time-step finite-element model, since assumedAtakes account of the larger mutual leakage flux linkage. Therefore, the practical model with assumedAis more accurate. The result provides reasonable reference to select synchronous generator models in power system simulation. [ABSTRACT FROM PUBLISHER]

This paper discusses tidal, ocean, and river free turbine functional design parameters and general considerations associated with tidal field developments. A particular focus is on the importance of considering mechanical fatigue and the associated calculation method when designing a turbine for the challenging hydrodynamic environment. The balance between high-fatigue resistances, costs associated with designing components, and potential for reduced turbine efficiency is discussed in regards to the potential energy extracted from a field site. A novel flexible foil vertical turbine concept with high-fatigue resistance, and simple installation and retrieval methods is shown to have a low kWh cost per production output compared to other hydrodynamic turbine concepts. Three possible field development concepts for the flexible foil turbine are described herein for river, ocean current, and tidal applications. [ABSTRACT FROM AUTHOR]

Hydraulic motor are increasingly used in various types of drives. An important feature is the torque. It is therefore necessary to be able to calculate in advance that torque from the beginning of design of the hydraulic motor. This article gives a chart analytical methodology for finding this one. [ABSTRACT FROM AUTHOR]

Successful, efficient turbine design requires a thorough understanding of the underlying physical phenomena. This paper investigates the flutter phenomenon of low pressure turbine (LPT) blades seen in aircraft engines and power turbines. Computational fluid dynamics (CFD) analysis will be conducted in a two-dimensional (2D) sense using a frequency domain Reynolds-averaged Navier--Stokes (RANS) solver on a publicly available LPT airfoil geometry: École Polytechnique Fédérale De Lausanne (EPFL's) Standard Configuration 4. An emphasis is placed on revealing the underlying physics behind the threatening LPT flutter mechanism. To this end, flutter sensitivity analysis is conducted on three key parameters: reduced frequency, mode shape, and Mach number. Additionally, exact 2D acoustic resonance interblade phase angles (IBPAs) are analytically predicted as a function of reduced frequency. Made evident via damping versus IBPA plots, the CFD model successfully captures the theoretical acoustic resonance predictions. Studies of the decay of unsteady aerodynamic influence coefficients away from a reference blade are also presented. The influence coefficients provide key insights to the harmonic content of the unsteady pressure field. Finally, this work explores methods of normalizing the work per cycle by the exit dynamic pressure. [ABSTRACT FROM AUTHOR]

The trend towards ultra compact thermal power generation, is constrained by the unavailability of fluid-machinery adequate for supersonic flow conditions. Conventional turbine designs exhibit unacceptable performances related to large aerodynamic losses and a narrow operation range. This paper provides for the first time in the open literature the design procedure, and subsequent analysis of the turbine performance of a turbine adequate for supersonic axial pulsating flows, as those encountered in innovative combustors. The design approach considers the most adverse condition, a steady inlet axial Mach number equal to 3.5. The possible turbine families were classified by the velocity triangles and discussed. A fundamental issue in supersonic passages is to ensure the normal shock at the start of the engine is swallowed through the turbine passages, namely the turbine passage is started. To ensure self-starting capability the turning is restricted to lower values than in the conventional subsonic turbines. The design procedure was based on the method of characteristics, converting the inlet uniform flow into a vortex flow field, such that the adequate deflection is inflicted to the supersonic flow. The performance of the supersonic passage was first assessed and then compared to conventional designs. The present design procedure and analysis of unconventional supersonic turbines provides guidelines for the design and optimization of efficient high supersonic passages, suitable to future tightly packed fluid machinery. [ABSTRACT FROM AUTHOR]