•Automated grid generation and actuator disk model for ducted wind turbines.•Design of Experiment analysis of the duct thickness, camber, chord and stagger.•All factors positively contribute to the ...power coefficient (maximum value 0.953).•Stagger, chord and camber are significant factors; the thickness is less significant.•The optimum design is also the most robust to the variation of the tip speed ratio.
Since the 1930s ducted-wind-turbines have received considerable attention due to the possibility of obtaining a significant increase in the extracted power compared to an open turbine with the same rotor swept area. The incomplete knowledge of the flow phenomena occurring in these devices and the large design-space to be explored generally hampers the development of an effective and robust design-procedure. This work investigates the performance of ducted wind turbines through a fully automated analysis procedure based on a Computational-Fluid-Dynamics-Actuator-Disk approach. The method duly takes into account the effects of the design parameters, the rotor-duct coupling, the wake rotation and expansion, and the spanwise variability of the rotor load. A Design-of-Experiment analysis is carried out to quantify the impact of the change of all geometric parameters and their mutual interactions. The latter explicitly account for the simultaneous variation of all design parameters. As such, it is a powerful pre-design tool that allows to reduce and confine the design space. It is found that the chord and stagger angle of the duct contribute more than 85% to the improvements of the turbine performance, while the effects of the thickness are negligible. Finally, the sensitiveness of the performance to the variation of the operating conditions is also analysed revealing that the optimal configuration is also the most robust.
This book tells the story of the power generation gas turbine from the perspective of one of the leading companies in the field over a period of nearly 100 years, written by an engineer. Especially ...in times of imminent global economic crises it appears to be worthwhile to reflect on real economic values based on engineering ingenuity and enduring management of technological leadership.
A thermal diagram of the combined gas-steam turbine unit of a hybrid cycle, which is an energy complex consisting of a base gas turbine engine with a steam turbine heat recovery circuit and a ...steam-injected gas turbine operating with overexpansion, is proposed. A mathematical model of a power plant has been developed, taking into consideration the features of thermodynamic processes of simple, binary, and steam-injected gas–steam cycles. Thermodynamic investigations and optimization of the parameters of a combined installation of a hybrid cycle for the generation of electrical energy have been carried out. Three-dimensional calculations of the combustion chamber of a steam-injected gas turbine were carried out, which confirmed the low emissions of the main toxic components.
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•A deflector optimal design via a modified Taguchi approach is developed.•The influential extents of design factors are analyzed by analysis of variance.•The VAWT with the optimized ...upper deflector can improve performance by 20%.•The VAWT with the optimized lower deflector can improve performance by 17%.•The optimal combinations of factors are accurately predicted by the modified model.
This study designs a deflector to enhance the performance of a three-bladed vertical axis wind turbine (VAWT) through the Taguchi method in association with a modified additive model (MAM). Two types of the deflector, namely, an upper deflector and a lower deflector, are individually considered. Analysis of variance (ANOVA) is applied to evaluate the influences of design factors on the performance, and the aerodynamic characteristics around the turbine blades are explored. The prediction suggests that the average power coefficients (Cp-) of the VAWT without deflector is 0.46. For the upper deflector design, the Cp- value using MAM can be raised to the highest value of 0.55, while the Cp- value for the lower deflector design is lifted to 0.54, accounting for 20% and 17% improvements compared with the VAWT without a deflector. The application of MAM shows that the distances from the center of the turbine to the bottom of the upper deflector and the top of the lower deflector are the most important factors to influence Cp-, and the interaction between the factors should be considered to provide accurate optimization results. The results of the ANOVA analysis are coincident with those of the Taguchi approach and confirm that a proper installation of a deflector can efficiently intensify the VAWT’s performance.
The aerodynamic interaction of vertical axis wind turbines in several array configurations was studied by conducting a series of wind tunnel measurements. Four configurations of two- and ...three-turbine arrays were tested and their results were compared with that of the isolated reference case. Two pairs of counter-rotating and co-rotating vertical axis wind turbines were tested where the free-stream wind was perpendicular to the two side-by-side turbines. The counter-rotating configuration resulted in a slight improvement in the aerodynamic performance of each turbine compared to the isolated case, while the co-rotating installation caused a slight performance reduction of turbines at some free-stream velocities. Several measurements were also performed for three-turbine arrays with different spacing where a vertical axis wind turbine was operating downstream of a counter-rotating pair, perpendicular to the free-stream wind. An enhancement in the aerodynamic performance of the downstream turbine was observed in almost all arrays and at most tested wind speeds. For the array spacing studied, the optimum range of the streamwise distance of the downstream turbine from the counter-rotating pair and the spacing between the pair was determined to be about three and one rotor diameters, respectively.
•Counter-rotating VAWTs have higher performance than the sum of the isolated turbines.•A counter-rotating pair of VAWTs increased the power output of a downstream turbine.•The optimum streamwise distance of a downstream turbine is three rotor diameters.•The optimum spacing between a counter-rotating pair of VAWTs is one rotor diameter.
•Presenting a new method to the off-design analysis of gas turbine engines.•In-depth understanding of the performance of the gas turbines and their components.•Introducing a comprehensive tool to ...perform the off-design calculations.•Off-design performance analysis of a micro-turbojet and a double-shaft gas turbine.•Use of a micro aero-derivative gas turbine as a driver of a compressor test rig.
This paper presents a new method to formulate the problem of simulating and off-design performance analysis of gas turbine engines and organizing this problem to solve. This method, without any simplification, follows an identical procedure for off-design analysis of all configurations of gas turbines. The method is based on solving an equations system, modular and flexible, and requires the least user experience. Details on the formulation of characteristic and compatibility equations and subsequently formation and details on solving the equations system were presented. The performance of the Olympus-HP micro turbojet engine was obtained from this method validated against test rig and manufacturer results. As an application, the off-design performance of a double-shaft gas turbine was investigated, which is configured from the Olympus-HP core and power turbines that are corresponding to the loads. A centrifugal compressor and a fan with 45 kW consuming power with different design speeds were utilized as the load. The running line and power map of the double-shaft engine were shown. The effects of the environmental changes on the engine performance evaluated. This engine will be used as a driver of a test rig facility of centrifugal compressors of micro gas turbines (MGTs).
•Aeromechanic performance of a downwind turbine was investigated experimentally.•The performance of a downwind turbine was compared with that of an upwind turbine.•Downwind turbine generates a ...slightly lower power than that of an upwind turbine.•Downwind turbine experiences a much higher fatigue loads due to tower shadow effect.
Traditional horizontal-axis wind turbines are mainly designed as upwind configuration. In order to avoid blade strikes, the rotor blades have to be positioned far enough away from the turbine tower and have to be designed as inflexible as possible. In addition, a complicated yaw control system is required to keep the turbine rotor facing the incoming wind. Due to these drawbacks, the turbine in downwind configuration is proposed to overcome these disadvantages because, first of all, rotor blades can be designed more flexible since there is no danger of blade strikes, and secondly, yaw control system could be eliminated if nacelle is designed appropriately to follow the incoming wind direction passively. In the present study, a comparative experimental investigation was conducted to quantify the aeromechanic performance of a downwind turbine (DWT), in comparison to that of a traditional upwind turbine (UWT). The thrust coefficient of the DWT model was found to be increased slightly in the time-averaged quantity, but have a significant augment in the fluctuations. Due to the shadow effect, the power outputs of the DWT model was found to be decreased by 3.2% when they were operated in a same atmospheric boundary layer (ABL) wind. In addition, a high-resolution particle image velocimetry (PIV) system was employed to characterize the ensemble-averaged and phase-locked wake flow structures to quantify the turbulent flow characteristics in the turbine wakes. The velocity deficit in the lower half turbine wake for the UWT case was found to be greater than that of the DWT case at the location of X/D < 1.0. The higher wind load fluctuations for the DWT system were found to be correlated well with the higher TKE distributions in the turbine wakes. The phase-locked PIV measurements illustrated that the wake regions can be divided into four zones, which are dominated by the vortices shedding from different turbine components. The detailed flow field measurements were correlated with the dynamic force and power measurement data to elucidate the underlying physics.
The growing demand for clean, sustainable, and viable energy in the twenty-first century prompted researchers to focus their efforts on developing renewable-based technologies. In that context, ...hydropower energy can be one of the feasible alternatives to meet future energy demands. It has been observed that at reservoir dams, the breakdown of flooded biomass and organic matter produces a significant amount of Green House Gas (GHG), which contributes to global warming. Small-scale hydro-based technologies produces GHG emissions when compared to dam hydropower since they produce most of their emissions during the building and maintenance phases. Small-scale hydro-based technologies such as hydrokinetics can be considered one of the preferable options, which generate energy from flowing water. A complete review of harnessing the power from flowing water by hydrokinetic turbines (HKTs) has been carried out in this article. Information regarding the state of the art and current status of cutting-edge technology has been gathered with the working principles of hydrokinetic turbines, classifications of HKTs and their applications, the terminology used for HKTs, the dam’s impact on the environment, and the selection of turbines, have been discussed thoroughly in this study. Furthermore, a detailed discussion of the design parameters of HKTs like solidity, power coefficient, Tip Speed Ratio (TSR), angle of attack, number of blades, type of blades, performance curve, Reynolds number, aspect ratio, blockage, augmentation and rotor mounting have been included. These parameters will aid in selecting HKT for a given environment condition. A comparison between the wind turbine and the hydrokinetic turbine has also been added. It has been observed that Micro Hydro River (MHR) technology is undergoing continuous R&D as compared to other rural electrification technologies. Various government policies, contemporary civilization, industrialization, and a standard way of life are also important factors that affect the use of HKTs as energy-harnessing devices.
•An interesting hysteresis phenomenon was analyzed using entropy production theory.•A function was used to calculate the entropy production in the wall region.•Generation mechanism of the hump and ...hysteresis characteristics was obtained.
The hydraulic loss due to friction and unstable flow patterns in hydro-turbines causes a drop in their efficiency. The traditional method for analyzing the hydraulic loss is by evaluating the pressure drop, which has certain limitations and cannot determine the exact locations at which the high hydraulic loss occurs. In this study, entropy production theory was adopted to obtain a detailed distribution of the hydraulic loss in a pump-turbine in the pump mode. In the past, the wall effects of entropy production were not considered, which caused larger errors as compared with the method of pressure difference. First, a wall equation was proposed to calculate the hydraulic loss in the wall region. The comparison of hydraulic loss calculated by entropy production and pressure difference revealed a better result. Then, through the use of the entropy production theory, the performance characteristics were determined for a pump-turbine with 19mm guide vane opening, and the variation in the entropy production was obtained. Recently, an interesting phenomenon, i.e., a hysteresis characteristic, was observed in the hump region in pump-turbines. Research shows that the hysteresis characteristic is a result of the Euler momentum and hydraulic loss; the hydraulic loss accounts for a major portion of the hysteresis characteristic. Finally, the hysteresis characteristic in the hump region was analyzed in detail through the entropy production. The results showed that the hump characteristic and the accompanying hysteresis phenomenon are caused by backflow at the runner inlet and the presence of separation vortices close to the hub and the shroud in the stay/guide vanes, which is dependent on the direction of discharge.
In present work, a new configuration of Darrieus type Vertical Axis Wind Turbine (VAWT) is introduced, and its aerodynamic performance is examined using three-dimensional numerical simulation by the ...solution of Reynolds averaged Naiver-Stokes equations. In comparison to each other, straight-blade VAWTs have higher average output torque and are simpler to manufacture while helical-blade VAWTs deliver non-oscillatory and smoother torque. To include advantages of both types of Darrieus VAWTs, a new straight-blade turbine is proposed which in general performs better than helical-blade VAWT. This turbine, called three-part-blade or simply 3-PB VAWT, includes straight blades where each of them is vertically cut into three parts. The objective of this paper is to show that while the proposed turbine is simple to manufacture, its performance is better than that of helical-blade VAWT. Present simulation is validated using experimental data. Having compared performance of the proposed turbine with a helical-blade VAWT, it is shown that 3-PB VAWT produces 6.06% higher average of total torque coefficient at low Tip Speed Ratio (TSR) of 0.44, and 158.19% at high TSR of 1.77. Based on these results, it is strongly recommended to use 3-PB VAWT considering its better aerodynamic performance and low cost of production.
•A new low-cost Darrieus wind turbine, called three-part-blade (3-PB), is proposed.•Each 3-PB blade is similar to a helical one but includes small straight blades.•The solution of transient 3D RANS equations with SST k−ω turbulence model is used.•Total torque of 3-PB and helical turbines are compared at various TSRs (up to 1.8).•3-PB turbine gives higher average torque with less fluctuations over helical blade.
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