Tubular Turbine Research Articles

Effect of internal stiffening rings and wall thickness on the structural response of steel wind turbine towers

In this paper, the structural response of steel tubular wind turbine towers with various design configurations is analysed using FEM modelling. Towers of various heights between 50 and 250m are considered and investigated with three different design options as follows: (i) thick walled tower with internal horizontal stiffening rings, (ii) thick walled tower without stiffening rings and (iii) thin walled tower with stiffening rings. Based on this analysis, weight reduction ratios are examined in relation to the horizontal sway and von Mises stress increase ratios in order to identify a more efficient design approach between reducing the wall thickness and adopting internal stiffeners. All studied design solutions satisfy the strength and serviceability requirements as specified by the design codes of practice. In the final part of paper, the dynamic characteristics of these three types of towers have been examined to obtain the natural frequencies and mode shapes. The studied model ignored the mass of nacelle-rotor system and the wind turbines, namely, only the isolated tower was included. Furthermore, the recommendations to avoid resonance for each height case are proposed.

Modal Analysis on a Runner Chamber for a Large Hydraulic Bulb Tubular Turbine

The vibration was severe for a runner chamber of a large hydraulic bulb tubular turbine, which caused some cracks. The PRO/E software was adopted to establish a 3D model of the runner chamber. Based on ANSYS Workbench V14.5, a modal analysis was done. Its natural frequencies and modal shapes were obtained. The influence on modal characteristics with the runner chamber’s structure was discussed. The study shows that the reinforce stiffener’s thickness, the circumferential endlessband and their thicknesses have few effect on the modal characteristics of the runner chamber, the latticed reinforce stiffener has more effect on the modal characteristics. These results will provide the basis for product optimum design, so that its natural frequencies stagger these frequencies of field vibration, the resonance and the crack do not occur in the runner chamber.

Inlet Passage’s Development and Optimization of New Tidal Unit-Shaft Tubular Turbine

A new type of tidal unit-vertical shaft tubular turbine is designed with high efficiency, large flow rate and low water head ,which has large power under the 2~3 meters water head. According to the data of the being installed tidal units and principles of tubular turbine’s design, the high efficiency vertical shaft tubular turbine was designed under large discharge and low head, which was suitable for the tidal power station. The design also considered the requirements of turbine’s size and the details of flow through the whole flow passage were attained. The turbine’s property was predicted by the 3-d numerical simulation software on the whole flow passage. Moreover, the influences of vertical shaft’s sizes were analyzed. And the terminal of vertical shaft with or without transverse brace and longitudinal brace were analyzed to get the influence. Considering the hydraulic performance of various methods, the best guide vane opening was chosen. The results show that, the turbine unit has the best performance on efficiency, hydraulic loss, etc. with the guide vane opening 62°, meeting the power station’s design requirements. The results show that the optimal designed flow passage’s efficiency reaches up to 88.4%, the flow rate becomes much larger and the power reaches 174.63kW. Without partial vortex, the flow pattern is smooth through the whole passage also with lower hydraulic loss.

Simulation of 3-D Unsteady Flows in a Tubular Hydro-Turbine on DES

Taking a hydropower station as the research object, the establishment of a numerical model that contains the full passage Tubular Turbine is given. Based on the transient incompressible N-S equations, a three-dimensional unsteady flow research is conducted. Numerical simulation of steady turbulent flow channel is calculated as the initial condition, the detached eddy simulation (DES) and slip grid technology are adopted to simulate the static-dynamic interference in the unsteady turbulent flow, The instantaneous pressure distribution in full channel and vorticity distribution of the representive section are obtained, so the three-dimensional transient vortex structures in full flow channel of the hydraulic turbine are captured. These studies aiming to explore the mechanism for the formation of vortex-induced vibration of hydro-turbine are valuable for the engineering reference.

Optimum design of exit guide vane on the bidirectional tubular turbine

Performance prediction about the forward generation condition based on a bidirectional through-flow turbine runner was conducted. The model characteristic curves and efficiency curve under reverse generation condition were plotted. In order to improve the reverse performance, exit guide vanes were lied behind the runner, the forward and reverse operating performance about a runner lied post-guide vane were numerically simulated. The results shows that the flow field distribution on forward generation condition did not significantly change after exit guide vanes were lied, and the energy conversion efficiency decreased. After exit guide vanes were lied, flow pattern of runner intake on under reverse generation condition were bettered, and the energy conversion efficiency increased. This study confirms that the exit guide vanes can improve the hydraulic performance of the turbine on reverse generation condition in view of numerical simulation.

Electrochemical and Exergetic Modeling of a Combined Heat and Power System Using Tubular Solid Oxide Fuel Cell and Mini Gas Turbine

In this article, a combined heat and power (CHP) system using a solid oxide fuel cell and mini gas turbine is introduced. Since a fuel cell is the main power generating source in hybrid systems, in this investigation, complete electrochemical and thermal calculations in the fuel cell are carried out in order to obtain more accurate results. An examination of the hybrid system performance indicates that increasing of the working pressure and rate of air flow into the system, cause the cell temperature to reduce, the efficiency and the power generated by the system to diminish, and the entropy generation rate and exergy destruction rate to increase. On the other hand, increasing the flow rate of the incoming fuel, the rise in cell temperature causes the efficiency, generated power, and exergy destruction rate of the system to increase.

Finite Element-Based Design of Grouted Connections with Shear Keys for Offshore Wind Turbines

Unexpected settlements in grouted connections caused concern in the offshore wind power industry. A grouted connection connects the transition piece of the tubular turbine tower to the monopile foundation by an annulus filled with high-strength grout. On several wind turbines, the transition piece has moved several centimetres downwards. Since the discovery of this serious problem, the generally applied codes for the design of grouted connections are under revision, and alternative solutions are investigated. Shear keys on the steel surfaces increase the capacity of the connection significantly. The paper discusses various approaches to finite element modelling of grouted connections with shear keys. For the design and the corresponding certifying process, advanced three-dimensional finite element models have been developed by the authors. The models consider the complex interface behaviour between steel and grout, the nonlinear material behaviour, and the detailed geometry of the shear keys. The results of the analysis are compared with laboratory tests on small-scale grouted connections and show good agreement. Furthermore, a comparison is made with recently published design guides.

Comparison of stiffening types of the cutout in tubular wind turbine towers

A very efficient type of wind turbine tower is the tubular steel tower configured as a cantilever cylindrical or conical shell, which is used considerably nowadays. A typical feature of such towers is the presence of a manhole cutout near the bottom. This cutout is of considerable dimensions and lowers significantly the tower strength including stress concentrations and increased danger of local buckling. Therefore, it is common to stiffen the region around the cutout aiming at compensating for this loss of strength. In this paper the most common types of stiffening are investigated by means of nonlinear finite element analyses calibrated via experimental testing and the efficiency of each type is highlighted. It is found that simple stiffening types consisting of either a peripheral frame or two vertical stringers and a ring are particularly efficient and can be used instead of more complex ones. Rules for dimensioning of the stiffeners are also proposed.

Optimization Study of Shaft Tubular Turbine in a Bidirectional Tidal Power Station

The shaft tubular turbine is a form of tidal power station which can provide bidirectional power. Efficiency is an important turbine performance indicator. To study the influence of runner design parameters on efficiency, a complete 3D flow-channel model of a shaft tubular turbine was developed, which contains the turbine runner, guide vanes, and flow passage and was integrated with hybrid grids calculated by steady-state calculation methods. Three aspects of the core component (turbine runner) were optimized by numerical simulation. All the results were then verified by experiments. It was shown that curved-edge blades are much better than straight-edge blades; the optimal blade twist angle is 7°, and the optimal distance between the runner and the blades is 0.75–1.25 times the diameter of the runner. Moreover, the numerical simulation results matched the experimental data very well, which also verified the correctness of the optimal results.

Bidirectional Power Performance of a Tidal Unit with Unilateral and Double Guide Vanes

To improve the bidirectional power performance of a tidal unit, two designs were investigated. The use of unilateral or double guide vanes in a tubular tidal unit influences the performance of the hydraulic unit. Based on the N-S equations and the RNG k-ε turbulence model, the SIMPLEC algorithm was used for 3D steady-state numerical simulation of the entire turbine flow passage with unilateral and double guide vanes. The internal flow condition under positive and reverse power generation conditions was also analyzed. At the same time, the turbine, with a runner 1.6 m in diameter, was scaled down to 0.35 m diameter for model tests. The model tests were based on a multifunction hydromechanical test bench at Hohai University. The water head, discharge, and torque of the tubular turbine were, respectively, tested using a pressure difference sensor, electromagnetic flow meter, and torque meter under different guide-vane openings. The results show that turbine efficiency in the model test is slightly lower than that predicted by numerical simulation under the same conditions. However, the difference is not large. With double side guide vanes, although the efficiency of positive power generation decreased, the efficiency of reverse power generation is greatly improved.

CFD and Experimental Study in the Optimization of an Energy Converter for Low Heads

This paper deals with new design of low head turbines, as feasible solutions to solve the lack of energy in rural and remote areas, or to provide energy from urban water pipe systems. Propeller turbines are then the subject of this research because they are suitable for small heads, discharges with little variability, easy to manufacture and with low costs associated. Hence, the aims are the design of quite simple tubular propeller turbines and the analysis of hydrodynamic behaviour for different number and configuration of blades, based on CFD analyses and experimental tests development. An advanced hydrodynamic code based on the finite volume method, as well as blades configuration and mesh specific models are used for the impeller and the turbine design. The blade geometry is optimized using mathematical formulations and experimental results, concerning the possible range of operation under best efficiency conditions. Performance curves are obtained for typical characteristic parameters allowing comparisons between CFD and experimental results. Based on the similarity theory applied to turbomachines it is possible to evaluate the hydrodynamic behaviour through a tubular propeller for different sizes, in a scale model application.

Development and optimization design of pit turbine with super low-head

Tubular turbines have many advantages such as large flow, high-speed, high efficiency, wide and high efficiency area, compact structure, simple layout, etc. With those advantages, tubular turbine is becoming one of the most economic and suitable types of turbines to develop low head hydraulic resources. According to the general situation of the hydropower station in the north of Jiangsu, a super low head pit turbine which head is set as about 2m is developed by the research to utilize the low head hydraulic resource.The CFD technology was used to calculate the flow field. The computing zone was meshed with unstructured gird. The whole flow passage of shaft type tubular turbine was calculated by 3-d steady turbulent numerical simulation. The detail of flowthrough the whole flowpassage was attained and the influence to the turbine's performance was analyzed by the low head runner blade's various diameters, airfoils and setting angles. The best turbine runner was obtained by considering all the methods. Meeting the station's requirements, the results show that the runner exhibits the highest performance in the efficiency, hydraulic loss and static pressure sides with 1.75m diameter, optimized airfoil and 23 degree setting angle. The developed super low head pit turbine shows highest efficiency under the design condition of 2.1m water head and 10m3/s flow rate. GD-WS-35 turbine model test was carried out tostudy the performance of the turbine. On the basis ofmodel transformation principle,the numerical simulationresultof GD-WS-175turbine was compared with the model results. It's showed that the model test result is basically consistent with numerical simulationresult. The producing error in the numerical computation is not easy to control. The efficiency's error range is ±3%.

Analysis on the roundness of bulb turbine generator based on the unbalanced magnetic

Because of design, manufacture, installation and operation, there are some relatively eccentric in bulb tubular turbine units under operating condition. It easily caused uneven air gap, unbalanced magnetic field, unbalanced magnetic pull and torque. It could also increase the bending and torsion vibration of generator,at the same time, the roundness of stator and rotor would be aggravated which often caused by accidents such as generator sweep chamber. In this paper, basing on the design, installation and operation experience, the reasons of the unbalanced magnetic pull, mechanism and operation research were analyzed by theoretical calculation and the prototype test.

Experiments and CFD Analyses for a New Reaction Microhydro Propeller with Five Blades

AbstractThis works aims to develop and study a new reaction microhydro tubular propeller turbine with five blades as a promising answer to solve the lack of energy in rural and remote areas. The first stage is to validate numerical and experimental tests made for the flow behavior for different values of head, discharge, and rotational impeller speed. Using specific mathematical formulations, a blade model configuration is developed based on the velocity triangles at the impeller inlet and outlet and experimental results based on pressure, discharge, and velocity profiles in different turbine sections. Through characteristic parameters, performance curves are obtained allowing comparisons between experimental and computational fluid dynamics (CFD) results. Also, an evaluation of the hydrodynamic behavior is made for a scaled model application by similarity turbo machines theory.

Stress Analysis of Tubular Turbine Based on Fluid-Structure Coupling

A brief introduction of fluid-structure coupling and its classification were given, then according to the solving characteristics and application conditions of different coupling methods; sequential coupling method is chosen to calculate the stress distribution of a tide power plant tubular turbine. Stress calculations of the tubular turbine were conducted under the maximum water head, the designed water head, the average water head and the minimum water head working conditions in ANSYS Workbench. The research shows that in all of the four calculated working conditions, the maximum equivalent stress of the runner is located at the connection between the blades and the hub where stress concentration is obvious; the maximum deformation of the runner lies in the outer edge of the blades and the deformation increases from the root to the outer edge; the maximum equivalent stress of the guide vane is located at the root and the maximum deformation lies in the outer edge. The maximum value of maximum equivalent stress of the runner and the guide vane occurs on the maximum water head working condition, whereas it is far less than the material yield limit, which means that static stress will not lead to the cracks of the blade or the guide vane. But it is still necessary to avoid stress concentration appearing periodically in case it causes fatigue failure.

Static Behavior Study for Latticed Concrete-Filled Steel Tubular Wind Turbine Tower Joints

Six latticed concrete-filled steel tubular (CFST) wind turbine tower K-shape joints were carried on the static load test, which included the weld intersecting joint and gusset plate joint. The failure mechanism and characteristics on the two kinds of K-shape joints, the deformation development process after joints entered plastic stage and the stress state and distribution of joint intersection area were studied. The results show that the failure mode and mechanical behavior of CFST K-shape joints are greatly different from that of the hollow steel tube K-shape joints because of the existence of core concrete, the failure mode of the weld intersecting joints showed the local buckling of compression web member and that of the gusset plate joints presented as the compression buckling and tension tearing of the gusset plates, while the plastic deformation failure of tower column tube wall in joint area was not appear. It is also shown by test results that the stress distribution of tower column tube wall and gusset plate in joint intersection is extremely non-uniform, individual parts already enter plastic state but some other parts are still in elastic state. According to the failure mode and stress distribution conditions of the two kinds of K-shape joints, some design suggestions are drawn, which can provide reference for the latticed CFST wind turbine tower joints.

현장시험에 의한 소수력발전용 튜블러수차시스템 성능계측

Recently, small hydropower attracts attention because of its renewable, clean and abundant energy resources to develop. Therefore, a tubular type hydro turbine is proposed for small hydropower in this study because the turbine has relatively simple structure and high possibility of applying to small hydropower. The purpose of this study is to investigate the performance characteristics of the turbine by field test. Field test iss conducted using one tubular turbine system as well as serial arrangement system by two tubular turbines taking into consideration of actual operation conditions. The results show that efficiency of test turbine changes considerably by the runner vane angle. Best efficiency of one turbine arrangement is higher than that of two turbine serial arrangement.

Mixed-flow vertical tubular hydraulic turbine: determination of proper design duty point

A new vertical single-regulated mixed-flow turbine with conical guide apparatus and without spiral casing is presented in this paper. Runner blades are fixed to the hub and runner band and resemble to the Francis type runner of extremely high specific speed. Due to lack of information and guidelines for the design of a new turbine, a theoretical model was developed in order to determinate the design duty point, i.e. to determine the optimum narrow operation range of the turbine. It is not necessary to know the kinematic conditions at the runner inlet, but only general information on the geometry of turbine flow-passage, meridional contour of the runner and blading, the number of blades and the turbine speed of rotation. The model is based on the integral tangential lift coefficient, which is the average value over the entire runner blading. The results are calculated for the lift coefficient 0.5 and 0.6, for the flow coefficient range from 0.2 to 0.36, for the number of the blades between 5 and 13, and are finally presented in the Cordier diagram (specific speed vs. specific diameter). Calculated results of the turbine optimum operation in Cordier diagram correspond very well to the adequate area of Kaplan turbines with medium and low specific speed and extends into the area of Francis turbines with high specific speed. Presented model clearly highlights the parameters that affect specific load of the runner blade row and therefore the optimum turbine operation (discharge—turbine head). The presented method is not limited to a specific reaction type of the hydraulic turbine. The method can therefore be applied to a wide range from mixed-flow (radial-axial) turbines to the axial turbines. Applicability of the method may be considered as a tool in the first stage of the turbine design i.e. when designing the meridional geometry and selecting the number of blades according to calculated operating point. Geometric and energy parameters are generally defined to an extent that these parameters are considered in detailed design using turbulent viscous flow CFD solver.

Methodology for seismic risk assessment for tubular steel wind turbine towers: application to Canadian seismic environment

The seismic response of tubular steel wind turbine towers is of significant concern as they are increasingly being installed in seismic areas and design codes do not clearly address this aspect of design. The seismic hazard is hence assessed for the Canadian seismic environment using implicit finite element analysis and incremental dynamic analysis of a 1.65 MW wind turbine tower. Its behaviour under seismic excitation is evaluated, damage states are defined, and a framework is developed for determining the probability of damage of the tower at varying seismic hazard levels. Results of the implementation of this framework in two Canadian locations are presented herein, where the risk was found to be low for the seismic hazard level prescribed for buildings. However, the design of wind turbine towers is subject to change, and the design spectrum is highly uncertain. Thus, a methodology is outlined to thoroughly investigate the probability of reaching predetermined damage states under any seismic loading conditions for future considerations.

Electricity Generation by the Tidal Barrages

Concern over global climate change has led policy makers to accept the importance of reducing Greenhouse gas emissions. A tidal barrage utilizes the potential energy of the tide and has proven to be very successful, despite opposition from environmental groups. Tidal barrages make use of the potential energy of the tides. A tidal barrage is typically a dam, built across a bay or estuary that experiences a tidal range in excess of 5 m. Electricity generation from tidal barrages employs the same principles as hydroelectric generation, except that tidal currents flow in both directions. A typical tidal barrage consists of turbines, sluice gates, embankments and ship locks. The turbines that are used in tidal barrages are either unidirectional or bi-directional, and include bulb turbines, straflo or rim turbines and tubular turbines. Tidal barrages can be broken into two types: single-basin systems and double-basin systems. This paper discussed about the tidal barrage, wave energy, environmental impacts and special conditions in there process