The prediction of the hydrodynamic performance of marine current turbines

The development of a blade element momentum (BEM) model for the hydrodynamic design of marine current turbines is presented. The model includes routines for interpolation of 2D section data and extrapolation for stall delay. The numerical model is compared with experimental data obtained from tests of an 800 mm diameter model rotor carried out in a cavitation tunnel. The theoretical predictions are in good agreement with the experiments. Using this validated model, a typical 3D rotor is used to demonstrate parametric variations of the design parameters. The effect of tip immersion on possible cavitation is assessed for this rotor. The model is then used to solve the dynamic effects of a tidal profile. The effect of an increase in blade roughness is presented, indicating a relatively small reduction in power. This work demonstrates that the numerical model developed can provide a useful tool for the investigation of the hydrodynamic design and operation of marine current turbines.     

Fundamentals applicable to the utilisation of marine current turbines for energy production

The potential of electric power generation from marine tidal currents is enormous. Tidal currents are being recognised as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation and advantageous when compared to other renewables. There is a paucity of information regarding various key aspects of system design encountered in this new area of research. Virtually no work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship’s propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. This paper reviews the fundamental issues that are likely to play a major role in implementation of MCT systems. It also highlights research areas to be encountered in this new area. The paper reports issues such as the harsh marine environment, the phenomenon of cavitation, and the high stresses encountered by such structures are likely to play a major role on the work currently being undertaken in this field.     

A computational hydrodynamics method for horizontal axis turbine – Panel method modeling migration from propulsion to turbine energy

A computational hydrodynamics method was formulated and implemented for horizontal axis tidal turbines. This paper presents a comparative analysis between screw propellers and horizontal axis turbines, in terms of geometry and motion parameters, inflow velocity analysis and the implementation methodologies. Comparison and analysis are given for a marine propeller model and a horizontal axis turbine model that have experimental measurements available in literature. Analysis and comparison are presented in terms of thrust coefficients, shaft torque/power coefficients, blade surface pressure distributions, and downstream velocity profiles. The effect of number of blades from 2 to 5, of a tidal turbine on hydrodynamic efficiency is also obtained and presented. The key implementation techniques and methodologies are provided in detail for the propeller based panel method tool to migrate as a prediction tool for tidal turbine. While the method has been proven to be accurate and robust for many propellers tested in the past, this numerical tool could be validated further for turbines. To further refine and validate the panel method for various turbines, it requires substantial additional experimental measurements. These measurements include downstream velocity profile by using LDV and/or SPIV, which are essential for numerical wake vortices descritization.     

Development of a hydraulic control mechanism for cyclic pitch marine current turbines

Tidal power generation by means of marine current farms is potentially a large renewable energy resource which could be harnessed in many coastal waters. Its availability is highly predictable in time, and the technology promises high energy conversion efficiency along with a relatively low impact on sea life due to its relatively small disturbance of natural tidal flows.A series of devices have so far been proposed and developed for the extraction and conversion of kinetic energy present in tidal flows into useful electrical power [1]. Designs include horizontal axis turbines, vertical axis turbines, and devices with oscillating lift surfaces. Up to date no technology has firmly established itself.This paper describes a novel hydraulic control mechanism designed for vertical-axis marine current turbines of the straight-bladed Darrieus type. It has been found to significantly improve turbine efficiency over conventional Darrieus turbines when operated at low blade tip-speed to tidal-flow-velocity ratios (TSR) and to give the turbine the ability to self-start reliably. The control mechanism enforces a cyclic pivoting motion on the turbine blades as they move around their circular flight-path. The movement of the pitch control is of sinusoidal shape and is continuously variable in amplitude. The blade actuation is powered by the turbine's own rotation and is implemented using a swash-plate mechanism in conjunction with a hydraulic circuit for every blade. For surface piercing turbines, this control mechanism may be remotely positioned in a dry nacelle above sea level. If the appropriate design is applied, this can offer access to the cyclic pitch control mechanism, gearbox and generator, even when the turbine is operational, promising lower maintenance and operating costs compared with submerged systems.     

Tidal stream energy resource assessment in the Qiantang River Estuary,China

A tidal stream energy resource assessment can be achieved through direct measurements of tidal elevations or flow velocities, theoretical formulas, and numerical models. This paper first described the development of renewable energy in China. Then, the tidal stream energy resource in the Qiantang River Estuary was assessed. The present work established a 2D numerical model for calculating the power density in the estuary and validated it with in situ water level, tidal current, and suspended sediment concentration measurements. Three possible sites found near the Hangzhou Bay Bridge were selected for detailed resource assessment. The results indicated that if only 50 turbines are deployed to each site, the tidal stream energy output by all turbines would be 7.5?GWh/year. Finally, building a tidal stream power generation device into an existing bridge structure was proposed at the Qiantang River Estuary.     

Marine current energy resource assessment and design of a marine current turbine for Fiji

Pacific Island Countries (PICs) have a huge potential for renewable energy to cater for their energy needs. Marine current energy is a reliable and clean energy source. Many marine current streams are available in Fiji's waters and large amount of marine current energy can be extracted using turbines. Horizontal axis marine current turbine (HAMCT) can be used to extract marine current energy to electrical energy for commercial use. For designing a HAMCT, marine current resource assessment needs to done. A potential site was identified and resource assessment was done for 3 months. The coordinates for the location are 18°12′1.78″S and 177°38′58.21″E; this location is called Gun-barrel passage. The average depth is 17.5 m and the width is nearly 20 m – the distance from land to the location is about 500 m. A multi cell aquadopp current profiler (ADCP) was deployed at the site to record marine currents. Strong marine currents are recorded at this location, as a combination of both tidal and rip currents. The maximum current velocity exceeds 2.5 m/s, for days with large waves. The average velocity was 0.85 m/s and power density for the site was 525 W/m². This site has good potential for marine current and HAMCT can be installed to extract power. A turbine with diameter between 5 and 8 m would be suitable for this site. Therefore, a 5 m HAMCT is designed for this location. The HF10XX hydrofoils were used from blade root (r/R = 0.2) to tip (r/R = 1.0). HF10XX series hydrofoil sections were designed to operate at varying turbine operating conditions; these hydrofoils have good hydrodynamic characteristics at the operating Reynolds number. The turbine is designed to operate at rated marine current speed of 1.5 m/s, cut in speed of 0.5 m/s and cut off speed of 3 m/s at a tip speed ratio (TSR) of 4.2.     

CAD技术在舰用燃气轮机设计中的应用

本文论述了计算机辅助设计(CAD)技术及其在舰用燃气轮机设计工作中应用的前景,并提出了舰用燃气轮机CAD 系统实现的方案和方法。     

Numerical analysis of the characteristics of vertical axis tidal current turbines

Tidal current is considered to be one of the promising alternative green energy resources. Tidal current turbines are devices used for harnessing tidal current energy. The development of a standard for tidal current turbine design is a very important step in the commercialization of tidal current energy as the tidal current industry is growing rapidly, but no standard for tidal current turbines has been developed yet. In this paper, we present our recent efforts in the numerical simulation of the characteristics (e.g., power output, torque fluctuation, induced velocity, and acoustic emission) of tidal current turbines related to the development of the standard. The relationship between the characteristics and the parameters of an example turbine are extensively discussed and quantified. The findings of this paper are expected to be helpful in developing the standards for tidal current turbines in the near future.     

Experimental verifications of numerical predictions for the hydrodynamic performance of horizontal axis marine current turbines

The conversion of the kinetic energy presented by ocean or marine currents offers an exciting proposition as it can provide regular and predictable energy resource. The majority of the proposed designs for converting this type of kinetic energy are based on the concept of the horizontal axis turbines, which has common characteristics to those being used in wind energy. Although a lot can be learnt and transferred from wind turbine technology, there are significant differences. These include the effects of the free surface and the occurrence of cavitation. Consequently, any developed numerical methods need to be verified. This study reports on the development and verification of simulation tools based on blade element momentum theory—a commercial code (GH-Tidal Bladed) and an academic in-house code (SERG-Tidal). Validation is derived from experimental measurements conducted on a model 800 mm diameter turbine in a cavitation tunnel and a towing tank. The experimental data includes measurements of shaft power and thrust generated by the turbine for a series of blade pitch settings and speeds. The results derived from the two codes are compared. These indicate that the two developed codes demonstrate similar trends in the results and provide a satisfactory representation of the experimental turbine performance. Such results give the necessary confidence in the developed codes resulting in appropriate tools that can to be utilised by developers of marine current turbines.     

Simulated electrical power potential harnessed by marine current turbine arrays in the Alderney Race

Utilising marine currents for electricity generation could offer a distinct advantage over other renewable energy sources due to the regular and predictable nature of the resource. This paper details the design of a horizontal axis Marine Current Turbine using 2D aerofoil data and a blade element momentum software package. Tidal current data from the Race of Alderney situated in the Channel Islands is used to run simulations of the turbine over various flow regimes and yield the energy capture with time. The results of the simulations are combined with an analytical method that details the layout and energy capture potential throughout a large-scale array. Several array configurations, sizes, and the impact of spacings (between rows and turbines) on the velocity distribution were considered in the analysis. The optimum configuration predicted an annual energy output of 1340 GW h at a rated array capacity of approximately 1.5 GW.     

Tidal current energy resource assessment in Ireland: Current status and future update

Interest in renewable energy in Ireland has increased continually over the past decade. This interest is due primarily to security of supply issues and the effects of climate change. Ireland imports over 90% of its primary energy consumption, mostly in the form of fossil fuels. The exploitation of Ireland's vast indigenous renewable energy resources is required in order to reduce this over-dependence on fossil fuel imports to meet energy demand. Various targets have been set by the Irish government to incorporate renewable energy technologies into Ireland's energy market. As a result of these targets, the development in wind energy has increased substantially over the past decade; however this method of energy extraction is intermittent and unpredictable. Ireland has an excellent tidal current energy resource and the use of this resource will assist in the development of a sustainable energy future. Energy extraction using tidal current energy technologies offers a vast and predictable energy resource. This paper reviews the currently accepted tidal current energy resource assessment for Ireland. This assessment was compiled by Sustainable Energy Ireland in a report in 2004. The assessment employed a 2-dimensional numerical model of the tidal current velocities around Ireland, and from this numerical model the theoretical tidal current energy resource was identified. With the introduction of constraints and limitations, the technical, practical, accessible and viable tidal current energy resources were obtained. The paper discusses why the assessment needs updating including the effect on the assessment of the current stage of development of tidal current turbines and their deployment technology.     

Study on the rotor design method for a small propeller-type wind turbine

Small propeller-type wind turbines have a low Reynolds number, limiting the number of usable airfoil materials. Thus, their design method is not sufficiently established, and their performance is often low. The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines. To that end, we designed two rotors: Rotor A, based on the rotor optimum design method from the blade element momentum theory, and Rotor B, in which the chord length of the tip is extended and the chord length distribution is linearized. We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis. Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A, but the maximum output coefficient increased by approximately 38.7%. Rotors A and B experienced a large-scale separation on the hub side, which extended to the mean in Rotor A. This difference in separation had an impact on the significant decrease in Rotor A’s output compared to the design value and the increase in Rotor B’s output compared to Rotor A.     

两种常用漂浮式风力机平台动态特性分析

分别针对MIT/NREL TLP和Umaine-Hywind Spar两种海上风力机浮式平台主体的水动力特性进行研究,旨在分析两者的系泊稳定性.基于海洋水动力学和结构动力学理论,建立了平台/缆索系统耦合模型,在水深和外界载荷激励相同的情况下,利用有限元分析ANSYS软件中的水动力学计算模块进行时域、频域响应分析,研究了两种平台在海风、海流和随机波联合作用下的动态响应,并分析了两种平台随波浪频率的响应变化.结果表明:MIT/NREL TLP平台的动态响应较大,而Umaine-Hywind Spar平台动态响应较小;两平台均在低频波浪作用下产生响应峰值.     

船用燃气轮机技术的发展方向及我国发展途径的思考

介绍了船用燃气轮机技术在应用领域中取得的进展,对其技术发展和应用的趋势作了分析。论述了当前船用燃气轮机的主要发展途径,对我国船用燃气轮机的发展途径提出了一些设想和建议。指出,作为轻型燃气轮机,船用燃气轮机的设计开发应该遵循高起点、一机多用、一机广用的开发方针。少量引进几型先进的机组,采用通用性设计(比例放大/比例缩小、压气机模化设计、压气机加级/压气机减级等)开发出功率加大型和功率减小型机组,形成我国所需要功率档次的船用燃气轮机系列。     

Wave energy utilization: A review of the technologies

Sea wave energy is being increasingly regarded in many countries as a major and promising resource. The paper deals with the development of wave energy utilization since the 1970s. Several topics are addressed: the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave energy absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes; and the development of specific equipment (air and water turbines, high-pressure hydraulics, linear electrical generators) and mooring systems.     

舰用燃气轮机的热经济性分析

阐述了热经济学的思路,针对舰用燃气轮机的热力学模型,建立了燃气轮机的热经济学模型,并讨论了燃气轮机购置费用的估算方法。实例计算结果表明,舰用燃气轮机的总费用率存在一个最小值,且燃料的市场价格、动力装置的年运行时数对装置的总费用率影响较大。     

某船用汽轮机短座阀流量与提升力特性数值模拟计算

由于汽轮机内部空间的限制及船用汽轮机多工况的要求,部分船用汽轮机采用了短座阀。因扩压段长度的大幅减小．阀门的气动性能及强度振动特性产生较大变化,对汽轮机总体性能有较大的影响。本文对某短座阀在试验研究的基础上进行了数值计算分析：通过气动试验,得到某船用汽轮机短座阀的流量系数与提升力系数曲线簇;基于可压缩,N-S方程,利用S-A湍流模型及有限积分法,采用四面体非结构性网格．对此阀门进行了数值模拟计算。通过对该阀门的数值计算得到在不同相对开度及不同压比下的计算结果与试验结果吻合良好;得到对各种短座阀广泛适用的计算方法．为船用调节阀、旁通阀的设计和性能分析提供了重要依据。     

Design and model confirmation of the intermediate scale VolturnUS floating wind turbine subjected to its extreme design conditions offshore Maine

Floating offshore wind turbines are gaining considerable interest in the renewable energy sector. Design standards for floating offshore wind turbines such as the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbine Installations are relatively new and few if any floating wind turbines have yet experienced the prescribed design extreme environmental conditions. Only a few pilot floating turbines have been deployed in Europe and Japan. These turbines have been designed for long return period storm events and are not likely to see their extreme design conditions during early deployment periods because of the low probability of occurrence. This paper presents data collected for an intermediate scale floating semi‐submersible turbine intentionally placed offshore Maine in a carefully selected site that subjects the prototype to scale extreme conditions on a frequent basis. This prototype, called VolturnUS 1:8, was the first grid‐connected offshore wind turbine in the Americas, and is a 1:8 scale model of a 6 MW prototype. The test site produces with a high probability 1:8 scale wave environments, and a commercial turbine has been selected so that the wind environment/rotor combination produces 1:8‐scale aerodynamic loads appropriate for the site wave environment. In the winter of 2013–2014, this prototype has seen the equivalent of 50 year to 500 year return period storms exercising it to the limits prescribed by design standards, offering a unique look at the behavior of a floating turbine subjected to extreme design conditions. Performance data are provided and compared to full‐scale predicted values from numerical models. There are two objectives in presenting this data and associated analysis: (i) validate numerical aeroelastic hydrodynamic coupled models and (ii) investigate the performance of a near full‐scale floating wind turbine in a real offshore environment that closely matches the prescribed design conditions from the ABS Guide. Copyright © 2015 John Wiley & Sons, Ltd.     

A review of the potential water quality impacts of tidal renewable energy systems

The continued increase in the demand for energy, growing recognition of climate change impacts, high oil and gas prices and the rapid depletion of fossil fuel reserves have led to an increased interest in the mass generation of electricity from renewable sources. Traditionally, this has been pursed through riverine hydropower plants, with onshore wind systems growing steadily in popularity and importance over the years. Other renewable energy resources, which were previously not economically attractive or technically feasible for large scale exploitation, are now being considered to form a significant part of the energy mix. Amongst these, marine and in particular, tidal energy resource has become a serious candidate for undergoing mass exploitation in the near future, particularly in places with a tidal range of 4 m or more. Tidal renewable energy systems are designed to extract the kinetic or potential energy flow and convert it into electricity. This can be achieved by placing tidal stream turbines in the path of high speed tidal currents or through tidal range schemes, where low head turbines are encapsulated in impoundment structures, much like in low head riverine hydropower schemes. It is thought that these systems, when implemented at scales required to generate substantial amounts of electricity, have the potential to significantly alter the tidal flow characteristics, which could have knock-on impacts on the hydro-environment. This review gathers together knowledge from different research areas to facilitate an evaluation of the potential hydro-environmental impacts of tidal renewable energy systems, with a particular focus on water quality. It highlights the relevance of hydro-environmental modelling in assessing potential impacts of proposed schemes and identifies areas where further research is needed. A case study is presented of recent modelling studies undertaken for the Severn Estuary.     

WR_21_新一代的船用燃气轮机

ＷＲ－２１是２１世纪初的新一代船用燃气轮机,由于采用了间冷、回热技术,使其具有优良的变工况性能。本文综述了该机的研制历程,发动机的性能,各主要部件的设计和维护特点。