Gasifier-based power generation: Technology and economics

The paper describes a 100 kW power generation system installed at Port Blair, Andaman and Nicobar Islands, under a project sponsored by the Department of Non-Conventional Energy Sources, Government of India. The system consists of a wood gasifier utilising the waste wood from a saw mill and a diesel engine genset. The performance of the total system and its elements are presented along with economics of operation. To bring out the economics of using such renewable energy devices for power generation, some realistic situations are considered for which the effective cost of power and the pay-back period for the investment are evaluated. The economics is compared with that of a similar system of 3·7 kW capacity.     

液化天然气冷能利用发电技术浅析

阐述了国内外LNG利用的形势,论述了LNG作为燃料的优势.通过分析LNG冷量利用原理及对LNG进行的分析,得出回收LNG冷量发电不仅有效利用能源,而且减少机械制冷造成的大量电能消耗,具有可观的经济效益和社会效益.对国内外利用LNG冷量发电方式进行总结分类,具体给出一些典型流程图和成功的应用范例.     

Octree‐based reasonable‐quality hexahedral mesh generation using a new set of refinement templates

An octree‐based mesh generation method is proposed to create reasonable‐quality, geometry‐adapted unstructured hexahedral meshes automatically from triangulated surface models without any sharp geometrical features. A new, easy‐to‐implement, easy‐to‐understand set of refinement templates is developed to perform local mesh refinement efficiently even for concave refinement domains without creating hanging nodes. A buffer layer is inserted on an octree core mesh to improve the mesh quality significantly. Laplacian‐like smoothing, angle‐based smoothing and local optimization‐based untangling methods are used with certain restrictions to further improve the mesh quality. Several examples are shown to demonstrate the capability of our hexahedral mesh generation method for complex geometries. Copyright © 2008 John Wiley & Sons, Ltd.     

漂浮式潮流能发电装置振动与波浪响应试验研究

为了研究基于竖轴水轮机的漂浮式潮流能发电装置的振动与波浪响应,设计试验模型和装置,进行水轮机转与不转的静水拖航试验和波浪试验,测量系泊链拉力和模型的纵摇响应。试验发现,系泊系统具有高频振动现象,V等于0.7m/s、0.9m/s,水轮机不转时,以及V等于0.9m/s,水轮机转动时,系泊系统具有明显的慢摇现象,水轮机转动还带来了系泊链的低频拉力响应。水轮机转动使系泊系统的纵摇周期增大,载体模型的共振波长增加。与水轮机不转时相比,水轮机转动使低波长-载体模型长度比下模型的纵摇运动响应减小,对高波长-载体模型长度比下模型的纵摇运动影响较小。试验研究可为基于竖轴水轮机的漂浮式潮流能发电装置的理论研究与工程应用提供参考和借鉴。     

Design and modelling of dispersion-engineered rib waveguide for ultra broadband mid-infrared supercontinuum generation

We report a dispersion-engineered As₂Se₃ chalcogenide glass rib waveguide structure for ultra broadband mid-infrared supercontinuum generation across molecular ‘fingerprint region’. The proposed rib waveguide structure offers non-linear coefficient as high as 18,250 W^?1 km^?1 at 2.5 μm. Supercontinuum spectrum spanning 2–15 μm, which not only covers the both atmospheric transparent windows (3–5 μm and 8–13 μm) in the mid-infrared domain but also covers the important molecular ‘fingerprint domain’, is obtained using only 4 mm-long rib waveguide structure. To the best of our knowledge, such broadband mid-infrared supercontinuum spectrum in As₂Se₃-based chalcogenide waveguide geometry is reported for the first time. The proposed design of rib waveguide has potential for robust, integrated and low-cost supercontinuum sources in various applications including frequency comb generation, chemical sensing, food quality control and early cancer diagnostics.     

Analysis of a triangulation based approach for specimen generation for discrete element simulations

Discrete element methods are emerging as useful numerical analysis tools for engineers concerned with granular materials such as soil, food grains, or pharmaceutical powders. Obviously, the first step in a discrete element simulation is the generation of the geometry of the system of interest. The system geometry is defined by the boundary conditions as well as the shape characteristics (including size) and initial coordinates of the particles in the system. While a variety of specimen generation methods for particulate materials have been developed, there is no uniform agreement on the optimum specimen generation approach. This paper proposes a new triangulation based approach that can easily be implemented in two or three dimensions. The concept of this approach (in two dimensions) is to triangulate a system of points within the domain of interest, creating a mesh of triangles. Then the particles are inserted as the incircles of these triangles. Extension to three dimensions using a mesh of tetrahedra and inserting the inspheres is relatively trivial. The major advantages of this approach include the relative simplicity of the algorithm and the small computational cost associated with the preparation of an initial particle assembly. The sensitivity of the characteristics of the particulate material that is generated to the topology of the triangular mesh used is explored. The approach is compared with other currently used methods in both two and three dimensions. These comparisons indicate that while this approach can successfully generate relatively dense two-dimensional particle assemblies, the three- dimensional implementation is less effective at generating dense systems than other available approaches. The research presented in this paper made use of software developed by other researchers. For the two-dimensional study the program Triangle developed by Jonathan Shewchuk was used. The three-dimensional analysis used the Geompack++ program developed by Barry Joe as well as an implementation of the Jodrey and Tory (1985) algorithm by Monika Bargiel and Jacek Moscinski called NSCP3D.     

Design of a partially compliant crank rocker mechanism using Ionic Polymer Metal Composite for path generation

Four-bar mechanisms traditionally are made of rigid links and they are used for path, motion or function generation. Actively changing the length of the rocker in a crank rocker four-bar mechanism results in the tip of the rocker following a closed path. In this paper a crank rocker mechanism has been designed with a variable length rocker using an Ionic Polymer Metal Composite (IPMC). A pseudo rigid body model is used to represent the IPMC bending during path generation and a dynamic model is developed to relate the position of the rocker tip and the input voltage required to bend the IPMC. A simple control system has been designed that can apply a desired voltage to the IPMC using pulse width modulation, for obtaining a particular deformation. Experimental results of a path generated using the proposed mechanism is presented. This mechanism has wide application in micro robots for pick and place applications, actively controllable partially complaint mechanisms, adaptive structures, etc.     

Diaion SP-850 resin as a new solid phase extractor for preconcentration-separation of trace metal ions in environmental samples

A solid phase extraction method was developed for the preconcentration and separation of trace amounts of chromium, manganese, iron, cobalt, copper, cadmium and lead from environmental samples by complexation with alpha-benzoin oxime followed by adsorption onto Diaion SP-850-solid phase extraction column. One molar per liter HNO(3) was used as eluent. The recoveries of analytes at pH 8.0 with 700 mg of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. The detection limits by three sigma for analyte ions were 0.65 microg l(-1) for Cr(III), 0.42 microg l(-1) for Mn(II), 0.28 microg l(-1) for Fe(III), 0.73 microg l(-1) for Co(II), 0.30 microg l(-1) for Cu(II), 0.47 microg l(-1) for Cd(II) and 0.50 microg l(-1) for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials. The presented procedure was applied to the determination of analytes in tap, river and sea waters, rice, wheat, canned tomato and coal samples with successfully results (recoveries greater than 95%, R.S.D.'s lower than 8%).     

基于LabVIEW的颤振激励信号生成与测试系统研究

基于NI公司的数据采集硬件设备,结合跨音速风洞颤振试验特点,用LabVIEW语言为颧振试验设计了一套激励信号生成与多通道同步动态信号采集系统.设计的系统成功实现了新型IEPE传感器和传统电荷式传感器兼容、加速度信号与应变信号同步采集、激励信号生成与多通道数据采集同步、直接内存读取数据、数据尤限时存盘、信号实时显示等方面的功能.经试验验证,该系统设计方案完全满足颤振试验数据采集的要求,获得良好的测试结果,在多功能同步采集系统设计方丽取得了技术性应用成果.     

Importance sampling for stochastic systems under stationary noise having a specified power spectrum

We develop an importance sampling simulation scheme for estimating an extremely small probability of system failure with respect to a time-dependent stochastic system excited by stationary random noise having a specified power spectrum. First, we construct a system of random differential equations driven by a Wiener process, which can approximately give such a stationary random noise by the use of an extended version of the well-known Ornstein–Uhlenbeck process. Next, we suppose a stochastic response system driven by the constructed stationary random noise. Next, formulating the probability of system failure, we give an importance sampling scheme through the probability measure transformation based upon the Girsanov theorem, where multi design times are introduced to cope with stationary or almost stationary behavior of the system. Finally, we give numerical examples to demonstrate the efficiency of the proposed scheme.     

Characterisation of oxide scale formation on a new single crystal superalloy for power generation applications

Abstract

The oxidation behaviour at 950°C of a prototype nickel-based single crystal superalloy containing ~15 wt%Cr is studied, with and without silicon alloying. It is demonstrated that the alloy is a marginal alumina former, with further alloying by Si promoting the formation of a continuous, protective alumina scale. Transmission electron microscopy reveals that out-growing alumina forms during the early stages of oxidation. The presence of silicon within the alumina is detected using atom probe tomography.     

回收PAFC废热与LNG冷能的动力循环分析

在液化天然气(LNG)作为磷酸型燃料电池(PAFC)燃料的电站中,大量的LNG冷能和PAFC废热被释放.提出一种利用LNG和环境作为冷源的双冷源动力循环和LNG直接膨胀做功相结合的回收PAFC废热和LNG冷能的能量系统.对循环的分析表明,当工质为水时,该循环对PAFC废热和LNG冷能的可用能的回收效率最大可达47%左右.     

Design of a high power heater for the cryogenic hydrogen system at J-PARC

The cryogenic hydrogen system, which provides the supercritical hydrogen with the pressure of 1.5 MPa and the temperature of around 20 K, adopts to moderate and convert high-energy neutrons into cold neutrons for neutron scattering experiments in the J-PARC. Large pressure fluctuation caused by the intense pulsed-proton-beam injection and trip should be mitigated by both an active heater control and a passive accumulator control. A compact high power heater should be required to compensate the heat load corresponding to the nuclear heating while the proton beam stopping. In this study, the high power heater used in the cryogenic hydrogen was designed and a numerical analysis was performed. Then the results confirmed that the heater could apply kW-order heat powers to supercritical hydrogen without any disturbance.     

Exact-solution of entropy generation for MHD nanofluid flow induced by a stretching/shrinking sheet with transpiration: Dual solution

In this article, attempts are made to present an exact solution for the fluid flow and heat transfer and also entropy generation analysis of the steady laminar magneto-hydrodynamics (MHD) nanofluid flow induced by a stretching/shrinking sheet with transpiration. This paper is the first contribution to the study of entropy generation for the nanofluid flow via exact solution approach. The governing partial differential equations are transformed into nonlinear coupled ordinary differential equations via appropriate similarity transformations. The current exact solution illustrates very good correlation with those of the previously published studies in the especial cases. The entropy generation equation is derived as a function of the velocity and the temperature gradients. The influences of the different flow physical parameters including the nanoparticle volume fraction parameter, the magnetic parameter, the mass suction/injection parameter, the stretching/shrinking parameter, and the nanoparticle types on the fluid velocity component, the temperature distribution, the skin friction coefficient, the Nusselt number and also the averaged entropy generation number are discussed in details. This study specifies that nanoparticles in the base fluid offer a potential in increasing the convective heat transfer performance of the various liquids. The results show that the copper and the aluminum oxide nanoparticles have the largest and the lowest averaged entropy generation number, respectively, among all the nanoparticles considered.