A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

The twin unidirectional turbine topology was recently proposed with the promise of very significant improvements in the energy capture in Oscillating Water Column (OWC) based wave energy plants. Here, we present the initial results of the experimental validation of the twin unidirectional impulse turbine topology. A scale model of the concept was built and tested using simulated bidirectional flow. The model consists of two 165 mm impulse turbines each individually coupled to 375 W grid connected induction machines. An oscillatory flow test rig was used to simulate bidirectional flow to test the model. The results of the experiments validate the concept of the twin turbine configuration. The proposed topology utilizes no moving parts and achieves more than 50% efficiency over a broad range of flow coefficients. A comparison with other competing turbines (viz, a twin Wells’ turbine, a linked guide vane impulse turbine and a fixed guide vane impulse turbine) is done, based on actual measurements in the Indian wave energy plant. The results from the experiments are scaled to evaluate the design features of a 50 GWh wave energy plant.     

Loss analysis and design optimization of a small scale mixed-flow pump turbine using the orthogonal method

为了研究各部件对小型混流式水泵水轮机水泵工况和水轮机工况下水力性能的影响,对一小型水泵水轮机进行不同流量下的全流道数值模拟,针对两工况下总压损失集中的叶轮进行正交设计优化。应用L9（3⁴）正交表,选取4个叶轮关键设计参数,以水泵工况扬程偏离率、效率和水轮机工况效率作为目标,进行4因素3水平的正交设计,并通过全流道数值模拟方法和极差分析方法进行选优。结果表明叶片出口直径对泵和水轮机工况性能影响最大,优化后水泵设计工况效率提高了1.06%,水轮机设计工况效率提高1.62%,其相应最优工况点因包角增加而向小流量工况移动。     

Enhanced multi-objective optimization of a microchannel heat sink through evolutionary algorithm coupled with multiple surrogate models

A liquid flow microchannel heat sink has been optimized with the help of three-dimensional numerical analysis and multiple surrogate methods. Two objective functions, thermal resistance and pumping power have been selected to assess the performance of the microchannel heat sink. The design variables related to the width of the microchannel at the top and bottom, depth of the microchannel, and width of fin, which contribute to objective functions, have been identified and a three-level full factorial design was selected to exploit the design space. The numerical solutions obtained at these design points were utilized to construct surrogate models, namely Response Surface Approximations, Kriging and Radial Basis Neural Network. A hybrid multi-objective evolutionary algorithm coupled with surrogate models is applied to find out global Pareto-optimal solutions. The accuracy of the surrogate models has been discussed in view of their predictions and trade-off analysis was performed in view of conflicting nature of the two objectives. The Pareto-optimal sensitivity of the design variables has been found out to economically compromise with the design variables. The application of the multiple surrogate methods not only improves quality of multi-objective optimization but also gives the feedback of the fidelity of the optimization model.     

Torque and efficiency maximization for a wave energy harvesting turbine: an approach to modify multiple design variables

Multiple design variables modifications are carried out for a bidirectional flow turbine used in an oscillating water column wave energy converter to enhance its performance by maximizing the peak torque‐coefficient (TC) and the corresponding efficiency (EFF), which are the objective functions of this problem. The Latin hypercube sampling technique selects samples from a designed space created by the design parameters defined for the blade sweep and aerofoil profile thickness modifications. The objective function values are obtained by solving Reynolds‐averaged Navier–Stokes equations and are approximated by surrogate models. The models help in generating populations of the genetic algorithm, which finally produces a set of optimal designs in a Pareto optimal front. Only two extreme designs among the five clustered points are further evaluated by solving Reynolds‐averaged Navier–Stokes equations to cross‐check the validity of the optimization steps. It is found that the TC is increased by 33% and the EFF is decreased by 5% at one extreme cluster point, while the other extreme point gives that both the TC and the EFF are higher by 1.8% and 2.9%, respectively, as compared with the reference geometry. The optimal geometry has a wider operating range, which is an important parameter to get continuous power from a wave energy converter. Copyright © 2016 John Wiley & Sons, Ltd.     

非均匀热负荷条件下的平板冲击冷却优化

冲击冷却是涡轮冷却中常见的方式,其优化设计涉及多种几何参数,是典型的高维问题。在冲击冷却结构的设计过程中,需要根据涡轮的热负荷情况适应性地设计冷却结构,以提高综合冷却效率和表面温度的均匀性。实验或数值模拟耗时长且成本高,而代理模型可以快速预测结果,配合计算机自动寻优算法可显著提高设计效率和效果。为了降低优化设计的成本、提高优化过程的效率,以平板冲击冷却为研究对象,同时考虑非均匀热负荷的影响,通过数值模拟构建数据集,建立了基于迭代算子神经网络的代理模型,并使用遗传算法对斑状非均匀热载荷条件下孔位置排布进行了优化。优化结果显示：对于优化潜力较低的结构,优化策略保持了靶板平均温度水平不变;对于优化潜力较高的结构,可以降低靶板平均温度约2.6 K;所研究各结构的表面温度标准差普遍降低70%以上。     

短距起飞/垂直降落战斗机升力风扇驱动方案研究

为了降低短距起飞/垂直降落战斗机轴驱动升力风扇驱动系统的设计制造难度,提出了一种利用发动机外涵道抽气在小涡轮中做功以驱动升力风扇的新方案,并建立了小涡轮驱动方式下的总升力和热效率计算模型。对总升力和热效率的计算结果表明,在选取合适的抽气比及小涡轮进气温度时,小涡轮驱动方式所产生的总升力与轴驱动方式相当或更大。小涡轮驱动方式除垂直起降阶段系统热效率略低外,在质量控制、设计开发难度、调节与控制、升力风扇布置灵活性等方面均具有优势。     

Efficient incorporation of fatigue damage constraints in wind turbine blade optimization

Wind turbine design is a challenging multidisciplinary optimization problem, where the aerodynamic shapes, structural member sizing, and material composition must all be determined and optimized. Some previous blade design methods incorporate static loading with an added safety factor to account for dynamic effects. Others incorporate dynamic loading, but in general limit, the evaluation to a few design cases. By not fully incorporating the dynamic loading of the wind turbine, the final turbine blade design is either too conservative by overemphasizing the dynamic effects or infeasible by failing to adequately account for these effects. We propose an iterative method that estimates fatigue effects during the optimization process while quickly converging to the true solution. We also demonstrate an alternate approach where a surrogate model is trained to efficiently estimate the dynamic loading of the wind turbine in the design process. This surrogate model, once trained, was then incorporated in the optimization loop of the wind turbine blade. In contrast to the iterative method, there is significant upfront computational cost to construct the surrogate model. However, this surrogate model has been generalized to be used for different rated turbines and can predict the fatigue damage of a wind turbine with less than 5% error for baseline wind turbines of the same family. These methods can be used instead of the more computationally expensive method of calculating the dynamic loading of the turbine within the optimization routine.     

基于自适应Kriging代理模型的叶型气动优化设计

基于自适应Kriging代理模型的近似代理技术,采用Bézier函数实现叶型几何参数化,并结合CFD性能求解,建立了叶型优化设计方法,改进了该代理方法的寻优过程,通过Bézier控制点实现叶型几何变化的控制,自动完成某涡轮叶型头部型线的优化设计.结果表明:优化后的叶型压力恢复系数有所增大,提高了叶型的性能,验证了该优化系统的可靠性,提高了叶型优化的效率.     

A novel radial self-rectifying air turbine for use in wave energy converters. Part 2. Results from model testing

The paper presents results from model testing of a self-rectifying radial-flow air turbine, that is being developed as an alternative to the axial-flow self-rectifying turbines for applications in wave energy conversion. In the new machine, named biradial turbine, the flow into, and out of, the rotor is radial. The rotor is surrounded by a pair of radial-flow guide-vane rows. The downstream guide vanes are prevented from obstructing the flow coming out of the rotor by axially displacing the whole guide vane set. The turbine model, with a 0.488 m diameter rotor, was tested in unidirectional flow. Experimental results are shown, in dimensionless form, for efficiency, power and pressure head versus flow rate. They are compared with predictions from CFD computations. The results from model testing were used to estimate the time-averaged efficiency of the turbine subject to the irregular bidirectional air flow induced by random waves.     

船用重油多元模型燃料的构建与验证

为了复现实际船用重油燃料燃烧特性,基于化学解构法原理,提出了重油多元模型燃料。选择了正十四烷、2,6,10-三甲基十二烷、四氢化萘和正癸基苯作为基础燃料,表征实际重油的正构烷烃、异构烷烃、环烷烃和芳烃成分。模型燃料的比例依据带权欧几里得距离算法进行最优化求解。针对发展的多元模型燃料,基于流动反应器试验平台对模型燃料的中低温氧化特性进行点对点比较,多组分模型燃料成功复现了典型反应物、中间产物和生成物浓度随温度变化的趋势。基于"解耦法"的机理简化方法,发展了重油多组分模型燃料骨架机理。该机理成功预测了重油馏分的中低温氧化特性。基于该骨架机理进行敏感性分析,得到烷烃类自由基主导的基元反应与重油碳烟生成密切相关的结论。此外,基于定容燃烧装置数值仿真结果,证明了重油多组分模型燃料对近发动机条件下的喷雾燃烧过程具有较高的预测能力。     

某国产300MW汽轮机经济性分析及优化改进

文章从宏观通流匹配设计方面对某国产亚临界双缸双排汽凝汽式300MW汽轮机的高、中压通流的效率进行了客观分析，并在此分析基础上提出了改进设计思路，按照改进思路完成了改进设计方案，用三维CFD方法对改进前后机组的经济性水平进行了评价。改造前后的经济性分析及机组的实测热耗结果表明，改进设计后机组的经济性达到同类机组的世界先进水平。     

某型航改燃气轮机机匣安装边结构参数优化设计

航改燃气轮机机匣安装边的性能受多个结构参数和载荷参数的影响,为了在给定的结构参数和载荷参数范围内设计性能最优的安装边结构,提出一种机匣安装边结构参数优化设计方法。首先,采用拉丁超立方抽样方法进行实验设计,构建仿真算例样本空间;其次,采用有限元分析方法分析了螺栓孔中心距、螺栓孔直径、安装边厚度等结构参数和机匣内介质压力、介质温度、单个螺栓预紧力等载荷参数对安装边最大等效弹性应力、接触面平均间隙和接触面最大接触压强等特性的影响规律;然后,构建了机匣安装边密封性能计算的代理模型,并对给定工况下燃气轮机机匣安装边结构进行了参数优化设计;最后,针对安装边结构优化设计结果,试验验证了其密封性能以及代理模型的计算精度。结果表明：基于代理模型计算得到的机匣安装边结构密封性能与试验结果误差在10%以内,该方法可用于航改燃气轮机机匣安装边结构的工程优化设计与性能评估。     

基于CFD的微水头双向水轮机叶片比选及整机性能分析

针对微水头双向灯泡贯流式水轮机叶片翼型和形状对其性能的影响,在相同设计水头下,对3种叶片的微水头双向贯流式水轮机进行了CFD数值模拟,对比分析了正反向工况下3种叶片的水轮机的外特性(流量、效率、出力)、叶片表面静压分布和相对流速矢量分布,最终确定了叶片C为较优叶片,进而分析了较优水轮机模型下的各部分水头损失以及内部流场规律。结果表明,正向工况下由于灯泡体后置,使得出水流道内出现回流、漩涡等不良流态,增加了撞击损失,故正向工况的效率低于反向工况。     

燃气涡轮机导片与转子叶片交互作用的非定常流场数值模拟

采用ICEM-CFD软件建构O-H网格系统,分别模拟两种不同的涡轮导片及转子叶片间隙在转动效应下流场结构.模拟的数据与实验值做比较后,发现本研究在涡轮导片及转子叶片流场预测上,已能有效预测流场的边界层流、分离流的发展以及导角叶片与转子叶片间的多震波的流场现象,另外亦能针对涡轮叶片压力总损失及轮机效率加以分析,为涡轮机的改进设计和优化提供了理论依据.     

向心透平内部流动的数值分析及叶轮的改进设计

本文对一微型燃气轮机向心透平内部的三维流场进行了数值研究。在流场模拟的基础上对原结构的内部流场进行了分析探讨,指出原设计中可以改进的地方并成功的对叶轮进行了改进设计,使向心式透平效率提高了二点几个百分点。     

冲动式与反动式汽轮机的优劣比较

文中就冲动式汽轮机和反动式汽轮机在结构特点、蒸汽流动特性以及运行效率上作了详细的分析比较。说明了两类汽轮机在技术及选型中相辅形成的辩证关系。     

Numerical simulation of tip clearance flow passive control in axial turbine

This paper focuses on the effects of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip, a double squealer tip, a pressure side tip shelf with inclined squealer tip on a double squealer tip, a tip platform extension edge in pressure side and in suction side respectively. A pressure-correction based, 3D Reynolds-averaged Navier-Stokes equations CFD code with Reynolds Stress Model was adopted. The variable specific heat was considered. The detailed tip clearance flow field with different squealer rims was described with the streamline and the velocity vector. Accordingly, the mechanisms of five passive controls were elucidated; the effects of the passive controls on turbine efficiency and tip clearance flow field were illuminated. The results showed that the secondary flow loss near the outer casing including the tip leakage losses and the passage vortex losses could be reduced in all the five passive control methods. The turbine efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine efficiency, and the efficiency increased by 0.215%.     

叶片开度对贯流式水轮机飞逸过程的影响

为有效降低水轮机飞逸过程中机组的振动问题,通过水轮机试验模型改变导叶开度和桨叶开度对水轮机过渡过程进行研究,分析了多个监测点的压力、频率流量等工作参数的变化情况.结果 表明,由于转速和流量的增加,水轮机在导叶开度60°和桨叶开度4°运行时振动最为强烈,水轮机在低频时振动剧烈.由于受到导叶和桨叶动静影响,转轮出口振动强烈...     

多级涡轮三维黏性流场的数值模拟

采用多叶片排网格生成技术，利用实质为标准κ-ω模型的改进型BSL双方程湍流模型对一个四级低压动力涡轮进行了数值模拟，其中多叶片排间参数传递采用“混合平面”方法。通过设计工况下计算结果和设计参数的对比，分析了此型多级涡轮的气动特点。末级导叶正弯优化设计显示弯叶片提高了此型多级涡轮的通流性能，同时也表明了弯叶片优化设计时进行多级黏性流匹配计算的必要性。     

跨音速向心汽轮机气动设计分析

通过一维设计与三维数值模拟分析相结合的方法,对一台300kW向心汽轮机进行了气动设计。汽轮机整级焓降达到248.5kJ,压比达到4.17,为了提高整级效率,反动度值比较小,致使导叶栅中存在超音速流。对导叶和叶轮内部流动特性进行具体分析,并对设计过程中碰到的一些问题进行探讨。