船用复合材料螺旋桨性能数值预报工具开发和应用

为进行船用复合材料螺旋桨性能的数值预报,用Python和MATLAB程序编程,通过有限元法和涡格法(Vortex Lattice Method,VLM)相结合的方法,开发考虑螺旋桨桨叶变形与流体之间相互影响的复合材料螺旋桨水动力性能预报工具.用网格算法生成结构化网格,进行变形和压力插值交换和迭代计算,解决复杂几何螺旋桨的快速精确建模问题以及结构变形计算与水动力性能预报之间的数据交换问题,实现船用复合材料螺旋桨的性能预报.     

基于iSIGHT平台DOE方法的螺旋桨敞水性能优化设计

传统的螺旋桨设计方法已经满足不了进一步提升其性能的要求,并且现代环境的变化不再仅仅要求螺旋桨某一性能的最优,而是多方面综合性能的最优.iSIGHT多学科优化设计平台提供了完整的设计综合环境和先进的优化设计方法,能够完成设计过程的自动化和智能的设计探索,确定最佳设计参数.基于iSIGHT平台的实验设计方法建立的螺旋桨敞水性能优化方法使螺旋桨效率和最小压力系数都有提高,实现了优化目的.     

螺旋桨静推力数值模拟与实验对比分析

针对飞艇项目研制的工程实际需求,通过经验公式和CFD数值模拟两种方法对螺旋桨的静推力特性进行了计算和对比分析;最后通过设计发动机-螺旋桨推力实验台的实验对上述两种方法得出的结果进行了验证.分析结果表明螺旋桨静推力经验公式和实验结果相吻合,公式可以在以后的工程应用中使用;在一定的边界条件下,CFD计算的结果与实验值接近,说明使用的CFD计算方法是可取的.在CFD数值模拟计算过程中,实验值和经验公式估算值可以在确定CFD的边界条件以及确认计算结果的准确性方面提供重要的参考依据.     

大型螺旋波纹管内流动与传热的数值模拟研究

利用流体仿真软件FLUENT对不同结构参数的某大型螺旋波纹管管内烟气的流动和传热进行了三维稳态数值模拟,比较和分析了螺旋波纹管和光滑管的换热性能,并通过控制变量法研究了螺纹高度、螺纹宽度和螺距等结构参数对螺旋波纹管综合换热性能的影响。研究表明,随着螺纹高度和螺距的增大,螺纹宽度的减小,螺旋波纹管的综合换热性能获得相应的提高。本文还依据模拟的结果,通过回归分析拟合出了努赛尔数、摩擦因数以及综合换热效率的相应关联式,并且通过优化给出了换热管综合换热效率最高时的结构参数,为螺旋波纹管的工业应用提供了理论支持和技术储备。     

海浪扰动下水下航行器的动力定位性能分析

水下航行器动力定位是通过对水下航行器的多个螺旋桨推进器的转速、推力进行控制调节以抵御外界环境扰动,体现了水下航行器在外界环境扰动下执行各种任务的能力.通过对随机波浪扰动下的水下航行器前向动力定位进行建模仿真,分析得到各个状态特性与环境扰动分量对水下航行器动力定位性能的影响.进行了水下航行器的运动方程和螺旋桨动力学特性的精确建模;再针对波频扰动下的变参数问题以及控制器的鲁棒性和自适应性要求,建立了水下航行器动力定位滑模控制器;最后,将PM谱的随机波浪扰动应用于动力定位仿真研究,仿真结果显示,螺旋桨的动力学特性、幅值限制以及波浪的流速与加速度信息直接影响了水下航行器的动力定位性能.     

2自由度振荡水翼推进性能分析及实验研究

为了研究仿生水翼推进性能,设计了一种2自由度振荡水翼推进装置.实现了基于升力/阻力模式的2种振荡水翼推进方式.研制了振荡水翼推进性能实验平台,在循环水池环境下完成了不同参数耦合情况下振荡水翼推进性能实验.利用6轴力传感器测量水翼振荡时产生的推力/升力,并将实验结果与数值模拟结果对比,分析不同参数对推进性能的影响.实验结果表明,在升力推进模式下,增加拍旋运动幅值和振荡频率可以提高平均推力;随着位旋运动幅值的增加,平均推力呈现先增大后减小的趋势;随着来流速度的增大,平均推力逐渐减小.在阻力推进模式下,增加拍旋运动幅值和振荡频率均可提高平均推力.     

可调距螺旋桨推进特性分析及控制系统研究

介绍了可调螺距螺旋桨的定义及工作原理,并归纳了可调螺距螺旋桨推进装置的工作特性及特点,通过与定距桨进行的对比分析,总结出适用于可调螺距螺旋桨的三类船舶;目前调距桨控制系统一般采用传统的PID控制方法,但由于PID控制器的参数不便于调节,不能取得良好的控制效果,从而提出了基于模糊神经网络控制的调距桨控制系统的设计,以提高调距桨在各种工况下的控制效果,仿真试验结果表明了调距桨控制系统设计的合理性.     

扭振测量方法及新型扭振测试系统研究

轴系的动态扭矩及扭转振动是影响机械工作可靠性与使用寿命的主要因素之一,对轴系扭转振动的测红分析,可以得到机器工作性能和轴系受力情况等重要信息.对于扭振分析,其最直接或最简单的是在对测点处的扭矩信号进行分析,与阶次分析原理相同,扭振分析的最终结果是得到不同转速下,不同谐次下的扭矩信号的幅值,然后依此为基础找到轴系的共振转速.在此基础上,可以根据计算数,得到轴系不同位置处的应力或者扭矩幅值,从而达到测试或监测扭振信号.研制了扭振测试分析仪,并对扭振测试方法和实现途径进行了阐述,通过买例证明,此方案简单、可行,可用于实际工程.     

基于BP神经网络的VVP水动力系数预报

将BP神经网络应用于全方位推进器周期螺距状态推力系数和转矩系数预报.针对BP神经网络在训练中存在的学习速度慢、易于陷入局部最小等缺点,采用变学习率的BP算法加以改进.对全方位推进器周期螺距状态推力系数和转矩系数进行预报,结果表明,预报值的精度明显高于由近似公式计算所得的值,采用BP神经网络对全方位推进器周期螺距状态的推...     

静止和旋转孤立车轮局部流场的评价

为研究车轮周围流场特征,分别对某孤立车轮静止和旋转工况下周围流场进行数值研究,并给予试验验证.计算采用定常雷诺时均纳维斯托克斯方程.在1∶15的模型风洞中进行试验.数值模拟结果与试验数据吻合.针对数值模拟结果,详细分析静止和旋转孤立车轮周围流场的流动情况、表面压力因数、气动阻力因数和气动升力因数等,得到孤立车轮旋转对车轮附近局部流场的影响以及形成机理.车轮的转动使总体压差减小,降低气动阻力和升力,改善气动性能。     

Interactive computer programme to facilitate diesel engine/propeller matching

The general problem of matching a diesel engine to a propeller is solved using a computer programme. The programme can deal with any engine specified by constraints on its power speed characteristic readily available from manufacturers, and any hull form provided resistance vs speed curves are available either from scale model experiments, standard curves or sea trials. For any selected propeller diameter, gear ratio or propeller blade area ratio the programme automatically calculates the maximum ship speed which just satisfies the engine constraints over a range of propeller pitch ratio values. The calculation is based on using a data bank of previously. stored model series thrust and torque parameters, and the resulting forward speed vs pitch ratio curve is presented on a graphics terminal. Families of these characteristics can be automatically generated for selected variations in propeller diameter, blade area ratio, gear ratio or for different resistance vs speed curves which may represent other ship displacements, trims or account for fouling, weather, etc. The display curves are stored and may be interactively retrieved under light pen control so that rapid comparisons can easily be drawn between different parameter selections.As an example of the use of the programme the paper describes the design of a propulsion system for a small commercial vessel using hypothetical data, and thus demonstrates the sensitivity of speed vs pitch ratio characteristic variations with propeller diameter, gear ratio, blade area ratio and displacement, and some general conclusions may be drawn from the results presented.     

Analysis of underwater thruster model with ambient flow velocity using CFD

Thrust force is a very important factor for underwater vehicles. The thrust force that is determined by the pressure gradient between a propeller and a thruster can be represented by the ambient flow velocity introduced as the control volume and the axial flow velocity of a propeller. Because a change in ambient flow velocity triggers a change in the pressure gradient between a propeller and a thruster, a model taking account of the ambient flow velocity is required for an unmanned underwater vehicle (UUV) system. However, the axial flow velocity introduced into a propeller is very difficult to measure without accurate test devices. Therefore, in this study, the axial flow velocity is calculated with the computational fluid dynamics (CFD) method to use it as a basis for estimating the approximate value of the thrust force. As a result, a relatively accurate analysis of the effect of the ambient flow velocity on the thrust force can be obtained with considerable time and cost effectiveness as compared to the existing experimental methods. To evaluate the validity of the data from the CFD analysis results depending on the change in ambient flow velocity and the pressure gradient of a thruster, the resulting CFD values were compared with the thrust forces obtained in the previously performed thrust force experiment of a thruster depending on the ambient flow velocity in a circulating water channel.     

Development of a dual-shaft propeller thruster equipped with rotational speed sensor for UVMS control

Majority of underwater robots utilize single propeller thrusters for navigation. A disadvantage of using a single-shaft propeller thruster is that the thrust force generated from a single propeller for reverse and forward thrust is asymmetric due to the disturbed flow caused by the thruster’s body which may reduce thruster efficiency. Moreover, measurement procedures to precisely calculate propeller’s rotation speed were also not available. To address these problems, this paper proposes a dual-shaft magnetic coupling-driven propeller thruster for underwater robot, equipped with sensors for measuring propeller’s rotational speed. Numerical studies and experimental results on the position and orientation control of the proposed thruster are presented. Detail comparison of the rotational speed, thrust force and duty ratio between numerical calculation and actual experimental measurement results show the effectiveness of the proposed thruster. This paper also demonstrated that by using the proposed thruster, the control performance of an underwater robot can be improved significantly compared to commercially available thruster. The ability to determine propeller rotation directions is also a major advantage of this work.     

Controllable pitch propeller optimization through meta-heuristic algorithm

This paper describes a methodology to design and optimize a controllable pitch propeller suitable for small leisure ship boats. A proper range for design parameters has to be set by the user. An optimization based on the Particle Swarm Optimization algorithm is carried out to minimize a fitness function representing the engine’s fuel consumption. The OpenProp code has been integrated in the procedure to compute thrust and torque. Blade’s geometry and tables about pitch, thrust and consumption are the main output of the optimization process. A case study has been included to show how the procedure can be implemented in the design process. A case study shows that the procedure allows a designer to sketch a controllable pitch propeller with optimal efficiency; computational times are compatible with the design conceptual phase where several scenarios must be investigated to set the most suitable for the following detailed design. A drawback of this approach is given by the need for a quite skilled user in charge of defining the allowable ranges for design parameters, and the need for data about the engine and boat to be designed.

     

基于CFD的船舶斜浪三自由度运动仿真研究

针对船舶在斜浪中的多自由度耦合运动问题, 建立了三维粘性流耐波性数值波浪水池, 采用边界条件造波法生成高精度的斜向规则波, 通过同时求解RANS方程和刚体运动学方程, 结合网格整体移动方法和滑移网格方法, 实现了船舶斜浪航行的垂荡、纵摇及横摇三自由度耦合运动数值模拟。给出了DTMB5512船模斜浪中的垂荡、纵摇及横摇的频率响应函数, 与线性切片理论计算结果进行比较, 吻合良好。该方法可为船舶斜浪航行的耐波性预报提供一种有效的途径。     

基于CFD近似模型的船尾线型多目标综合优化

为提高船体的优化效率,以国际标准船型KCS为研究对象,以船舶总阻力和桨盘面伴流不均匀度为优化目标,建立近似模型,完成KCS船尾线型的优化,得到优化船型．通过优化结果可知：对于母型船,在满足工程约束条件下,通过船尾优化可以得到总阻力未增加、船尾流场品质有明显改善的船体线型．     

A multi-level optimization technique based on fuel consumption and energy index in early-stage ship design

Reducing lifetime fuel consumption (LFC) and energy efficiency design index (EEDI) are two of the main concerns of shipping industry in recent years. This paper presents a multi-disciplinary and multi-level optimization scheme-based software (HPS-MOP2) to design a hull–propeller system simultaneously from the LFC and EEDI point of view in early-stage ship design. Calculations of the ship resistance and propeller performance are essential to optimize the ship hull–propeller system. Two numerical methods with variable fidelity, non-uniform rational basis spline (NURBS) geometry modelling technique and new version of multi-objective evolutionary algorithm based on decomposition (MOEA/D) are three main parts of the proposed methodology. A bulk carrier propelled by a well-known propeller is used as a base model in three different study cases based on specific fuel oil consumption (SFOC) curves provided by the engine manufacturers Wartsila, MAN and Caterpillar. The presented results illustrate that the employed approach may achieve cost- and energy-efficient designs.

     

Dynamic positioning of drilling vessels with a fuzzy logic controller

A fuzzy logic controller for dynamic positioning of drilling vessels in deep water is presented. The core of the fuzzy controller is a set of fuzzy associative memory (FAM) rules that correlate each group of fuzzy control input sets to a fuzzy control output set. A FAM rule is a logical if-then-type statement based on one's sense of realism and experience or can be provided by an expert operator. The design of the fuzzy controller is very simple and does not require mathematical modelling of the complicated nonlinear system based on first principles. The fuzzy controller uses measured vessel heading, yaw rate, distance and velocity of the vessel relative to the desired position (location and heading) to generate the control outputs to bring the vessel to and maintain it in the desired position. The control outputs include the rudder angle, propeller thrust and lateral bow thrust. The effectiveness and robustness of the fuzzy controller are demonstrated through numerical time-domain simulations of the dynamic positioning of a drill ship of Mariner Class hull with use of nonlinear ship equations of motions.