螺旋桨尾流场的数值分析

为了研究螺旋桨尾流场的分布规律,用数值方法计算了螺旋桨的扰动速度.在质量守恒定理和动量守恒定理的基础上建立不可压缩流体的控制方程.在数值计算过程中,采用了湍流模型和SIMPLEC算法,分析了螺旋桨的推力、扭矩以及表面压力分布情况.对螺旋桨的尾流场进行了数值计算,给出了在不同进速时螺旋桨诱导的径向、周向以及轴向诱导速度.分析了螺旋桨诱导速度的分布规律及其和进速系数之间的关系.从计算结果可以看出,进速系数越大,螺旋桨自身形状对其诱导流场的影响越大;进速系数越小,螺旋桨转速对其诱导速度影响越大.     

基于滑移网格技术的船桨相互干扰研究

船体和螺旋桨的相互干扰是非定常的,采用力场模拟和混合面模拟等方法,虽然能解决一些实际问题,但是在模拟实际流场的非定常性上则显得不够精确.为了研究船桨相互干扰的非定常水动力性能,基于滑移网格技术,使用CFD前处理软件ICEM CFD划分流场网格,采用DES湍流模型,实现了船体、螺旋桨、完整船桨组合这3种模型的水动力性能研究.预报值和试验值的比较显示,这3种模型的预报结果都和试验值吻合良好.同时,计算结果揭示了船体和螺旋桨的这种相互干扰,对湍流边界层影响不大,但是对船体表面和螺旋桨桨叶的静压力分布影响很大.     

旋翼无人机螺旋桨静拉力性能的计算与试验验证

针对旋翼无人机螺旋桨的设计需求,研究了旋翼无人机小型螺旋桨静拉力性能的工程计算方法,并构建了基于虚拟仪器的螺旋桨性能测控系统.采用涡流理论作为螺旋桨静拉力特性的计算方法,结合图形化设计软件LabVIEW,构建了螺旋桨静拉力测控试验台.通过该测控试验台对计算结果进行了对比验证,分析结果表明计算结果与实验数据趋势一致,最大平均相对误差不超过10%,吻合较好,准确度较高.     

螺旋桨模型喷气降噪试验与实船效果预报研究

螺旋桨若发生空化,空化就是全船最主要的辐射噪声源。采用喷气降噪技术可以降低螺旋桨的空化噪声。试验证实,在螺旋桨推力损失不大时,采用导边喷气、喷气环喷气、组合喷气三种方式都可以使噪声谱级大幅下降。根据喷气孔出口速度的无量纲值相等可以换算出实船喷气量。实船预报表明,采用喷气后总声级降低5 d B以上。     

EXPLICA: An Explorative Imperialist Competitive Algorithm based on the notion of Explorers with an expansive retention policy

Meta-heuristic algorithms are of considerable importance in solving optimization problems. This importance is more highlighted when the problems to be optimized are too complicated to achieve a solution using conventional methods or, the traditional methods are somehow not applicable for solving them. Imperial Competitive Algorithm has been proved to be an efficient and effective meta-heuristic optimization algorithm and it has been successfully applied in many scientific and engineering problems. By introducing the concept of explorers and retention policy, the original algorithm is enhanced with a dynamic population mechanism in this paper and hence, the performance of the Imperial Competitive Algorithm is improved. Performance of the proposed modification is tested with experiments of optimizing real-values functions and results are compared with results obtained with the original Imperialistic Competitive Algorithm, Genetic Algorithm, Particle Swarm Optimization and Simulated Annealing. Also, the applicability of the proposed improvement is verified by optimizing a ship propeller design problem.     

真空练制泥段的螺旋纹缺陷及其解决途径

阐述了陶瓷制品生产中真空练制泥段的螺纹缺陷及其解决途径。在陶瓷原料的组成、物理化学性能及含水率适宜,颗粒级别及其级配比例合适,泥料的陈腐处理得当以及坯体的干燥工艺参数合理的情况下,搅泥螺旋应优先采用适宜的螺旋升角(15～25°),挤泥螺旋及螺旋推进器的螺旋升角选用10～14°,挤泥螺旋与输泥筒间隙宜为3～5mm,并宜采用三轴卧式真空练泥机。同时,应采用双头、三头甚至四头螺旋的前倾型叶片的螺旋推进器,并在机头内腔泥料的入口处设置阻止泥料因惯性作用跟随螺旋推进器旋转的阻转棒及阻转筛板等装置。此外,还应确保挤泥螺旋(包括螺旋推进器)、输泥筒、机头和机嘴的同轴度,努力提高螺旋、输泥筒、机头和机嘴等工作表面的光滑平整度,并作好真空练泥机的维修保养、均匀加泥及抽真空装置的密封等工作。使泥料的可塑性得到较大提高,挤出的的泥料机械强度较大、致密度较高、含水率适宜及表面平整光洁,最大限度地减少泥段的螺旋纹缺陷。     

一体化氧化沟弯道流态特性研究

根据实测数据从流速分布的角度对增设水下推动器和弯道导流墙的一体化氧化沟弯道流态进行了研究分析，在实测和分析的基础上，提出了水下推进器和曝气转盘的合理设置位置，阐明了弯道导流墙对弯道流态的作用并提出了导流墙的合理设置方式，为实际工程设计提供了理论依据和参考。     

制造船用螺旋桨不锈钢材料的研究进展

船用螺旋桨是一种靠桨叶在水中旋转并将船舶主机转动功率转化为推力的装置，是船舶上重要的配件之一。随着北极航线的开通，冰区船舶引起各国船东极大的兴趣，从而将高强度不锈钢的螺旋桨推上了舞台。对制造船用螺旋桨的不锈钢材料进行了概述，介绍了目前国内外用于制造螺旋桨的不锈钢材料的研究现状，分析了国内外研究制造螺旋桨的不锈钢材料中存在的问题，指出了制造船用螺旋桨的不锈钢材料未来的发展趋势。     

Analysis of calibration results from cup and propeller anemometers. Influence on wind turbine Annual Energy Production (AEP) calculations

The calibration coefficients of several models of cup and propeller anemometers were analysed. The analysis was based on a series of laboratory calibrations between January 2003 and August 2007. Mean and standard deviation values of calibration coefficients from the anemometers studied were included. Two calibration procedures were used and compared. In the first, recommended by the Measuring Network of Wind Energy Institutes (MEASNET), 13 measurement points were taken over a wind speed range of 4 to 16 m s^?1. In the second procedure, 9 measurement points were taken over a wider speed range of 4 to 23 m s^?1. Results indicated no significant differences between the two calibration procedures applied to the same anemometer in terms of measured wind speed and wind turbines' Annual Energy Production (AEP). The influence of the cup anemometers' design on the calibration coefficients was also analysed. The results revealed that the slope of the calibration curve, if based on the rotation frequency and not the anemometer's output frequency, seemed to depend on the cup center rotation radius. Copyright © 2010 John Wiley & Sons, Ltd.     

Scale effects on propeller cavitating hydrodynamic and hydroacoustic performances with non-uniform inflow

Considering the lack of theoretical models and ingredients necessary to explain the scaling of the results of propeller cavitation inception and cavitating hydroacoustics from model tests to full scale currently, and the insufficient reflection of the nuclei effects on cavitation in the numerical methods, the cavitating hydrodynamics and cavitation low frequency noise spectrum of three geometrically similar 7-bladed highly skewed propellers with non-uniform inflow are addressed. In this process, a numerical bridge from the multiphase viscous simulation of propeller cavitation hydrodynamics to its hydro-acoustics is built, and the scale effects on performances and the applicability of exist scaling law are analyzed. The effects of non-condensable gas(NCG) on cavitation inception are involved explicitly in the improved Sauer’s cavitation model, and the cavity volume acceleration related to its characteristic length is used to produce the noise spectrum. Results show that, with the same cavitation number, the cavity extension on propeller blades increases with diameter associated with an earlier shift of the beginning point of thrust decline induced by cavitation, while the three decline slopes of thrust breakdown curves are found to be nearly the same. The power of the scaling law based on local Reynolds number around 0.9R section is determined as 0.11. As for the smallest propeller, the predominant tonal noise is located at blade passing frequency(BPF), whereas 2BPF for the middle and both 2BPF and 3BPF for the largest, which shows the cavitating line spectrum is fully related to the interaction between non-uniform inflow and fluctuated cavity volume. The predicted spectrum level exceedance from the middle to the large propeller is 6.65 dB at BPF and 5.94 dB at 2BPF. Since it just differs less than 2 dB to the increment obtained by empirical scaling law, it is inferred that the scale effects on them are acceptable with a sufficient model scale, and so do the scaling law. The numerical implementation of cavitating hydrodynamics and hydro-acoustics prediction of propeller in big scale in wake has been completed.