摘要：无人自治水下机器人作为一种高技术海洋探测手段,近年来得到了广泛的重视和快速发展。无人自治水下机器人完成测量任务返回水面时,其抛缆机构抛射出一个浮子,浮子上系有用于回收的缆索。文中设计了用于回收浮子打捞锚钩的抛射枪。首先利用计算流体力学软件来计算锚钩的空气阻力系数,然后对抛射体运动进行动力学分析。通过研究锚钩重量、初速度和抛射角等参数对抛射距离的影响,确定锚钩重量和发射初速度等设计参数。在此基础上设计了储能弹簧和抛锚枪总体结构。该枪可实现空仓挂机,具有安全方便、工作可靠的优点。

摘要：目的为了优化精密涂布印刷机的设计,并研究在精密涂布过程中薄膜的传输稳定性。方法将空气阻力模化为随从力,通过微分求积法,分析随从力、张力比和长宽比对薄膜稳定性的影响。结果通过编程计算分析得到,相同条件下的对边固支对边自由的不稳定区域大于四边固支的不稳定区域,且随着张力比的增加,系统的稳定区域逐渐减小。结论薄膜在相同随从力的作用下,张力比对薄膜振动的稳定性有显著影响。为精密涂布印刷机的优化设计制造以及精密涂布过程中薄膜的传输稳定性提供理论指导和依据。

摘要：本文以计算流体力学(CFD)为基础,采用有限体积法探求了应用计算流体力学(CFD)研究汽车车身外部流场的可行性。计算机数值解提供了诸如:气动压力场、速度场等车身压力、速度分布以便于获得气动阻力、气动升力和气动侧向力及其由此可得的相关力矩等信息。三维理想轿车车身空气动力学特性参数的数值模拟结果与风洞实验数据吻合较好。进一步应用于实车分析表明:数值模拟研究汽车空气动力学特性切实可行。

摘要：With the continuous improvement of the train speed, the dynamic environment of trains turns out to be aerodynamic domination. Solving the aerodynamic problems has become one of the key factors of the high-speed train head design. Given that the aerodynamic drag is a significant factor that restrains train speed and energy conservation, reducing the aerodynamic drag is thus an important consideration of the high-speed train head design. However, the reduction of the aerodynamic drag may increase other aerodynamic forces (moments), possibly deteriorating the operational safety of the train. The multi-objective optimization design method of the high-speed train head was proposed in this paper, and the aerodynamic drag and load reduction factor were set to be optimization objectives. The automatic multi-objective optimization design of the high-speed train head can be achieved by integrating a series of procedures into the multi-objective optimization algorithm, such as the establishment of 3D parametric model, the aerodynamic mesh generation, the calculation of the flow field around the train, and the vehicle system dynamics. The correlation between the optimization objectives and optimization variables was analyzed to obtain the most important optimization variables, and a further analysis of the nonlinear relationship between the key optimization variables and the optimization objectives was obtained. After optimization, the aerodynamic drag of optimized train was reduced by up to 4.15%, and the load reduction factor was reduced by up to 1.72%.

摘要：当速度大于300 km/h的高速列车紧急制动时,风阻制动是一种行之有效的辅助制动措施。基于三维定常不可压的黏性流场N-S和k-ε双方程模型,采用计算流体动力学方法对带制动风翼板的高速列车气动性能做初步分析,分别从列车所受气动阻力、垂向力、横向力、流场气动干扰效应、气动噪声等方面对首排制动风翼板在不同纵向位置、不同迎风角度和不同组风翼板纵向布置的选择做了详细计算说明。初步研究表明:(1)当头车车顶安装单排制动风翼板的高速列车在行驶速度为350 km/h的过程中采取紧急制动时,列车所受的空气制动阻力比未安装风翼板时增大约45%,所受垂向升力增大约70%;(2)采用风阻制动时制动风翼板迎风面所受最大压力和平均压力随着速度增大从远环境压力值呈抛物线形式增加,所受最小压力从远环境压力值呈倒抛物线形式减小;(3)在首排风翼板安装位置距离头车司机室前端流线型尾端连接处2 m范围内,列车空气阻力随着距离的增大而降低,所受垂向升力基本保持不变,风翼板前后形成的正负压区范围逐渐变小减弱;(4)首排制动风翼板迎风角在45°~90°内逐渐扩大时,列车所受空气阻力基本保持不变,垂向升力呈先增大后缓降的趋势,气动干扰效应和风翼板迎风面的高压区域逐步减弱;(5)在列车头车车顶最大等间距布置多组制动风翼板时,随着风翼板布置组数的增多,列车承受的空气阻力缓慢增加,垂向升力基本保持不变,制动风翼板间气动干扰效应逐渐增强,风翼板迎风面受压呈现出第1组的受压最大,后续各组压力峰值基本保持一致,略有波动。

摘要：高空坠物落点研究对建筑高空坠物的安全防护设计具有意义,目前的研究主要偏重于统计和经验。基于高空坠物的物理过程,考虑空气阻力的影响,提出了高空坠物落点理论模型;基于高空物体意外踢落过程中的能量转换,提出了高空物体意外踢落后水平初始速度计算的理论公式;根据施工现场坠落物的特点,基于高空坠物落点理论模型,计算了施工现场高空坠物散落半径,给出了施工现场地面安全防护水平宽度。

摘要：为了探究结构参数对空冷元件流动传热特性的影响规律,为空冷凝汽器优化选型提供参考,通过实验室性能试验,研究不同结构尺寸的单排管直接空冷换热元件的热动力性能。结果表明:迎面风速增加,单排管空冷元件传热系数增大,空气阻力亦随之增大;在元件结构参数基本相同的前提下,迎面风速一定,随着翅片厚度减小,空气阻力降低,换热效果增强。据此,将单排管空冷元件与双排管空冷元件的流动换热特性进行技术对比,发现在工程设计常用的迎面风速下,单排管空冷元件与双排管空冷元件的换热系数相当,而单排管空冷元件的阻力明显小于双排管。

摘要：水舌挑距是泄洪消能最基本参数之一,消能形态、冲击区域、冲坑深度、水流衔接均与其密切相关。为研究高海拔地区气压降低对挑射流特性的影响,采用减压模型试验的方法研究了环境气压对水舌挑距的影响程度。结果表明,气压与水舌挑距呈良好的线性关系,气压越低,因空气阻力越小,水舌挑距越远;气压每下降15kPa,对水舌内缘与外缘的最大影响程度分别为1.67%、1.48%;低气压环境下水舌空中扩散与掺气减弱,水舌厚度变薄,水流呈集中趋势。基于气压与空气阻力影响系数关系,修正规范水舌挑距计算公式,为高海拔地区挑射流设计提供参考。

摘要：制动系统是高速列车关键技术之一。随着列车运行时速的提高,采用组合制动方式来保证高速列车紧急制动时达到规定的制动距离成为常见的做法。近年来,传统机械制动方式日趋成熟,因此,不依赖轮轨间黏着的非黏着制动方式越来越受到相关设计人员的重视。介绍了一种基于某型速度400 km/h动车组列车开发的高速列车“蝶形”风阻制动装置,该型风阻制动装置采用小型风阻板进行空气动力制动,质量较轻,结构较简单。通过在车顶合理布置,可将风阻制动力分散于整车,提升紧急制动时的运行稳定性。阐述了其基本原理、开闭机构、响应时间等性能和技术指标,并采用计算流体力学(CFD)方法对其进行了不同工况下制动力的计算评估。

摘要：Convection heat transfer coefficient and air pressure drop in sinter layer are important factors for the design of sinter cooling craft. Due to the lack of necessary data, the two parameters are studied by experimental method. The experimental results show that heat conduction of sinter impacts the measurement of convection heat transfer coefficient. Convection heat transfer increases with the increase of air volumetric flow rate. Sinter layer without small particles(sample I) gives higher convection heat transfer coefficient than that with small particles(sample II). Under the considered conditions, volumetric convection heat transfer coefficient is in the range of 400-1800 W/(m3·°C). Air pressure drop in sinter layer increases with the increase of normal superficial velocity, as well as with the rise of air temperature. Additionally, air pressure drop also depends on sinter particle size distribution. In considered experimental conditions, pressure drop in sinter sample II is 2-3 times that in sinter sample I, which resulted from 17% small scale particles in sinter sample II.