叶片扩压器进口安装角对离心压缩机性能影响的数值与实验研究

对不同扩压器进口安装角下离心压缩机的性能进行了实验研究,并详细计算分析了相应的流场分布。分析表明, 不同的进口安装角对压缩机的流动有较大的影响,压缩机的性能曲线也有不同程度的左右偏移;进口处较大的正冲角和负冲角均会在扩压器叶片表面出现大尺度的分离涡团;在给定的流量工况下,应存在一个最佳的进口安装角,使得扩压器效率最高;设计工况下,最高效率所对应的冲角并非为零。     

空间可见光相机的杂散光分析与抑制

当空间可见光相机对地物目标进行成像时,视场内外的辐射会引起像面上产生杂散辐射,从而降低相机的成像质量,严重时可能会造成相机无法正常工作。为了提高相机的成像性能,介绍了可见光系统中杂散光的产生机理及其抑制措施,建立了相机的光机模型,分析了系统的杂散光,改进了遮光系统的设计。利用建立的杂光系数测量装置测量了相机镜头的杂光系数,并验证了建模分析结果。     

离轴三反空间相机外遮光罩组件的研制

杂散光抑制对提高空间相机的成像品质起着至关重要的作用。通过合理地设置外遮光罩可以有效地抑制杂散光。为了满足空间相机外遮光罩轻质、高刚度、高强度和高尺寸稳定性的要求,选取增强基碳纤维复合材料作为空间相机外遮光罩的材料,并提出了相机主支撑结构与外遮光罩独立安装的设计思想,从而最大限度地降低了外遮光罩变形对光学元件尺寸稳定性的影响。利用有限元分析技术对外遮光罩结构进行了热特性及动态特性分析,并对结构参数进行了优化设计,最终得到了质量为5.2kg、一阶固有频率为113Hz的外遮光罩结构。动力学试验测试结果表明,外遮光罩一阶谐振频率为106.8Hz,在正弦振动和随机振动试验中加速度放大倍率小于10倍,最大应力为86.6MPa,远远小于碳纤维复合材料屈服应力,结构刚度、强度完全满足设计指标要求。     

微型风力发电演示仪

设计制作了一种基于风光互补原理的微型风力发电演示仪.该仪器由风力发电机、光伏太阳能电池板、控制器、蓄电池、负载等各部分组成.整个系统以控制器为核心,由风力发电机、光伏太阳能电池板把风能和光能转变为电能并储存于蓄电池中供负载使用.该仪器作为演示实验仪不仅小型、直观、模块化和操作简便,而且演示内容突显物理与工程相结合的知识...     

连续螺旋折流板蒸发器壳侧流动换热数值模拟研究

本文对相同几何尺寸的连续螺旋折流板蒸发器与传统弓形折流板蒸发器进行对比性的数值模拟研究,结果表明:在相同壳侧体积流量和折流板数条件下,连续螺旋折流板蒸发器的传热因子和摩擦因子约是弓形折流板的1/3和1/4;当以换热因子和摩擦因子比值评价蒸发器综合性能时,连续螺旋折流板蒸发器比弓形折流板蒸发器提高57%;当最小流通截面流...     

双螺旋与中间搭接螺旋折流板换热器性能研究

采用数值模拟方法研究了40°螺旋角时螺旋折流板换热器双螺旋和中间搭接两种折流板布置形式对壳程性能与螺旋流动的影响,并与30°和40°螺旋角时单螺旋连续搭接结构的进行了对比.结果表明,40°螺旋角时双螺旋和中间搭接结构会强化壳程流体的螺旋流动,使同流量下壳程换热系数与压降增加,但同压降下的换热系数显著下降且均低于30°螺...     

带鳍通道性能的遗传算法优化

与光滑通道相比,带鳍通道有更高的传热系数,附加的鳍,极大地增强了通道的传热.然而,传热的增强又与压降的升高相关联,这又导致泵动力需求的增加,因此应该寻求对该系统的优化设计.该文的主要目的是,通过如下方式来精确地确定鳍的位置和尺寸:利用遗传算法实现最小压降时达到最优传热.鳍的每种布局作为问题(遗传算法中的一个个体)的一个解.通常,首先随机地产生一个初始种群,然后该算法在所有这些解中搜索,利用布局函数迭代出新解,最后得到鳍的优化设计.     

漩涡阻止器水力性能的PIV试验分析及其机理研究

漩涡阻止器是用来防止或减少漩涡发生的特殊装置,它具有特殊的几何形状,能够优化水力机械内部的流动。在水泵吸水池内部,尤其在吸入口的周围存在着较大的漩涡,在吸入口的下方,安装一个“T”型的漩涡阻止器,应用PIV技术测出安装漩涡阻止器前后吸水池内部的流场分布,并对其流动特性进行深入分析,证明了该阻止器能够有效的减小漩涡发生。对这种“T”型漩涡阻止器的作用过程进行深入的研究发现,能够用摩阻理论来解释它的作用机理。     

Attenuation of shock waves propagating over arrayed baffle plates

The paper reports results of shock tube experiments of the attenuation of shock waves propagating over arrayed baffle plates, which is motivated to simulate shock wave attenuation created accidentally at the acoustic delay line in synchrotron radiation factory upon the rupture of a metal membrane separating the acceleration ring at high vacuum and atmospheric test chambers. Experiments were carried out, by using double exposure holographic interferometry with double path arrangement, in a 100 mm×180 mm shock tube equipped with a test section of 180 mm×1100 mm view field. Two baffle plate arrangements were tested: Oblique and staggered baffle plates; and vertical symmetric ones. Pressures were measured along the shock tube sidewall at individual compartments for shock Mach numbers ranging from 1.2 to 3.0 in air. The results were compared with a numerical simulation. The rate of shock attenuation over these baffle plates was compared for vertical and oblique baffle plates. Shock wave attenuation is more pronounced in the oblique baffle plate arrangements than in the vertical ones. PACS 47.40.Nm; 42.40.Kw Communicated by C. Needham     

Correlation of swirl number for a radial-type swirl generator

An experimental investigation was undertaken to derive a new correlation for the swirl number of a radial-type swirl generator under various Reynolds numbers and various vane angle conditions. A radial-type swirl generator with 16 rotary guide vanes was used to generate an annular swirling jet flow. The Reynolds numbers ranged from 60 to 6000, and the vane angles from 0° to 56°. Quantitative measurements for the velocities were made by using an optical method of laser-Doppler anemometry (LDA). Three-component velocity profiles of axial, radial, and azimuthal components at the swirling jet exit were measured for various flow conditions. A flow visualization method using smoke-wire and still photography was also applied to observe the flow patterns of the recirculation region behind the circular bluff body. Under low Reynolds number conditions, the swirl strength was found to be strongly dependent on the Reynolds number as well as on the guide vane angle. Based on the experimental results, a modified swirl number S is derived to characterize the swirling flow, which is useful for the design of a swirl generator.