Inviscid transonic flow field analysis

This paper describes a method for analysing inviscid transonic flow. This method is based on the fact that the angle made by the streamline of the transonic flow and of the corresponding incompressible flow is usually small. By using curvilinear coordinates, the differential equation of the stream function of an inviscid compressible flow is simplified and a general solution of the equation obtained. As examples of the method, transonic solutions are given for flow through twodimensional and axisymmetric Laval nozzles of different throat wall radii together with sonic lines and iso-Mach lines. To determine the discharge coefficients of Laval nozzles, an integral relation is developed. The general behaviour of the transonic flow in the throat region is presented, and the effect of the mass discharge on the Mach number distribution in the nozzle analysed. The effects of the ratio of the specific heats on the characteristics of the flow in the throat region are discussed. For transonic flow around a circular cylinder and a sphere, sonic lines and iso-Mach lines are presented for free-stream Mach number varying from the subcritical to the supercritical, including a free-stream Mach number of one. Part of the results obtained are compared with those available in current literature. For the two-dimensional hyperbolic Laval nozzles, the iso-Mach lines are compared with those given by Cherry (1959) and Serra (1972). For, axisymmetric Laval nozzles, the discharge coefficient and the Mach number at the throatsection for various throat wall radii are compared with those given by Sauer (1944), Hall (1962), Kliegel & Levine (1969), and Klopfer & Holt (1975). The theoretical discharge coefficients are compared with the experimental results by Backet al (1975), Durham (1955), Norton & Shelton (1969) etc. For the transonic flow around a circular cylinder, the iso-Mach lines are compared with Cherry’s exact solution for the quasi-circular cylinder for.M∞ equal to 0.51. The. Mach number distributions on the surface of the circular cylinder are compared with those given by Imai (1941) forM∞ equal to 0.4, by Cherry (1947) forM∞ equal to 0.51, by Dorodnicyn (1956) forM∞ equal to 1, and by Hafez, South & Murman (1979) forM∞ equal to 0.51. The present method has a much wider scope of application, requires simpler computation and gives results with good accuracy. It is being used to analyse supercritical wings and cascades, and we expect to extend its application to the field of transonic unsteady flow.     

瓷砖装饰用压电喷墨打印头关键技术研究

压电喷墨技术是一种广泛应用于工业数字印刷领域的喷墨打印技术。根据压电陶瓷变形模式不同,压电喷墨可分为挤压式、弯曲式、推动式和剪切式4种驱动原理。该文介绍了4种压电喷墨原理及相关研究方法。有限元分析和流体动力学计算可模拟墨滴生成与飞行的过程,便于研究喷头电学参数和几何尺寸对喷墨性能的影响。并讨论了喷墨打印头的压电元件、喷嘴板等材料优化,以及压电喷墨头研究进展及未来展望。     

Use of pulsations to enhance the distribution of liquid injected into fluidized particles with commercial‐scale nozzles

Gas‐atomized liquid injections into fluidized beds are commonly used in industrial processes such as fluid coking, fluid catalytic cracking (FCC), and pharmaceutical granulation, where it is important to optimize the distribution of the injected liquid to prevent the formation of unwanted liquid–solid agglomerates and maximize product yields. This injection is typically a two‐phase, gas‐atomized liquid injection. One issue with such a liquid injection is that most of the liquid is deposited at the end of the jet tip within the reactor. This study proposes introducing artificial fluctuations into the injection flow, which causes the jet penetration to vary, allowing for a more even spread of liquid throughout a fluidized bed reactor. The effect of artificial pulsations in the atomized injection, of various frequency and amplitude, was investigated in this study. Using pulsations, greatly enhanced the liquid distribution on the bed particles. © 2012 American Institute of Chemical Engineers AIChE J, 59: 719–728, 2013     

燃油雾化理论研究

液体雾化在工业生产过程中应用非常普遍,雾化质量的好坏,直接影响燃油的燃烧过程.本文介绍了雾化的机理,分析了影响雾化油滴粒径的主要因素,给出了影响雾化质量的评价指标.     

凹印机喷风嘴风速损失问题的流体动力学分析

现有凹印机干燥装置喷风嘴出风速度达不到要求,导致印品干燥不充分,同时降低了印刷速度.实际上,干燥效率低已经成为制约凹印机速度的主要因素.通过流体动力学的计算来模拟热风在风嘴内的流动状态,从结构设计上找出影响热风速度的主要因素,为干燥装置的优化改进提供理论依据,解决设计生产过程中的盲目性.通过对现有的喷风嘴结构的数值模拟...     

平面撞击流振荡特性

对两对置平面喷嘴形成的撞击流的振荡特性进行了实验研究。采用高速摄像仪、烟线流场显示和热线测量的方法,研究了不同喷嘴间距、不同喷嘴出口气速下平面喷嘴撞击流的振荡行为。研究结果表明,平面撞击流的振荡特性主要有流向拟周期振荡和偏斜振荡两种,当L<5H时主要为流向拟周期振荡模式,当L>5H时主要为偏斜振荡模式。     

喷油嘴喷孔加工工艺技术

基于日益严格的排放法规对喷油嘴的孔径,孔形,孔的位置度和喷孔的流量系数提出的越来越严格的要求,介绍了喷孔加工的最新工艺手段及相关设备的应用,加工基准的选择,各坐标轴系统的调整要求,K系数倒锥的加工成型,电脉冲电源的设计特点等技术手段,为喷孔加工工艺提供了设计经验。     

湛江发电厂3号汽轮机汽流激振分析及处理

对湛江发电厂3号汽轮机汽流激振的机理进行简要分析,并根据3号机组汽流激振的特点提出了消除与预防对策。     

“田”字型双级双向热底冷盖熔铝炉

介绍一种与地方铝厂技术水平,生产规模,产品结构相适应原新型铝炉。该炉是将中,小型企业无法操作使用的巨型熔铝炉分解成两组双级,双向炉,采用冷炉盖,热底连体结构,与普通单炉相比可减少１６个散热面;采用炉料预热罩强制烟气循环预热炉可节省４０％以上。     

双射流流化床空隙率的分布

在 ３００ ｍｉｎ×５０ ｍｉｎ×２６００ ｍｍ的二维射流床中,采用内径为 １１ ｍｍ的对称双射流管,研究了等速射流条件下射流管间距、喷口射流气速、静床高度对床层空隙率分布的影响,发现射流管间距、喷口射流气速是双射流产生射流区合并的主要原因;并得到了具体实验条件下空隙率分布的数据．同时研究了双射流管不等速射流条件下空隙率分布的规律．