导弹水下发射时喷管的气体流动

针对导弹水下发射时喷管的气体流动问题 ,建立了水下喷管流的简化模型 ,定性地研究水环境的惯性对水下喷管内气体流动造成的阻滞作用。计算显示受阻滞流量ΔQ及受阻滞时间Δt和喷管的喉部面积At 呈幂函数关系 ,固定其他参数仅改变水深 ,ΔQ及Δt和进口处气体的滞止压力p0 与当地水下静压之间的压力差也有幂函数关系。结果表明喷管所处的水下深度越大 ,喷管内气体流动受阻滞状况也就越严重 ,而减小喉部面积At 和适当增加膨胀比Ab/At 以及增加滞止压力p0 ,均有助于改善水环境对喷管喷出气体造成的阻滞状况。

水下超声速气体射流回击现象的实验研究

对水下超声速气体射流的动力学行为进行了实验研究．通过流动可视化揭示了回击现象的演化过程,利用探针排获得了射流近场区的脉动压力分布,实验结果表明:在超声速喷管出口两倍直径处,射流形貌的变化导致气体中出现了大幅值压力脉冲．通过流场可视化与压力测量的同步校验,证实了喷口端面处回击事件与流场气相区中压力脉动之间相关性．

Pressure drop of the film-enlarged tube bundles in air-water two-phase cross flow in evaporative air cooler

An experiment was carried out to investigate the relation of the maximum velocity of air passing through narrowest passage, mass flux of spray water in one square meter in one hour and the pressure drop of tube bundles. Twelve equations were obtained for the relation. The results show that the pressure drop of the tube bundles increases with increase of the maximum velocity of air and the mass flux of spray water. Comparing the pressure drop of the bare tube bundles with that of the film-enhanced tube bundles, it is found that the pressure drop of the film-enhanced tube bundles is lower about 11% and the surface roughness of the film-enhanced plates is a main factor that influences the pressure drop. The data and method obtained in the paper can be used to compute the pressure drop of the film-enhanced tube bundles and is helpful for selection of fan.