基于热响应法的航天器推进剂质量测量热模型

本文以热响应法测量航天器微重力条件下贮箱推进剂剩余质量为背景,建立了航天器贮箱内外热环境耦合作用下的整体热分析模型,通过将航天器贮箱外部热环境视为第二类浮动热边界条件,实现贮箱气液两相分布下的热分析解耦计算,为热响应法提供精确的温度场计算方法。采用该方法,针对热响应法测量微重力条件下某航天器贮箱内部推进剂质量所需的温度场分布,通过数值仿真获得了空间在轨阶段,热响应法加热工作时贮箱内外热环境整体耦合下的温度场分布,并依据特定检测点的瞬态温度变化,反演得到了剩余推进剂的质量。研究发现采用热响应法测量推进剂质量时,贮箱温度场不仅受贮箱内部加热影响,在轨外部热环境也会明显影响贮箱壁面温度的均匀性。     

微型超高压宝石喷嘴内部的空化与磨损

宝石喷嘴是影响超高压水射流切割系统工作效率的重要部件,而宝石内部的空化直接影响射流的形成,也是宝石磨损的重要原因之一。对400 MPa压力范围内宝石孔内部的空化两相流进行了数值模拟,阐述了射流在宝石内的形成过程,分析了长径比、压力和入口形状对宝石内空化的影响,并在相应压力下对宝石喷嘴的磨损进行了实验研究。结果表明:宝石内部的空化发展程度随着长径比的增大而减弱;在一定的长径比范围内,空化可以发展到喷嘴出口,并最终使射流的初始直径小于喷嘴直径,且在此条件下当压力升高时,射流的初始直径增大;良好的入口形线可以降低空化的发展程度;宝石入口的磨损较出口更显著,空蚀和高压水的冲蚀造成了宝石孔边缘形状的破坏,这种破坏随着压力的升高而加剧,选择合适的长径比是减少冲蚀磨损的有效途径。     

实验条件对二氧化钛纳米棒形貌和光电流密度的影响

采用简单的水热合成法,以四异丙醇钛为钛源,制备出整齐有序的二氧化钛纳米棒阵列。探索了钛源浓度、反应液酸度、反应时间、温度等实验条件对纳米棒的形貌和光电流密度的影响。实验结果表明:钛源浓度和反应液酸度对纳米棒的生长有非常大的影响,最佳反应液的组分为10 mL去离子水、10 mL盐酸和0.4 mL钛源。另外,随着反应时间的增加,纳米棒的长度会明显的增加,但纳米棒的直径和光电流密度却变化不大。同时,纳米棒的长度也随着反应温度的增高而增加,其光电流密度随之呈现先增大后减小的趋势,但其直径没有明显改变。     

微通道脉管非线性交变振荡微观机理的分子动力学研究

采用分子动力学方法,对He在微通道脉管内的非线性交变振荡的热力学响应进行仿真,研究气体振荡诱导管内轴向压力梯度、温度场的形成,并阐述微通道长径比对温差与相位的影响.结果表明：微通道内伴随压差驱动力在管内形成类似正弦函数压力波、速度波、质量流量波与半正弦的温度波.振荡周期随脉管管径的增大而缩短,随脉管长度的增加而增长,受直径影响很小;微通道两端的时均温差随长度的增加而增大,受直径的影响很小.预测针对不同的脉管直径存在一个最佳长径比与振荡周期,其数值随直径的增大而增大,为优化脉冲管的性能提供理论依据.     

超临界压力CO_2水平管内冷却换热机理研究

采用SSTk-ω模型对冷却条件下超临界压力CO_2在水平管内的对流换热进行了数值研究,分析了流体物性、热流密度、直径以及浮升力等对其在拟临界点附近的流动换热特性的影响,并从场协同的角度分析了超临界压力CO_2的传热机理。结果表明:浮力效应使流体在流动截面上出现温度场不对称和二次流现象;下壁面的对流换热系数比上壁面先达到峰值,但换热系数小于上壁面;增大热流密度对换热系数的影响较小但能够使换热系数的峰值向入口段移动;增大热流密度和增大直径能够增强浮力效应对流体换热特性的影响;场协同原理可以解释同一截面处的换热不均匀现象。     

低温液氮贮箱静置增压及放气特性分析

由于外部漏热的影响,静置时低温贮箱内的气枕压力会逐渐升高,压力升高相应地会改变贮箱内气相空间的温度分布。文中对低温液氮贮箱进行了静置增压过程实验,结果表明:增压所耗时间随气枕压力升高而增大,气相空间垂直方向各温度在实验压力范围内也相应升高;低温贮箱在不同的气枕压力下进行了放气过程实验,并对泄压过程中气体流量随气枕压力的变化进行了分析。     

多喷嘴喷雾场数值模拟分析

本文建立了多喷嘴喷雾场的三维物理数学模型,运用欧拉-拉格朗日法对多喷嘴下的喷雾场进行了详细数值模拟,得到了双喷嘴及三喷嘴情况下喷射入口压力和流量变化对喷雾场内雾滴索太尔直径和雾滴速度的影响规律;并通过与单喷嘴情况进行对比,给出了喷嘴数目对喷雾场内雾滴速度及粒径大小分布的影响。     

蒸汽浸没射流凝结引起的冲击特性研究

本文在广泛的蒸汽压力和过冷水温度范围内,针对饱和蒸汽通过不同出口直径的喷嘴在过冷水中浸没射流凝结引起的压力冲击特性进行了实验研究,测量得到了不同轴向位置和径向位置的冲击压力,并分析了入口蒸汽压力,过冷水温度和喷嘴出口直径对冲击压力的影响规律。结果表明冲击压力主要受入口蒸汽压力和过冷水温度的影响;同时,当汽水参数以及无量纲轴向和径向距离相同时,不同出口直径的喷嘴对应的冲击压力变化很小,从而表明喷嘴出口直径对压力冲击影响很小。     

两段式喷嘴对CO_2两相流引射制冷系统性能的影响

文章对采用两段式喷嘴的引射器及其两相流引射制冷系统在不同工况、不同几何尺寸条件下进行了实验研究。实验结果表明,在实验工况固定的条件下,采用两段式喷嘴的CO_2两相流引射制冷系统的COP随引射器第一喉部直径的增大而增大,引射比随第一喉部直径的增大而减小;系统COP和引射比随引射器中间连接直径的增大而减小。对于固定几何尺寸的引射器,系统COP随气冷器出口压力的升高而增大,引射比随气冷器出口压力的升高先减小后增大,在9MPa时引射比最小。与传统的CO_2制冷系统相比,采用两段式喷嘴的CO2两相流引射制冷系统的COP在不同工况的条件下均高于传统系统的COP,最大可提高约15%。     

基于正交试验方法的涡流管优化设计

为了寻求涡流管最大能量分离效果的最优化几何尺寸参数,该文探讨了喷嘴数目、分离孔板直径、涡流管长度、热端调节阀角度对涡流管最大制冷效应的影响,并采用极差分析法分析了试验结果。得出:喷嘴数目对涡流管能量分离影响程度最大,而调节阀锥度的影响程度最小,涡流管长度和分离孔板直径对其影响程度处在两者之间。该文利用正交试验法设计涡流管实验,为涡流管的研究提供了一个新的思路。     

Experimental investigation of the effect of nozzle numbers on Ranque–Hilsch vortex tube performance

The present study investigates the effects of the orifice nozzle number and the inlet pressure experimentally on the cooling performance of the counter flow-type vortex tube. The energy generation has been conducted using a stream-tek generator (model GNMD-KIT) with different numbers of nozzles (2, 3, and 6), an aspect ratio of 1:6, and an inner diameter of 7.5 mm. In the experiments, for each of the orifices, inlet pressures have been adjusted from 200–600 kPa. The energy separation investigated here focuses on the cold temperature difference and coefficient of performance for cooling. The experimental results concluded in this article prove that the greatest effect of nozzle number is for three nozzles, and hence, that nozzle number could affect the energy separation efficiently. A comparison of the present experiments with other published works has been conducted. An analytical study of the characteristics equation has been carried out to evaluate the best correlation of the ratio of cold temperature difference to the inlet temperature as a function of pressure, cold mass fraction, and nozzle number.     

New method for measuring diesel nozzle orif ice inlet structures based on synchrotron X-ray tomography

Spray behavior is regarded as one of the main factors influencing engine performances, fuel consumption and emissions for diesel engines. Under high injection pressure, diesel spray behaviors are extremely sensitive to the nozzle internal geometries, especially the geometric structures of orifice entrance. Based on the synchrotron radiation X-ray tomography technique, the 3D digital models of nozzle tips can be constructed. A new automatic method is presented to reveal the inlet structures according to these nozzle orifice models. The planes passing through the orifice axis are determined and used to cut the models, and then the corresponding cutting images are applied to measure the inlet chamfer radii around the orifice axis automatically. The orifices of a single-hole nozzle and an eight-hole nozzle are measured according to this method. The results show that this method can automatically measure the orifice inlet chamfer radii around the orifice axis with high precision. The obtained inlet chamfer radius shows the whole profile of the orifice entrance, which is a precise feedback for nozzle designing and manufacturing, and it also provides precise geometrical boundary conditions for the study of spray behaviors.     

喷雾腔压力及喷嘴孔径对相变喷雾冷却性能的影响

为了满足大功率激光器件高热流密度及低表面温度的冷却需求,以R22为冷却工质,实验研究了在闭式系统中改变喷雾腔压力及喷嘴孔径对相变喷雾冷却中临界热流密度、冷却温度等冷却性能的影响,实验结果表明:在喷雾入口压力为0.8 MPa,喷雾高度为22 mm,入口温度为-3 ℃的实验条件下,当喷雾腔压力在0.2~0.4 MPa范围内变化时,随着喷雾腔压力的升高,临界热流密度值（CHF）先增大后减小,存在最优的临界热流密度,冷却壁面温度随着喷雾腔压力的升高而上升;当改变喷嘴孔径时,CHF存在最优值,过小及过大的孔径均会影响喷雾冷却性能;当喷嘴孔径为 0.4 mm,喷雾腔压力为0.34 MPa时, CHF值最高,为276.1 Wcm-2,其对应的被冷却表面温度为26.8 ℃,表面换热系数为 66 640 Wm-2K-1。     

Inlet Efficiency Study for the TSI Aerodynamic Particle Sizer

The paper reports on the particle. sampling efficiency of the inlet system for the Aerodynamic Particle Sizer (TSI, Inc., St. Paul MN). Large particles are depleted from the sampled aerosol by two mechanisms: super-isokinetic sampling at the entrance of the inlet, and inertial impaction on the inner nozzle. A fluorometric technique was used to separately characterize these mechanisms. Numerical studies were also performed. The experimental results show that the inlet's overall efficiency drops from around 90% for 3 μm particles to less than 45% for particles larger than 10 gm. Several high efficiency inlets were developed and tested. These inlets provide higher sampling efficiencies, but reduce the instrument's sizing resolution. Measurements of 7.3 μm oleic acid particles with a high efficiency inlet showed a 5% spread in measured diameter at 50% count, while less than a 1076 spread was observed using the standard inlet. It was also found that the super-isokinetic condition reduces particle losses on the inner nozzle. The standard inlet is recommended for verifying test aerosol monodispersity. An alternative to the standard inlet is suggested for measurement of size distributions.     

Effect of Nozzle Shape on Amplitude of Well Acoustic Emitter Generation

An experimental study of the generation of pressure fluctuations in a well acoustic emitter with nozzles of various shapes has been carried out. The effect of a smooth nozzle inlet section on the generation amplitude, the optimum jet length, and the outlet diameter has been studied. The formation of a region of reverse currents connecting to the cavity in the nozzle between the channel wall and the jet periphery has been considered. A significant increase in the generation amplitude produced at the smooth nozzle inlet and the formation of a uniform velocity profile in the nozzle channel have been observed.     

线性喷管构形对激光推力器冲量耦合系数的影响

 喷管是激光推力器的重要组成部分。在设计喷管构形时，可以使其与聚光系统一体化设计，也可以把聚光系统和喷管分离设计。针对聚光系统与喷管分离设计的工作模式，建立了一种辅助聚焦系统的点火模型。通过改变喷管的构形，分析了圆锥形、圆台形喷管的冲量耦合系数与喷管顶部直径与出口直径之比以及喷管长度与出口直径之比之间的关系。通过对推力曲线的分析，阐述了喷管结构参数对其性能影响的原因。研究结果显示，圆台形喷管的推进性能优于圆锥形和圆筒形。     

过膨胀超音速蒸汽浸没射流凝结的实验研究

针对入口压力为 0.20～0.60 MPa 的饱和蒸汽在 20～70℃过冷水中形成的过膨胀超音速蒸汽浸没射流凝结进行了实验研究.观察到了渐缩形、收缩-膨胀-收缩形、收缩-膨胀-发散形和发散形汽羽,汽羽形状主要由入口蒸汽压力和过冷水温度决定,给出了汽羽凝结形态分布图.同时,给出了汽羽的轴向和径向温度分布规律,在靠近喷嘴附近,温度变化幅度比较大,在远离喷嘴处,温度变化趋于平缓;汽羽的轴向温度分布与汽羽的形状密切相关.