空间变过载下液氢输送管内气泡动力学特性仿真研究
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摘要
针对火箭发动机空间二次点火前上面级燃料系统必须将输送管内气泡排空的需求,以处于空间环境的液氢输送管为对象,借助CFD仿真手段研究了管内气泡的生成与分布规律,对比分析了小过载正推、小流量排放下管内两相流瞬态特性。研究表明:微重力下管内小气泡将合并,形成尺度与管径相近的大气泡;提供小过载正推后,大气泡可能破碎形成小气泡,并从管路顶端溢出;输送管内气泡完全排出时间与管内初始含气率关系不大,主要受过载水平的影响;存在临界过载加速度,当所加载的加速度小于该临界值,气泡无法排出;液体小流量排放时,管内气泡在液流惯性推动与冷凝湮灭两种机制下排出。
All the bubbles inside the delivery pipeline of the upper stage fuel system should be discharged completely prior to on-orbit rocket engine reignition. In this paper, the computational fluid dynamics(CFD) approach was used to simulate the bubble characteristics and its distribution inside the delivery pipeline of a space liquid hydrogen system. The transient two-phase flow behaviors under booster sink operation and low flux liquid discharge conditions were compared and analyzed. The results showed that under zero-gravity condition, the collision effect of boiled bubbles yielded large bubbles, and the maximum bubble size could reach the size of the pipe diameter. Supplying booster sink acceleration force, the large bubbles may be broken into small bubbles and then be spilled upward from the pipe inlet. The complete discharge of bubble inside the pipe was mainly determined by the supplied acceleration force, while the initial volume fraction and bubble size had slight influence on the discharging time. For a specific delivery pipeline, there was a critical acceleration force, and a lower sink force than this critical value could not discharge the bubble inside the pipeline. When subcooled liquid phase flowed through the pipeline, the bubbles could also be discharged under two different mechanisms, including inertia impulsion associated with the liquid flow and bubble condensation under heat exchange between gas and liquid phases. The results of the present study is beneficial for understanding the two-phase flow characteristics inside cryogenic delivery system under microgravity condition, and the conclusions could provide guidelines for the setting of operation procedures of propellant management.
All the bubbles inside the delivery pipeline of the upper stage fuel system should be discharged completely prior to on-orbit rocket engine reignition. In this paper, the computational fluid dynamics(CFD) approach was used to simulate the bubble characteristics and its distribution inside the delivery pipeline of a space liquid hydrogen system. The transient two-phase flow behaviors under booster sink operation and low flux liquid discharge conditions were compared and analyzed. The results showed that under zero-gravity condition, the collision effect of boiled bubbles yielded large bubbles, and the maximum bubble size could reach the size of the pipe diameter. Supplying booster sink acceleration force, the large bubbles may be broken into small bubbles and then be spilled upward from the pipe inlet. The complete discharge of bubble inside the pipe was mainly determined by the supplied acceleration force, while the initial volume fraction and bubble size had slight influence on the discharging time. For a specific delivery pipeline, there was a critical acceleration force, and a lower sink force than this critical value could not discharge the bubble inside the pipeline. When subcooled liquid phase flowed through the pipeline, the bubbles could also be discharged under two different mechanisms, including inertia impulsion associated with the liquid flow and bubble condensation under heat exchange between gas and liquid phases. The results of the present study is beneficial for understanding the two-phase flow characteristics inside cryogenic delivery system under microgravity condition, and the conclusions could provide guidelines for the setting of operation procedures of propellant management.
引文
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[2] 赵自强,刘汉兵,吴志亮.国内外上面级发动机技术发展现状与趋势[J].国际太空,2016(12):46-52.Zhao Z Q,Liu H B,Wu Z L.Development situation and trend of domestic and foreign upper stage engine technologies[J].Space International,2016(12):46-52.(in Chinese)
[3] 尹亮,刘伟强.液氧/甲烷发动机研究进展与技术展望[J].航空兵器,2018(4):21-27.Yin L,Liu W Q.Research progress and technical prospects of liquid oxygen/methane engine[J].Aviation Weapons,2018(4):21-27.(in Chinese)
[4] 刘桢,褚桂敏,李红,等.运载火箭上面级微重力环境下的推进剂管理[J].导弹与航天运载技术,2012(4):20-26.Liu Z,Yan G M,Li H,et al.Propellant management in the microgravity environment of the launch vehicle[J].Missile and Space Vehicle Technology,2012(4):20-26.(in Chinese)
[5] 刘桢,王丽霞,林宏,等.液体重定位推力时序的优化研究[J].导弹与航天运载技术,2018(1):106-110.Liu Z,Wang L X,Lin H,et al.Optimization of liquid relocation thrust timing[J].Missile and Space Vehicle Technology,2018(1):106-110.(in Chinese)
[6] Yang H Q,West J.Validity of miles equation in predicting propellant slosh damping in baffled tanks at variable slosh amplitude[R].NASA TR-M17-6064,2018.
[7] 齐宝金,魏进家,王雪丽,等.微重力下加热面尺寸对气泡动力学行为的影响[J].空间科学学报,2017,37(4):455-467.Qi B J,Wei J J,Wang X L,et al.Effects of heating surface size on bubble dynamics under microgravity[J].Chinese Journal of Space Science,2017,37(4):455-467.(in Chinese)
[8] 杨延杰.低温推进剂多相界面气泡动力学研究[D].长沙:国防科学技术大学,2015.Yang Y J.Study on Bubble Dynamics of Multiphase Interface of Low Temperature Propellant [D].Changsha:National University of Defense Technology,2015.(in Chinese)
[9] Zhao J F,Liu G,Wan S X,et al.Bubble dynamics in nucleate pool boiling on thin wires in microgravity [J].Microgravity Science and Technology,2008,20(2):81-89.
[10] Zhang Y,Wei J,Xue Y,et al.Bubble dynamics in nucleate pool boiling on micro-pin-finned surfaces in microgravity [J].Applied Thermal Engineering,2014(70):172-182.
[11] 马原,孙培杰,李鹏,等.低温流体微重力池沸腾气泡脱落特性研究[J].西安交通大学学报,2018,52(9):89-94.Ma Y,Sun P J,Li P,et al.Study on boiling bubble drop characteristics of cryogenic fluid microgravity pool[J].Journal of Xi’an Jiaotong University,2018,52(9):89-94.(in Chinese)
[12] 刘亦鹏.低温气液两相弹状流流动特性和流场结构的实验及数值研究[D].上海:上海交通大学,2013.Liu Y P.Experimental and Numerical Study on Flow Characteristics and Flow Field Structure of Low Temperature Gas-Liquid Two-Phase Slug Flow [D].Shanghai:Shanghai Jiaotong University,2013.(in Chinese)
[13] Tai C F.Cryogenic Two-Phase Flow and Phase-Change Heat Transfer in Microgravity [D].Gainesville:University of Florida,2008.
[14] Ma X,Cheng P,Gong S,et al.Mesoscale simulation of saturated pool boiling heat transfer under microgravity conditions [J].International Journal of Heat and Mass Transfer,2017(114):453-457.
[15] Bellur K,Konduru V,Kulshreshtha M,et al.Contact angle measurement of liquid hydrogen (LH2) in stainless steel and aluminum cells [J].Journal of Heat Transfer,2016,138(2):020904.