微重力下火箭推进系统液氧贮箱内气泡脱离半径研究

On Bubble Departure Radius in Liquid Oxygen Tank of Rocket Propulsion System under Microgravity

研究微重力下液氧贮箱内气泡脱离半径是运载火箭推进系统推进剂在轨沸腾与换热计算的基础.与常重力和低重力环境不同,微重力下Marangoni效应变得突出.为了求解气泡脱离半径,构建包含浮力、惯性力、压差力、表面张力、黏性阻力和Marangoni力的气泡动力学模型.针对现有Marangoni力计算公式适用范围狭窄的问题,依托数值仿真方法,拟合得到了更精确的修正因子计算公式,进而扩充了Marangoni力计算模型的适用范围.使用运载火箭液氧贮箱常规工作压力0.3 MPa下的饱和液氧物性参数,计算得到气泡所受合力随半径的变化关系以及气泡脱离半径随重力的变化关系.结果表明,气泡的脱离行为可以由微重力区、过渡区和低重力区三个区域来划分.微重力区内可以形成厘米级甚至米级的大气泡,而低重力区内只能形成0.1 mm级的小气泡.相比之前的模型,本文模型可以同时适用于三个区,更全面地揭示了微重力下液氧贮箱内的气泡脱离特性,可以为液氧贮箱换热特性分析提供理论支撑.

Studying the bubble departure radius in the liquid oxygen tank under microgravity is the basis for the propellant boiling and heat transfer calculation of the launch vehicle propulsion system in orbit.Unlike regular or low gravity environments,the Marangoni effect becomes essential in microgravity.To calculate the bubble departure radius,Firstly,a bubble dynamics model is developed,including buoyancy,inertia,pressure,surface tension,drag,and Marangoni forces.Secondly,to solve the problem of the narrow application range of the existing Marangoni force formulas,a more accurate correction factor is fitted by numerical simulation.Consequently,the Marangoni force model is extended.Finally,using the physical parameters of saturated liquid oxygen at 0.3 MPa,a conventional working pressure for the liquid oxygen tank of the launch vehicle,the change of the total force with the radius and the departure radius with gravity are calculated,respectively.The results show that bubbles'departure behavior can be divided into three zones:microgravity zone,transition zone,and low gravity zone.The microgravity zone can form large bubbles of a centimeter or even meter scale,while the low gravity zone can only form tiny bubbles of 0.1 mm scale.Compared with the previous models,the model in this work can be applied to all three zones.Therefore,it comprehensively reveals the bubble departure characteristics in the liquid oxygen tank under microgravity.It can also provide theoretical support for analyzing the heat transfer characteristics in the liquid oxygen tank.