微重力储箱内非均匀气液两相低温流体的热力学排气机理研究

This proposal is to investigate the operating mechanism of the thermodynamic vent system (TVS) as well as the transient behavior of the non-homogeneous two-phase cryogens in tanks at micro gravity, which is the fundamental scientific problem to be solved for the technology of long-term on-orbit storage of cryogenic propellants. Modeling of the characteristics of the thermodynamic vent system working for conditions with gravities from several g down to zero g is to be accomplished. It is expected to clarify how the conditions such as non-uniformed heat leakage, initial filling rate, container geometries, venting pressure control strategy and initial thermodynamic state of the fluid will contribute to the performance of TVS, the behaviors of evaporation and stratification, as well as the coupling relationships between the periodical variation of temperature and pressure of the cryogen everywhere. The model will be validated by the results of a small scale experimental setup capable of simulating the processes of self-pressuring and thermodynamic venting of liquid nitrogen. Experiments will demonstrate how the internal spay flow mixes the residual cryogen in the tank and eliminates the thermal stratification causing additional self-pressuring. The couple process of the throttling and internal heat exchange between two streams will be examined experimentally in details. The behavior of the self-pressuring and pressure releasing of the two-phase cryogen in the tank will be measured under desired conditions by either mixing or venting or both. The outcome of this project is expected to be valuable scientific references for the development of on-orbit propellant storage technology.

拟针对低温推进剂在轨长期储存技术中涉及的根本科学问题“微重力下储箱内热力学排气系统的工作机理及其作用下的低温流体非均匀气液两相瞬态特性”进行研究。建立既适用于超重力和正常重力环境，也适用于微重力环境的气液两相低温流体热力学排气系统的热力学模型和耦合传热的三维计算流体力学模型。揭示非均匀辐照漏热、初始充注率、容器几何结构、压力控制策略和流体初始热力学状态等因素对热力学排气系统的运行特性低温储箱内流体气液相分布、蒸发特性、热分层规律以及温度压力周期性耦合关系的作用机理。通过搭建液氮自增压和热力学排气实验系统验证模型正确性，并通过可视化方法揭示内流喷射对于消除储箱内低温流体热分层现象的作用规律，剖析节流效应与热交换内耦合热力过程，探究具有喷射混合消除热分层及排气双重作用下的箱内气液两相流体自增压特性。研究成果将为我国今后面向实际应用的空间推进剂储存技术的发展提供重要理论依据和实验指导。

随着我国深空探测计划的推进，对以大比冲、高能量密度的低温推进剂为燃料的火箭需求显著增加。本项目旨在通过实验和理论两方面来探讨低温推进剂在轨储存中所涉及的热力学、传热学机理问题，揭示低温贮箱内的增压规律和热分层特性，获得低温贮箱内热力排气系统运行工况下降压效率、温度响应及传热传质特性等。.在实验方面，项目搭建了240L液氮贮箱自增压及热力排气实验系统，研究了不同压力控制策略、贮箱充注率和喷射参数下的TVS排气控压实验，获得了全贮存周期内箱体内的温度分布，气枕压力和间歇性排气流量数据。提出评价气枕升压因素贡献的无量纲参数，并通过实测气枕升温速率和比体积变化定量描述液氮贮箱在不同TVS阶段内的增压机制；在理论方面，分别基于热力节点法和计算流体力学构建了适用于长期和短期自增压计算的数值模型。针对不同的应用需求，实现了对贮箱内100秒至２个月的跨时间尺度的仿真计算。分析了热力排气贮箱尺寸、长宽比，挡板尺寸及排布对贮箱内自增压的影响。获得了在地面模拟微重力实验时贮箱尺寸设计的准则和预期偏差。对包含吸液、节流、换热、排气、喷射的在轨全流程热力排气过程进行了统一建模，获得了喷射过冷度、喷射混合模式和喷射速度对降压效率的影响规律。.通过本项目的研究，丰富了低温流体热力排气过程的事实和理论依据，增强了对低温流体热力排气技术的理解和掌握。获得的实验数据和理论模型为我国今后面向深空探测的推进剂管理技术的发展提供了理论依据和技术支撑。