{MC COMMENT: PA CORRECTION}Theoretical study of ullage washing with mixed inert gas in a non-equilibrium state

The Mixed Inert Gas (MIG) produced by the novel Green OnBoard Inerting Gas Generation System (GOBIGGS) mainly consists of carbon dioxide, nitrogen and oxygen. Because of the large solubility of carbon dioxide in jet fuel compared with nitrogen, the no gas release or equilibrium model could not be employed any more. In this paper, first, a mathematical model of the ullage washing was set up to predict the variation of the oxygen concentration on ullage and in the fuel, and the gas evolution and dissolution rate were calculated by Fick’s second law. Then, an experimental apparatus was constructed to verify the accuracy of the model. Finally, the numerical comparisons of ullage washing using Nitrogen Enriched Air (NEA) and MIG are presented under various flow rates and fuel loads, and the result reveals that the variation of the oxygen concentration on ullage is nearly identical whatever the inert gas is NEA or MIG. However, the variation of the oxygen concentration in the fuel is disparate, and the oxygen concentration decreases rapidly if the inert gas is MIG, especially when the fuel load is low or the flow rate of the inert gas is high. Besides, MIG could suppress the rising trend of the oxygen concentration on ullage when the aircraft ascends if the fuel tank is fully washed into an equilibrium state on ground.     

驻涡燃烧室凹腔温度变化规律及气量分配

通过对单双涡燃烧室进行热态试验研究,研究余气系数、进口气流参数对凹腔壁温分布的影响,并通过三维数值模拟对燃烧室及凹腔气流量进行计算,得到壁温分布规律,为燃烧室材料选择以及气量分配的后续优化做好铺垫.试验结果表明,单涡试验件的最高壁温出现在凹腔后壁面;燃烧室余气系数变化改变了双涡试验件最高壁温的位置;数值模拟结果比较准确的得到了驻涡燃烧室的气流量分布.     

Experimental study of an aircraft fuel tank inerting system

In this work, a simulated aircraft fuel tank inerting system has been successfully established based on a model tank. Experiments were conducted to investigate the influences of different operating parameters on the inerting effectiveness of the system, including flow rate of the inert gas(nitrogen-enriched air), inert gas concentration, fuel load of the tank and different inerting approaches. The experimental results show that under the same operating conditions, the time span of a complete inerting process decreased as the flow rate of inert gas was increased; the time span using the inert gas with 5% oxygen concentration was much longer than that using pure nitrogen;when the fuel tank was inerted using the ullage washing approach, the time span increased as the fuel load was decreased; the ullage washing approach showed the best inerting performance when the time span of a complete inerting process was the evaluation criterion, but when the decrease of dissolved oxygen concentration in the fuel was also considered to characterize the inerting effectiveness, the approach of ullage washing and fuel scrubbing at the same time was the most effective.     

Multipoint optimization on fuel efficiency in conceptual design of wide-body aircraft

Aircraft conceptual design optimizations that maximize the performance at a design condition (single-point) may result in designs with unsatisfying off-design performance. To further improve aircraft efficiency under actual flight operations, there is a need to consider multiple flight conditions (multipoint) in aircraft conceptual design and optimization. A new strategy for multipoint optimizations in aircraft conceptual design is proposed in this paper. A wide-body aircraft is taken as an example for both single-point and multipoint optimizations with the objective of maximizing the specific hourly productivity. Boeing 787-8 flight data was used in the multipoint optimization to reflect the true objective function. The results show that the optimal design from the multipoint optimization has a 7.72% total specific hourly productivity increase of entire flight missions compared with that of the baseline aircraft, while the increase in the total specific hourly productivity from the single-point optimal design is only 5.73%. The differences between the results of single-point and multipoint optimizations indicate that there is a good option to further improve aircraft efficiency by considering actual flight conditions in aircraft conceptual design and optimization.     

涡轮泵式供油系统流体瞬变过程的高速摄影研究

本文是涡轮泵式供油系统流体瞬变过程研究工作的一部分.将泵进、出口流体瞬变过程的高速摄影照片与参数测量结果进行了对比,着重对系统中流体瞬变引起液柱分离和气-液两相流的机理和它们对系统性能的影响进行了分析,提出了防止流体瞬变对涡轮泵式供油系统造成危害的措施.     

航天飞机用冲压发动机设计性能及燃料问题

本文论证了高M_α数亚燃冲压发动机用于航天飞机的可能性。并对用液氢、甲烷、丙烷等作为燃料的冲压发动机特性作了详细的计算分析。讨论了冲压发动机的工作菱形区、发动机特性及各截面的协调关系等问题。计算结果表明,在M_α=2～6及H=0～40km范围内,亚燃冲压发动机能满足航天飞机对动力装置的要求。在一定的条件下,液氢、甲烷和丙烷均可以被选为航天飞机用的冲压发动机的燃料。     

军用航空发动机加力控制系统的研究和发展

对国外军用航空发动机加力控制系统的研制现状和今后的发展方向进行了归纳和分析，讨论了加力燃油泵、加力燃油调节器、加力燃油计量和分配装置、喷口油源泵和喷口调节器的技术特点、方案选择和研究动向。全权限数字电子控制技术的研究和应用，将会对军用航空发动机的研究和发展产生巨大的影响。     

脉冲爆震发动机供油自适应控制优化设计

研究了带气动阀PDE的供油自适应控制优化设计，通过在油管中设置单向阀和通过油管自身(无单向阀)，成功实现PDE的供油自适应控制，在爆震管直径为180mm，长度为2m，管内流速为25m／s的PDE中，可以产生稳定的爆震波，并获得2MPa以上的压力和1500N以上的峰值推力。通过对不同油管长度、不同工作频率的压力、推力曲线对比研究，分析了供油自适应控制的机理，及供油相对进气滞后时间的长短对PDE工作的影响。     

在非垂直横向气流中直射式喷嘴雾化细度的实验研究

在文献[1-4]中关于横向气流中直射式喷嘴雾化的实验研究的基础上,研究了非垂直横向气流中直射式喷嘴的雾化细度.结果表明部分逆喷可大大地加强雾化,特别是在较低气流速度下尤为明显,对于一定的喷射方向、气流速度及喷嘴压力降,SMD并不是总随着喷口直径的增加而增加,在一定的喷口直径下,有一最小值.     

航天器相对运动的两点边界值问题解析解

针对无摄椭圆轨道,推导了表示真实相对位置速度的状态转移矩阵,进而推导出了相对运动两点边界值问题的一阶解析解。所得结果不仅可指定转移时间、还可在时间范围内进行全局的燃料优化或在时间和燃料两者间折中;对于周期和非周期的相对运动均适用。仿真结果表明此解的归一化精度达到10^－6。进一步的仿真发现相对转移过程的燃料消耗会随目标轨道偏心率的增加而增加;随长半轴的增加而减少;随初始真近点角的增加呈现周期性变化;随着转移时间增加,燃料消耗的总趋势是减少的。