基于试验设计-遗传算法的船用柴油机冷却系统多目标优化

为了获取某型船用柴油机冷却系统的最佳运行参数,在柴油机可靠运行的前提下,尽量提升动力性和经济性。建立了柴油机工作过程-燃烧室-冷却系统耦合仿真模型,提出试验设计-遗传算法优化算法,该算法具备节省试验成本和多目标全局寻优的优势,选取柴油机的6个典型推进工况点进行研究,采用该算法对冷却系统运行参数开展多目标优化设计,优化设计以海、淡水泵转速为变量因子,以提升动力性参数和经济性参数为目标,以涡前排温、淡水出机温度和峰值缸压为约束条件,优化后,在低负荷点,淡、海水泵节省功耗79.4%、71.73%,扭矩提升7.2%,有效功率提升7.6%,热效率提升8%,耗油率降低6.73%,摩擦功降低9.71%,峰值缸压降低5%。研究结果表明：耦合仿真模型与实机更加贴近;试验设计-遗传算法在解决强耦合、非线性系统的多目标优化问题具备成本低、效率高、精度高的优点。     

Experimental investigations of the spray structure and interactions between sectors of a double-swirl low-emission combustor

In this paper, the spray characteristics of a double-swirl low-emission combustor are analyzed by using Particle Imaging Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) technologies in an optical three-sector combustor test rig. Interactions between sectors and the influence of main stage swirl intensity on spray structure are explained. The results illustrate that the swirl intensity has great effect on the flow field and spray structure. The spray cone angle is bigger when the swirl number is 0.7, 0.9 than that when the swirl number is 0.5. The fuel distribution zone is larger and the distribution is more uniform when the swirl number is 0.5. The fuel concentration in the center area of the center plane of side sector (Plane 5) is larger than that of the center plane of middle sector (Plane 1). The spray cone angle in Plane 5 is larger than that in Plane 1. The width of spray cone becomes larger with the increase of Fuel–Air Ratio (FAR), whereas the spray cone angle under different fuel–air ratios are absolutely the same. The results of the mechanism of spray organization in this study can be used to support the design of new low-emission combustor.     

航空燃油齿轮泵滑动轴承非线性瞬态性能数值分析

为研究航空燃油齿轮泵滑动轴承在复杂交变载荷扰动下的瞬态润滑行为,建立了燃油齿轮泵滑动轴承的瞬态计算模型。该模型考虑了滑动轴承油膜空化边界的质量守恒和其所处非线性动态承载环境的影响。在此基础上使用批处理技术实现了燃油齿轮泵和滑动轴承的联合仿真计算,在滑动轴承的瞬态润滑计算过程中计入了燃油泵瞬态内流场和其动态载荷的耦合作用。以此进行了恒定载荷和动态载荷工况下的轴心轨迹稳定性分析以及轴承瞬态润滑性能分析研究。研究结果表明：滑动轴承计算模型的计算结果与实验数据较为吻合,误差保持1.2%以内;燃油齿轮泵的动态载荷对轴心轨迹的影响体现在轨迹启动段偏移的增大以及静平衡位置的消失;通过不同关键参数的对比研究发现：合理的增大宽径比或减小间隙比可以获得更为理想的轴心轨迹静平衡位置,但对于轴承转子运动的稳定性,间隙比由0.2%增至0.6%时,未稳定阶段轴心位置的变化趋势由双峰变为单峰,速度稳定段曲线的波动幅值先增大后趋于不变;当宽径比由0.6增至1.2时,全周期内速度响应曲线的偏移降低,轴心运行的稳定性提高;在轴承瞬态润滑特性中对于轴承载荷变化泄露流量具有的敏感性较强而最小油膜厚度的敏感性较差。     

航天飞行器热防护涂层研究进展

近年来,新研航天飞行器气动热环境往往具有高焓、高热流密度和长时间加热等特点,这促使防热材料的研制朝着低密度、高抗烧蚀、优良隔热等性能的方向发展。受自身材料类型的限制,无论烧蚀型(树脂基)或非烧蚀型(陶瓷基)防热材料都可以通过对烧蚀表面进行涂层处理的手段达到弥补材料性能短板,提高使用性能的目的。本文试图梳理、总结国内外近年来热防护系统用涂层材料的发展状况,探讨各自的优势和缺点,并提出了针对树脂基复合材料热防护涂层可能趋势的推测。     

考虑轨道摄动的外热流计算分析

为改进传统外热流算法未考虑外热流经多次反射后的吸收和国外商业软件未考虑轨道摄动及太阳矢量变化对外热流的影响等不足,重新定义了外热流角系数和外热流辐射传递因子,综合SGP4轨道模型和Gebhart方法,给出了考虑摄动等因素的辐射传递因子和轨道外热流计算模型,以及相应的计算流程。通过仿真分析论证了考虑多次反射及摄动等因素的重要性。     

Aerothermodynamic and stability analyses of a deployable re-entry capsule

Recent research projects, in the field of atmospheric re-entry technology, are focused on the design of deployable, umbrella-like Thermal Protection Systems (TPSs). These TPSs are made of flexible high temperature resistant fabrics, folded at launch and deployed in space for de-orbit and re-entry operations. In the present paper two possible sphere–cone configurations for the TPS have been investigated from an aerodynamic point of view. The analyzed configurations are characterized by the same reentry mass and maximum diameter, but have different half-cone angles (45° and 60°). The analyses involve both the evaluation of thermal and aerodynamic loads and the assessment of the capsule longitudinal stability. The aerothermodynamic analysis has been performed for the completely deployed heat shield in transitional and continuum regimes, while the longitudinal stability has been analyzed in free molecular, transitional and continuum regimes, also taking into consideration the heat shield deployment sequence at high altitudes.     

Remote upgrading of a space-borne instrument

The main purposes of experiment “Obstanovka” (“Environment” in Russian) consisting of several instruments are to measure a set of electromagnetic and plasma phenomena characterizing the space weather conditions, and to evaluate how such a big and highly energy consuming body as the International Space Station disturbs the surrounding plasma, and how the station itself is charged due to the operation of so many instruments, solar batteries, life supporting devices, etc. Two identical Langmuir electrostatic probes are included in the experiment “Obstanovka”. In this paper the Langmuir probes for “Obstanovka” experiment are described, including the choice of geometry (spherical or cylindrical), a more reliable method for the sweep voltage generation, an adaptive algorithm for the probe’s operation. Special attention is paid to the possibility for remote upgrading of the instrument from the ground using the standard communication channels.     

数值仿真技术在热真空试验中的应用

由于热真空试验中温度测点有限，且关键部位布置困难，不能反映试验过程部件整体和关键部位的温度结果，导致试验有效性和产品安全性难以判断。通过数值仿真技术对试验过程进行模拟，得到所有部件详细温度场，验证试验有效性与产品安全性；发现影响产品温度分布的因素，研究提高产品可靠性措施。通过对某天线热真空试验过程模拟，得到天线详细温度场，并发现产品散热板安装＂不紧密＂缺陷，是影响天线温度均匀性的＂关键点＂。     

可展开式辐射器热控对航天器轨道调整的适应性分析

为提高航天器热控系统对轨道调整的适应能力，本文研究了与流体回路耦合的可展开式辐射器热控方案在不同轨道高度下的热控性能，分析了不同轨道高度时辐射器面临的热环境的影响，在不同轨道高度下比较了固定辐射器与可展开辐射器的热控特性。结果表明，随着辐射器展开角度的变化，辐射器吸收的空间热流随之发生变化，从而对热控系统的散热能力带来直接影响，调节辐射器的角度可以扩大其对外散热能力。在工程应用中，基于热控流体回路，通过调节可展开式辐射器的展开角度，可以有效提高航天器的轨道热适应能力。     

An equivalent ground thermal test method for single-phase fluid loop space radiator

Thermal vacuum test is widely used for the ground validation of spacecraft thermal control system. However, the conduction and convection can be simulated in normal ground pressure environment completely. By the employment of pumped fluid loops’ thermal control technology on spacecraft, conduction and convection become the main heat transfer behavior between radiator and inside cabin. As long as the heat transfer behavior between radiator and outer space can be equivalently simulated in normal pressure, the thermal vacuum test can be substituted by the normal ground pressure thermal test. In this paper, an equivalent normal pressure thermal test method for the spacecraft single-phase fluid loop radiator is proposed. The heat radiation between radiator and outer space has been equivalently simulated by combination of a group of refrigerators and thermal electrical cooler(TEC) array. By adjusting the heat rejection of each device, the relationship between heat flux and surface temperature of the radiator can be maintained. To verify this method,a validating system has been built up and the experiments have been carried out. The results indicate that the proposed equivalent ground thermal test method can simulate the heat rejection performance of radiator correctly and the temperature error between in-orbit theory value and experiment result of the radiator is less than 0.5 C, except for the equipment startup period. This provides a potential method for the thermal test of space systems especially for extra-large spacecraft which employs single-phase fluid loop radiator as thermal control approach.