CFRP蜂窝夹层结构板埋件集群区域的热应力失效模式分析及补强设计

航天结构中,蜂窝板常采用在内部镶嵌埋件的方式使其与其他部件连接.为了分析CFRP蜂窝夹层结构板埋件集群区域面板在温度应力作用下失效的原因,进行了失稳破坏应力理论计算和数值分析,由分析结果发现是面板失稳导致了结构破坏.提出了加厚面板和局部加强两种补强方法并分析了其可行性和效率,通过对比发现局部补强的方法更加可行和高效.最...     

Design and analysis of a novel hybrid cooling method of high-speed high-power permanent magnet assisted synchronous reluctance starter/generator in aviation applications

To improve the heat dissipation performance, this paper proposes a novel hybrid cooling method for high-speed high-power Permanent Magnet assisted Synchronous Reluctance Starter/Generator (PMaSynR S/G) in aerospace applications. The hybrid cooling structure with oil circulation in the housing, oil spray at winding ends and rotor end surface is firstly proposed for the PMaSynR S/G. Then the accurate loss calculation of the PMaSynR S/G is proposed, which includes air gap friction loss under oil spray cooling, copper loss, stator and rotor core loss, permanent magnet eddy current loss and bearing loss. The parameter sensitivity analysis of the hybrid cooling structure is proposed, while the equivalent thermal network model of the PMaSynR S/G is established considering the uneven spraying at the winding ends. Finally, the effectiveness of the proposed hybrid cooling method is demonstrated on a 40 kW/24000 r/min PMaSynR S/G experimental platform.     

Selective thermal emission and infrared camouflage based on layered media

Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention. By eliminating thermal radiation differences between the object and the background, it is possible to hide a given object from infrared detection. Infrared camouflage is an important element that increases the survivability of aircraft and missiles, by reducing target susceptibility to infrared guided threats. Herein, a simple and practicable design is theoretically presented based on a multilayer film for infrared stealth, with distinctive advantages of scalability, flexible fabrication, and structural simplicity. The multilayer medium consists of silicon substrate, carbon layer and zinc sulfide film, the optical properties of which are determined by transfer matrix method. By locally changing the thickness of the coating film, the spatial tunability and continuity in thermal emission are demonstrated. A continuous change of emissive power is further obtained and consequently implemented to achieve thermal camouflage functionality. In addition, other functionalities, like thermal illusion and thermal coding, are demonstrated by thickness-engineered multilayer films.     

RBCC发动机火箭出口结构热防护研究

基于目前RBCC组合发动机开展了火箭出口位置结构热防护的研究，该发动机结构形式为火箭从冲压发动机燃烧室侧壁嵌入，火箭出口紧贴冲压发动机燃烧室壁面。火箭出口超高温、高热流、冲刷大的特点，导致该位置热环境非常严酷，为了探索火箭出口位置热防护结构，开展了三种结构热防护方案的试验研究。研究结果表明，石英/酚醛内壳和高温合金外壳复合结构热防护方案能够满足30s量级的地面试验，能够满足火箭出口恶劣环境的热防护要求。研究结果还表明，热防护材料至关重要，高温合金材料不适合应用于火箭出口热防护；高硅氧/酚醛材料虽然基本能满足试验的热防护需求，但其抗烧蚀性能略低，尤其当材料完全炭化后产生的强度降低、收缩、分层、热导系数增加等问题，在更长时间试验中会导致热防护失效，针对这些问题，本文提出了进一步研究建议。     

基于气凝胶的防隔热一体化材料研究进展北大核心CSCD

新型高速飞行器的快速发展对热防护系统提出了更高要求,基于气凝胶的防隔热一体化材料对提升热防护系统的防隔热性能和结构效率有重要意义。本文基于防热层材料的不同,分类概述了基于气凝胶的防隔热一体化材料的研究进展、结构形式和性能特点,并简要阐述未来防隔热一体化材料发展需要解决的问题。     

蜂窝增强低密度硅基烧蚀防热材料性能

高速再入飞行器通常采用烧蚀防热材料作为外表面大面积的热防护材料。本文对两种蜂窝增强低密度硅基烧蚀防热材料的力学性能、热物理性能和烧蚀性能进行了测试,并结合试验结果对烧蚀机理进行了研究分析。结果表明,材料的密度越高、拉伸强度就越高,但拉伸模量相近;两种材料的隔热性能参数都较低。两种材料在不同热流密度条件下的电弧风洞烧蚀后退速率都较低,在部分烧蚀条件下有轻微膨胀。两种材料的烧蚀背温都较低,烧蚀表面形貌良好,能满足设计指标要求,是一种适用范围较广的烧蚀防热材料。     

Effects of swirl and hot streak on thermal performances of a high-pressure turbine

Advanced civil aero-engines tend to adopt lean burn combustors to meet emission requirements. The exit of a lean burn combustor experiences highly non-uniformities in both temperature (Hot Streak, HS) and flow (swirl). This paper presents a numerical investigation on the behaviors of a High-Pressure (HP) turbine under a combined effect of swirl and hot streak. The investigation was conducted on a GE-E3 HP turbine with unsteady numerical simulations, which considered the realistic clocking position of the HP Nozzle Guide Vane (NGV) relative to the combustor. The influences of swirl orientations on the HS migration and thermal performances on the blade surface were examined. Results indicate that, inside the NGV passage, the swirl’s induced incidence angle effect dominates the HS radial migration. The transversal movement of HS follows the cross flow and thus makes itself approach the Suction Side (SS) and keep away from the Pressure Side (PS) as passing through the NGV, so that HS near the SS is more influenced by the incidence angle effect than that near the PS. As for the heat transfer, swirl affects the Heat Transfer Coefficient (HTC) on the NGV’s PS and SS mainly through the incidence angle effect. Different from the NGV, the inlet swirl and HS have limited effect on the HTC on the rotor blade’s PS, while on the rotor blade’s SS, the original vortex system dominates; therefore, the inlet non-uniformities merely enhance the HTC on the SS rather than alter its distribution characteristics.     

气凝胶隔热材料制备及航天热防护应用研究进展北大核心CSCD

我国航天事业的不断发展对航天器热防护材料提出了更高的要求,气凝胶作为一种纳米网络多孔材料,因其纳米尺度效应,具有超级隔热性能,是近年来超级隔热材料研究的热点和前沿。本文以航天热防护应用为背景,综述了气凝胶隔热材料近十年来的研究进展,包括无机氧化物气凝胶、有机气凝胶、炭气凝胶、碳化物气凝胶隔热材料等,以及其制备方法、隔热性能和热防护应用现状,结合当前航天领域需求和气凝胶隔热材料研究的难点问题,提出气凝胶隔热材料的未来发展方向。     

国产高模碳纤维/环氧复合材料的太阳电池板热循环适应性研究

国产CCM40J-6K高模碳纤维基板的空间高低温热循环耐受性是决定其是否可以大规模应用于空间太阳电池板的关键因素，必须解决交变热环境下的面板与电池电路的匹配性和长寿命问题。本文以国产CCM40J-6K高模碳纤维/环氧复合材料的太阳电池板为研究对象，开展了热循环环境适应性试验研究，分别从国产和进口碳纤维基板适应高低温交变能力对比、国产碳纤维基板铺设电池电路后适应热环境能力以及电池板在轨寿命等3个方面进行测试试验。结果表明：国产碳纤维CCM40J-6K所构成的电池板综合性能与进口M40JB-6K相当，CCM40J-6K基板与三结砷化镓电池片匹配性良好，国产碳纤维电池板经疲劳热循环后的开路电压和短路电流的变化率分别为0.55%和0.24%，太阳电池片和玻璃盖片外观完好无损，太阳电池电路与基板聚酰亚胺面保持绝缘，且碳纤维表面无脱粘现象。说明国产碳纤维CCM40J-6K能够应用于太阳电池板研制。     

编织复合材料在高温热结构中的应用

通过对使用2.5D编织工艺生产的复合材料发动机支撑结构的高温热传导分析,得到了薄壁回转体构件承受高温作用后的传导特性;通过地面富氧状态下的考核试验,验证了该结构能够满足壁面950℃高温长时间使用要求;有限元分析与考核试验结果一致,验证了有限元计算的正确性和地面试验各项热流补偿参数的合理性,对此类产品在工程应用中的分析与预示具有很强的指导意义。