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。     

Recent developments in thermal characteristics of surface dielectric barrier discharge plasma actuators driven by sinusoidal high-voltage power

Flow control using surface Dielectric Barrier Discharge(DBD) plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry. The induced flow field of the plasma actuator, with the starting vortex in the wall jet,plays an important role in flow control. However, the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator, and most of the total energy i...