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211.
为模拟高速可压缩湍流问题,对剪应力输运(SST)湍流模型进行了可压缩修正。数值格式采用改进的总变差减小(TVD)格式,并对湍流模型的负值强制项进行了隠式处理。在此基础上计算了绕平板以及基本无分离和具有分离流动结构的压缩拐角的高超声速流动。计算结果和实验数据及半经验公式的对比表明:SST湍流模型的可压缩影响项为密度加权脉动速度的平均与压力梯度的标量乘积。经可压缩修正后的SST湍流模型与原模型及其它可压缩修正模型相比,所计算的壁面压力、摩擦阻力和壁面热流分布具有更高的精度。 相似文献
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One of the biggest challenges of the exploration of the Moon is the survival of the crew and the lunar assets during the lunar night. The environmental conditions on the lunar surface and its cycle, with long periods of darkness, make any long mission in need of specific amounts of heat and electricity to be successful. We have analyzed two different systems to produce heat and electricity on the Moon's surface. The first system consists of Thermal Wadis, sources of thermal power that can be used to supply heat to protect the exploration systems from the extreme cold during periods of darkness. Previous results showed that Wadis can supply enough heat to keep lunar devices such as rovers above their minimum operating temperature (approximately 243 K). The second system studied here is the Thermal Energy Storage (TES), which is able to run a heat engine during the lunar night to produce electricity. When the Sun is shining on the Moon's surface, the system can run the engine directly using the solar power and simultaneously heat a thermal mass. This thermal mass is used as a high temperature source to run the heat engine during the night. We present analytical and numerical calculations for the determination of an appropriate thermal mass for the TES system. 相似文献
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为了研究吸热型碳氢燃料在新型飞行器中的再生冷却性能,采用电加热方式,在热流密度0.1-1.0MW/m2和质量流速500-1000kg/m2s条件下,小通道圆管内(D=1.6mm)研究了超(近)临界压力下(P=3MPa)航空煤油RP-3的拟沸腾流动传热特性。研究发现了超(近)临界压力航空煤油的拟过冷沸腾传热现象。拟过冷沸腾壁温变化特征和传热恶化特征与亚临界压力下的相应特征存在差异。超临界压力航空煤油传热区域划分为类液态强制对流传热区、拟过冷沸腾区和类气态强制对流传热区。拟过冷沸腾壁温和传热系数随流体温度增加而缓慢增加,起到传热强化的作用;拟临界温度区域,存在传热系数极小值点,燃料发生传热弱化;燃料温度大于拟临界温度,燃料处于超临界类气态,传热大幅强化。 相似文献
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An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations (such as leading-inlet, leading-middle, leading-exit, trailing-inlet, trailing-middle and trailing-exit) and four blocking ratios (ranging from 0.1 to 0.4) are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness. 相似文献
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《中国航空学报》2021,34(7):85-113
Gas turbines have been used extensively for aircraft and marine propulsions as well as land-based power generation because of their high thermal efficiency and large power to weight ratios. To further increase the thermal efficiency, numerous prior researches on gas turbine blade internal cooling have been intensively carried out, majorly under stationary conditions. However, the stationary studies neglect the effects of Coriolis and buoyancy forces, which should change the velocity, turbulence and temperature distribution under rotating conditions. To elucidate the rotational effects on gas turbine internal cooling, the extensive results collected from recent investigations are discussed, which include the rotation and buoyancy effects on the rib turbulated cooling, pin fin cooling, jet impingement cooling, dimple/protrusion cooling, latticework cooling as well as swirl cooling. The rotational effects on the friction factors and the most employed experimental and numerical methods are also presented. Moreover, recommendations for future research are outlined. Therefore, this review article provides extensive literature information for the design of the next-generation high-efficiency internal cooling for rotating turbine blades. 相似文献
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通过在激波风洞中开展转捩试验,选取来流马赫数分别为6和8,单位雷诺数分别为4.1×10 6m -1 、2.6×10 7m -1 和4.4×10 7m -1 的来流条件,研究马赫数、单位雷诺数以及攻角变化对钝锥边界层和平板边界层转捩位置的影响。结果表明,攻角增大使钝锥迎风面和背风面边界层转捩位置均前移,使平板边界层转捩位置也前移;钝锥边界层在低马赫数时更容易转捩,平板边界层转捩受马赫数影响在攻角有差异时有所不同;单位雷诺数的增大促进转捩,但对于钝锥边界层而言,该参数增加到试验选定的上限时,转捩位置的变化并不明显;在转捩过程中平板边界层的脉动压力系数与热流具有相同的变化趋势。试验捕捉到了第二模态扰动。 相似文献
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