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271.
水燃比是水冲压发动机的重要工作参数。水燃比过大易造成内流场温度降低,实际工作中低温可能引起水蒸汽液化和金属/水反应停止,以致降低发动机性能。为减少这类情况的出现,针对两次进水的水冲压发动机,提出了试验总水燃比及一、二次水燃比选择方法。该方法以发动机热力计算的最优理论水燃比为基础,考虑试验过程中实际热损失的影响对其进行了修正。针对不同水燃比的影响,对某型试验水冲压发动机进行了地面直连试验研究,结果显示存在最佳总水燃比及一次水燃比使发动机性能达到最优,同时证明了该水燃比选择方法合理可行。 相似文献
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温度对2A12铝合金在模拟油箱积水环境中初期腐蚀行为的影响 总被引:3,自引:0,他引:3
基于飞机油箱舱内的铝合金在油箱积水环境中发生的腐蚀损伤问题,通过研究腐蚀形貌、最大点蚀坑深度、最大点蚀坑开口面积、表面腐蚀损伤度、交流阻抗响应等变化,分析了温度对2A12铝合金在模拟油箱积水环境中初期腐蚀行为的影响。研究发现,最大点蚀坑深度、开口面积、表面腐蚀损伤度都随着温度的升高而增加,特别当温度升高到65℃和75℃时,腐蚀严重加剧,各项评价指标显著增大。在25、35、45、55℃模拟油箱积水环境中,最大点蚀坑深度及开口面积随时间的关系呈现幂函数变化规律,而在65℃、75℃时,其遵循最小二乘法多项式拟合。电化学交流阻抗谱测试结果表明,2A12铝合金在3个特征温度(常温25℃、中温55℃及高温75℃)下的腐蚀速度快慢为V75℃ > V55℃ > V25℃。 相似文献
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针对水中上升气泡对水体携带作用一直难以测量的问题,特提出利用气泡上升携带水量来表征其能力大小的思想,进而专门设计了相应的实验装置,重点开展了双液分离转相精测技术的实验研究。实验时选取柴油和水构成双液,并分别采用直接测量和转相精测两种方法测量气泡上升携带水量。结果表明:采用双液法可有效分离气泡携带的上升水体;气泡上升携带水量的转相精测值精度高于其直接测量值,且携带水量越小其精度优势越明显,特别是当携带水量很小,直接测量法可能因误差太大而根本无法实施,但转相精测法却可顺利进行。 相似文献
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Arijit De Animesh Maitra 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):290-297
The objective of this study is to investigate cloud attenuation at 30 GHz frequency using ground-based microwave radiometric observations at a tropical location, Kolkata. At higher frequencies and lower elevation angles, cloud attenuation is of major concern at a tropical location. The location experiences high value of liquid water path (LWP), which is responsible for cloud attenuation, during the Indian summer monsoon (ISM) and pre-monsoon season. Significant amount of cloud attenuation has been observed during monsoon season at 30 GHz. Two years observations of exceedance probability of cloud attenuation and worst month statistics are presented. The variation of cloud attenuation with frequencies for different elevation angles has also been investigated. The seasonal and diurnal patterns of cloud attenuation are examined. Cloud attenuation, inferred from radiometric measurements before rain commencement, has been compared to rain attenuation at Ku-band. Exceedance probabilities of cloud and rain attenuation have been compared. 相似文献
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Sandip Banerjee Palanisamy Shanmugam 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):266-289
Hyperspectral resolution image products of a synthetic sensor featuring the high spatial resolution of the space-borne sensor can offer cost-effective means for enhancing our current capabilities in terms of providing an array of images in lieu of designing an expensive system for image acquisition, which can serve the expanding needs of the scientific and user communities for various critical water color applications. Despite several studies on enhancing the capability of land remote sensing sensors, full spectrum reconstruction of water color images with varying spectral bands is hampered by the lack of methods and accurate atmospheric correction procedures. In the present work, a novel method is developed for reconstruction of hyperspectral resolution images from high spatial-resolution Sentinel 2 Multispectral Instrument (MSI) data representative of many complex waters in coastal and inland zones. This method uses a deep neural network (DNN) with multiple blocks of deconvolution and dense layers. The spectral reconstruction of hyperspectral resolution images from multispectral data was based on rigorous training data from the atmospherically-corrected and validated HICO normalized water-leaving radiance products (with spectral resolution 438-868 nm sampled at 5.7 nm) of diverse water types. The generalizability and versatility of the DNN method was tested and evaluated systematically by means of various qualitative and quantitative analyses using concurrent space-borne (MSI and HICO) and in-situ measurements from different regional waters. Reconstructed hyperspectral resolution radiances obtained from the MSI images closely matched with independent HICO and MSI measurements within the desired accuracy. Successful reconstruction and validation of the hyperspectral radiances indicate that the proposed state-of-the-art method provides possible future directions for enhancing our current capabilities of space-borne sensors for various research purposes and societal applications at local, regional and global scales. 相似文献