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排序方式: 共有392条查询结果,搜索用时 578 毫秒
91.
磨粒监测与分析系统在航空发动机状态监控中的应用(英文) 总被引:2,自引:0,他引:2
磨损颗粒是研究机器磨损状态时最直接、最重要的信息元 ,通过对滑油中的磨粒进行监测与分析以判断机械设备的磨损状况 ,可以监测并预防机械设备的磨损故障。本文介绍的磨粒监测与分析系统 ( DMAS)具有制谱简单、自动化程度高、能及时准确预报及诊断机器的各种磨损类故障等特点 ,可以有效地保障机器安全可靠地运行。本文详细地阐述了这套系统的基本原理、软硬件组成 ,以及在航空发动机磨损状态监测中的应用 相似文献
92.
以固体火箭发动机的翼柱形药柱的优化设计为例,通过建立翼柱形药柱的计算模型,固体火箭发动机的能量模型,提出了翼柱型药柱的优化设计方法。药柱的计算采用了混合罚函数法,根据得出的计算结果中各设计变量对目标函数的影响大小,确定出各设计变量提最佳值。该方法还可用地其它型号的翼柱形药柱的优化设计。 相似文献
93.
近年固体火箭推进技术发展趋势 总被引:3,自引:0,他引:3
讨论了在冷战结束后的政治、军事环境下固体发动机应用领域的动向和固体火箭推进技术的发展特点,重点了发动机设计及固体推进剂、壳体、喷管、点火系统等单项技术的发展趋势。 相似文献
94.
It has been well known that nozzle end-clearances in a Variable Nozzle Turbine (VNT) are unfavorable for aerodynamic performance, especially at small openings, and efforts to further decrease size of the clearances are very hard due to thermal expansion. In this paper, both the different sizes of nozzle end-clearances and the various ratios of their distribution at the hub and shroud sides were modelled and investigated by performing 3D Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations with a code of transferring the aerodynamic pressure from the CFD results to the FEA calculations. It was found that increasing the size of the nozzle end-clearances divided equally at the hub and shroud sides deteriorates turbine efficiency and turbine wheel reliability, yet increases turbine flow capacity. And, when the total nozzle end-clearances remain the same, varying nozzle end-clearances’ distribution at the hub and shroud sides not only shifts operation point of a VNT turbine, but also affects the turbine wheel vibration stress. Compared with nozzle hub clearance, the shroud clearance is more sensitive to both aerodynamic performance and reliability of a VNT turbine. Consequently, a possibility is put forward to improve VNT turbine efficiency meanwhile decrease vibration stress by optimizing nozzle end-clearances’ distribution. 相似文献
95.
Redundantly actuated planar rotational parallel mechanisms (RAPRPMs) adapt to the requirements of robots under different working conditions by changing the antagonistic internal force to tune their stiffness. The geometrical parameters of the mechanism impact the performances of modulating stiffness. Analytical expressions relating stiffness and geometrical parameters of the mechanism were formulated to obtain the necessary conditions of variable stiffness. A novel method of variable stiffness design was presented to optimize the geometrical parameters of the mechanism. The stiffness variation with the internal force was maximized. The dynamic change of stiffness with the dynamic location of the mechanism was minimized, and the robustness of stiff-ness during the motion of the mechanism was ensured. This new approach to variable stiffness design can enable off-line planning of the internal force to avoid the difficulties of on-line control of the internal force. 相似文献
96.
This paper conducts a simulation study of a novel aircraft environmental control system based on membrane dehumidification(MD-ECS),and compares the system with the up-to-date four-wheel high pressure de-water system(4WHPDW-ECS).Mathematical models for the two systems are established,and a system simulation using a numerical technique is performed to analyze and compare the cooling performance of the two systems.Simulation results show that the cooling capacity of MD-ECS is much higher than that of 4WHPDW-ECS under the same working conditions,indicating that the novel system is theoretically feasible and promising.The effects of the sweep ratio of the membrane dehumidifier on the dehumidification and cooling performance of the system is also investigated. 相似文献
97.
98.
分析了小角度正弦激光干涉仪的有关特性,叙述了这种方法的测量原理,计算了几种因素对测量准确度的影响,指出提高测量准确度的解决办法。 相似文献
99.
Chen Yan Ding Lanying Fu Yucan Su Honghua Wu Jie Xu Jiuhua Xu Hongjun 《南京航空航天大学学报(英文版)》2014,(1):104-110
The purpose of this study is to investigate the effect of graphite lubricant on the dry grinding performance of Ti-6Al-4Valloy,using graphite-coated,brazed monolayer,cubic boron nitride(cBN)wheels.Brazed monolayer cBN wheels both with and without a coating of polymer-based graphite lubricant are fabricated and subsequently compared for grinding performance based on measurements of grinding temperature,surface microstructure and grinding.In terms of grinding temperature,considerable improvement in dry grinding performance of titanium alloy is achieved using coated brazed monolayer cBN wheels,with 42%—47%reduction in grinding temperature as opposed to uncoated wheels.The grinding force ratio with the coated wheels is observed to remain between 1.45to1.85despite material removal rates reaching up to 1 950mm3/mm.No tangible change in ground titanium surface microstructure is noted as a result of grinding with the graphite coated wheels as opposed to the uncoated ones. 相似文献
100.
LiHui Qiu Xiaomin Zuo Tao Yu YangYi Sun Yifan Qi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3606-3611
This study employs the Horizontal Wind model 2014 to calculate the intensity of the Vertical ion convergence (VIC) to examine the role of neutral wind shear in the global distribution of the Es occurrence rate. The global S4 observations from the FORMOSAT-3/COSMIC GPS Occultation Experiment (GOX) are used to derive global information on the Es occurrence. Both the simulation and observation suggest that the Es highly occurs in the mid-latitude regions of the summer hemisphere. 相似文献