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84.
Transient aeroelastic responses and flutter analysis of a variable-span wing during the morphing process 总被引:1,自引:0,他引:1
To investigate the transient aeroelastic responses and flutter characteristics of a variablespan wing during the morphing process,a novel frst-order state-space aeroelastic model is proposed.The time-varying structural model of the morphing wing is established based on the Euler-Bernoulli beam theory with time-dependent boundary conditions.A nondimensionalization method is used to translate the time-dependent boundary conditions to be time-independent.The time-domain aerodynamic forces are calculated by the reduced-order unsteady vortex lattice method.The morphing parameters,i.e.,wing span length and morphing speed,are of particular interest for understanding the fundamental aeroelastic behavior of variable-span wings.A test case is proposed and numerical results indicate that the flutter characteristics are sensitive to both of the two morphing parameters.It could be noticed that the aeroelastic characteristics during the wing extracting process are more serious than those during the extending process at the same morphing speed by transient aeroelastic response analysis.In addition,a faster morphing process can get better aeroelastic performance while the mechanism comlexity will arise. 相似文献
85.
以大推力氢氧火箭发动机为研究对象,对其瞬态特性进行了研究。根据模块化的建模和仿真思想,建立了发动机各组件的动态数学模型,开发了发动机系统各组件的仿真模块,开展了发动机动态特性仿真分析与起动时序试验研究。仿真结果表明,推力室氧阀采用25%初级与100%全开的双开度形式,氧涡轮侧设置10%分流流量的燃气分流阀,燃气发生器在火药启动器工作至70%~80%时间段点火的系统优化配置方案,有利于控制发动机点火起动混合比,提高起动可靠性。通过添加故障因子,当涡轮效率由于故障从0.29降至0.19时,发动机工况降至故障前的78%工况,当效率降至0.06时,发动机工况降至故障前20%工况,发动机故障仿真结果与地面试验故障结果吻合较好,有利于故障分析定位。 相似文献
86.
High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators(EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump. 相似文献
87.
利用非稳态阶跃平面热源法对SiO2气凝胶的热参数进行了高温实验研究,获得了不同温度和压力条件下SiO2气凝胶的热导率、热扩散率以及比热容等.结果表明,SiO2气凝胶800℃的热导率比室温增大约62%.在相同气压且低于600℃时,其热导率受比热容影响,而在高于600℃时,则受热扩散率影响;在相同温度且高于10 kPa时,热导率亦受热扩散率影响. 相似文献
88.
Mehdi Eshagh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The satellite gravity gradiometry (SGG) data can be used for local modelling of the Earth’s gravity field. In this study, the SGG data in the local north-oriented and orbital frames are inverted to the gravity anomaly at sea level using the second-order partial derivatives of the extended Stokes formula. The emphasis is on the spatial truncation error and the kernel behaviour of the integral formulas in the aforementioned frames. The paper will show that only the diagonal elements of gravitational tensor at satellite level are suitable for recovering the gravity anomaly at sea level. Numerical studies show that the gravity anomaly can be recovered in Fennoscandia with an accuracy of about 6 mGal directly from on-orbit SGG data. 相似文献
89.
FENG Xueshang 《空间科学学报》2002,22(Z1)
This is an overview of progresses in heliospheric physics made in China in the period of June, 2000 to May, 2002. The report is focused on theoretical studies,modelling and observational analysis of interplanetary physical phenomena, and consists of five sections: the acceleration and heating of the solar wind, corona structures, coronal mass ejections, magnetic reconnection phenomena, and in terplanetary transient phenomena. The main achievements made recently by Chinese scientists in related areas are simply listed in corresponding sections without any priority, only certain editorial consideration. 相似文献
90.
益小苏 《南京航空航天大学学报》1987,(4)
工程胶粘剂固化过程中的热焓变化与反应转换率成正比,由此可根据化学反应动力学理论实验确定反应动力学参数,获得反应转换率和时间温度的关系式。胶粘剂的固化反应不仅与时间和温度有关,还受温度变化条件的控制。恒温固化的速度通常大于等速升温固化的速度。 相似文献