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201.
《中国航空学报》2020,33(12):3288-3305
The modal vibration of the rotor is the main cause of excessive vibration of the aero-engine overall structure. To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control, the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method. A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper. The transmission, conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape, the conical whirling modal shape and the translational modal shape are analyzed, respectively. The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy, the kinetic energy and the energy dissipated by the damping of the structure. The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different. Especially for the first-order bending modal shape, the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft, resulting in large deformation at this part. To attenuate this harmful vibration, the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow. This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective. 相似文献
202.
G.A. Bazilevskaya M.B. KrainevV.S. Makhmutov Yu.I. StozhkovA.K. Svirzhevskaya N.S. Svirzhevsky 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Observations of charged particle fluxes in the stratosphere of the polar regions represent the cosmic rays variations with energy above 100 MeV. At the end of 2009 these fluxes reached the highest level for the time of observations from mid 1957 and were by 17% higher than the previous extremum value of May 1965. In the mean time the ground-based neutron monitors showed the remarkably less count rate enhancement. These results argue for the significant change in the energy spectrum of incoming particles in 2008–2009 in the energy range of ∼100–1500 MeV/n. 相似文献
203.
204.
通过一种同轴水工质脉冲等离子体推进器的LCR放电回路的理论分析和实验来探讨其在运行过程中的能量平衡和能量转换效率。理论分析认为储能电容中的储存能量通过放电转化为加速动能及被传输线和电容的等效电阻消耗掉,并且根据等效电阻的分配情况定义了水工质脉冲等离子体推进器的加速动能和电磁力转换效率。实验研究表明:该水工质脉冲等离子体推进器的存储能量(E0=4.86J)转换成加速动能的能量转换效率是28%,其中11%用于电磁加速及17%用于电热加速,其余72%的存储能量消耗在储能电容和传输线内阻所造成的能量损失上。 相似文献
205.
206.
采用基于Mindlin一阶剪切理论的连续壳单元,建立了预测含分层损伤复合材料层板在压缩疲劳载荷作用下的分层扩展3D模型,分析了含穿透分层复合材料层板在压缩疲劳载荷作用下的分层扩展行为。利用累积损伤理论,对层板内出现的各种典型损伤进行相应的刚度折减,并在循环加载过程中对材料性能进行强度弱化。利用虚裂纹闭合技术(VCCT)计算分层前缘处的能量释放率,结合混合断裂判据判断分层是否扩展,进而得到压缩疲劳载荷作用下分层扩展规律。计算模型通过大型商用有限元软件和自编程序实现。通过对数值仿真结果和试验结果进行比较,验证了模型的合理性和准确性。 相似文献
207.
P.A. Sedykh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
It is clear that the primary energy source for magnetospheric processes is the solar wind, but the process of energy transfer from the solar wind into the magnetosphere, or rather, to convecting magnetospheric plasma, appears to be rather complicated. Bow shock is a powerful transformer of the solar wind kinetic energy into the gas dynamic and electromagnetic energy. A jump of the magnetic field tangential component at front crossing means that the front carries an electric current. The solar wind kinetic energy partly transforms to gas kinetic and electromagnetic energy during its passage through the bow shock front. The transition layer (magnetosheath) can use part of this energy for accelerating of plasma, but can conversely spend part its kinetic energy on the electric power generation, which afterwards may be used by the magnetosphere. Thereby, transition layer can be both consumer (sink) and generator (source) of electric power depending upon special conditions. The direction of the current behind the bow shock front depends on the sign of the IMF Bz-component. It is this electric current which sets convection of plasma in motion. 相似文献
208.
209.
马芬芬 《西安航空技术高等专科学校学报》2008,26(3):53-54
通过对凝结水及其余热回收的经济效益分析,提出了凝结水回收具有重要的节能作用,并从技术上阐述了凝结水回收的方法及技术措施,以便在实际设计、施工中给予重视。 相似文献
210.
Two freedom linear parameter varying μ synthesis control for flight environment testbed 总被引:2,自引:0,他引:2
To solve the problem of robust servo performance of Flight Environment Testbed(FET)of Altitude Ground Test Facilities(AGTF) over the whole operational envelope, a two-degree-offreedom μ synthesis method based on Linear Parameter Varying(LPV) schematic is proposed, and meanwhile a new structure frame of μ synthesis control on two degrees of freedom with double integral and weighting functions is presented, which constitutes a core support part of the paper. Aimed at the problem of reference command's rapid change, one freedom feed forward is adopted, while another freedom output feedback is used to meet good servo tracking as well as disturbance and noise rejection; furthermore, to overcome the overshoot problem and acquire dynamic tuning,the integral is introduced in inner loop, and another integral controller is used in outer loop in order to guarantee steady errors; additionally, two performance weighting functions are designed to achieve robust specialty and control energy limit considering the uncertainties in system. As the schedule parameters change over large flight envelope, the stability of closed-loop LPV system is proved using Lyapunov inequalities. The simulation results show that the relative tracking errors of temperature and pressure are less than 0.5% with LPV μ synthesis controller. Meanwhile, compared with non-LPV μ synthesis controller in large uncertainty range, the proposed approach in this research can ensure robust servo performance of FET over the whole operational envelope. 相似文献