球锥组合体在热外压作用下的稳定性

球锥组合体作为飞行器头部,热外压稳定性是结构设计的主要问题。本文对薄壳结构进行稳定性分析,将临界外压的有限元计算值与试验修正的理论值进行对比,获得有限元分析的修正系数为0.8;然后采用数值和试验相结合的方法、并考虑材料力学性能的温度效应,对复合材料球锥组合体在热外压载荷下的稳定性进行研究,高温下材料性能退化对临界载荷的影响显著,加热不均匀对临界载荷也有一定影响,线胀系数对临界载荷的影响很小。     

叶顶吹气对低速轴流压气机间隙流动 影响的数值研究

为了评价叶片顶部吹气对间隙流动的影响,采用NUMECA软件对带有叶顶吹气的叶栅流场进行了计算,并将其与不带吹气的基准叶栅流场结果进行了对比、分析.结果表明:叶顶吹气的位置和角度都对间隙流动有着较大影响.按周向和径向方向吹气时对泄漏流量密度的分布有一定的影响,但对稳定工况范围的影响不大;按一定的轴向方向吹出时可抑制间隙引起的流动分离,进而增大压气机的失速裕度.      

Simulating clefts in pumpkin balloons

The geometry of a large axisymmetric balloon with positive differential pressure, such as a sphere, leads to very high film stresses. These stresses can be significantly reduced by using a tendon re-enforced lobed pumpkin-like shape. A number of schemes have been proposed to achieve a cyclically symmetric pumpkin shape, including the constant bulge angle (CBA) design, the constant bulge radius (CBR) design, CBA/CBR hybrids, and NASA’s recent constant stress (CS) design. Utilizing a hybrid CBA/CBR pumpkin design, Flight 555-NT in June 2006 formed an S-cleft and was unable to fully deploy. In order to better understand the S-cleft phenomenon, a series of inflation tests involving four 27-m diameter 200-gore pumpkin balloons were conducted in 2007. One of the test vehicles was a 1/3-scale mockup of the Flight 555-NT balloon. Using an inflation procedure intended to mimic ascent, the 1/3-scale mockup developed an S-cleft feature strikingly similar to the one observed in Flight 555-NT. Our analysis of the 1/3-scale mockup found it to be unstable. We compute asymmetric equilibrium configurations of this balloon, including shapes with an S-cleft feature.     

处理机匣/压气机非定常相互作用分析

实验研究了三个不同槽数圆弧斜槽处理机匣对压气机气动性能的影响,实验结果显示,只有当处理槽数确定的处理机匣/压气机非定常相互作用频率锁定在压气机分离绕流流场非定常特征频率附近时,处理机匣才能展示出满意的扩稳能力.实验利用25孔总压耙测量压气机静子出口S3流面总压流场结构,测量结果表明,处理机匣/压气机非定常相互作用不但大幅度改善了压气机分离绕流流场结构,还影响了压气机总压升径向分布.      

计量标准装置不确定度的分析与评定

不确定度是测量工作的质量和测量结果可信赖程度和评价。按JJF10 5 9- 1999、GJB375 6 - 1999标准规定 ,对我计量测试站的计量标准装置不确定度进行了详细分析 ,并按GJB/J2 74 9- 1996要求对计量标准进行了重复性和稳定性考核以及不确定度的验证 ,最后给出了各项计量标准装置的不确定度。     

Takagi-Sugeno fuzzy model identification for turbofan aero-engines with guaranteed stability

This paper is concerned with identifying a Takagi-Sugeno (TS) fuzzy model for turbofan aero-engines working under the maximum power status (non-afterburning). To establish the fuzzy system, theoretical contributions are made as follows. First, by fixing antecedent parameters, the estimation of consequent parameters in state-space representations is formulated as minimizing a quadratic cost function. Second, to avoid obtaining unstable identified models, a new theorem is proposed to transform the prior-knowledge of stability into constraints. Then based on the aforementioned work, the identification problem is synthesized as a constrained quadratic optimization. By solving the constrained optimization, a TS fuzzy system is identified with guaranteed stability. Finally, the proposed method is applied to the turbofan aero-engine using simulation data generated from an aerothermodynamics component-level model. Results show the identified fuzzy model achieves a high fitting accuracy while stabilities of the overall fuzzy system and all its local models are also guaranteed.     

高速对称刚性转子碰摩运动的稳定性分析

分析了高速对称刚性转子圆柱形和圆锥形碰摩运动。当转子两端的轴承同时发生不良润滑,造成转子两端同时与轴承接触,产生圆柱形碰摩运动,给出了发生圆柱形碰摩运动时系统的稳定范围,讨论了摩擦系数、轴承径向间隙、碰摩发生时的初始角度与失稳涡动角速度的关系。当转子一端的轴承发生不良润滑,而另一端的轴承正常工作时发生圆锥形碰摩运动,分析发现其碰摩运动的稳定性取决于其系统本身物理参数,进行了分岔分析。      

带快速大角度机动附件的卫星在俯仰平面内的运动控制与稳定性研究

研究一类带快速、大角度机动附件的卫星本体的控制与稳定性问题。给出了一类附件作快速、大角度机动时卫星在俯仰平面的动力学方程。采用传统的PD控制,并证明了类闭环系统的一类线性时变系统是指数稳定的,同时证明了在有界激励下,该系统仍能保持稳定。最后仿真验证了分析的正确性。     

月球着陆器着陆稳定性仿真分析

随着中国深空探测的发展,在月球表面进行着陆探测成为新的关注热点,因此月球着陆器的着陆稳定性研究成为一项重要课题。文章利用ADAMS软件及其用户子程序,对一种可展开四腿式月球着陆器的着陆稳定性进行了研究,研究结论为着陆器的着陆缓冲机构及总体设计提供参考。     

四频激光陀螺腔体材料及元件

本文介绍了激光陀螺的工作原理及四频激光陀螺的特点。对四频激光陀螺的稳定性与所使用的材料和元件作了论述。