唇口斜切修型对S形进气道RCS影响

采用基于迭代物理光学法与等效边缘电磁流法的雷达散射截面计算程序,分析了水平、垂直两种极化方式下唇口斜切修型对菱形进口S形进气道边缘绕射场及腔体内部散射场的影响。计算结果表明：在水平、垂直两种极化方式下,斜切修型可有效降低边缘绕射场的雷达散射截面,但随斜切角度的增大,其减小幅度降低;正负斜切角度对应的绕射场雷达散射截面分布关于0°探测角对称;斜切修型对腔体内部散射场的影响较小。     

The lower ionosphere response to its disturbances by powerful radio waves

The paper presents data from some campaigns at Sura heating facility in 2011–1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil’sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50–120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil’sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil’sursk and backscattered signals in Observatory were observed at the height at 40–100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed.     

Modified robust optimal adaptive control for flight environment simulation system with heat transfer uncertainty

To solve the rapid transient control problem of Flight Environment Simulation System (FESS) of Altitude Ground Test Facilities (AGTF) with large heat transfer uncertainty and disturbance, a new adaptive control structure of modified robust optimal adaptive control is presented. The mathematic modeling of FESS is given and the influence of heat transfer is analyzed through energy view. To consider the influence of heat transfer in controller design, we introduce a matched uncertainty that represents heat transfer influence in the linearized system of FESS. Based on this linear system, we deduce the design of modified robust optimal adaptive control law in a general way. Meanwhile, the robust stability of the modified robust optimal adaptive control law is proved through using Lyapunov stability theory. Then, a typical aero-engine test condition with Mach Dash and Zoom-Climb is used to verify the effectiveness of the devised adaptive controller. The simulation results show that the designed controller has servo tracking and disturbance rejection performance under heat transfer uncertainty and disturbance; the relative steady-state and dynamic errors of pressure and temperature are both smaller than 1% and 0.2% respectively. Furthermore, the influence of the modification parameter γ is analyzed through simulation. Finally, comparing with the standard ideal model reference adaptive controller, the modified robust optimal adaptive controller obviously provides better control performance than the ideal model reference adaptive controller does.     

整体叶盘电解加工阴极修正方法与试验

电解加工是航空发动机整体叶盘制造的主要技术之一,阴极修正是该加工技术的重要环节。为了提升阴极修正精度,提出了恒采样点空间法向修正方法。该方法将阴极型面设计、加工误差分析、工具阴极修正统一至阳极采样点空间法向的一维坐标系中,将复杂的三维曲面修正简化为离散的一维修正,消除了加工误差与修正量的错位。以某整体叶盘为例,在自行研制的整体叶盘型面电解加工机床上开展工具阴极修正试验,采用三坐标测量机对修正前后的加工样件进行检测,经过一次修正,叶片电解加工精度由0.25mm提高至0.04mm,试验结果表明该阴极修正方法合理有效,具有较强的可行性。     

基于物理量梯度修正的RBF数据传递方法

径向基函数是复杂外形飞行器多场耦合计算中重要的数据传递方法。复杂飞行器物理量分布通常与局部流动特征密切相关且在不同区域变化剧烈,如何在具备各向同性特征的径向基函数中考虑实际物理量各向异性分布因素的影响成为制约其精度进一步提升的关键。针对径向基函数的问题,提出了一种基于局部物理量梯度对径向基三方向权重进行自适应修正的数据传递新方法。采用高超声速舵面、翼身组合体算例对该方法在单次数据传递中的可行性及效果进行了验证,同时基于该方法对压缩拐角外形开展了气动力/热/结构多场耦合数值模拟,并与风洞试验结果进行了对比分析,以验证该方法在实际耦合问题计算长时间高频次数据传递中的适用性及可靠性。研究结果表明该方法能够很好地提升如薄板样条插值（TPS）、多重二次函数插值（MQ）等全域基函数的单次插值效果,并且有效地改进了MQ方法对形态参数的鲁棒性,而对于梯度修正后的紧支基函数,其改进效果更佳,以较少的点达到了TPS、MQ等全域基函数的插值效果,实现了数据传递效率和精度的兼顾。采用该方法获得的耦合计算结果与试验对比一致,表明了该方法的可用性以及在复杂外形多场耦合问题中的良好工程应用前景。     

某型涡喷发动机状态空间模型的提取与修正研究

以某型单转子涡喷发动机为研究对象,在提取该型发动机状态空间模型的基础上,提出了单转子涡喷发动机状态空间模型的稳态及动态的修正算法,获得基于稳态及动态的修正模型.以阶跃输入响应对模型进行了检验,检验结果表明使用该方法修正的状态空间模型具有与原非线性数学模型完全一致的稳态及动态过程响应,解决了单转子涡喷发动机状态空间模型检验与修正的问题.     

弧齿锥齿轮低敏感性修形

为了改善航空弧齿锥齿轮的啮合稳定性,提出了齿面低敏感性修形.基于齿面误差和误差敏感性矩阵,建立齿面误差修正模型,用广义逆矩阵的最小二乘法求解超越方程组,获得机床调整参数的修正量;对齿面进行3段抛物线修形,将修形后的齿面作为目标齿面,采用齿面误差修正的方法求得相应的机床调整 参数;仿真算例表明:经过低敏感性修形,降低了齿面印痕的误差敏感性、提高了齿轮副的容差范围,但齿根弯曲强度下降了4.28%.因此,通过合理选择齿面修形系数,可降低齿根强度的变化,改善齿轮副啮合稳定性.      

航空钛合金抗疲劳表面改性技术研究进展

重点介绍了提高钛合金疲劳性能的表面改性技术的最新研究进展。主要从喷丸强化、激光冲击强化、挤压、滚压、离子注入、滚磨光整加工、水射流喷丸等典型方式对钛合金的加工能力、作用机理,以及加工后零件的残余应力水平和疲劳性能等方面进行了阐述,以期为航空钛合金零件的表面改性提供借鉴。     

激光冲击强化研究现状与展望

激光冲击强化是一种新型的表面改性技术,相比于传统的喷丸强化技术有诸多突出优势.对激光冲击强化技术原理进行分析,总结激光冲击强化技术的各个工艺参数,并对激光冲击强化后材料表层性能变化进行阐述.讨论激光冲击强化技术的发展与现状,并对该技术在未来的运用进行展望.     

差曲面拓扑的齿轮啮合刚度计算与承载接触分析

基于齿条-齿轮等切共轭产形原理,构建齿面数值模型、ease-off差齿面,对ease-off蕴含的齿面啮合信息进行解析,获得了齿面接触路径、传动误差、接触线瀑布图;综合ease-off拓扑仿真与轮齿刚度非线性单元耦合解析,给出了修形拓扑齿面的啮合刚度、承载传动误差的计算方法。沿接触路径遍历接触线序列,获得了轮齿时变啮合刚度、承载传动误差与载荷分布图;给出了2阶抛物面对称与对角拓扑两种修形形式算例,求出了系列载荷作用下的啮合刚度、承载传动误差、齿面载荷分布。结果显示:随着载荷的增加,轮齿啮合刚度时变效应明显减弱;承载传动误差波动与啮合刚度、修形梯度密切相关;对角修形在啮合刚度、传动误差、载荷分布特性方面好于对称修形。