Experimental investigation and correlation development of jet impingement heat transfer with two rows of aligned jet holes on an internal surface of a wing leading edge

Extensive experimental studies on the heat transfer characteristics of two rows of aligned jet holes impinging on a concave surface in a wing leading edge were conducted, where50000 Rej 90000, 1.74 H/d 27.5, 66° a 90°, and 13.2 r/d 42.03. The finding was that the heat transfer performance at the jet-impingement stagnation point with two rows of aligned jet holes was the same as that with a single row of jet holes or the middle row of three-row configurations when the circumferential angle of the two jet holes was larger than 30°. The attenuation coefficient distribution of the jet impingement heat transfer in the chordwise direction was so complicated that two zones were divided for a better analysis. It indicated that: the attenuation coefficient curve in the jet impingement zone exhibited an approximate upside-down bell shape with double peaks and a single valley; the attenuation coefficient curve in the non-jet impingement zone was like a half-bell shape, which was similar to that with three rows of aligned jet holes; the factors,including Rej, H/d and r/d, affected the attenuation coefficient value at the valley significantly.When r/d was increased from 30.75 to 42.03, the attenuation rates of attenuation coefficient increased only by 1.8%. Consequently, experimental data-based correlation equations of the Nusselt number for the heat transfer at the jet-impingement stagnation point and the distributionof the attenuation coefficient in the chordwise direction were acquired, which play an important role in designing the wing leading edge anti-icing system with two rows of aligned jet holes.     

基于CATIA V5系统的复杂机加件模线样板设计方法探索

模线样板是检验零件几何尺寸和外形轮廓的量具,在航空制造中有着极其重要的作用.对于复杂的机加件,其空间曲面的展开和结构轮廓的提取一直是机加件模线样板设计过程中的一个技术难题.针对飞机复杂机加零件模线样板设计中的两类典型问题提出三种有效、实用的解决方法,即"边界拟合曲面法"、"分割生长提取法"和"草图线面相合法".     

Reliable flight performance assessment of multirotor based on interacting multiple model particle filter and health degree

Multirotor has been applied to many military and civilian mission scenarios. From the perspective of reliability, it is difficult to ensure that multirotors do not generate hardware and software failures or performance anomalies during the flight process. These failures and anomalies may result in mission interruptions, crashes, and even threats to the lives and property of human beings. Thus, the study of flight reliability problems of multirotors is conductive to the development of the drone industry and has theoretical significance and engineering value. This paper proposes a reliable flight performance assessment method of multirotors based on an Interacting Multiple Model Particle Filter (IMMPF) algorithm and health degree as the performance indicator. First, the multirotor is modeled by the Stochastic Hybrid System (SHS) model, and the problem of reliable flight performance assessment is formulated. In order to solve the problem, the IMMPF algorithm is presented to estimate the real-time probability distribution of hybrid state of the established SHS-based multirotor model, since it can decrease estimation errors compared with the standard interacting multiple model algorithm based on extended Kalman filter. Then, the reliable flight performance is assessed with health degree based on the estimation result. Finally, a case study of a multirotor suffering from sensor anomalies is presented to validate the effectiveness of the proposed method.     

基于1553B和SpaceWire组合网络的星载数据管理软件设计

为同时满足对于星务管理数据和高速载荷数据的传输要求,国内外的飞行器趋于使用1553B和SpaceWire组合网络来进行星上数据传输。复杂而灵活的数据传输要求使得卫星数据流设计中引入了大量标准协议,同时大大增加了星载数据管理软件的复杂度。对一种基于1553B和SpaceWire组合网络的星载数据管理软件的协议体系进行了介绍,通过对协议进行分析,改进了已有的软件框架,形成了一种基于标准协议的分层的软件架构,以空间包为单位实现星内数据交互,实现了软件应用层与数据链路协议的分离。软件实现结果表明,合理的协议分层和有效的接口封装提高了软件的可拓展性和可移植性,有利于软件产品化。     

我国物流标准化存在的问题及对策

当前我国物流标准化存在以下问题:总体发展滞后、基础薄弱、体制"瓶颈"、采用国际标准少、对行政力量过于依赖,等等.解决的对策有:发挥政府部门作用、加快体系研究、借签国外经验、发挥行业协会作用、加大宣传力度,等等.     

单向阀三维动态流场稳定性仿真研究

对单向阀自激振动机理进行研究,采用线性分析方法提出了单向阀的临界稳定曲线。应用泵阀仿真软件PumpLinx的动网格技术,开展了单向阀三维动态流场仿真分析,数值研究了不同工作压力、不同质量流量条件下的单向阀动态稳定特性。结果表明:在某一工作压力条件下,小流量时单向阀工作不稳定,会形成周期性的阀门颤振,随着质量流量增大,单向阀动态稳定性增强;当质量流量足够大时,单向阀工作稳定,单向阀保持稳定开度工作;质量流量一定时,工作压力降低,单向阀动态稳定性增强。单向阀三维动态流场仿真结果与线性稳定性结论相一致,从三维动态流场角度验证了单向阀自激振动机理及线性稳定性分析方法的有效性。     

跨声速压气机转子的二次流旋涡结构

为了明确跨声速轴流压气机内部流场结构,数值模拟了NASA Rotor37转子,结合λ2准则分析流场参数,探索流动的规律和旋涡结构。研究发现,压气机转子的旋涡模型主要由马蹄涡、壁角涡、径向涡、脱落涡、泄漏涡、诱导涡和分离涡等7个旋涡组成。马蹄涡吸力面分支耗散,压力面分支向相邻的吸力面发展。壁角涡与脱落涡位于叶根角区,引起流动损失和角区失速。径向涡位于激波后吸力面的分离区内,它扩大吸力面分离、引起低能流体向叶顶堆积。激波与叶尖泄漏在叶顶通道中形成3涡:泄漏涡、诱导涡和分离涡,而叶栅通道出口存在分离涡和由泄漏涡与诱导涡合成的叶顶通道涡。泄漏涡与诱导涡破碎在流道中间产生的堵塞区,分离涡造成吸力面尾缘的低速区,共同触发跨声速压气机的失稳。     

某圆周缝型救生伞的充气性能研究

为获得新型圆周缝结构救生伞的充气性能,文章采用任意拉格朗日欧拉流固耦合方法对该救生伞进行了充气过程的数值模拟,用空投试验结果验证了该数值方法的可行性。数值结果得到了绕伞衣流场、伞衣外形、运动的动态信息,对数值结果的分析发现初始充气阶段后期流场对上部伞衣影响很大,为充气过程中上部伞衣的控制提供了依据,但是初始充气期救生伞的摆动角度小于充满期。对于结构透气量不对称设计的伞衣,不对称充气是绝对的,圆周缝会首先在结构透气量少的部位张开。结果表明,对不同的圆周缝节点设计不同的开缝力将有助于保持良好的对称充气状态,改变开缝力的设计参数将会改变圆周缝的开缝时间及圆周缝完全张开所需的时长,将达到更好的减载效果。研究结果对圆周缝型降落伞的优化设计有一定的参考作用。     

基于光纤F-P可调谐滤波器的有害气体检测方法

光谱分析法在气体成分监测领域有着广泛的应用,实现小型紧凑高分辨率的光谱测量装置是热门的研究课题。文章创造性的提出了基于光纤法布里-帕罗（F—P）的可调谐滤波器提高吸收光谱分辨率,为构建紧凑高分辨率的光谱仪提供了一种新的方案。基于光纤F-P的可调谐滤波器成功实现了微型光栅光谱仪（分辨率约1nm）对甲烷吸收光谱的测量,对比无光纤F—P可调谐滤波器直接测量的结果,该方法测得的吸收光谱强度至少提高了一个数量级。此研究成果可用于紧凑高分辨率的星载气体检测仪的研制。     

MPPT不调节母线电源系统稳定性分析

提出了一种MPPT不调节母线电源系统拓扑结构,介绍了其控制策略。分别建立了两域控制模式下太阳电池阵源端与负载端稳态分析的等效电路模型,基于小信号等效分析及状态空间方程特征根求解方法,对系统稳定性进行分析,归纳了提高此类电源系统稳定性设计的方法,此研究结果可为MPPT控制技术在未来空间电源系统中应用提供设计参考。