尾翼式弹道修正弹Hopf分岔特性分析

为分析尾翼式二维弹道修正弹锥形运动失稳原因,提高其修正精度,建立了该弹丸有控飞行阶段四维非线性角运动方程。利用Matcont软件确定系统分岔点后,运用中心流形定理对系统进行降维,并对降维后系统的Hopf分岔点类型进行判别,最后数值仿真验证了理论分析方法的正确性。在此分析方法基础上针对修正机构参数对角运动稳定性影响进行分析。结果表明,为保证弹箭飞行稳定性并使其具有良好气动布局,应将修正机构靠近质心位置安装。     

射流控制条件下超声速尾翼弹的气动特性

研究表明,主动式射流涡流发生器可有效控制超声速流动边界层的分离,且能根据实际情况进行自适应调节。该文基于制式122尾翼弹,通过在弹肩前端加装射流涡发生器控制边界层的流动分离,研究其对尾翼弹气动性能的影响。采用DES方法数值模拟了超声速条件下尾翼弹有无射流控制的流场变化情况,分析了加装射流前后尾翼弹表面流体边界层结构及其气动性能的变化规律。数值结果表明,射流控制可有效抑制弹体表面的流体分离,提高尾翼弹的升力与俯仰力矩、减少弹身震动,有利于提高其飞行稳定性及打击精度,可为超声速尾翼弹的改进提供指导。     

基于数值仿真与飞行试验的弹道修正火箭弹阻力系数简易辨识

作为单通道鸭舵控制弹道修正火箭弹研究的关键技术之一,气动系数的辨识是实现弹体飞行控制的前提与基础。该文以阻力系数简易辨识为主要研究内容,主要探讨数值仿真与飞行试验相结合对阻力系数进行辨识的方法。利用Grigen网格划分技术和Fluent流体力学仿真(CFD)相结合,获得弹道修正火箭弹的仿真气动数据;通过弹体的受力和力矩分析,建立六自由度弹道模型;根据飞行试验数据,对比分析弹道模型与仿真气动数据,对阻力系数进行修正优化。通过试验验证,经过修正的阻力系数精度得到很大提高,对于研究弹道修正弹的弹道特性规律和制导控制设计具有参考价值。     

弹道修正机构永磁电机的仿真设计及应用测试

依据弹道修正基本原理,对弹道修正装置的气动布局进行分析.完成了弹道修正机构中永磁电机的设计,并对永磁电机齿槽力矩的影响因素进行分析.通过仿真,减小硅钢片槽口宽度可以减小永磁电机的齿槽力矩.利用应变式测力装置,对永磁电机的力矩实际测量可知,修正弹飞行在可修段时永磁电机的力矩大于风阻力矩的20%.结果表明,设计的永磁电机能够满足对舵机的精确控制要求.     

超声速旋转火箭弹气动流场的微楔控制

超声速弹箭表面的流体分离是影响飞行稳定的主要影响因素之一。研究表明,微楔涡流发生器可有效控制超声速流体边界层的流动分离。该文基于制式122火箭弹,通过在弹肩前端安装微楔来研究边界层流动分离控制对火箭弹气动性能的影响。运用DES方法数值模拟了122火箭弹在有无加装微楔条件下的流场变化,对比分析了微楔对弹体表面边界层结构以及弹气动数据的改变,讨论了微楔对弹的气动力及稳定性作用。数值结果表明,微楔可以抑制弹体表面流体分离,提高火箭弹的升力及俯仰力矩,减小马格努斯力矩,有利于提高其飞行稳定性及射击精度,可为相关旋转火箭弹的改进提供指导。     

二维修正弹的控制力矩电机可行性分析

阐述了二维修正弹的力矩电机控制的两种方案,分析了PWM控制方案的优点.提出了十字型固定翼鸭舵的修正机构设计方案,并详细说明了鸭舵控制原理和控制过程.对弹道修正弹飞行各时段所受的力矩进行分析.对舵机修正力矩的计算与分析说明,该控制力矩电机方案是可行的.     

尾翼稳定弹近弹故障分析

以某坦克炮出现发射尾翼稳定杀伤爆破弹故障为背景,对可能引起该故障的因素进行了故障机理分析,通过计算得出了满足尾翼张开的最低膛压条件,建立了近弹故障树,并对故障树进行了定性分析,然后按照故障树对故障模式进行逐一的排查,对排查过程中尚不能确定的可能引起尾翼弹飞行故障的膛压不足的故障模式,用Matlab软件混合装药的膛压进行模拟仿真,验证了尾翼弹近弹的原因为混合装药配比不合适导致膛压不足。以初速和膛压为考察对象,用Matlab软件对混合装药条件下装药方案进行了优选设计,经试验验证,使用装药优选方案的杀伤爆破弹飞行正常。     

考虑理论修正的钢管混凝土拱桥气弹模型试验研究

对于超大跨度钢管混凝土拱桥,由于受模型缩尺比所限,通常在气弹模型试验中不能单独模拟出拱肋中单根钢管的刚度,目前常采用集中刚度法用一个芯棒模拟整个钢管桁架的刚度.由于芯棒的位置只能放置在钢管桁架的形心处,因此模型中芯棒的存在必然破坏结构的气动外形,使得模型的气动外形不能满足与实桥气动外形成相似关系.基于以上原因,提出了一种试验与理论分析相结合的修正方法,对外形改变给试验结果带来的影响进行理论分析,从而获得修正系数对试验结果进行修正.     

二维弹道修正引信制导控制系统半实物仿真

为给固定鸭舵式二维弹道修正引信设计适用的半实物仿真系统,在掌握修正引信工作原理和研究引信运动状态的基础上,采用两部电机实时模拟引信修正组件和弹体滚转通道的姿态角信息,并使用光电码盘标定地磁测角模块的测角准确度,在过程控制软件的协调下实现弹上计算机和仿真计算机的数据交互,实现弹上机对固定舵制动控制的有效模拟。研究二维弹道修正引信半实物仿真试验的试验步骤,并针对某型迫弹进行仿真试验。仿真试验表明:所设计的半实物仿真系统可有效检验引信制导控制系统各分系统和整机的性能。该半实物仿真系统适用于安装该型引信的所有尾翼稳定弹箭,对其他类型的采用双旋结构的制导弹箭具有借鉴意义。     

低振动旋翼桨尖代理优化设计

为探索直升机低振动旋翼的工程设计方法,将代理优化与旋翼气弹耦合分析相结合,开展了旋翼桨尖几何外形设计,推导了非平直桨叶气弹动力学方程,训练了旋翼功率、模态阻尼以及振动载荷预测的Kriging代理模型.以气动性能与气弹稳定性为约束,以桨毂振动载荷最小化为目标,采用自适应加点准则设计了优化流程.以某旋翼为例,计算了其气动性...     

滑翔增程弹的气动特性仿真研究

研究了滑翔增程弹气动布局对弹道增程效果的影响,建立了不同气动布局下的弹体模型,并对其进行气动仿真,得出了不同空气动力数据.通过建立适合增程弹的弹体模型,得到了舵片在不同布局时的增程能力数据.仿真结果表明,舵片位置越远离弹体头部,相应增大舵偏角,增程能力将会增强,因此,在满足全弹气动布局、飞行稳定的基础上,尽量使舵片远离弹体头部,并相应增大舵偏角,可提高増程的能力.     

Experimental and numerical study on the flight and penetration properties of explosively-formed projectile

The whole process of formation, flying and penetration of explosively-formed projectile (EFP) is simulated by a 3D coupled hydrocode of Ls_dyna. The caliber of the shaped charge is 60 mm and EFP is a kind of overturned shaped charge. The Arbitrary Lagrangian–Eulerian (ALE) method is adopted to consider the fluid–solid coupling problem. The velocity attenuation equation is fitted to forecast the flight distance of EFP. The penetration property of EFP to the armor plate is studied by similarity theory and numerical simulation. For validating the equation, a test is designed to study the residual velocity after penetrating a 25 mm thick steel plate from a distance of 48 m. Therefore, some important solutions are obtained from the comparison of the simulation and experiment. The solutions are optimized charge structure of EFP, the ideal shape of projectile, the attenuation rule of flight process and the penetration property after 48 m flight. The numerical solution fits the experimental data well and the study results provide important reference to the design of EFP in engineering.     

Floquet stability analysis of the longitudinal dynamics of two hovering model insects

Because of the periodically varying aerodynamic and inertial forces of the flapping wings, a hovering or constant-speed flying insect is a cyclically forcing system, and, generally, the flight is not in a fixed-point equilibrium, but in a cyclic-motion equilibrium. Current stability theory of insect flight is based on the averaged model and treats the flight as a fixed-point equilibrium. In the present study, we treated the flight as a cyclic-motion equilibrium and used the Floquet theory to analyse the longitudinal stability of insect flight. Two hovering model insects were considered—a dronefly and a hawkmoth. The former had relatively high wingbeat frequency and small wing-mass to body-mass ratio, and hence very small amplitude of body oscillation; while the latter had relatively low wingbeat frequency and large wing-mass to body-mass ratio, and hence relatively large amplitude of body oscillation. For comparison, analysis using the averaged-model theory (fixed-point stability analysis) was also made. Results of both the cyclic-motion stability analysis and the fixed-point stability analysis were tested by numerical simulation using complete equations of motion coupled with the Navier–Stokes equations. The Floquet theory (cyclic-motion stability analysis) agreed well with the simulation for both the model dronefly and the model hawkmoth; but the averaged-model theory gave good results only for the dronefly. Thus, for an insect with relatively large body oscillation at wingbeat frequency, cyclic-motion stability analysis is required, and for their control analysis, the existing well-developed control theories for systems of fixed-point equilibrium are no longer applicable and new methods that take the cyclic variation of the flight dynamics into account are needed.     

Terminal ballistic effect on the crack growth assessment of a helicopter rotor drive

An experimental impact test of a 7.62 NATO projectile perforating a helicopter tail rotor shaft is briefly presented. With the aim to reproduce the operational worst case, the damage occurs during the flight, the impacted specimen is subsequently tested with a multiaxial testing machine. This procedure allows the evaluation of the capability of the shaft to withstand a recovery mission, which is simulated by applying a torsional fatigue spectrum to the shaft. The nucleation and propagation of fatigue cracks have been monitored during the test.Finite element analyses have been carried out to simulate both impact and crack propagation. The state of stress is multiaxial: it is induced by torque, residual stress field and shape of the damage. Mixed mode propagation has hence been considered by means of an equivalent SIF. Numerical results are in agreement with experimental data.     

A note on stability of motion of a projectile

A projectile is stabilised using either gyroscopic or aerodynamic stability. But subcalibre projectiles with sabot have both spin and fins. Separate stability criteria are researched generally for each type of projectile. In this paper a stability criterion which can be used for all such bodies has been developed through the Liapunov second method.     

计转数空炸引信动态测试

在计转数空炸引信测试中,可编程引信作用距离是关键量,而全备弹丸飞行转动圈数则是求取该关键量的测量难题.在分析连续波雷达测量弹丸瞬时转速的工作原理基础上,针对小口径弹丸特点,建立了转速调制模型,提出利用数字解调、运动补偿等处理方法,基于微多普勒信息提取榴弹转速,由瞬时转速求得转动圈数,并对其中产生的误差进行了有效消除,实现了高精度定距空爆.方法在相关试验中得到了验证,为小口径空炸弹的系统考核与毁伤效力发挥提供了技术支撑.