直升机旋翼试验塔电力拖动系统特性分析与仿真计算

直升机旋翼试验塔主拖动系统功率大、负载特性特殊,选择以中压变频交流调速系统作为主拖动是一种较为理想的方案。本文针对旋翼负载特性,建立了基于矢量控制的变频调速系统仿真模型,分析计算了不同机型旋翼负载的起动特性及调速性能,论证了三电平中压变频调速方式用于直升机旋翼试验系统的可行性,为旋翼试验塔的研制设计提供了理论依据。     

基于支持向量机的结构损伤程度识别研究

支持向量机(SupportVector Machine,SVM)是一种基于统计学习理论的机器学习算法,能够较好的解决小样本的学习问题,具有很优秀的回归特性。本文提出了一种基于支持向量机辨识结构损伤程度的方法,构造模态频率作为损伤标识量训练支持向量机对损伤程度进行预测,并以悬臂梁为例进行了仿真计算。结果表明:支持向量机是一种很有潜力的结构损伤识别方法,具有很好的应用前景。     

轴对称激波诱导矢量喷管三维两相流数值模拟

运用颗粒轨道模型对轴对称激波诱导矢量喷管内流场进行了数值模拟,并与纯气相条件下的计算结果进行了对比分析,研究了1～30μm不同直径颗粒的运动轨迹和内流场参数的分布特征,并对矢量喷管的推力性能进行了研究。结果表明,颗粒相的加入对射流推力矢量喷管内流场和推力性能都带来很大影响,影响规律与颗粒直径密切相关。为两相流条件下射流矢量喷管的试验研究提供了一定依据。     

固体动能拦截器助推段飞行方案研究

针对三维空间内的高速飞行目标,提出了一种可用于固体动能拦截器助推段的导引方法。建立了固体动能拦截器与目标的相对运动关系模型,分析确定了转移轨道的约束条件,并在此基础上推导出转移轨道的轨道根数计算方法。同时根据拦截器的待增速度给出了助推器推力矢量方向的确定方法。仿真结果表明,该方法能有效实现固体动能拦截器助推段的制导控制。     

基于粒子群算法-最小二乘支持向量机算法的磁化曲线拟合

磁化曲线是强非线性函数,提高磁化曲线的拟合精度对含有铁磁材料的电气设备建模准确性至关重要。提出了一种基于粒子群算法-最小二乘支持向量机(PSOLSSVM)算法的磁化曲线拟合方法。该方法用粒子群优化算法解决了最小二乘支持向量机(LSSVM)参数的选择问题。仿真结果显示PSOLSSVM算法能获得最优的LSSVM参数,且采用PSOLSSVM算法拟合的磁化曲线与实际测量的磁化曲线基本无偏差,拟合精度较高。     

基于灰色近似支持向量机的加速度计参数预测

温度、振动等环境载荷使得石英挠性加速度计参数产生漂移,直接影响了惯导系统的测量精度和性能,石英挠性加速度计参数变化趋势为非线性的,很难用常规的建模方法进行趋势预测。基于灰色理论适合进行小样本、贫信息不确定型系统建模以及近似支持向量机不需要求解二次规划就能求得非线性模型参数的优点,提出了基于灰色近似支持向量机进行石英挠性加速度计参数预测的方法。为了验证该方法的有效性,针对自然贮存的加速度计进行了固定周期的参数标定,结果表明灰色近似支持向量机具有很好的预测效果。     

Numerical study of a trapezoidal bypass dual throat nozzle

Bypass Dual Throat Nozzle (BDTN) is a novel type of fluidic thrust vectoring nozzle. To improve the infrared stealth performance of BDTN, a nozzle based on BDTN is proposed and numerically simulated. Each cross-section along the x-axis of the novel nozzle becomes a trapezoid, which is named “BDTN-TRA.” The main numerical simulation results show that BDTN-TRA can produce a thrust vectoring angle when the upper or lower bypass valve is open. The angle difference between the two conditions mentioned above is usually approximately 1°–2°. Even if the two bypasses are closed, BDTN-TRA can produce a small thrust vectoring angle at around 3°–5°. When the sidewall angle increases from 60° to 90°, the thrust coefficient and thrust vectoring angle under each work condition usually decrease. A larger aspect ratio indicates better performance. As the aspect ratio increases over 7.2, the performance of BDTN-TRA is quite close to that of BDTN with rectangular cross-sections at the same aspect ratio. These features will benefit the control and trimming for future aircraft design, especially for the flying wing layout aircraft. Last but not least, BDTN-TRA has a more extraordinary mixing performance compared with BDTN. The distributions of static temperature and axial velocity along the x-axis of BDTN-TRA with sidewall angle of 60° decrease faster than those of BDTN. When the total temperature of the inlet equals 1600 K, the static temperature difference between BDTN-TRA with sidewall angles of 60° and 90° is over 360 K at twice the length of the nozzle downstream of the nozzle exit, which is the reflection for excellent infrared stealth for the fighter.     

AHPSO-SVM预测超声内圆磨削ZTA陶瓷的边界损伤

为解决普通加工方式易出现工程陶瓷边缘碎裂的问题,本文对超声内圆磨削工程陶瓷边界损伤预测系统进行了研究。在35 kHz轴向超声磨削与普通磨削两种条件下独立进行试验,运用支持向量机研究工艺参数与边界损伤影响规律,采用改进的粒子群算法优化支持向量机,建立采用混合核函数的AHPSO-SVM预测模型。研究结果表明,超声激励下试件边界损伤降幅为10.05%～21.23%,AHPSO-SVM预测模型MSE为0.378 4、平均相对误差为1.369 0%、30次适应度值标准差为0.020 2。相比于普通磨削,超声磨削可使ZTA陶瓷边界损伤值显著降低;建立的AHPSO-SVM模型具有较好的学习能力、泛化性能与良好的稳定性。     

Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic (MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.     

火箭多台发动机并联推力传递结构动静耦合计算方法

针对运载火箭多台发动机并联推力传递结构在工作中力学环境适应性问题，开展了动静耦合动力学计算方法研究。该研究分析了动静耦合机理，并以此为基础，计算了有无静载的结构模态频率和推力传递结构关键部位随机振动响应。结果表明，火箭推力传递结构在大推力作用下，结构的刚度发生改变，进而影响动力学特性。相关研究结果为火箭多台发动机并联推力传递结构动静联合试验提供了参考意义。