相对流速对非球形铝滴旋转受力的影响

针对固体火箭发动机中非球形铝滴的旋转受力问题进行数值模拟,详细分析流速变化对颗粒的受力影响。计算结果表明,非球颗粒在流场中的升力系数与无量纲转速之间已经不再满足经典的理论关系式。雷诺数Re1时,周向升力系数存在着交替出现的2组极大值与极小值;升力系数均为正值,且周向变化较为平缓。随来流速度增加,阻力系数变得均衡,系数值向0值逼近;升力系数也急速降低。当相对流速由0.5 m/s提高到5 m/s时,颗粒所受阻力锐降89%。颗粒的阻力系数与雷诺数之间满足新的关系式。     

Aerodynamic design of tractor propeller for high-performance distributed electric propulsion aircraft

Aiming to maximize the aerodynamic performance of the Distributed Electric Propulsion (DEP) aircraft, a hybrid design framework which focuses on the aerodynamic performance of the propeller/wing integration has been developed and validated numerically. Variable-fidelity modelling for propeller aerodynamics has been used to achieve computational efficiency with reasonable accuracy. By optimizing the aerodynamic loading distributions on the tractor propeller disk, the induced slipstream is redistributed into a form that is beneficial for the wing downstream, based on which the propeller blade geometry is generated through a rapid inversed design procedure. As compared with the Minimum Induced Loss (MIL) propeller at a specified thrust level, significant improvements of both the lift-to-drag ratio of the wing and the propeller/wing integrated aerodynamic efficiency is achieved, which shows great promise to deliver aerodynamic benefits for the wing within the propeller slipstream without any additional devices.     

吸气式高超声速飞行器多参数灵敏度分析

为实现吸气式高超声速飞行器多参数情况下的灵敏度分析及参数分类,降低设计的复杂度,在吸气式高超声速飞行器参数化建模的基础上,首先采用正交试验设计生成样本,再通过计算流体力学(CFD)进行高精度气动力性能计算,最后运用方差分析法进行气动性能的参数灵敏度分析,在运用较少的试验样本点的情况下,即可完成多参数、复杂构型条件下气动性能的参数灵敏度分析。结果表明,该方法可以正确地分析出参数对飞行器气动性能的敏感程度,得到参数对气动性能的影响规律。同时,通过灵敏度分析的计算样本,还可以初步选出气动性能较优的飞行器构型,为地面试验和优化设计提供参考。     

伞衣透气性对翼伞气动特性的影响

为了提高翼伞的飞行性能,需要研究伞衣织物透气性对翼伞气动特性的影响。使用不可压雷诺时均Navier-Stokes(RANS)方程模拟伞衣外部流场,建立了包含附加动量源项的多孔介质域控制方程模拟伞衣,对2种透气性材料模型和无透气性影响传统模型的气动特性和流场分布进行了二维和三维定常数值模拟。数值结果表明,求解多孔介质域控制方程可以得到较准确的伞衣透气速度,伞衣表面的湍流度急剧增加;使用较大透气量材料制作伞衣时,升力系数大幅下降,阻力系数大幅上升,同时会造成内腔泄压影响翼伞的外形保持;使用微透气量材料制作伞衣时,升力系数在小迎角时小于不透气模型,在大迎角时大于不透气模型,较小的透气速度能在大迎角时延缓边界层分离。     

基于小波尺度函数的WSK-SV算法 及其气动性能预测

提出了一种将小波的尺度函数与SV(support vector)算法相结合的WSK-SV(wavelet scaling kernel-support vector)新算法,并将Daubechies小波以及Shannon小波的尺度函数分别构成尺度核函数,而且分别作为SV算法中一个可容许的支持向量核函数使用.该算法充分利用了Daubechies小波函数的紧支集与正交等特点以及小波的MRA(multi-resolution analysis,多分辨分析),并注意了尺度核函数能够满足Mercer条件.该算法除了具有通常SVM(support vector machine)所具有的优点外,还具有很好的收敛性以及泛化能力,能够有效地提高学习与预测效率.典型算例选取了不同的小波尺度函数,数值计算表明:在一维、二维和三维问题中,这些小波的尺度函数均可以用于WSK-SV算法,进而显示了这个新算法的可行性与通用性.      

Experiment of drag characteristics of a novel variable geometry flame-holder

A novel variable geometry flame-holder (VGF) based on V-gutter was presented. The structural characteristics of the flame holder were introduced. Experimental study on drag characteristics of the VGF on un-burning and burning states was conducted in a rectangular combustion test rig. The influence of the change of gutter trailing edge width w on pressure recovery in different operating conditions was analyzed emphatically. Furthermore,drag characteristics in different trailing edge width variation modes were discussed. Results show that: (1) Narrowing w can observably raise the total pressure recovery σ but the highest σ is not obtained at minimum w. (2) The relationship of drag coefficient ψ and w in the un-burning conditions can be well expressed in a form of exponential equation (w/d>0.4). (3) Drag characteristics are not sensitive to the variation modes and speeds of w . (4) In the burning condition,σ decreases with the increasing of w basically and the course can be divided into three stages. The results and experimental data presented in this paper would enhance the phenomenological understanding of this type of VGF,and would contribute to the next experimental study and numerical calculus of this novel VGF.      

低雷诺数小型折叠无人机翼型优化设计

实现了一种可用于低雷诺数小型折叠无人机翼型优化设计的方法。采用Ferguson曲线对翼型进行参数化描述,并引入折叠状态下截面的几何关系作为附加约束,使用遗传算法和序列二次规划相结合作为寻优算法,对翼型升阻比和折叠空间允许的最大弦长进行优化。在isight平台上集成xFoil和matlab实现了这一优化流程。实例表明了方法的有效性,优化结果可以作为此类无人机翼型设计的参考。     

基于状态空间法的快速俯仰运动建模研究

通过对过失速机动运动规律和气动力特性进行简要分析,说明了过失速机动气动力建模思路;采用状态空间法建立了快速俯仰运动气动力模型,并对模型的输出方程进行了分析和简化;验证结果表明,气动力模型具有较好的预测结果。     

鸭式布局地效翼数值研究

针对地效飞行器气动特性和纵向静稳定性这两个重要问题,应用数值模拟的方法对鸭式布局地效飞行器进行了研究。在鸭式布局中,主翼和鸭翼互相干扰,流场比较复杂。简化了地效飞行器模型,只考虑了主翼和鸭翼,通过改变鸭式布局地效飞行器中鸭翼相对主翼的位置和角度,分析其对气动特性和纵向静稳定性的影响。     

基于虚拟仪器的数字式气动失稳仿真系统的研制与应用

设计了基于航空发动机动态压力失稳特征的数字式仿真系统,重点阐述了基于虚拟仪器技术仿真系统的优化搭建过程及其关键技术,并在某型涡扇发动机消喘系统研制过程中成功地进行了应用。结果表明,新的优化方案能对发动机的失稳特征进行有效控制,其实时性和适用性均有实质提高。