固体火箭发动机推力振荡特性数值研究

为了揭示固体火箭发动机推力振荡特性,以大型助推器P230的缩比发动机为基础,使用大涡模拟方法,对障碍物旋涡脱落诱发的振荡流场开展数值模拟,通过对比燃烧室压力、推力的振频和振幅,总结了推力振幅的估算方法.研究结果表明,推力振幅对压力振幅放大机理的关键参数是喉通比,放大比例与喉通比成反比;奇数阶声振型对推力振幅的贡献最大,偶数阶声振型对推力振幅的影响可以忽略,旋涡脱落对推力振幅的作用小于奇数阶声振型,且随涡/声耦合程度的增大而增强.     

Effect of multiple rings on side force over an ogive-cylinder body at subsonic speed

Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of attack for the case without a ring. This increase was mainly due to the increase in the asymmetry of the existing vortex pair in the wake of the body. Attempts were made to completely reduce the existing side force at the angle of attack ranging from 35° to 45°.Three rectangular cross-sectioned circumferential rings having a height of 3% of the local diameter were placed at axial distances of 2.5, 3.5 and 4.5 times the base diameter from the tip of the body so as to reduce the side force. The results obtained indicate that inclusion of three rings completely alleviated the side force on the slender body at the angle of attack ranging from 0° to 45°. The presence of rings was found to alter the growth of the vortices that helped in the reduction of the side force. Computations performed were in reasonable agreement with the experiments.     

Tomography-like flow visualization of a hypersonic inward-turning inlet

The flow field in a typical inward-turning inlet was visualized using the Planar Laser Scattering (PLS) method in a shock tunnel with a nominal Mach number of 6. The opaque inlet, which is truncated at a series of sections, and the following transparent isolator, are combined to enable the optical access at different streamwise locations. The sequential PLS images provide a tomography-like flow visualization, which confirm the existence of streamwise Counter-rotating Vortex Pairs (CVPs) in both external and internal flow field of the inlet. Generation mechanisms of these CVPs are unraveled with the help of a numerical simulation, among which the cowl notch plays an important role in the generation of surface trailing CVPs along the centerline of the cowl. Moreover, the cowl shock sweeps the internal boundary layer towards the body side, which ultimately accumulates low-momentum flow on the body side in forms of a large CVP propagating downstream through the isolator. The CVPs formed in the shape-transition are responsible for the nonuniform flow field of the inward-turning inlet. This study indicates that the V-shaped cowl notch affects the downstream flow significantly and, therefore, should be examined thoroughly in practical applications.     

硬铝合金剥蚀速率测试方法的研究

ＡＳＴＭＧ３４－９０标准定性评定的剥蚀等级相一致,而且更准确、严谨。     

用端壁造型减小涡轮叶栅二次流损失的数值研究

分别对常规叶栅、下端壁上凸和下端壁下凹叶栅的流场进行了详尽的数值模拟,通过将下端壁上凸和下端壁下凹叶栅中的通道涡的发生、发展过程与常规叶栅进行对比分析,对非轴对称端壁造型减小涡轮叶栅二次流损失的机理进行了初步的探讨。结果表明:下端壁上凸叶栅出口处的总压损失比常规叶栅下降了4.2%,下端壁下凹叶栅出口处的总压损失比常规叶栅增加了11.9%;在下端壁上凸叶栅中,下通道涡的形成比常规叶栅和下端壁下凹叶栅滞后,失去了充分发展的"机会"。这是非轴对称端壁造型能够减小涡轮叶栅二次流损失的根本原因。     

射流式旋涡发生器对涡轮流动分离控制

通过数值计算,研究了稳态小孔射流式旋涡发生器VGJs(Vortex Generator Jets)对低雷诺数涡轮流动分离的控制。通过对VGJs射流孔径、孔间距的几何参数研究,分析了射流对分离流动的控制机理。在此基础上,提出并详细研究了多种不同孔径射流孔组合排列结构对分离流动的控制效果与作用机理。研究结果表明,射流孔组合排列结构,以大孔射流为主,采用小孔小流量射流对大孔射流控制的分离流场进行"弥补"与调节,可实现总压损失进一步降低22%,射流流量减小25%。     

流动和油气参数对驻涡燃烧室燃烧性能的影响

针对新型驻涡燃烧室开展了燃烧性能实验研究.研究首先设计研制了驻涡燃烧室模型和实验系统,然后在此基础上开展了不同油气比、进口温度和进口流量等参数影响驻涡燃烧室燃烧性能的实验研究.结果表明燃烧室可以在不同工况下顺利点火和稳定工作,同时研究表明随着进口流量的增加(0.45～0.7 kg/s),点火性能基本不受影响,熄火特性变差;随着进口气流温度的上升(360～510 K),点火和熄火性能改善,燃烧效率提高.     

扰流柱排内部流场的实验研究

在小型风洞上,测量了叉排型扰流柱排内部的流场分布,得到了叉排型扰流柱排内部流场速度、旋涡和压力的详细分布情况,发现奇数和偶数测量截面上的速度分布规律不同,在奇数截面上可以观察到通道涡,在偶数截面的端壁附近存在马蹄涡     

受周向扰动的涡环的直接数值模拟

采用作者自己发展的柱坐标系中的谱方法对受周向扰动后的涡环的非线性演变过程以及向湍流转捩的初期行为进行了直接数值模拟。结果表明，在自诱导与整体应变场的作用下涡线逐渐前倾，与z轴成45°角，并逐渐拉伸，扰动增长的结果是小尺度运动以能量级串方式逐渐生长，最终向湍流转捩；与稳定性预测一致，扰动波不沿周向传播。     

涡与涡以及涡与附面层之间相互作用的试验研究

涡由叠合式三角形涡流发生器产生。对涡与涡之间的相互作用研究表明,反向旋转涡之间相互作用使得相邻涡之间向上或向下速度增加。同向旋转涡之间相互作用造成相邻涡的干扰,使涡变弱。对涡与附面层之间的相互作用研究表明,涡改变了附面层的速度分布,使附面层内层速度分布饱满,减小了附面层形状因子。附面层对涡的作用使得涡的耗散大大加快,涡量减小,涡核半径变大,涡的有效作用距离减小。