燃烧加热类高超声速高温风洞流场校测与评估

为建立统一的燃烧加热类高超声速高温风洞流场品质评价标准,针对国内6座不同喷管出口直径的燃烧加热类高超声速高温风洞,从统一的皮托压探针、总温探针和流场校测排架设计出发,分别研制了流场校测装置,完成了典型试验状态的流场校测试验。根据相同的数据处理和分析方法得到了相关风洞喷管出口截面的速度场、温度场及均匀区信息。6座风洞速度场均匀区直径分别对应喷管出口直径的73.3%、76.5%、75.0%、80.0%、74.7%、83.3%。根据各风洞流场校测结果,初步掌握了国内同类型风洞流场品质整体水平,提出了当前燃烧加热类高超声速高温风洞流场品质参考评价指标。对于马赫数4.5~6.0的试验状态,风洞速度场均匀区直径应不小于喷管出口直径的70%,均匀区内马赫数标准偏差与平均马赫数的比值应小于2%,总温标准偏差与平均总温的比值应小于5%。     

Neal-Smith准则改进分析

驾驶员在环振荡判定准则较多,其中Neal-Smith准则的应用较为普遍.但Neal-Smith准则并不能准确反映PIO趋势,与驾驶员评估结论也存在一定差异.根据Neal-Smith准则进行飞机纵向驾驶员在环振荡分析的基本方法与程序,结合系统频域响应估算工具,分析得出满足系统性能要求的驾驶员相位补偿和增益区域,并基于该区域面积定义了新的PIO判断准则.与现有Neal-Smith准则相比,新的PIO判断准则可反映一类和二类PIO趋势随闭环系统参数的连续变化情况.     

基于Kano模型的旅客机场选择行为分析

研究旅客在区域多机场中的机场选择行为,如何选取影响旅客机场选择行为的关键因素是最基础最重要的部分,现有的研究对关键因素的选取缺乏系统全面的分析.因此,基于Kano理论模型,通过因素整理、问卷调研等进行因素的筛选,得到影响旅客机场选择行为的6个关键因素,与现有研究对比分析并进行机场实地调研,研究结果验证了6个所选关键因素的合理性,为机场选择行为研究的进一步建模分析提供了理论依据.     

建筑物附近气流特征及湍流扩散的模拟试验

用非静力、能量闭合的大气边界层模式对建筑物附近的气流和湍流特征进行了模拟,为了检验模拟结果,将风场和湍流场输入到扩散模式获得了建筑物附近腔区和尾流区内的污染物浓度分布。结果与同样条件下的风洞测试的结果吻合。本文研究结果表明,在来流风速增大的情况下,建筑物下游的尾流区范围变化不大,而腔区范围增大,湍流运动增强。本文所用方法比采用拟合经验公式描述尾流、腔区的特征更能反映不同建筑物、不同来流的影响。     

挤压油膜阻尼器失效的判据

 挤压油膜阻尼器(简称SFD)设计不当,会导致功能失效.对弹支-挤压油膜阻尼器来说,失效有2种形式:一是过不了临界,即转子系统的振幅随转速的上升而一直增大;二是出现双稳态特性.2帧失效判据图已经作出:一是双稳态区域图,只要轴承参数和质量偏心率数组不选在双稳态区域内,便不致产生双稳态特性;二是减振失效边界图,只要前述数据组不在失效边界的一侧,便不致产生过不了临界的现象.经实验证明,上述结论从正反2个方面看都是正确的.实验也进一步确认了挤压油膜阻尼器优越的减振功能.     

出口宽高比及旋流角对双涵道S弯喷管温度分布的影响

采用数值方法研究了出口宽高比及旋流角对基于真实排气混合器构型的双涵道S弯喷管内/外流场温度分布的影响.结果显示:在圆转方弯曲构型的作用下,波瓣混合器及尾锥诱导产生的流向涡在第二弯通道及等直段内部卷吸着热流冲击S弯喷管壁面形成"热斑".在完全遮挡高温部件准则的约束下,随着出口宽高比的增加,S弯喷管壁面的"热斑"温度先增大...     

单层网壳结构缺陷敏感区域研究

提出了结构缺陷敏感区域的概念。借助结构缺陷稳定分析的改进随机缺陷法,研究了单层网壳结构的缺陷敏感区域。通过50m跨度的K6型凯威特网壳算例,得出它的缺陷敏感区域由前12类结点组成。并发现支座结点缺陷对K6型凯威特单层网壳结构影响不大;而主肋上结点与次肋上结点的缺陷对K6型网壳的影响相似,均会使其临界荷载下降很多。结果证明该方法可定量和准确地分析结构的缺陷敏感区域。     

微通道内亲疏水壁面特性对入口段长度的影响

针对水力直径为200μm的微尺度通道,采用数值模拟的方法研究了壁面亲疏水特性产生的速度滑移对微尺度通道入口段长度的影响,建立了包含滑移长度影响的入口段长度修正计算公式.研究表明:相同流量下,速度滑移的存在使得微尺度通道充分发展段的最大速度减小,从而缩短了入口段长度,且在低雷诺数区域,入口段的缩短效应更为显著.针对不同的...     

Efficiently constructing collision-free regions of tool orientations for holder in five-axis machining of blisk

Blisks with the integral structure are key parts used in new jet engines to promote the performance of aircrafts, which also increases the complexity of tool orientation planning in the five-axis machining. It is an essential task to find the collision-free tool orientation when the tool holder is pushed deep into the channel of blisk to increase rigidity and reduce vibration. Since the radius of the holder varies with the height, the line-visibility is no longer applicable when constructing collision-free regions of tool orientation. In this paper, a method of constructing collision-free regions without interference checking is proposed. The work of finding collision-free regions resorts to solving the local contact curves on the checking surfaces of blisk. And it further transforms into searching the locally tangent points (named critical points) between the holder and surface. Then a tracking-based algorithm is proposed to search the sample critical points on these local contact curves. And the corresponding critical vectors are also calculated synchronously. Besides, the safety allowance, discrete precision and acceptable deviation are introduced in the algorithm to ensure accuracy by controlling the angle between two adjacent critical vectors properly. After that, the searched critical vectors are mapped orderly to two-dimensional space and the collision-free regions are constructed. This method is finally verified and compared with a referenced method. The results show that the proposed method can efficiently construct collision-free regions for holder under the given accuracy.     

Integrated supersonic wind tunnel nozzle

In supersonic wind tunnels, the airflow at the exit of a convergent-divergent nozzle is affected by the connection between the nozzle and test section, because the connection is a source of disturbance for supersonic flow and the source of disturbance generated by this disturbance propagates downstream. In order to avoid the disturbance, the test can only be carried out in the rhombus area. However, for the supersonic nozzle, the rhombus region is small, limiting the size and attitude angle of the test model. An integrated supersonic nozzle is a nozzle and a test section as a whole, which is designed to weaken or eliminate the disturbance. The inviscid contour of the supersonic nozzle is based on the method of characteristics. A new curve is formed by the smooth connection between the inviscid contour and test section, and the boundary layer is corrected for the overall curve. Integrated supersonic nozzles with Mach number 1.5 and 2 are designed, which are based on this method. The flow field is validated by numerical and experimental results. The results of the study highlight the importance of the connection about the nozzle outlet and test section. They clearly show that the wave system does not exist at the exit of the supersonic nozzle, and the flow field is uniform throughout the test section.