针栓式推力室冷却特性试验研究

针栓式发动机具有推力调节简单、声学燃烧稳定性好和成本低廉等一系列优点,但目前对针栓式推力室的冷却特性掌握还不够深入,研制过程中曾多次出现因推力室冷却组织不好而烧蚀的问题。采用针栓式推力室试验件,对身部的冷却特性进行了深入研究,结果表明:推力室圆柱段前端的温度较低,无需采用专门的冷却措施;末端内侧气壁温度会达到约1650℃,局部存在明显的烧蚀现象,必须采取有效的热防护措施;下游冷却液膜量的变化对圆柱段的冷却特性影响较小。     

SiO32-浓度对KMnO4/FeSO4工艺除磷过程的影响

考察了天然水体中常见的SiO_3~(2-)对KMnO_4/FeSO_4工艺混凝除磷的影响。SiO_3~(2-)存在时KMnO_4/FeSO_4工艺混凝除磷的效能随着溶液pH的升高呈现先增加后降低的趋势。SiO_3~(2-)浓度为1.0 mmol/L,溶液pH值为4～6时,SiO_3~(2-)可促进KMnO_4/FeSO_4工艺除磷的效能,KMnO_4/FeSO_4工艺对磷的去除效果分别增加了6.0%,9.9%和6.3%;溶液pH值为7～9时,SiO_3~(2-)可显著抑制KMnO_4/FeSO_4工艺除磷的效能,KMnO_4/FeSO_4工艺对磷的去除效果分别降低了14.76%,32.6%和17.3%。KMnO_4/FeSO_4工艺形成的絮体颗粒物表面ζ电位显著降低,溶液中残余铁的量明显提高。另外,水中SiO_3~(2-)对KMnO_4/FeSO_4工艺形成的絮体颗粒物的组成和表面特征均有一定影响。该研究为KMnO_4/FeSO_4工艺混凝除磷技术的推广提供了必要的理论基础。     

嫦娥四号动力下降段图像可视化传输方案

针对嫦娥四号降落相机在动力下降段的图像可视化传输需求和深空通信下行数传信道带宽受限的矛盾，文章提出了一种动力下降段速率自适应的可视化图像传输方案，对如何保证降落相机图像下传的实时性、完整性、速率自适应性等关键问题进行了讨论，并对方案中涉及的抽帧回放算法、帧格式识别方法、合路调度算法等关键技术进行了详细说明。同时，文中给出了该方案在嫦娥四号在轨的验证情况，结果表明，在数传通信速率受限的情况下该方案实现了降落相机图像的存储管理和可视化下传，具有实时性高、速率自适应、图像下传完整等特点，可以为其他航天器数据管理系统设计提供参考。     

The Kumtag meteorite strewn field

The Kumtag meteorite strewn field was found in the Kumtag desert, 132 km south of Hami city in the Xinjiang province, China. It is an ellipse of 2.5 × 7.9 km, with a long axis extending along the northeast-southwest direction. The largest individual meteorite of the strewn field weighs about 10 kg; the smallest individual has a mass of only 27 g. In total, more than 100 individuals with a total mass of more than 180 kg were collected. The location and the distribution of the fragments suggest that the Kumtag meteoroid entered the atmosphere in the direction Northeast-Southwest. All meteorites collected in this strewn field are samples from the same unique meteorite shower. The Kumtag meteorite is an H5 ordinary chondrite with a shock stage S2, and a weathering grade W2. The cosmic ray exposure age of Kumtag is 6.7 ± 0.8 Ma, which is rather typical for H chondrites and which indicates that Kumtag was derived from the massive impact event on its parent body ~7 Ma ago. A significant amount of He has been lost during certain unknown processe(s) before the Kumtag meteorite was ejected from its parent body.     

Numerical investigation of flow mechanisms of tandem impeller inside a centrifugal compressor

This study numerically investigated a single stage centrifugal compressor ‘‘Radiver’’ with a wedge diffuser and several tandem-designed impellers to explore the flow phenomena within the tandem impeller and the potential to enhance compressor performance. The results demonstrate that tandem design and clocking fraction (λ_s) significantly affects the compressor performance. The compressor stage with tandem impellers of Series A of boundary layer growth interruption alone are observed to have a widely operating range but efficiency and total pressure ratio penalty compared with that of conventional impeller. The tandem impeller with at least the same impeller efficiency as the conventional design is considered as a critical design criteria so that further modification process based on the flow characteristic of tandem impeller is necessary. In order to restrain the inducer wake and exducer shock losses, parameters modification of blade angle and thickness distributions are necessary and the modified tandem impeller of Series B is obtained. The modified tandem impeller with 25% clocking arrangement shows an 8.45% stall margin increase and maintains the total pressure ratio and efficiency as the conventional design, which proves the potential of tandem impeller to improve compressor stage performance. It is noteworthy that the tandem impellers of Radiver have not shown obviously balanced exit flow field and the fundamental mechanism of stall margin extending of tandem impeller lies on the improved impeller/diffuser matching performance resulting from the incidence angle variation at diffuser inlet.     

PS-PVD用CeO2掺杂8YSZ团聚粉末及其涂层

在纳米ZrO₂-8%Y₂O₃(摩尔分数)(8YSZ)粉末中掺杂20%(质量分数)微米级CeO₂粉末,并通过喷雾干燥合成CeO₂-8YSZ(CYSZ)复合团聚粉体。借助激光粒度仪和扫描电镜(SEM)及附带能谱仪(EDS)考察羧甲基纤维素黏结剂(carboxymethyl cellulose,CMC)质量分数对复合团聚粉体性能影响。采用PS-PVD制备具有柱状结构的CYSZ热障涂层,对涂层截面和表面进行EDS分析。采用X射线衍射(XRD)和X射线光电子能谱(XPS)分析涂层物相。结果表明:黏结剂质量分数达到2%时可获得球形度高、粒度分布均匀的团聚粉体;制备的涂层中Ce元素呈均匀分布;涂层物相基本为t-相结构,其中Ce⁴⁺取代Zr⁴⁺进入ZrO₂晶格形成类质同象的固溶体结构,显示出CeO₂掺杂对t-相向m-相转变的抑制作用;所制备CYSZ涂层在1100℃,水冷循环100次后仍保持完整,展现出较高的抗热冲击性能。     

提高形状记忆合金丝工作频率的一种方法

研究了提高形状记忆合金（SMA）工作频率的物理方法--研制细丝。给出了拉拔细丝的工艺流程,从理论上分析了在不同的加热和冷却过程中丝径与响应速度的关系,对2种丝径的SMA丝进行了性能对比测试。同时测定了2种丝径的SMA的响应速度。结果表明,丝径的减小对丝的相变性能,如最大恢复应变、最大恢复应力等影响不大,但可显着提高其动作频率。     

基于MSC/Patran的结构优化系统前后置开发与应用

在UNIX环境下,以MSC/Patran为平台,利用平台提供的二次开发工具PCL,通过客户化、增设特定的命令和窗体等技术开发了结构优化系统的前后置模块,并集成现有数值计算模块,形成工程程序系统.由此开发的系统前后置保持平台的原有强大功能,且易实现和赢得用户.最后通过算例说明了系统的实用性和工程有效性.      

二维变厚板的J积分分析

本文将J.R.Rice提出的J积分公式扩充应用到二维变厚板。本文把变厚度的影响以修正项形式引入J积分公式,从而推导出二维变厚板的J积分扩充表达式。