低排放驻涡燃烧室冷态流场特性试验

利用粒子图像测速仪(PIV)对低排放驻涡燃烧室模型进行冷态流场测量,获得该燃烧室流场的变化规律和压力损失的变化情况.试验结果表明:低排放驻涡燃烧室涡系结构稳定,在主流后方的驻涡区存在主副双涡结构,联焰板后方的驻涡区存在单涡结构,两者之间特征截面呈现出双涡涡系逐渐向单涡涡系过渡,涡心位置也随截面的变换而变化.随着进口马赫数(0.15~0.30)的增大,主涡面积随之增加,副涡面积在进口马赫数为0.2时最大,而各特征截面上主副双涡及单涡的涡心位置基本不变.驻涡区涡系强度及其边缘的气流速度,以及主燃区的气流速度均随进口马赫数增大而提高.总压损失随进口马赫数(0.15~0.30)的增大而增加.      

用于超声速民机的变循环发动机研究进展

虽然自"协和"式民机退出蓝天后,在役民机止步于高亚声速,但是研究人员追寻超声速民用运输的脚步却从未停止,并且自第1代超声速民机以后,对超声速民机的研究就从未脱离过变循环发动机的技术探索。叙述了国外超声速民机用变循环发动机的发展历程,着重介绍了美国超声速巡航研究(SCR)计划、美国高速研究(HSR)计划、欧洲超声速研究(ESRP)计划、日本高超声速运输机推进系统研究(HYPR)计划、美国商业超声速(CST)计划下的变循环发动机研制情况,总结了各计划下变循环发动机的结构特点、性能优势及发展目标,论述了进/发匹配、低噪声、低排放等超声速民机用变循环发动机的关键技术及研究进展,为中国超声速民机用变循环发动机的发展提供一定的参考。     

某无人机爬升过程中燃油温度变化规律仿真研究

采用 RON95# 车用汽油或 100LL 航空汽油为燃料的中空长航时无人机在爬升过程中容易遭遇气阻。利用 Flowmaster 软件搭建某型无人机燃油系统的仿真模型,以实际飞行试验中的环境温度、初始燃油温度、初始燃油量、耗油率等参数作为边界条件,通过仿真得到飞行过程中油箱内燃油温度,并与实际飞行试验数据进行对比,验证仿真模型的可行性;利用该模型定量研究环境温度、燃油油量、耗油率、爬升速度等因素对燃油温度变化规律的影响。结果表明:对于某型无人机燃油系统,在连续爬升过程中燃油温度的变化受初始外界环境温度、爬升速度的影响比较大,而燃油油量、耗油率则对燃油温度变化的影响较小;初始外界环境温度越低、燃油油量越少、耗油率越快、爬升速度越大则燃油温度下降幅度越大。     

一种解决经验模态分解端点效应的边界延拓法

用于电子设备或系统辐射发射趋势预测的数据大多呈现非线性、样本量小的特点,这大大增加了预测建模的难度,而经验模态分解(EMD)可以将非线性、非平稳的数据分解成若干个呈现一定周期性的本征模态函数(IMF),并且EMD具有完备性和正交性,可通过分别对分解得到的IMF分量建模,从而完成对原始数据的建模。但EMD被端点效应问题所困扰,为了提高EMD的分解精度,针对分解过程中的端点效应问题,以及辐射发射趋势预测的时间序列数据样本量小的特点,利用建立灰色均值GM(1,1)预测模型所需数据量小的优点,提出了一种基于灰色均值GM(1,1)预测模型的边界延拓方法,在原始数据两端各拓展一个极大值和一个极小值,对原始数据进行边界延拓,从而抑制EMD的端点效应。仿真对比结果表明:该方法在分解层数和平均相对误差方面均优于未经延拓处理的EMD,且对数据样本量要求不高。     

同心分级旋流结构的动态响应特征

实验探索了LESS(low emissions with stirred swirls)燃烧室头部出口附近的固有流动特征,及其对外界激励的响应.实验结果表明:预燃级旋流区域存在着周期性流动结构,而主燃级出口区域没有周期性流动结构;当外界激励的频率与流动固有频率耦合时,会引起预燃级流场畸变,并导致周期性流动的流速振荡幅值急剧增大.      

The radio recombination lines of hydrogen

The impact theory of spectral line broadening is used to obtain complete profiles for radio recombination lines broadened by electron and proton impact. Electron impact dominates but proton impact becomes increasingly significant as Δn$\mathrm{\Delta }n$ increases. Thus these new calculations essentially confirm previous results and so a longstanding discrepancy between observation and theory remains unresolved.     

World Space Observatory-Ultraviolet: ISSIS,the imaging instrument

The Imaging and Slitless Spectroscopy Instrument (ISSIS) will be flown as part of the science instrumentation in the World Space Observatory-Ultraviolet (WSO-UV). ISSIS will be the first UV imager to operate in a high Earth orbit from a 2 m class space telescope. In this contribution, the science driving the ISSIS design and the main characteristics of this instrument are presented.     

O2 evolution and cyclic electron flow around photosystem I in long-term ground batch culture of Euglena gracilis

Based on the purpose of better exploring the function of green producers in the closed aquatic biological life support system, the condition of dynamic O₂ evolution and performance of cyclic electron flow around photosystem I (CEF-PSI) in long-term ground batch culture of Euglena gracilis were studied, the relationship between linear electron flow (LEF) and CEF-PSI was revealed, the function of CEF-PSI was investigated. Excellent consistency in O₂ evolution pattern was observed in cultures grown in both closed and open containers, O₂ evolution was strictly suppressed in phase 1, but the rate of it increased significantly in phase 2. CEF-PSI was proposed to be active during the whole course of cultivation, even in the declining phase 3, it still operated at the extent of 47–55%. It is suggested that the relationship between LEF and CEF-PSI is not only competition but also reciprocity. CEF-PSI was proposed to contribute to the considerable growth in phase 1; it was also suggested to play an important protective role against photosystem II (PSII) photoinhibition at the greatly enhanced level (approximately 80–95%) on the 2nd day. Our results in this research suggest that E. gracilis had very particular photosynthetic characteristics, the strict O₂ evolution suppression in the initial culture phase might be a special light acclimation behavior, and CEF-PSI could be an important mechanism involved in this kind of adaptation to the changeable light environment.     

A photoionization method for estimating BLR “size” in quasars

We describe an alternate way to estimate Broad Line Region (BLR) radii for type-1 AGN based on determination of physical conditions in the BLR under the assumption that the line emitting gas is photoionized by a central continuum source. We derive “diagnostic” intensity ratios involving UV lines Aliiiλ$\lambda$1860, Siiii]λ$\lambda$1892 and Civλ$\lambda$1549 which enable us to compute the ionizing photon flux, and hence BLR radius from the ionization parameter definition. We compare our estimates of BLR radii with values independently obtained from reverberation monitoring of Hβ$\beta$ and, in a few cases, of C ivλ$\lambda$1549. We analyze the interpretation of the photoionization estimates in the 4D eigenvector 1 context, and discuss in some detail the case of 3C 390.3. For this object we are able to provide not only the ionizing photon flux, but also an estimate of density and ionization parameter from the measured diagnostic ratios. We also compare black hole masses obtained from this method with values derived from widely-applied correlations between mass, line broadening and luminosity. Good agreement is found for both radius and black hole mass comparisons.