Quasi-biennial oscillation (QBO) of tropical total ozone under alternative QBO scenarios of equatorial stratospheric wind

Equatorial total column ozone variations with quasi-biennial periodicity are described by paying attention to their coupling with the quasi-biennial oscillation (QBO) of zonal wind in equatorial stratosphere. Analysis is made for the 35-year time interval from 1978 to 2013 using the zonal mean total ozone (TOZ) data in latitude band from 5° S to 5° N derived from satellite measurements by means of Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI). The study was performed using strong seasonal regularities of the wind QBO and the discrete variation of the QBO-period revealed earlier. The forecast of the wind QBO evolution made in Gabis (2012) is fully justified. The comparison between predicted and actually observed changes of the height wind structure shows the prominent accordance, which confirms the forecast validity. It is shown that variations of deseasonalized TOZ are in strong coupling with changes of equatorial wind QBO that coincides with the numerous previous researches. However our results contradict the assumption about quite complicated ozone response in the equatorial region due to continuously varying with time relationship between annual and quasi-biennial cycles and irregularly variable wind QBO-period. The total ozone changes actually observed clearly corresponds to the mean ozone variations calculated for different QBO scenarios and aligned according to the sequence of QBO scenarios already occurred in fact. This close association indicates the possibility of forecasting the equatorial total ozone QBO based on the predicted wind QBO.     

多级会切场推力器振荡特性模拟研究

目前多级会切场推力器数值模拟研究采用的主要手段是全粒子模拟方法,但是这种全粒子模拟对计算机的要求较高,因此文章通过建立HEMPT的一维流体模型,再现HEMPT的振荡现象,对放电电流和等离子体参数之间的关联性及等离子体参数分布规律进行研究。沿着两条典型的电子传导路径,利用MATLAB中Simulink模块建立一维流体模型。结果分析表明,推力器内部等离子体参数的振荡周期与放电电流振荡周期一致。推力器的主电离区在两个磁尖端之间,电势降主要集中在出口附近。     

火箭发动机泵后供应系统水力激振试验

为了研究某型发动机泵后供应系统的动力学特性,对全尺寸的氧泵后供应系统在中、高频范围内开展了水力激振试验。试验数据表明:供应系统的谐振特性被激发起来。在试验条件下,可以清晰地辨识出泵后供应系统的前4阶谐振频率和振型。第1阶谐振频率响应幅值最高,第2阶和第3阶相当,响应幅值次之,第4阶响应幅值再次之。在外界扰动下,该发动机泵后供应系统能够较容易地达到流体谐振状态,当外界扰动频率接近其谐振频率时,供应系统沿程脉动压力出现了明显的共振波形。在不同的谐振频率下,喷前腔位置均为压力振荡的波节位置,也即为流量振荡的波腹位置。      

非定常条件下喷嘴结构对燃油流量脉动的影响

假设油路处于小脉动条件下,燃油流量连续,以流量数为中间变量,推导了燃油流量脉动关于喷嘴结构的关系模型.得出结论:当外部激励一定时,燃油流量脉动与流量数成正比,与平均燃油压降的0.5次方成反比.通过喷嘴标定得出了减小流量数进而减小燃油流量脉动的方法:增加节流级数、减小节流面积,并用脉动试验证明了此方法的正确性,为喷嘴设计者在面对不稳定性问题时提供了一般的设计步骤.      

Effects of pressure oscillation on aerodynamic characteristics in an aero-engine combustor

The effects of pressure oscillation on aerodynamic characteristics in an aero-engine combustor are investigated. A combustor test rig is designed to simulate the pressure drop characteristics of a practical annular combustor. The pressure drop characteristics are firstly measured under atmosphere condition with non-reacting flow (or cold flow), and the air mass flow proportion of each component (dome/liner) are obtained; these properties are base lines for comparison with combustion state. The combustion tests are then carried out under conditions of inlet temperature 340–450 K, fuel air ratio 0.010–0.028. The stability map and the oscillation frequencies are obtained in the tests, the results show that pressure oscillation amplitude increases with the increase of fuel air ratio. Phase trajectory reconstruction is applied to classify the pressure oscillation motion; there are three motions captured in the tests including: “disk”, “ring” and “cluster”. The pressure drops across the dome under strong pressure oscillation are distinctly divergent from the cold flow, and the changes of pressure drops are mainly affected by pressure oscillation amplitude, but is less influenced by pressure oscillation motion nor oscillation frequencies. Based on the mass flow conservation, the reduction of effective flow area of combustor under strong pressure oscillation is demonstrated. Liner wall temperatures are analyzed through Multiple Linear Regression (MLR) method to estimate the reduction of the air mass flow proportion of the liner cooling under strong pressure oscillation. Finally, the air mass flow proportions of each component under strong pressure oscillation are estimated, the results show that the pressure oscillation motion also has influence on air mass flow proportion.     

采用强制降噪和多尺度融合的地磁导航方法

针对地磁数据测量易受各种噪声和干扰影响,导致地磁匹配导航精度、概率和可靠性降低的问题,提出了一种采用小波强制降噪和多尺度融合的地磁匹配导航方法。该方法利用地磁数据高频部分易受噪声干扰影响而低频部分稳定性好、各尺度下的匹配结果具有相对独立性的特点,将含噪地磁基准图和实时图进行多尺度分解,在所选的多个尺度下经强制降噪后分别进行匹配,并融合各尺度下的匹配结果表决产生最终的导航结果。地磁匹配导航仿真实验结果表明该方法可有效提高导航的精度、概率和可靠性。     

一个有理递归序列解的稳定性条件研究

方程xn 1=(a bx2n)/(c x2n-k),a,b,c∈[0,∞),a b>0,n,k∈{0,1,2…}的解有很多有意义的性质.Li证明了当a相似文献   

一类有正阻尼的强非线性振动问题的近似解

用线化法,权残法和插值摄动法相结合的方法求得了一类有正阻尼的强非线性振动问题的近似瞬态解,精度好。     

ABDOM的参数规范化与离散化改进

为了更好利用叠加式双阻尼振荡模型(ABDOM,Accumulative Bi-Damped Oscillation Model)来描述、预测和评估真实软件缺陷发现时序过程,在提出理想软件缺陷发现时序过程范型(ISPSDD,Ideal Sequential Process of Software Defects Discovery)的基础上,对ABDOM中软件缺陷发现阻尼 a 和软件缺陷发现周期阻尼 b 的规范化进行了进一步讨论,提出了软件缺陷发现时序过程质量评价指数 Q ,给出了其典型取值和相关意义,并将其引入ABDOM,最终得到了经过参数规范化和离散化改进后的ABDOM-Q_d,并利用一个真实的工程实践项目数据对ABDOM-Q_d 进行了验证.     

边界条件对三维空腔流动振荡的影响

基于全隐式无分裂方法,数值求解三维非定常雷诺平均的N av ier-S tokes方程,紊流模型采用修正的B-L代数模型。运用此方法,本文数值模拟了三维开式空腔的超声速、跨声速、亚声速流动。研究了空腔口处剪切层的非定常运动现象,着重探讨了入口边界条件对三维空腔流自持性振荡的影响。数值计算结果表明,与层流速度型相比,入口条件为紊流速度型和特征边界型得到的结果能够吻合。