交叉式多股流板翅式换热器数值研究

借鉴顺逆式板翅式换热器研究成果,分析了交叉式多股流板翅式换热器传热机理,建立了基于有限容积法的多股流板翅式换热器传热数学模型,经过合理假设将翅片间距与单元格尺寸独立,拓展了前人数学模型适用范围.同时,以机载交叉式3股流板翅式换热器为例,对单元格尺寸选取进行了探讨,对同一通道单元格内流体流动横向传热进行了分析,证明了忽略流动横向传热的可行性,从而在保证精度不变条件下提高了计算效率;并在流体变入口参数条件下进行试验,对数值计算方法进行验证,通过与试验数据对比,理论计算误差小于7.9%,证明了数值计算方法的合理性.      

3J33C小孔镗削温度测量实验及有限元模拟

基于3J33C弹性合金小孔镗削温度测量实验及Advant Edge有限元温度仿真试验,验证了有限元模型及结果的可靠性,得到其不同镗削参数时基体最高温度的变化规律及温度范围。基于有限元仿真结果建立了3J33C小孔镗削的温度经验公式,结果表明,随着镗削转速、进给速度及径向切深的增大,镗削温度都呈现升高趋势,并且在这三个因素中镗削转速影响最大,进给速度影响次之,径向切深影响最小。     

钝前缘三角翼的高阶湍流数值模拟研究

模拟钝前缘三角翼的特殊双（内、外侧）主涡流动结构和流动分离点的情况,通过定常的RANS计算和基于SA模型的DES计算表明,计算结果与试验数据吻合度较好,可以比较准确地捕捉了三角翼的双主涡结构。同时,应用SA-DES方法可以提高漩涡的模拟精度。     

高温升多旋流燃烧室的数值分析

为了探索高推重比航空发动机可能用到的燃烧组织方式,基于燃烧室空气分级技术,对高温升多旋流燃烧室展开研究。在保证与某型单环腔燃烧室(SAC)扩压器尺寸、外机匣最大直径及燃烧室出口尺寸和边界条件等相同的基础上,对设计模型进行3维数值模拟,并与现有的单环腔燃烧室数值模拟结果和试验结果进行对比分析。研究结果表明:在设计油气比为0.037的情况下,采用多旋流的设计方案,温升达到1153 K,出口温度分布系数达到0.170,同时可获得理想的性能参数,满足高温升燃烧室的设计指标。     

Experiments on film cooling with sonic injection into a supersonic flow

Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes, the mass flow ratio, and the hole spacing on the film cooling effectiveness. The mainstream was obtained by the hydrogen-oxygen combustion, entering the experimental section at a Mach number of 2.0. The nitrogen with ambient temperature was injected into the experimental section at a sonic speed. The measured mainstream recovery temperature was approximately 910K. The mass flow ratio was regulated by varying the nitrogen injection pressure. The experimental results show that for the investigated cooling surface, the cooling effectiveness increases with the increase in the number of the injection holes with other parameters held constant. For a fixed cooling configuration, the cooling effectiveness increases with the increase in the mass flow ratio. Different from the subsonic film cooling, the optimal mass flow ratio is not observed. When the hole spacing is less than 4, no obvious difference is observed on the cooling effectiveness and lateral uniformity. With the mass flow ratio increasing further, this difference becomes much smaller. The shock wave also has an effect on the cooling effectiveness. Downstream the incident point of the shock wave, the cooling effectiveness is lower than that in the case without the shock wave.     

高校课程的双语教学探索和实践

近年来,双语教学已经逐步成为我国高校教学改革的一个热点,各地高校纷纷参与到双语教学的改革实践中来。通过开展双语教学的实践和理论探索,对我国高校推行双语教学的目标、现状及存在的主要问题进行分析,提出高校应面向教学实际,分层次开展双语教学的建议,以期为高校双语教学的成功实践提供参考。     

基于F代表点的高斯过程矩匹配滤波

提出了一种基于F偏差代表点的高斯过程矩匹配滤波方法。该方法通过高斯过程学习系统的过程函数和观测函数,在高斯矩匹配滤波的框架下利用F偏差代表点进行数值计算。在单变量非线性模型及静基座初始对准中进行的仿真实验表明,该方法的精度不低于解析计算的高斯过程假设密度滤波（GP-ADF）,远高于高斯过程无迹卡尔曼滤波（GP-UKF）。     

基于结构随机跳变系统的制导交班边界设计

为了减小最终脱靶量,研究了系统存在随机扰动时交班切换边界定位问题。首先建立了具有中制导和末制导的结构随机跳变系统模型,然后根据结构随机跳变系统理论进行系统概率分析,并在此基础上结合优化算法,得到最优的交班切换边界,使得当前脱靶量的数学期望和方差最小。最后,进行了某型导弹纵向俯仰通道仿真,验证了该方法的有效性。     

低速风洞均匀吸气地板下阻塞对地板边界层影响的研究

为了研究低速风洞地板下部阻塞对地板上表面边界层的影响以及控制方法，在国防科技大学KD-03低速风洞利用均匀吸气地板系统进行了实验研究。地板下部阻塞对地板上表面主流区的流动产生干扰，并影响边界层的分布和发展，随着地板下部阻塞度的增加，地板上表面边界层的厚度有增加的趋势；在某一阻塞度和吸气系数下，来流速度越大，地板下部的阻塞对主流区流动的影响越小；地板的均匀吸气使边界层的厚度显著降低，也有效减小因地板下部阻塞引起的主流区流动的不均匀性。该实验的研究结论为8m×6m风洞均匀吸气地板系统研制提供了参考。     

Solar wind origins in coronal holes and in the quiet Sun

Coronal hole (CH) and the quiet Sun (QS) are considered to account for sources of fast and slow solar wind streams, respectively. The differences between the solar wind streams flowing out from the CH and the QS are thought to be related with different plasma generation and acceleration mechanisms in the respective source regions. Here we review recent studies on the solar wind origin in the CH and the QS, compare the possible flow geometries and magnetic structures in these two kinds of solar regions, and summarize the physics associated with two different origin scenarios.