水下航行器热尾流试验研究

水下航行器热尾流温度分布研究对红外探潜和鱼雷制导都有重要意义.建立了一套用于实验室热尾流测量的温度测量系统,实验研究了水下航行器排放冷却水形成的热尾流温度分布特征,通过对水下航行器在稳定温度分层水池中航行形成的热尾流的温度测量及红外摄像,发现水下航行器排放热水形成的热尾流中的温度分布特征规律明显,实验结果与数值计算结果符合较好,分析了影响热尾流温度分布的主要因素,为舰艇热尾流的数值预报研究提供了基础.     

Euler computation of the nearfield wake vortex of an aircraft in take-off configuration

Numerical simulations based on the three-dimensional Euler equations are used to investigate the predictive capability of an Euler code for calculations of the nearfield wake of a narrow-body airliner wind tunnel model in take-off configuration up to a half span behind the wing tip trailing edge. Simulation results on both structured and unstructured grids are presented. The results on the block-structured grid were obtained within the scope of the EU-project EUROWAKE. The simulation quality of the vortex formation and spatial development is analysed by comparison to wind tunnel measurements of the spanwise lift distribution available from the EU-project DUPRIN II and to experimental PIV data available from the EU-project EUROWAKE.     

空间等离子体环境中的高能带电粒子加速机制

空间环境中充满能量从几十keV到几MeV的高能带电粒子,这些粒子可导致在轨航天器表面和内部带电甚至单粒子效应,从而引发航天器故障。高能粒子的产生和日地空间环境中的爆发现象如耀斑、磁层亚暴等密切相关。文章综述了与这些爆发现象相关的磁重联、激波和等离子体波动等加速带电粒子的物理过程。     

临近空间高超声速飞行器RCS特性研究

首次系统地对升力体外形临近空间飞行器雷达散射截面（RCS）特性开展了研究,主要研究内容包括本体及绕流RCS特性研究,亚密湍流尾迹RCS特性研究和层流尾迹的RCS特性研究等。结果显示：等离子体绕流将降低飞行器后向RCS;亚密湍流尾迹对低频段RCS影响明显,对高频段影响不明显。另外,双站雷达对临近空间高超声速飞行器也会有较好的探测效果。     

激励强度对等离子体合成射流的影响

通过在Navier-Stokes方程组中添加体积力源项的方法,模拟了不同激励强度下等离子体合成射流,并研究了激励强度对流场特性的影响。计算结果表明,随着激励强度的增大,激励器附近壁面处的涡量增大,对应的涡对中心诱导的流向速度增大,从而导致涡核更加远离壁面,并被拉伸变长。对于等离子体合成射流的时均流场,其中轴线上的流向速度随着激励强度增大整体变大。在较小的激励强度下,射流半宽度随着激励强度的增大而增大;而激励强度很大时(>6 Dc0),激励强度对半宽度基本没有影响。沿流向的动量通量也随激励强度的增大单调增加。     

Unsteady Flow Variability Driven by Rotor-stator Interaction at Rotor Exit

Numerical investigation of the unsteady flow variability driven by rotorstator interaction in a transonic axial compressor is performed. Two models with close and far axial gap between rotor and stator rows are studied in the simulation. Particular attention is attached to the analysis of mechanisms involved in driving rotor wake oscillation, rotor wake skewing and flow angle fluctuation at rotor exit. The results show that smaller axial gap is favorable to enhance the interaction in the region between two adjacent rows, and the fluctuation of the static pressure difference between two sides of rotor wake is improved by potential field from down stator, which is the driving force for rotor wake oscillation. The interaction between rotor and stator is weakened by increasing axial distance, rotor wake shifts to suction side of rotor blade with 5%-10% of rotor pitch, the absolute value of flow angle at rotor exit is less than that in the case of close interspace for every time step, and the fluctuation amplitude is also decreased.     

液相等离子喷涂纳米ZrO2热障涂层的显微结构及抗热震性能研究

采用液相等离子喷涂技术制备了纳米氧化锆热障涂层。用透射电镜、扫描电镜和X射线衍射研究了涂层的晶粒特性、显微结构和晶体结构,同时研究了纳米氧化锆热障涂层的热震性能。结果表明:液相等离子喷涂制备的涂层晶粒约30nm;涂层具备均匀的孔隙结构;涂层热震前后的主相为稳定的四方相晶体结构;涂层的特殊孔隙结构有利于缓解热震循环过程中产生的应力、阻止裂纹的形成和扩散,从而提高了涂层的抗热震性能。     

Dust acoustic dressed solitons in a four component dusty plasma with nonthermal electron

Nonlinear dust acoustic dressed soliton are studied in a four component dusty plasma. Nonthermal distributions for electrons are considered. The Korteweg–de Vries (KdV) equation is derived by using reductive perturbation technique. A higher order inhomogeneous differential equation is obtained for the higher order correction. The expression for dressed soliton is obtained by the renormalization method. The expressions for higher order correction are determined using a series solution technique.     

超燃燃烧室等离子体点火和火焰稳定性能

为了研究热等离子点火器在超燃冲压发动机中的应用,在来流马赫数2.0工况下,针对乙烯和氢气两种燃料,进行了超燃环境中等离子体点火的试验和仿真研究.在来流总温1 500~1 950 K,燃料当量比0.1~0.55范围内对等离子点火器的点火和改善燃烧性能的性质进行了详细分析.结果显示:对于氢气和乙烯燃料,等离子体点火器使两种燃料的点火性能均得到明显改善,点火延迟时间大大缩短,燃料着火范围扩大、贫燃极限当量比降低.但未观察到其在加速掺混以及改善燃烧性能方面的明显作用.进行了与乙烯燃烧试验对应的数值仿真工作,选用了两种乙烯化学反应模型进行对比研究.仿真结果显示:8步9组分反应模型与试验结果符合较好,而3步6组分反应模型过高的估计了反应剧烈程度,燃烧室压力值偏高,压力起始上升位置偏向上游.所用的8步模型比3步模型更适合于超燃燃烧室中乙烯反应的模拟.     

端壁等离子体气动激励抑制高负荷压气机叶栅角区流动分离实验

为揭示端壁等离子体气动激励抑制高负荷压气机叶栅角区流动分离的影响规律和流场特征,在不同流场参数和激励条件下分别开展了微秒脉冲和纳秒脉冲等离子体气动激励抑制叶栅流动分离的实验研究.结果表明:端壁等离子体气动激励可以有效抑制叶栅角区的流动分离,其作用效果在攻角为3°时最佳,随攻角的增大逐渐下降;微秒脉冲激励的流动控制效果随来流速度的增大而降低,随激励电压和占空比的增大而提高,最佳非定常脉冲频率为500Hz;在较高来流速度下,微秒脉冲激励的作用效果十分微弱,但纳秒脉冲激励能够有效抑制角区流动分离;纳秒脉冲激励的流动控制效果随激励电压增大而提高,激励频率对控制效果至关重要,作用效果随激励频率的增大而不断增强,但当激励频率为5kHz时,作用效果有所下降.