轴向超声速通流串列构型弦长比对气动性能影响的数值研究

为避免高马赫数、大攻角来流引发的叶片颤振,将串列叶片技术引入到超声速通流风扇叶栅中,对其进行串列改型及气动性能研究。利用准二维数值模拟,对串列叶片前、后排叶片的弦长比参数进行了详细的对比研究。结果表明：影响气动性能的关键因素是后排叶片进口压力侧激波的落点,在本文研究条件下,随着弦长比的减小总压损失呈减小的趋势,当弦长比由0.99减小到0.43时,设计攻角下,15°折转角叶型总压损失可减小27%,30°折转角叶型总压损失可减小38%。进一步的研究表明,通过减小弦长比可有效控制后排叶片前缘斜激波在相邻叶片吸力侧的落点以实现损失降低,并且这种降低效应在小弯角叶型上比大弯角叶型更容易实现。     

Review of shock wave detection method in CFD post-processing

In the present computational fluid dynamics (CFD) community, post-processing is regarded as a procedure to view parameter distribution, detect characteristic structure and reveal physical mechanism of fluid flow based on computational or experimental results. Field plots by contours, iso-surfaces, streamlines, vectors and others are traditional post-processing techniques. While the shock wave, as one important and critical flow structure in many aerodynamic problems, can hardly be detected or distinguished in a direct way using these traditional methods, due to possible confusions with other similar discontinuous flow structures like slip line, contact discontinuity, etc. Therefore, method for automatic detection of shock wave in post-processing is of great importance for both academic research and engineering applications. In this paper, the current status of methodologies developed for shock wave detection and implementations in post-processing platform are reviewed, as well as discussions on advantages and limitations of the existing methods and proposals for further studies of shock wave detection method. We also develop an advanced post-processing software, with improved shock detection.     

二维Euler方程的自适应网格矢通量算法

给出了二维轴对称欧拉方程的自适应网格隐式矢通量分裂差分格式和模拟结果,隐式矢通量分裂格式不需人工粘性项与人工耗散项,可以计算跨声速流场,也可以较准确地捕获激波,利用流场解的梯度信息对网格进行调整,可以提高激波的捕获精度,算例表明,该方法精度高稳定性好,不依赖于初始条件。     

旋转爆震发动机喷管非定常流动特性的数值模拟研究

为分析旋转爆震喷管内非定常流动特性,基于特征线方法和旋转爆震燃烧室出口时均参数设计了一种塞式喷管模型,通过改变塞锥式喷管的进出口压比π(π=15,30,45),分析了喷管内非定常流场结构与喷管工作性能之间的相互关系,并探究了喷管进出口压比变化对喷管工作性能的影响.研究结果表明:旋转爆震燃烧室下游斜激波进入喷管后,在喷管...     

激波管在压力传感器动态性能校准和实验上的应用

通过对最新研制的激波管法低压动态压力校准装置的介绍 ,结合实际工作经验阐述了激波管在压力传感器动态性能校准和实验上的应用。     

Strong interactions of incident shock wave with boundary layer along compression corner

The coherent structure and instability of the interaction of incident shock wave with boundary layer developing on a compression corner are experimentally studied. The experiments are carried out in a supersonic wind tunnel of Mach number 2. Particular attention is paid to shock patterns and unsteady shock motions induced by the separation bubble. The high-speed schlieren is used to visualize the flowfield evolution and to characterize the instability. The snapshot proper orthogonal decomposition of schlieren sequences is applied to investigate the primary coherent structure in the flowfield. Fast Fourier transform and continuous wavelet transformation are applied to characterize the instability. The results show that there are large-scale low-frequency oscillations of the shock waves and small-scale high-frequency pulsations in the separation region. The peak frequency of shock oscillation is mainly concentrated in the range of 100–1000 Hz. The pulsation of the small flow structure in the separation bubble is mainly concentrated above 12.5 kHz. Based on the results of experimental analysis, the preliminary mechanism of the large-scale instability of such interaction is obtained.     

DC-CD变换器控制技术研究与实现

DC-DC变换器工作在额定负载时，输入电压会出现扰动。工作在额定输入电压时，负载电阻也会发生突变。为了实现宽电压输入，保证变换器具有较高的输入电压调整率和负载调整率，设计了自动切换与控制策略。根据Buck-Boost型DC-DC变换器的工作特点，计算出开关的导通与关断时间点，从而精确地控制开关动作。基于并行运算和组合逻辑，在Matlab中搭建了模型，并进行了仿真和试验验证。结果表明，提出的控制方法能够有效地克服负载电流突变和输入电压扰动对变换器性能的影响。     

基于Labview的振动冲击测量系统设计

根据振动冲击试验设备测试要求,设计并研制一套测量系统。系统基于虚拟仪器测量技术设计,通过采集振动冲击所产生加速度信号的频率和幅值,运用FFT技术进行信号处理和分析,完成对振动冲击试验设备的测量。实验效果表明,该系统具有测量功能完善、测量结果准确可靠、软件操作简单等特点,能够满足目前在用的所有振动冲击试验设备的测量需求,在实践中已得到应用。     

基于激光激励的火工冲击响应及其特性研究

针对传统火工冲击激励方法在频率范围方面的局限性，研究新兴的激光激励方式、激励特性及其参数的影响，探究模拟火工冲击试验的可行性。首先参考经典的冲击试验方法，制定了激光激励试验的试验方案，设计了试验装置并进行了冲击试验；然后针对火工冲击和激光激励的试验结果，在时域、频域进行了时频分析和响应谱分析与对比；最后依据该试验方法，讨论了激光脉冲频率和激光脉冲能量对冲击响应的影响。研究提出的激光激励方法对火工冲击机理研究与地面模拟试验设计具有一定的参考价值。