基于压力涨落信号的气固流化床早期颗粒结块故障诊断研究

利用压力涨落信号对气固流化床颗粒结块故障进行早期诊断，有着重要的工业应用意义。本文首先从信号产生的物理背景出发，认为压力涨落信号可分解为分形布郎运动和高斯白噪声的加和。结合正交小波变换理论，应用期望最大化算法（ＥＭ），得到了压力涨落信号的自相似参数Ｈ和高斯白噪声强度σＷ的极大似然估计，从而证实了这种分解的可行性。应用参数Ｈ和σＷ对模拟颗粒结块故障的研究表明，流化床床层下部压力涨落信号的Ｈ和σＷ参数均对此故障敏感，本文对结果进行了物理解释。因此，Ｈ和σＷ参数有望应用于对此故障的早期诊断。

Study on Shock Wave and Turbulent Boundary Layer Interactions in a Square Duct at Mach 2 and 4

In this paper, the outline of the Mach 4 supersonic wind tunnel for the investigation of the supersonic internal flows in ducts was firstly described. Secondly, the location, structure and characteristics of the Mach 2 and Mach 4 pseudo-shock waves in a square duct were investigated by color schlieren photographs and duct wall pressure fluctuation measurements. Finally, the wall shear stress distributions on the side, top and bottom walls of the square duct with the Mach 4 pseudo-shock wave were investigated qualitatively by the shear stress-sensitive liquid crystal visualization method. The side wall boundary layer separation region under the first shock is narrow near the top wall, while the side wall boundary layer separation region under the first shock is very wide near the bottom wall.