气液两相流中上升气泡体积的计算方法

通过高速摄像机拍摄气液两相流中上升气泡的运动过程,分别记录不同直径的气孔所产生的单个气泡上升过程的连续图像,结合数字图像处理技术,提取了气泡的面积、当量直径、几何中心、速度、加速度等特征参数.并在此基础上,应用两种计算气泡体积的方法:几何方法和受力分析法,实现了气泡体积的初步计算.几何方法计算气泡体积是根据图像中气泡的形状构造一个与气泡体积相当的椭球体,进而计算椭球体的体积;而受力分析的方法则是通过分析气泡在垂直方向上的受力情况,根据牛顿第二定律推导出气泡体积的计算公式.并对两种方法计算出的气泡体积值进行分析对比,阐明了这两种方法适用情况,计算出单个气泡上升情况下的气相体积含气率.     

基于改进相空间重构的压缩机运行状态预测

精确的状态预测对于压缩机的平稳运行至关重要,同时,振动信号能够表征绝大多数压缩机的运行状态。为提高预测精度,文中提出改进的相空间重构法和神经网络相结合的预测模型。首先利用相空间重构技术,将一维时间序列振动信号扩展到高维空间。针对传统的G-P算法中无标度区识别过于依赖人工经验的不足,提出了DBSCAN聚类与粒子群优化算法相结合的无标度区自动识别方法,并以相关性指标最大和残差平方和最小为目标建立无标度区识别优化模型,使用粒子群算法获得最优解,实现无标度区的自动识别。使用BP神经网络对重构后的振动信号进行预测。预测结果表明相空间重构后的信号预测效果更好。     

Quantitative analysis of multicomponent mud logging gas based on infrared spectra

This work deals with quantitative analysis of multicomponent mud logging gas based on infrared spectra. An accurate analysis method is proposed by combining a genetic algorithm (GA) and a radial basis function neural network (RBFNN). The GA is used to screen the infrared spectrum of the mixed gas, while the selected spectral region is used as the input of the RBFNN to establish a calibration model to quantitatively analyze the components of logging gas. The analysis results demonstrate that the proposed GA-RBFNN performs better than FS-RBFNN and ES-RBFNN, and our proposed method is feasible.     

气水流动中气泡生成体积计算模型的改进

In order to address the bubble formation and movement in air-water two-phase flow,single bubble rising in stagnant water is experimentally studied by digital image processing.Bubbles are released individually from the submerged orifices with different diameters(1.81 mm,2.07 mm,2.98 mm,3.92 mm)at different detachment frequency.Images are recorded by a high-speed video camera and processed by digital image processing technique. The factors impacting the formed volume of bubble are discussed.The experimental results showed that a threshold of gas flow rate(400 mm 3 ·s- 1)divides the bubble formation into two regimes:the constant volume regime and the growing volume regime.Especially for the growing volume regime,the surface tension is taken into account.The bubble volume is consisted of two parts:the surface tension impacting part and the gas volume flow rate impacting part.An improved correlation for bubble volume prediction is developed for the two regimes and better coincidence with the experiment data than the previous models is obtained.     

基于虚拟双目的条纹结构光三维重建

为解决传统双目条纹结构光三维重建存在的同步性和成本高等问题,提出了基于虚拟双目的条纹结构光三维重建方法。采用单相机和两块双棱镜及投影仪设计了具有双目视觉功能的虚拟双目条纹结构光三维重建系统。通过双棱镜折射和分光改变被测对象表面反射光的路径,使用一个相机同时完成多视角的图像采集。通过多频外差法和立体匹配、双目标定得到被测对象的深度信息并重建点云。实验表明,文中提出的方法和真实双目结构光方法测量标准球的均方根误差分别为0.037 9 mm和0.030 5 mm。文中提出的方法可促进双目条纹结构光技术在快速、低成本、小型化等方面发展,同时该方法可推广到彩色相机条纹结构光三维重建及投影散斑结构光三维重建。