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Development of a fan-stirred constant volume combustion chamber and turbulence measurement with PIV

《能源前沿（英文）》 2022年第16卷第6期页码 973-987 doi: 10.1007/s11708-021-0762-z

摘要： A fan-stirred combustion chamber is deve-loped for spherically expanding flames, with P and T up to 10 bar and 473 K, respectively. Turbulence characteristics are estimated using particle image velocimetry (PIV) at different initial pressures (P = 0.5–5 bar), fan frequencies (ω = 0–2000 r/min), and impeller diameters (D = 100 and 114 mm). The flame propagation of methanol/air is investigated at different turbulence intensities (u′=0–1.77 m/s) and equivalence ratios (φ = 0.7–1.5). The results show that u′ is independent of P and proportional to ω, which can be up to 3.5 m/s at 2000 r/min. L_T is independent of P and performs a power regression with ω approximately. The turbulent field is homogeneous and isotropic in the central region of the chamber while the inertial subrange of spatial energy spectrum is more collapsed to –5/3 law at a high Re_T. Compared to laminar expanding flames, the morpho-logy of turbulent expanding flames is wrinkled and the wrinkles will be finer with the growth of turbulence intensity, consistent with the decline of the Taylor scale and the Kolmogorov scale. The determined S_L in the present study is in good agreement with that of previous literature. The S_L and S_T of methanol/air have a non-monotonic trend with φ while peak S_T is shifted to the richer side compared to S_L. This indicates that the newly built turbulent combustion chamber is reliable for further experimental study.

关键词： fan-stirred combustion chamber turbulence characteristics particle image velocimetry (PIV) methanol turbulent expanding flames

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圆形重力式网箱流场效应的试验研究

刘超,关长涛,崔勇,赵侠,李梦杰,李真真,王腾腾

《中国工程科学》 2014年第16卷第9期页码 69-77

摘要：种不同网目形状和不同网目大小的网箱模型（C1、C2、C3、C4），选取4 种不同水流流速（0.068 m/s、0.105 m/s、0.143 m/s、0.182 m/s），分别采用声学多普勒流速仪（ADV）和粒子图像测速（PIV结果表明，ADV试验与PIV技术测量结果基本一致；来流速度不同时，单个网箱范围内的水流衰减程度差异不大；来流速度相同时，小网目网箱的减流效果优于大网目网箱；网目大小相同时，菱形网目网箱减流效果优于方形网目网箱

关键词：网箱 ADV PIV 流速流场分布

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Image analyses for video-based remote structure vibration monitoring system

Yang YANG,Xiong (Bill) YU

《结构与土木工程前沿（英文）》 2016年第10卷第1期页码 12-21 doi: 10.1007/s11709-016-0313-6

摘要： Video-based vibration measurement is a cost-effective way for remote monitoring the health conditions of transportation and other civil structures, especially for situations where accessibility is restricted and does not allow installation of conventional monitoring devices. Besides, video-based system is global measurement. The technical basis of video-based remote vibration measurement system is digital image analysis. Comparison of the images allow the field of motion to be accurately delineated. Such information is important to understand the structure behaviors including the motion and strain distribution. This paper presents system and analyses to monitor the vibration velocity and displacement field. The performance is demonstrated on a testbed of model building. Three different methods (i.e., frame difference method, particle image velocimetry, and optical Flow Method) are utilized to analyze the image sequences to extract the feature of motion. The Performance is validated using accelerometer data. The results indicate that all three methods can estimate the velocity field of the model building, although the results can be affected by factors such as background noise and environmental interference. Optical flow method achieved the best performance among these three methods studied. With further refinement of system hardware and image processing software, it will be developed into a remote video based monitoring system for structural health monitoring of transportation infrastructure to assist the diagnoses of its health conditions.

关键词： structure health monitoring velocity estimation frame difference PIV optical-flow method