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Numerical Investigation on a Twin-Screw Multiphase Pump Under low IGVF
Shuaihui Sun,Pengbo Wu,Pengcheng Guo,Guangzhi Yi,Ahmed Kovacevic 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.4
A three-dimensional transient numerical model was developed to obtain the two-phase flow characteristics in a twin-screw multiphase pump based on dynamic mesh technology and the multiphase flow model. The pump performance under different inlet gas volume fractions (IGVF) was predicted by the numerical model and was tested. Then, the numerical model was validated after comparing the simulation and experimental results. After that, the flow field in the pump under 10% IGVF was analyzed. When the IGVF is 10%, the pressure increases step by step and is symmetrical from both ends to the middle of the screw rotors. The pressure distribution through a single working chamber is uniform. It falls rapidly at the inlet of the tooth tip gap and then drops linearly in the gap channel. At the outlet of the tip gap, the pressure temporarily falls due to the high-speed jet. The GVF distribution in the working chamber is uneven. The leakage flow is laminar in the tip gap, and the liquid concentrates on the top of the gap. When the last working chamber connects with the discharge chamber, the discharge jet flow causes the vortices in the discharge pipe. The gas gradually moves to the center of the vortices, forming four gas-phase aggregation regions. The velocity of the interlobe leakage is the largest. The maximum velocity appears at the second cross-section and reaches 35m/s. This research can be used to improve the performance of the twin-screw multiphase pump under two-phase working conditions.
Multi-Task FaceBoxes: A Lightweight Face Detector Based on Channel Attention and Context Information
( Shuaihui Qi ),( Jungang Yang ),( Xiaofeng Song ),( Chen Jiang ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.10
In recent years, convolutional neural network (CNN) has become the primary method for face detection. But its shortcomings are obvious, such as expensive calculation, heavy model, etc. This makes CNN difficult to use on the mobile devices which have limited computing and storage capabilities. Therefore, the design of lightweight CNN for face detection is becoming more and more important with the popularity of smartphones and mobile Internet. Based on the CPU real-time face detector FaceBoxes, we propose a multi-task lightweight face detector, which has low computing cost and higher detection precision. First, to improve the detection capability, the squeeze and excitation modules are used to extract attention between channels. Then, the textual and semantic information are extracted by shallow networks and deep networks respectively to get rich features. Finally, the landmark detection module is used to improve the detection performance for small faces and provide landmark data for face alignment. Experiments on AFW, FDDB, PASCAL, and WIDER FACE datasets show that our algorithm has achieved significant improvement in the mean average precision. Especially, on the WIDER FACE hard validation set, our algorithm outperforms the mean average precision of FaceBoxes by 7.2%. For VGA-resolution images, the running speed of our algorithm can reach 23FPS on a CPU device.
Numerical Analysis of Two-Phase Flow in a Micro-Hydraulic Turbine
Tiejun Chen,Shuaihui Sun,Ye Pang,Pengcheng Guo 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.4
In many industrial processes such as natural gas processing, seawater desalination et al, there is a large amount of liquid waste pressure energy, which can be converted into electric or mechanical energy by a micro-hydraulic turbine. But its efficiency and stability will deteriorate when the working fluid contains gas. Aiming at improving the hydraulic efficiency of the micro-turbine, the three-dimensional transient two-phase flow model which adopts the shear-stress-transport (SST) model as turbulence model and Eulerian-Eulerian model as two-phase flow model with the commercial code ANSYS-CFX was established and solved to study the two-phase flow characteristics of the micro-hydraulic turbine with fixed guide vane openings under different gas volume fraction (GVF). The numerical simulation results show that the power and efficiency of the turbine decrease by 24% and 21% respectively when the inlet GVF is 0.20. The area of low pressure in each impeller passage increases with the inlet GVF, and the pressure difference between the working and suction surface of the blade decreases. The GVF distribution in impeller passage is asymmetrical, which is caused by the gas-liquid separation in the volute. At the left lower part of impeller passage, the gas accumulates at the suction surface of the blades under the Coriolis force and its GVF reaches 90%. The asymmetrical GVF distribution will result in the asymmetrical pressure distribution in the impeller passage, which leads to the imbalance force on the blades. Moreover, the asymmetrical GVF distribution will reinforce the positive incidence at the lower part of impeller passage, and weaken it at the upper right impeller passage. The volute should be redesigned to ensure the uniform gas distribution at the inlet of each impeller passage.
Zhu Jun,Li Guanghua,Cao Di,Zhang Zhenyi,Li Shuaihui 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2
A 90° Halbach permanent magnet array coreless axial fux permanent magnet synchronous generator for wind power generation is compared with a conventional axial fux permanent magnet generator with cut cake type permanent magnet. 2D analytic model of generator is established. The air gap magnetic felds of two generators are analyzed by analytical method, and the air gap magnetic density and harmonic content are analyzed. Then the infuence of diferent parameters on voltage total harmonic distortion is analyzed by changing the pole arc coefcient, air gap length, permanent magnet thickness and number of turns. Two prototypes of generators are manufactured, and the correctness of the simulation results is verifed by experiments.