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Mechanism Study and Geometric Parameter Optimization of the Vortex Downhole Tool
Zhao Zhang,Rui-Quan Liao,Jie Liu,Jun Ma 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.4
In the present study, the mechanism of the vortex downhole tool (VDT) to improve gas well production efficiency is investigated and the optimal geometric parameter combination of VDT is obtained by an orthogonal experiment. Results show that VDT has the potential to reduce the critical gas velocity only when its helix angle is less than 63°, and the theoretical reduction will not exceed 21.5%, compared to the Turner model. Under the action of VDT, the friction factor of the gas-liquid two-phase flow is reduced, as well as the total flow pressure drop. The field testing results show that the proposed structure optimization method of VDT is feasible and the optimal VDT has greatly improved the production conditions of well A.
Stability of Hybrid Impulsive and Switching Stochastic Systems with Time-delay
Xuegang Tan,Bin Hu,Zhi-Hong Guan,Rui-Quan Liao,Jiang-Wen Xiao,Yuehua Huang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.4
This paper investigates a model of hybrid impulsive and switching stochastic systems (HISSS) with time-delay. Several stability criteria, including the globally asymptotical and exponential stability criteria in the pth moment and mean square, are established by using Itô formula, a generalized switching Lyapunov functions and some relating techniques. Especially, a more general Lyapunov-Krasivskii functional is constructed, and it is observed that the mean square asymptotic and exponential stability conditions of HISSS are delay-dependent. A numerical example shows that the obtained stability results can reduce the conservativeness.