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- 저자 : Qingfeng Gao (검색결과 2 건)
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Tieyu Gao,Junxiong Zeng,Qingfeng Xia,Jun Li,Jianying Gong 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
Flow and heat transfer characteristics of mist/steam cooling and mist/air cooling in a square channel with 60º rib angle are numerically investigated for a wide range of operating parameters, such as Reynolds number ranging from 10000 to 60000, reference pressure from 0.1 MPa to 0.5 MPa and inlet temperature from 120 °C to 200 °C. Also, the heat transfer characteristics of mist cooling are compared with the corresponding cases of single-phase coolant such as steam and air. The 3D steady Reynolds-averaged Navier–Stokes equations with a standard k-ω turbulent model are solved by using commercial software ANSYS CFX. The CFD model has been validated by experimental data for steam-only case with a good agreement. In addition, distribution and evolution of secondary flow in the ribbed channel are analyzed by vortex core technology and their effects on heat transfer are investigated for these four coolants. The results show that the strength of longitudinal secondary flow has a significant influence on the Nusselt number (Nu) distribution on the ribbed surface. The Nusselt number distribution is periodical in stream-wise direction for steam and air cooling, whereas Nusselt number gradually increases for mist/steam and mist/air cooling. It is found that longer travelling distance of droplets in the ribbed channel result in a higher heat transfer enhancement of mist cooling. The heat transfer characteristics of mist cooling are insensitive to pressure, but inversely correlated with coolant inlet temperature compared with steam and air cooling for the tested parameter ranges.
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Iterative tuning of decoupling controller for 3-DOF precision motion stage
Wei Teng,Qingfeng Gao,Xin Wu,Haihua Mu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.2
A practical iterative tuning algorithm of a decoupling controller is presented to eliminate intrinsic coupling among 3-DOF precision motion stage. General decoupling control cannot eliminate coupling completely, which will prevent the enhancement of control accuracy in high-precision motion system. The proposed algorithm can be used to tune the parameters of a decoupling controller iteratively through minimizing a quadratic cost function of the tracking error in non-movement direction when the stage moves in one direction. The tuning algorithm addressed for the motion stage needs only measurement signals in an actual motion system rather than a detailed model of the stage. The proposed algorithm is demonstrated by experimental results. It can be applied further in other multi-DOF motion systems.
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