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RISS 인기검색어
- 검색키워드
- 저자 : Yanting Ai (검색결과 3 건)
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Dan Sun,Shengyuan Li,Chengwei Fei,Yanting Ai,Rhea. P Liem 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
The cavitation phenomenon in journal bearing and journal whirl are considered to evaluate the static and dynamic characteristics of journal bearing, to be more consistent with the actual operating conditions of journal bearing. With a 3D CFD method, the cavitation and journal whirl are simulated by adopting mesh deformation technique and mixture phase-change model. By comparing the results with those of the traditional Reynolds equation, we observe that first, the phenomena of cavitation and journal whirl are very consistent with the actual operating conditions of journal bearing. Moreover, for single-phase and two-phase flow models, the distribution features of oil film pressure are similar in convergent wedge zone while largely different in divergent part of the gap. The oil film pressure and vapor phase volume fraction notably vary on different whirl positions of the journal. We also observe that as whirl frequency increases, the oil film force gradually increases and the stability of journal bearing decreases rapidly before reaching a plateau. The efforts of this paper provide an efficient method to accurately evaluate the static and dynamic characteristics of journal bearing and offer a useful insight into the accurate analysis and design of journal bearing.
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Dan Sun,Jian Gang Yang,Rui Guo,Wan Fu Zhang,Yanting Ai 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6
Static and dynamic characteristics of labyrinth seals are important in the prediction of the stability of turbomachinery. The paper presentsan effective numerical method to predict the static and dynamic performance characteristics of seals at off-center conditions withdifferent rotor whirling frequency. Modifications are introduced for the traditional turbulent bulk flow model to consider the circumferentiallyvarying flow. A trigonometric series expansion method is used to approximate parameters such as pressure and velocity in sealscavity. Numerical simulations show that 8-10 series terms with 5-10 iterations are enough for the solution of this set of nonlinear equations. The resulting nonlinear algebraic equations can be solved rapidly. The analytical results are verified by comparison with the simulatedCFD results. Parametric investigations showing the influence of eccentricity and whirling frequency on seals dynamics are alsopresented. The results show that the trigonometric series expansion based method gives an effective prediction of the static and dynamiccharacteristics of the eccentric seals.
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Dan Sun,Xudong Wang,Chengwei Fei,Shuang Wang,Yanting Ai 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9
This paper proposes a new type of negative dislocated seal (NDS) based on the dislocated bearing theory to investigate the influential parameters of static rotor eccentricity and dislocated ratio on the static and rotordynamic characteristics of an example seal solved with computational fluid dynamics (CFD) the flow field. The rotordynamic characteristics of the NDS were investigated in respect of the effects of rotor whirling frequency on response force, stiffness coefficients, damping coefficients and rotor system stability, by multifrequency elliptical orbit rotor whirling model. Based on the studies, we reached the following conclusions. The circumferential pressure distribution of NDS and conventional labyrinth seal (LS) presents sine periodic variation approximately, while relative to the LS, the NDS has two divergent wedge gaps and reduces the hydrodynamic pressure effects, then the circumferential pressure difference and tangential force on rotor surface decreases by about 40 %~190 %. The leakage of the NDS linearly increases with the rising eccentricity ratio and dislocation ratio approximately, and is larger (about 0.9 %~1.5 %) than the LS. The direct stiffness coefficients of the two seals increase with the rise of rotor whirling frequency, while the absolute values of both the cross-coupled stiffness coefficients and the damping coefficients decrease with raising rotor whirling frequency. Compared with the LS, the NDS has smaller (about 28.8 %~206.2 %) cross-coupled stiffness coefficient, larger (about 26.15 %~60.39 %) effective damping coefficient, and good stability of rotor system. This study has developed a novel seal structure to improve the seal performance of turbomachinery such as aeroengine.
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