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Temperature impact analysis of star gear bearing inner ring based on under-race lubrication passage
He-yun Bao,Chun-lei Wang,Feng-xia Lu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
In order to reduce the inner ring temperature and the oil consumption, temperature impact of star gear bearing inner ring based on under-race lubrication passage is analyzed, the flow and temperature fields of the inner ring are simulated using the realizable k-ɛ turbulence model based on the computational fluid dynamics (CFD) method, and experimental verification is performed. The results indicate that adding annular grooves to the star gear cylindrical roller bearing has a significant impact in reducing the temperature of the inner ring, and annular grooves with different cross-sectional sizes have different impacts in reducing the temperature of the inner ring. When the cross-sectional area of the annular grooves is 5 × 1.5 mm, the temperatures of the inner raceway of the left and right bearing decrease from 123.95 and 111.98 °C to 104.3 and 101.4 °C, respectively.
Feng Kang,Jianping Ao,Guozhong Sun,Qing He,Yun Sun 한국물리학회 2010 Current Applied Physics Vol.10 No.3
In this paper, polycrystalline CuInxGa1xSe2 (CIGS) thin film absorbers were prepared by selenizing electrodeposited (ED) precursors with two different levels of selenium content: rich in selenium and poor in selenium. Comparing the results obtained by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and illuminated current–voltage (J–V), it was found that absorber layers processed from Se-poor ED precursors shows better crystalline quality and increased gallium incorporation,which thus improved cell performance, compared to the layers grown using Se-rich ED precursors. The best cell fabricated from Se-poor ED precursor shows a conversion efficiency of 1.63% at AM1.5 global light.
Nonlinear dynamic analysis of an external gear system with meshing beyond pitch point
He-yun Bao,Guang-hu Jin,Feng-xia Lu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
A two-dimensional non-linear dynamics model of a gear with meshing beyond pitch point with six degrees has been established, considering time-varying meshing stiffness, time-varying bearing stiffness, time-varying friction, backlash and bearing clearance. Timevarying meshing stiffness is computed by using material mechanics method. The friction coefficient of Coulomb model and the friction coefficient of EHL theory are analyzed and compared in dynamic response. The global bifurcation characteristics caused by input speed, backlash, bearing clearance and damping are investigated. The maximum Lyapunov exponent which leads to chaos characters effect of changing parameters is analyzed. The verification experiment is carried out on the CL-100 test rig. Meshing frequency has main impact on vibration acceleration of ordinary spur gear and double meshing frequency has main impact on vibration acceleration of gear with meshing beyond pitch point. The results show that the gear with meshing beyond is better than ordinary spur gear whether in bifurcation characteristics or in vibration acceleration response.
Review of the Molecular Pathogenesis of Osteosarcoma
He, Jin-Peng,Hao, Yun,Wang, Xiao-Lin,Yang, Xiao-Jin,Shao, Jing-Fan,Guo, Feng-Jin,Feng, Jie-Xiong Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.15
Treating the osteosarcoma (OSA) remains a challenge. Current strategies focus on the primary tumor and have limited efficacy for metastatic OSA. A better understanding of the OSA pathogenesis may provide a rational basis for innovative treatment strategies especially for metastases. The aim of this review is to give an overview of the molecular mechanisms of OSA tumorigenesis, OSA cell proliferation, apoptosis, migration, and chemotherapy resistance, and how improved understanding might contribute to designing a better treatment target for OSA.
Nonlinear tribo-dynamic model of helicopter mid-reducer system under light loss of lubrication
Feng-xia Lu,Xuechen Cao,He-yun Bao,Rupeng Zhu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
When the helicopter tail transmission system loses oil due to damage, the system needs to persist for 30 minutes. Therefore, the nonlinear tribo-dynamics model of the helicopter intermediate reducer (HIR) is established, which is coupled with the loss of oil lubrication. To simulate condition of the HIR system under the loss of lubrication (LOL), this study begins by establishing a complete HIR system CFD model, and analyse the lubrication of the gear tooth surface and the oil churning/windage under different lubrication conditions. Then, a coupled model based on the result of the CFD is proposed to calculate the coefficient of friction (COF) under the condition of light loss of lubrication (LLOL). The results show that COF gradually decreases first and then increases rapidly.
Yun Jia,Feng-Chen Li,Xianzhu Wei,Xiao-Bin Li,Zhi-He Li 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9
It is of great importance to predict the deformation and vibration characteristics of the hydro-turbine structure accurately for the stable operation when the turbine is running under the alternating load of the flow field. In this paper, we proposed a methodology for analysis of the head cover deformation and vibration amplitude in the high-head Francis hydro-turbine system, in which Computational fluid dynamics (CFD) is employed to simulate the complex flow field in the head cover flow passage and the CFD-captured pressure distribution is provided for Finite element analysis (FEA) as a new load input to obtain more accurate head cover deformation and vibration calculation results. The results obtained by this method are compared with the results of the conventional algorithm and laboratory experimental results, demonstrated a better consistency. The great advantage of this method is that it allows vibration amplitude analysis and predictions under varied working conditions by adjusting the flow field parameters according to the specific working conditions. Therefore, it has supportive significance in optimization of the hydro-turbine structural turbine design as well as stabilizing operations at hydropower stations.
Oil film deposition characteristics and judgment of lubrication effect of splash lubricated gears
Feng-xia Lu,Kun Wei,Meng Wang,Mou Li,He-yun Bao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5
To study the oil film deposition characteristics of splash lubricated gears and determine whether their meshing area is completely lubricated, this study proposes the concept of judging the splash lubrication-deposition characteristics-inlet oil film thickness-lubrication effect. The critical oil film thickness that characterizes the full lubrication of the gear meshing area was obtained as 14.5428 μm by using elastohydrodynamic lubrication (EHL) theory. Based on computational fluid dynamics (CFD) method, based on the renormalization group (RNG) k-ɛ two-equation turbulence model, dynamic mesh model and volume of fluid (VOF) model, the numerical calculation of the intermediate gearbox in splash lubrication is carried out. The oil film deposition thickness of the gear tooth that was about to enter the meshing area was calculated to be 95.6207 μm. It was found that the meshing area is fully lubricated under the rated operating conditions.
Feng-xia Lu,Lijuan Yuan,Zhiqiang Zhao,Chun-lei Wang,He-yun Bao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9
On the basis of the computational fluid dynamics (CFD) method, this study calculates the surface convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing before and after the opening of the planetary gear of a fan-driven gearbox. A numerical fitting method is used to establish the calculation model of the convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing under the open-hole oilreturn condition. The convective heat transfer coefficients of each element are compared before and after the hole is bored, and the design method for the gearbox parameters with the objective of heat transfer performance is proposed. Result shows that the convective heat transfer coefficients of each element are increased after oil is returned from the hole of the planetary gear, and the change rate of the convective heat transfer coefficient of the raceway in the planetary gear bearing is the highest. When the aperture of the planetary gear is 7 mm and the number of holes is four, the heat transfer performance of the gearbox is the best. The maximum error between the convection heat transfer coefficient fitting formula value and the CFD simulation calculation result is 1.0558 %.
Yun-feng Zou,Zheng-yi Fu,Xu-hui He,Hai-quan Jing,Ling-yao Li,Hua-wei Niu,Zheng-qing Chen 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.4
Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.