Analysis on temperature field of friction pair of aviation friction clutch based on different groove shapes of friction disk

He-yun Bao,Weidi Kong,Xiaonan Hou,Rupeng Zhu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

To examine the influence of the groove shape of a friction disk on the transient temperature field in the engagement process of aviation wet friction clutch, a transient thermal analysis model of friction clutch was established, and the application method of thermal boundary conditions, including the calculation of convective heat transfer coefficient and heat flux density, was studied. The transient heat loading process was established by the partition method of friction disk and steel disk. The temperature characteristics of wet clutch friction pairs with different groove shapes during the engagement process were analyzed and tested on an SAE#2 testing machine. Results show that when the clutch is engaged, the temperature of the friction pair composed of two-way parallel groove, three-way parallel groove, and waffle groove friction disk increases continuously at first and finally decreases slightly; the highest temperature of the friction disk and steel disk is at the ring near the outer ring of the friction disk;and the waffle groove friction disk is more suitable for aviation wet friction clutch.

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.

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.

Calculation method of radial displacement in the engaging process of wet friction clutch

He-yun Bao,Xiang Li,Wei Huang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

The radial vibration of the wet friction clutch has a certain influence on the engagement characteristics during the engagement process, and this influence cannot be ignored. This paper takes a variable speed configuration as the research object, establishing a six-degree-of-freedom equivalent bending-torsional vibration model of the variable speed transmission system, and studies the calculation method of the meridional displacement during the engagement process of the clutch. The Runge-Kutta method is used in this paper to solve the dynamic model and analyzes the relationship between the joint state and the radial vibration amplitude. The verified experiment is then conducted. Simulation and test results show the following: the clutch eccentric distance and the radial vibration amplitude, as well as the mass of the driven disc of the clutch and the radial vibration amplitude, all increase. The supporting rigidity of the clutch becomes large, the amplitude of radial vibration becomes small.

Artemongolins A–K, undescribed germacrane-guaiane sesquiterpenoid dimers from Artemisia mongolica and their antihepatoma activities

Chong Shang,Yun-Bao Ma,Yuan Wang,Xiao-Feng He,Tian-Ze Li,Ji-Jun Chen 대한약학회 2023 Archives of Pharmacal Research Vol.46 No.10

Artemongolins A–K (1–11), which are undescribed sesquiterpenoid dimers, were obtained from Artemisia mongolica and characterized through comprehensive spectral data, including HRESIMS, IR, 1D and 2D NMR, and ECD calculations. The absolute configurations of compounds 1, 4, and 7 were undoubtedly determined by a single-crystal X-ray crystallography. Artemongolins A–K (1–11) featured a rare 5/7/5/5/5/10 hexacyclic system composed of a germacrene and a guaianolide by a fused 2-oxaspiro[4,4]nonane-1-one ring system. Antihepatoma evaluation against three human hepatoma cell lines demonstrated that the most active compounds 5 and 6 displayed inhibitory activity with IC50 values of 88.6 and 57.0 (HepG2), 59.1 and 26.4 (Huh7), and 67.5 and 32.5 (SK-Hep-1) µM, respectively.

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.

Parameter design method for the heat transfer performance of a fan-driven gearbox under planetary gear opening and oil-return 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 %.

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.