Numerical and Experimental Study for Unsteady Oil Film Thickness of the Rotating Cylinder Chamber Wall

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Zhao Jingyu ◽  
Liu Zhenxia
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Thickness ◽  
Rotation Speed ◽  
Film Formation ◽  
Rotating Cylinder ◽  
Chamber Wall ◽  
Wall Heat Transfer ◽  
Oil Film ◽  
Oil Flow

The oil film thickness on the bearing chamber wall directly affects the wall heat transfer efficiency, so a fundamental study on the motion of oil film on the rotating cylinder has been conducted to this end. On the one hand, the rotating cylinder test rig was designed, and an ultrasonic measurement system was established to measure the dynamic oil film thickness. On the other hand, the unsteady oil film heat and mass transfer movement model was also established, and the numerical simulation to solve oil film motion by using computational fluid dynamic (CFD) commercial software was carried out. Meanwhile, on the basis of study on the oil film formation process and film thickness verification, the oil film distributions on the chamber wall with rotation speed and oil flow rate were analyzed and studied. Results show that the oil film on the rotating chamber wall experiences a development process from the oil film formation to basic stability, about 1.0 s in this paper. And comparison between the numerical and experimental data shows that the maximum error between experimental data and numerical simulation is 7.76%. Moreover, for the oil film distributions in the stable state, oil film thickness shows a trend of decreasing with the increasing of rotation speed, but increasing with the increasing of oil flow rate. The research here will provide the basis for subsequent study of the interaction between oil film motion and the wall heat transfer.

Numerical Modeling of Unsteady Oil Film Motion Characteristics in Bearing Chambers

2015 ◽  
Vol 32 (3) ◽  
Author(s):  
Jingyu Zhao ◽  
Zhenxia Liu ◽  
Yaguo Lu ◽  
Jianping Hu
Keyword(s):  
Film Thickness ◽  
Theoretical Study ◽  
Rotation Speed ◽  
Three Dimensional ◽  
Lubricating Oil ◽  
Flow State ◽  
Oil Film ◽  
Model Based ◽  
Oil Flow ◽  
Motion Characteristics

AbstractTo obtain motion characteristics of the lubricating oil film on the aero-engine bearing chamber wall, a complete mathematical model based on theoretical study to solve three-dimensional unsteady oil film motion was established. On the basis of verifying the rationality of the computational model, the variations of the oil film thickness, velocity and temperature with the rotation speed and lubricating oil flow were analyzed and studied. The numerical results show that the following: In the stable oil film flow state, the oil film thickness shows a decreasing trend with increase in rotation speed and an increasing trend with increase in the lubricating oil flow. Particularly, comparison with the experimental work shows that the proposed numerical model based on theoretical study to solve unsteady oil film motion is a valuable technical means for the study of oil film movement mechanism and the design of actual bearing chamber.

scholarly journals The Piston Ring-Cylinder Bore Interface Leakage of Bent-Axis Piston Pumps Based on Elastohydrodynamic Lubrication and Rotation Speed

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lvjun Qing ◽  
Lichen Gu ◽  
Yan Wang ◽  
Wei Xue ◽  
Zhufeng Lei
Keyword(s):  
Film Thickness ◽  
Piston Ring ◽  
Rotation Speed ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Proposed Model ◽  
Minimum Film Thickness ◽  
Oil Flow ◽  
Discharge Pressure ◽  
Cylinder Bore

The bent-axis piston pump is the core component of electrohydrostatic actuators (EHA) in aerospace applications, and its wear of key friction interfaces is greatly related to the healthy operation of pumps. The leakage of the piston ring-cylinder bore interface (PRCB), as the important part of the return oil flow of the pump house that commonly assesses the wear of key friction interfaces in piston pumps, is changed with the rotation speed. Thus, the wear of key friction interfaces is usually inaccurate by using the leakage of PRCB. In order to obtain the relationship between the PRCB leakage and the rotation speed, an elastohydrodynamic lubrication model is proposed. First, the proposed model includes a minimum film thickness model of PRCB to analyze the dynamic change of oil film of PRCB when subject to the elastohydrodynamic lubrication. After that, a mathematical model of PRCB is induced by combining the minimum film thickness model with the flow equation, which helps produce the effects of the oil film on the leakage of PRCB. The proposed model is verified by numerical simulation and experiment. The results show that the leakage of PRCB has a negative effect on the return oil flow of the pump case in the range of rotation speed of 700–1300 r/min and discharge pressure of 10–20 MPa. Furthermore, the leakage of PRCB is proportional to the rotation speed, but the return oil flow of the pump case is decreased. The effects of rotation speed are enhanced under the high discharge pressure conditions.

scholarly journals Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 747
Author(s):  
Taewook Ha ◽  
Dong Kyu Kim
Keyword(s):  
Electric Vehicle ◽  
Flow Rate ◽  
Film Formation ◽  
Formation Rate ◽  
Cooling Performance ◽  
Oil Film ◽  
Injection Method ◽  
Cooling Method ◽  
Oil Flow ◽  
Oil Injection

The oil injection method was studied to maximize the cooling performance of an electric vehicle motor with a hairpin winding. The cooling performance of the motor using the oil cooling method is proportional to the contact area of the oil and the coil. A numerical analysis was conducted to examine the effect of the spray nozzle type on the oil flow. The dripping nozzle forms the thickest oil film on the coil, making it the most effective for cooling of hairpin-type motors. Subsequently, an experimental study was conducted to optimize the nozzle diameter and number of nozzles. When the inlet diameter and number was 6.35 mm and 6, the oil film formation rate was 53%, yielding the most uniform oil film. Next, an experiment was performed to investigate the effects of the oil temperature and flow rate on the oil flow. The oil film formation rate was the highest (83%) when the oil temperature was 40 °C and the flow rate was 6 LPM.

Influence of High Rotational Speeds on Heat Transfer and Oil Film Thickness in Aero-Engine Bearing Chambers

1994 ◽  
Vol 116 (2) ◽  
pp. 395-401 ◽  
Author(s):  
S. Wittig ◽  
A. Glahn ◽  
J. Himmelsbach
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Thermal Loading ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Facility ◽  
High Rotational Speed ◽  
Oil Film ◽  
Aero Engine

Increasing the thermal loading of bearing chambers in modern aero-engines requires advanced techniques for the determination of heat transfer characteristics. In the present study, film thickness and heat transfer measurements have been carried out for the complex two-phase oil/air flow in bearing chambers. In order to ensure real engine conditions, a new test facility has been built up, designed for rotational speeds up to n = 16,000 rpm and maximum flow temperatures of Tmax = 473 K. Sealing air and lubrication oil flow can be varied nearly in the whole range of aero-engine applications. Special interest is directed toward the development of an ultrasonic oil film thickness measuring technique, which can be used without any reaction on the flow inside the chamber. The determination of local heat transfer at the bearing chamber housing is based on a well-known temperature gradient method using surface temperature measurements and a finite element code to determine temperature distributions within the bearing chamber housing. The influence of high rotational speed on the local heat transfer and the oil film thickness is discussed.

Thermal Analysis of Flow in the Deformation Phase of Liquid Lubricated Plane Strain Forging

2000 ◽  
Vol 122 (4) ◽  
pp. 746-751 ◽  
Author(s):  
V. K. Bhatt
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Film Thickness ◽  
Incompressible Fluid ◽  
Plane Strain ◽  
Simple Form ◽  
Energy Equation ◽  
Film Formation ◽  
Lubricant Film Thickness ◽  
Deformation Phase

The generalized energy equation is reduced into a simple form for conduction and convection modes of heat transfer across a hydrodynamic incompressible fluid film in the deformation phase of plane-strain forging. Expressions for the temperature, velocity, and flow distributions are obtained by solving the energy equation with appropriate boundary conditions. Application of this analysis is illustrated for the film formation process in the deformation phase of liquid lubricated plane strain forging. The analysis indicates that the Peclet number plays an important role in deciding the variation of lubricant film thickness with position and time in the deformation phase. [S0742-4787(00)02504-2]

Internal Bearing Chamber Wall Heat Transfer as a Function of Operating Conditions and Chamber Geometry

1999 ◽  
Author(s):  
Stefan Busam ◽  
Axel Glahn ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Chamber Wall ◽  
Test Facility ◽  
Detailed Knowledge ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Dimensional Parameter ◽  
Secondary Air

Increasing efficiencies of modern aero-engines are accompanied by rising turbine inlet temperatures, pressure levels and rotational speeds. These operating conditions require a detailed knowledge of two-phase flow phenomena in secondary air and lubrication oil systems in order to predict correctly the heat transfer to the oil. It has been found in earlier investigations that especially at high rotational speeds the heat transfer rate within the bearing chambers is significantly increased with negative effects on the heat to oil management. Furthermore, operating conditions are reached where oil coking and oil fires are more likely to occur. Therefore, besides heat sources like bearing friction and churning, the heat transfer along the housing wall has to be considered in order to meet safety and reliability criteria. Based on our recent publications as well as new measurements of local and mean heat transfer coefficients, which were obtained at our test facility for engine relevant operating conditions, an equation for the internal bearing chamber wall heat transfer is proposed. Nusselt numbers are expressed as a function of non-dimensional parameter groups covering influences of chamber geometry, flow rates and shaft speed.

scholarly journals Liquid Film Thickness Estimation using Electrical Capacitance Tomography

2014 ◽  
Vol 14 (1) ◽  
pp. 8-15 ◽  
Author(s):  
Ziqiang Cui ◽  
Chengyi Yang ◽  
Benyuan Sun ◽  
Huaxiang Wang
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
High Speed ◽  
Liquid Film Thickness ◽  
Electrical Capacitance Tomography ◽  
Electrical Capacitance ◽  
Oil Film ◽  
Thickness Estimation ◽  
Oil Flow ◽  
Capacitance Tomography

Abstract In air/oil lubrication systems, the flow parameters, e.g., flow pattern, liquid film thickness, and air/oil flow rate, are of great importance to the transportation efficiency. In most cases, the on-going two-phase flow is annular flow with the oil moving along the tube wall and the air travelling at high speed in the center. This usually results in the formation of a thin oil film, the thickness of which is a key parameter determining the efficiency of the lubrication system. As the oil film thickness of the on-going air/oil flow varies dynamically, there is actually no applicable method for a non-intrusive test. In this paper, the use of electrical capacitance tomography (ECT) to investigate the air/oil flow has been studied. Capacitance measurements are made from an externally mounted electrode array in a non-invasive and non-intrusive manner. Both average and distributed oil film thicknesses can be calculated from the reconstructed ECT images. Simulation and experimental results show that the ECT technique can provide satisfactory results of online oil film thickness estimation

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