Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1995 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Oil Flow ◽  
Secondary Air ◽  
Aero Engines ◽  
Film Flows

For the design of secondary air and lubrication oil systems a sufficient knowledge on two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fibre-optic LDV-setup, measurements of oil film velocity profiles have been performed in our high speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches which have been derived from a force balance at a liquid film element, including geometrical conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1996 ◽  
Vol 118 (3) ◽  
pp. 578-583 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Geometric Conditions ◽  
Oil Flow ◽  
Secondary Air ◽  
Film Flows

For the design of secondary air and lubrication oil systems, a sufficient knowledge of two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fiber-optic LDV setup, measurements of oil film velocity profiles have been performed in our high-speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches, which have been derived from a force balance at a liquid film element, including geometric conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

scholarly journals Two-Phase Air/Oil Flow in Aero-Engine Bearing Chambers – Assessment of an Analytical Prediction Method for the Internal Wall Heat Transfer

1999 ◽  
Vol 5 (3) ◽  
pp. 155-165 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Prediction Method ◽  
Analytical Prediction ◽  
Two Phase ◽  
Gravity Forces ◽  
Lubrication Oil ◽  
Oil Flow ◽  
Aero Engines ◽  
Film Flows ◽  
Engine Bearing

The present paper gives a theoretical outline on liquid film flows driven by superimposed effects of interfacial shear and gravity forces and discusses related heat transfer processes which are relevant for lubrication oil systems of aero engines. It is shown that a simple analytical approach is able to predict measured heat transfer data fairly well. Therefore, it offers scope for improvements within the analysis of bearing chamber heat transfer characteristics as well as for appropriate studies with respect to other components of the lubrication oil system such as vent pipeline elements.

Experimental Characterization of the Flow Instabilities of a Mixed-Flow Multiphase Pump Operating Air and Water Through Local Visualization and Analysis of Dynamic Measurements

2015 ◽  
Author(s):  
Alberto Serena ◽  
Lars E. Bakken
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Operating Conditions ◽  
Test Facility ◽  
Two Phase ◽  
Flow Mechanisms ◽  
Local Measurements ◽  
Specific Geometry ◽  
Promising Development

Part load operation of pumps generates flow and machine instabilities, which are not desirable and should be avoided as they result in premature wear and mechanical problems. Two-phase flow introduces additional challenges, both at the design and operational stages, due to the different phase behavior and mutual interaction. The phenomena involved present an intermittent character and are strongly dependent on the specific geometry and operating conditions. Despite the recent promising development of numerical simulations capabilities, an accurate characterization of the flow mechanisms still relies on real tests, which are needed to validate the numerical models too. An advanced laboratory test facility built at the Norwegian University of Science and Technology provides the required optical access to the pump channels, and high-speed recordings, along with local measurements of the pressure pulsations, allow to describe the flow structures in terms of location, length and time scales, and relate them to overall machine measurements, such as flow, pressure and torque. This provides a wide collection of test data of great value for a further understanding of the surging phenomenon, the development of a surging onset prediction model and a control strategy. Tests are performed covering the whole range of flow rates; a characteristic surging condition is identified and described in the article.

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

Characterization of Two-Phase Flow Patterns in Small Round Tubes

2014 ◽  
Vol 525 ◽  
pp. 256-259
Author(s):  
Wen Peng Hong ◽  
Guo Qing Niu ◽  
Ming Liang Jin
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
High Speed Video ◽  
Video Systems ◽  
Small Tube

To investigate flow characteristics by high speed video systems, experimental study was conducted to gas-liquid two-phase flow in horizontal round small tube with diameter of 5.5 and 2.6 mm, the typical flow pattern images were obtained, but stratified flow of the conventional size horizontal channel had not been discovered. Gas and liquid superficial velocities range from 0.1 to 100 ms-1, and 0.01to 10.0 ms-1 respectively. Flow patterns for co-current flow of air-water mixtures in horizontal round tubes are determined by high-speed video analysis to develop flow regime maps and the transitions between these flow regimes. Comparisons with the relevant literatures show that diameter and surface tension effects play an important role in determining the flow patterns and transitions between them.

An Investigation into the Performance of Dynamically Loaded Journal Bearings: Theory

1966 ◽  
Vol 181 (2) ◽  
pp. 1-8 ◽  
Author(s):  
T. Lloyd ◽  
R. Horsnell ◽  
H. McCallion
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Rotational Velocity ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Maximum Pressure ◽  
Oil Film ◽  
Pressure Distributions ◽  
Routine Design ◽  
Oil Flow

The main and big-end bearings in reciprocating machinery are subjected to loads varying both in magnitude and direction. At present the only guidance available to the designer of such bearings may be a comparison of bearing performance in similar engines and it is fundamental to the introduction of improved design criteria that a prediction of the journal locus, peak pressures, and oil flow be readily available for a proposed geometry and loading. In this paper a numerical method of solution of this problem, utilizing a high-speed digital computer with a large one-level store, is described. The method rests on the assumption of isothermal conditions in the oil film and on the unimportance of the inertia forces associated with the journal accelerations. Numerical solutions of the Reynolds equation are obtained and stored for both wedge and squeeze film terms, at a number of journal eccentricities, by using an iterative method. The oil film force and the derivatives of this force with respect to both the journal centre position and its velocity are then found by summing these pressure distributions in the required proportions. At intermediate eccentricities, the required pressure distributions are obtained by interpolation before they are summed. The journal centre locus is obtained from a step-by-step solution of two simultaneous, ordinary differential equations involving the oil film data and the external load. In addition to the locus, the maximum pressure at any instant, the oil flow, and the friction work are calculated. For big-end bearings, journal rotational velocity is not constant and this is allowed for in the analysis. The computer program described needs no input apart from the bearing geometry and operating conditions and, because of refinement of the iteration and the integration procedures, it is economic to use for routine design studies.

Investigation of Air-Oil-Thermal Distribution in Floating Bush Bearing

2017 ◽  
Author(s):  
Yan Wang ◽  
Xiaodong Ren
Keyword(s):  
Thermal Effect ◽  
Thermal Effects ◽  
High Speed ◽  
Low Cost ◽  
Prediction Method ◽  
Cfd Modeling ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Two Phase ◽  
Oil Film

Owing to their low cost and reduced power losses, floating bush bearings are extensively used in high-speed rotors. The advantages are mainly the result of the rotation of the bush. When shaft speed is within a low speed range, bush rotation speed increases linearly with shaft speed. However, the bush-to-shaft speed ratio decreases sharply when the shaft speed reaches a certain range. The mechanism of this phenomenon is not completely clear yet, and a precise prediction method has not been established. The traditional theoretical model predicts that the speed ratio remains constant even when the shaft speed reaches the certain range. Some researchers have attempted to improve the prediction model by considering thermal effect on the assumption that a temperature increase decreases the viscosity of the inner oil film and consequently reduces the speed ratio. However, temperature rise alone is insufficient to induce that much drop of speed ratio. This paper focuses on the effect of air invasion flow in the inner oil film from the axial ends and evaluates the importance of air invasion and thermal effects. Computational fluid dynamics (CFD) modeling is adopted in this study because of its capacity to handle complicated calculation domain and calculate air-oil two-phase flow. Three series of CFD simulations with different models are conducted. These models consider the thermal effect (thermal model), the air invasion effect (air model), and the combination of the thermal and air invasion effects (hybrid model). CFD results of the different models are compared to weigh the importance of each effect. The CFD calculation indicates that a substantial amount of air invades the inner oil film when the shaft speed reaches a certain range. Speed ratio drop is not caused by a single factor, but it is the result of the combination of the air invasion and thermal effects. Air invasion, which researchers previously ignored, plays a greater role than the thermal effect.

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