Factors Affecting the Behaviour and Efficiency of a Targeted Jet Delivering Oil to a Bearing Lubrication System

2004 ◽  
Author(s):  
C. W. Lee ◽  
G. R. Johnson ◽  
P. C. Palma ◽  
K. Simmons ◽  
S. J. Pickering
Keyword(s):  
High Speed ◽  
Test Rig ◽  
Rotating Shaft ◽  
Factors Affecting ◽  
Oil Distribution ◽  
Jet Impact ◽  
Aero Engine ◽  
Visualization Techniques ◽  
Jet Structure ◽  
Engine Bearing

In this study oil delivery to an aero-engine bearing via a targeted jet was investigated using a bearing chamber test rig. The rig contains a high-speed rotating shaft of engine representative geometry within a stationary Perspex housing. Oil is collected from feedholes leading from scoops (scallops) on the shaft. The efficiency of this oil delivery system is dependent on jet structure and trajectory as it interacts with the rotating chamber flow. Flow visualization techniques and parametric tests are used to assess the influence of shaft speed and jet flowrate on oil collected through the feedholes. Detailed pictures of the structure of the jet in quiescent air are presented and compared with those from the rig, where there is a gas crossflow. As expected, jet break-up is accentuated in the rig. This influences jet impact behaviour at the scallop, and a consequent variation of oil distribution in the system is observed.

Influences on the Oil Split Between the Offtakes of an Aero-Engine Bearing Chamber

2012 ◽  
Author(s):  
Wolfram Kurz ◽  
Klaus Dullenkopf ◽  
Hans-Jörg Bauer
Keyword(s):  
Film Thickness ◽  
Test Rig ◽  
Oil Film ◽  
Aero Engine ◽  
The Impact ◽  
Engine Bearing

The aim of the presented work was to identify factors that influence the oil split between the two offtakes of a vented aero-engine bearing chamber. The impact of different vent and scavenge offtake designs was experimentally investigated with a test rig at the ITS. The generic bearing chamber was also equipped with ten film thickness sensors. The film measurements allowed a further evaluation of the mechanisms behind different oil splits. Two of the examined offtake features ensured a very constant oil split: a protruding vent and a covered ramp offtake. The latter also decreased the oil film thickness on the bearing chamber walls significantly. Furthermore, an influence of a non-uniform seal gap was detected which altered the oil split by several percent.

An Approach for Predicting the Flow Regime in an Aero Engine Bearing Chamber

2014 ◽  
Author(s):  
Wolfram Kurz ◽  
Hans-Jörg Bauer
Keyword(s):  
Flow Regime ◽  
Air Flow ◽  
Flow Regimes ◽  
Chamber Pressure ◽  
Test Rig ◽  
Oil Viscosity ◽  
Oil Film ◽  
Aero Engine ◽  
Oil Flow ◽  
Engine Bearing

The paper discusses an approach to predict the two-phase flow regime in an aero engine bearing chamber. In general, one of two distinct flow regimes can occur in a bearing chamber. At lower shaft speeds, the oil flow is only partially affected by the air flow, which is driven by the rotating shaft. At higher shaft speeds, however, the rotating air flow forces the oil film at the chamber walls to rotate, too. Thus, the two flow regimes correspond to two very different oil film distributions inside a bearing chamber presumably with significant consequences for the internal wall heat transfer. In order to determine the driving parameters for the flow regimes and the change between them, experiments were carried out with a bearing chamber test rig. With this test rig all relevant operating parameters as well as the geometry of the bearing chamber could be varied independently. The analysis of the experimental data allowed defining a general parameter which takes into account the chamber pressure, shaft speed, oil viscosity and chamber length. The influence of the oil flow rate and the overall dimensions are assessed qualitatively.

Thrust Load Measurement on Aero-Engine Bearing

1985 ◽  
Vol 107 (1) ◽  
pp. 181-186
Author(s):  
K. Jimboh ◽  
H. Aono ◽  
T. Chikata ◽  
Y. Hagiwara ◽  
K. Nakasu ◽  
...  
Keyword(s):  
High Speed ◽  
Open Space ◽  
Transient Condition ◽  
Load Cells ◽  
Aero Engine ◽  
Unit Cells ◽  
Thrust Measurement ◽  
Thrust Load ◽  
Engine Development ◽  
Engine Bearing

Aero-engine bearings operate in an extraordinarily high speed range (high DN number) and severe conditions. It is especially necessary to measure and adjust the bearing thrust load in the engine development phase, but it is very difficult to measure the thrust load accurately, because bearings and bearing housings are subjected to elevated temperature and oil environment. Open space permitted for installation of thrust measurement transducers is small and limited around the bearing housing. We tried to measure the thrust load by applying “Unit Cells,” which are installed between bearing and bearing housing. “Unit Cells” which have been specially designed to measure the bearing thrust load are very small and temperature-compensated load cells. We have been successful in measuring the actual thrust load using the above “Unit Cells,” both in the steady-state and transient condition. Repeatability and hysteresis of the data have been satisfactory. We have established the effect of seal clearance on the thrust load by the measurement. We also have obtained the dynamic characteristics of the thrust load versus rotor speed in low bypass fan engines. Procedure and obtained data are presented in detail.

Computational Study of a Customised Shallow-Sump Aero-Engine Bearing Chamber With Inserts to Improve Oil Residence Volume

2017 ◽  
Author(s):  
Akinola A. Adeniyi ◽  
Budi Chandra ◽  
Kathy Simmons
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Computational Study ◽  
Perforated Plate ◽  
Flow Characteristics ◽  
Positive Pressure ◽  
High Speed Engine ◽  
Aero Engine ◽  
Computational Fluid Dynamics Cfd ◽  
Engine Bearing

An aero-engine bearing chamber is a structure that is used to contain and collect oil used in lubricating and cooling the bearings supporting the high-speed engine shafts. There are various bearings in an aero-engine. Within the bearing chambers, there are typically the bearings, rotating shafts, seals and gears (in some designs). The walls of the bearing chamber are stationary and there are vents and sumps to take out the oil, via an offtake pipe, and the sealing air. The oil collected via the sump and vents is recycled and used again in the loop. To prevent oil degradation and reduce chance of coking in the chamber, it is desired that all of the oil goes through the recycling loop, with no oil staying longer than necessary in the chamber. The sealing air is used to maintain a positive pressure to keep the oil within the chamber. The flow inside a bearing chamber is highly turbulent and consists of a rotating mixture of oil and air. A smaller amount of the oil, mostly as oil-droplets, exits at the vents and is separated from the air using de-aerators [1]. It is expected that by gravity, most of the oil collects at the sump and can be easily scavenged. This is provided the sump can be large enough. The geometry of a bearing chamber is, however, complex largely because of space limitations. It is very important that oil is not resident longer than necessary to prevent over-heating and therefore deterioration or coking. Experimental observations by Chandra & Simmons [2], have shown that bearing chambers with deep sumps perform better that those with shallow sumps. Since shallow sumps are inevitable, a number of innovative studies have been done to improve bearing chamber designs. The presence of air in the oil (e.g. as bubbles) reduces the efficiency of the scavenging pump. Other factors such as oil momentum and windage can take oil away from the off-take pipe potentially increasing oil residence volume. Chandra & Simmons [2] placed inserts such as grille cover, perforated plate, etc, on a side of the bearing wall and improvements in the residence volume were seen. In this work, we are looking at a detailed computational fluid dynamics (CFD) simulation of one of the inserts that performed well. This will aid understanding of the flow characteristics of using an insert to improve oil residence in a bearing chamber.

Windage Losses of a Meshing Gear Pair Measured at Different Working Conditions

2018 ◽  
Author(s):  
D. Massini ◽  
T. Fondelli ◽  
B. Facchini ◽  
L. Tarchi ◽  
F. Leonardi
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Fluid Dynamic ◽  
Lubrication System ◽  
Test Rig ◽  
Rotating Speed ◽  
Aero Engine ◽  
Speed Up ◽  
Oil Jet

In recent years the aero-engine community is looking towards the reduction of specific fuel consumption by increasing the efficiency of gearing systems. Considering their weight contribution, internal power losses and lubrication requirements, they have indeed a direct impact on the engine overall efficiency. Even though nowadays gears have reached very high efficiencies, over 99%, all the power dissipated through losses is converted into heat that must be removed by the lubrication system. Heat reduction is hence beneficial for minimizing lubrication system dimensions that is crucial in aero engine applications where it is mandatory to limit the weight of every component. Among the sources of loss, two main categories may be distinguished: load dependent and load independent losses. The first ones are due to the transmission of torque and have been deeply studied in the last years, the latter are related to fluid-dynamic interaction between gears and the surrounding environment, they are negligible at low pitch line velocities, but become very important in high speed applications, typical of turbomachinery. This work deals with an experimental investigation of the load independent losses due to a couple of spur meshing gears working at different conditions in presence of an oil-jet lubrication system. The test rig allows the gears to rotate, at different velocities up to 15000 rpm, in a controlled environment contained in a sealed box. Test rig pressure can be imposed (0.3–1.0 bar) and monitored as well as the oil jet conditions, in terms of mass flow rate (jet volume flow rate up to 1.65 litres per minute), temperature (80–140 °C) and inclination angle. A high precision bearing-less torque meter, equipped with a speedometer, was exploited to measure at the same time the torque losses and rotating speed. Results of the experimental survey allowed a better understanding of load independent losses at pitch line speed up to 100 m/s and in different environmental conditions.

Further Computational Investigations Into Aero-Engine Bearing Chamber Off-Take Flows

2010 ◽  
Author(s):  
Adam Robinson ◽  
Carol Eastwick ◽  
Herve´ Morvan
Keyword(s):  
Experimental Work ◽  
Symmetry Plane ◽  
Two Phase ◽  
Pipe System ◽  
Aero Engine ◽  
Gravity Driven ◽  
Computational Fluid Dynamics Cfd ◽  
Modelling Assumptions ◽  
Static Head ◽  
Engine Bearing

Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper a simplified geometry of a sump section, here simply made of a radial off-take port on a walled inclined plane, is analysed computationally. This paper follows on work presented within GT2008-50634. In the previous paper it was shown that simple gravity draining from a static head of liquid cold be modelled accurately, for what was akin to a deep sump situation fond in integrated gear boxes for example. The work within this paper will show that the draining of flow perpendicular to a moving film can be modelled. This situation is similar to the arrangements found in transmission bearing chambers. The case modelled is of a walled gravity driven film running down a plane with a circular off-take port, this replicates experimental work similar to that reported in GT2008-50632. The commercial computational fluid dynamics (CFD) code, Fluent 6 [1] has been employed for modelling, sing the Volume of Fluid (VOF) approach of Hirt and Nichols [2, 3] to capture the physics of both the film motion and the two phase flow in the scavenge pipe system. Surface tension [4] and a sharpening algorithm [5] are used to complement the representation of the free surface and associated effects. This initial CFD investigation is supported and validated with experimental work, which is only depicted briefly here as it is mainly sued to support the CFD methodology. The case has been modelled in full as well as with the use of a symmetry plane running down the centre of the plane parallel to the channel walls. This paper includes details of the meshing methodology, the boundary conditions sued, which will be shown to be of critical importance to accurate modelling, and the modelling assumptions. Finally, insight into the flow patterns observed for the cases modelled are summarised. The paper further reinforces that CFD is a promising approach to analysing bearing chamber scavenge flows although it can still be relatively costly.

scholarly journals The Influence of the Axial Rub Added in the Radial Rub on the Wear of the Seal Fins during the High Speed Rub of Labyrinth-Honeycomb Seal

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1997
Author(s):  
Bin Lu ◽  
Haijun Xuan ◽  
Xiaojian Ma ◽  
Fangjun Han ◽  
Weirong Hong ◽  
...  
Keyword(s):  
Wear Rate ◽  
High Speed ◽  
State Of The Art ◽  
Negative Influence ◽  
Axial Thrust ◽  
Cross Sectional ◽  
Honeycomb Seal ◽  
Aero Engine ◽  
Honeycomb Seals ◽  
Clearance Change

Labyrinth-honeycomb seals are a state-of-the-art sealing technology commonly used in aero-engine interstage seal. The undesirable severe rub between the seal fins and the honeycomb due to the clearance change may induce the cracking of the seal fins. A pervious study investigated the wear of the seal fins at different radial incursion rates. However, due to the axial thrust and mounting clearance, the axial rub between the seal fins and the honeycomb may occur. Hence, this paper focuses on the influence of the axial rub added in the radial rub on the wear of the seal fins. The rub tests results, including rubbing forces and temperature, wear rate, worn morphology, cross-sectional morphology and energy dispersive spectroscopy results, are presented and discussed. Overall, the participation of the axial rub leads to higher rubbing forces, temperature, and wear rate. The tribo-layer on the seal fin is thicker and the cracks are more obvious at high axial incursion rate. These phenomena indicate the axial rub has a negative influence on the wear of the seal fins and should be avoided.

Reynolds-averaged Navier–Stokes simulation of hydrofoil effects on hydrodynamic coefficients of a catamaran in forced oscillation

2016 ◽  
Vol 231 (2) ◽  
pp. 364-383
Author(s):  
Amin Najafi ◽  
Mohammad Saeed Seif
Keyword(s):  
High Speed ◽  
Experimental Approach ◽  
Navier Stokes ◽  
Hydrodynamic Coefficients ◽  
Laboratory Equipment ◽  
Factors Affecting ◽  
High Frequencies ◽  
Frequency Independent ◽  
Reynolds Averaged Navier Stokes

Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using Reynolds-averaged Navier–Stokes method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly and requires meticulous laboratory equipment; therefore, utilizing the numerical methods and developing a virtual laboratory seem highly efficient. In this study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency-independent especially at high frequencies.

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