Experiments on a Large Flexure Pivot Journal Bearing: Summary of Test Results and Comparison With Predictions

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Giuseppe Vannini ◽  
Filippo Cangioli ◽  
Enrico Ciulli ◽  
Matteo Nuti ◽  
Paola Forte ◽  
...  
Keyword(s):  
High Speed ◽  
Maximum Load ◽  
Numerical Code ◽  
Test Facility ◽  
Temperature Management ◽  
Unit Load ◽  
Rolling Element ◽  
Oil Flow ◽  
Static And Dynamic Loads ◽  
The University

Abstract Flexure pivot® journal bearings (FPJBs) have typically been used in small high-speed applications such as integrally geared compressors and multistage high-speed compressors, where the temperature management and the rotordynamic stability of the machine are the main targets. Nevertheless, the need for high-speed applications may also be applicable to large compressors and for this reason a large 280 mm diameter four-pad FPJB with L/D = 0.7 has been designed, built, and tested by the Authors. The test facility is a novel rig, setup at the University of Pisa, that includes a floating test bearing and a rigid rotor supported by two stiff rolling element bearings. Both static and dynamic loads are applied through hydraulic actuators, capable of 270 kN static and 40 kN overall dynamic load. The instrumentation can measure all the relevant test boundary conditions as well as the static and dynamic quantities that characterize the bearing performance. This paper presents the results from a test campaign conceived to explore not only the design conditions (7000 rpm rotational speed and 0.75 MPa unit load) but also the sensitivity to the unit load (from 0.2 MPa minimum load up to 2.2 MPa maximum load) as well as the oil flow. The results are discussed and compared with predictions from an existing numerical code.

Experiments on a Large Flexure Pivot Journal Bearing: Summary of Test Results and Comparison With Predictions

2019 ◽  
Author(s):  
Giuseppe Vannini ◽  
Filippo Cangioli ◽  
Enrico Ciulli ◽  
Matteo Nuti ◽  
Paola Forte ◽  
...  
Keyword(s):  
High Speed ◽  
Maximum Load ◽  
Numerical Code ◽  
Test Facility ◽  
Temperature Management ◽  
Unit Load ◽  
Rolling Element ◽  
Oil Flow ◽  
Set Up ◽  
The University

Abstract Flexure Pivot® Journal Bearings (FPJBs) have typically been used in small high-speed applications such as Integrally Geared Compressors (IGCs) and multistage high-speed compressors, where the temperature management and the rotordynamic stability of the machine are the main targets. Nevertheless, the need for high-speed applications may also be applicable to large compressors and for this reason a large 280mm diameter four-pad FPJB with L/D = 0.7 has been designed, built and tested by the Authors. The test facility is a novel rig, set up at the University of Pisa, that includes a floating test bearing and a rigid rotor supported by two stiff rolling element bearings. Both static and dynamic loads are applied through hydraulic actuators, capable of 270kN static and 40kN overall dynamic load. The instrumentation can measure all the relevant test boundary conditions as well as the static and dynamic quantities that characterize the bearing performance. This paper presents the results from a test campaign conceived to explore not only the design conditions (7000rpm rotational speed and 0.75MPa unit load) but also the sensitivity to the unit load (from 0.2MPa minimum load up to 2.2MPa maximum load) as well as the oil flow. The results are discussed and compared with predictions from an existing numerical code.

The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber

2005 ◽  
Vol 127 (1) ◽  
pp. 182-186 ◽  
Author(s):  
Michael Flouros
Keyword(s):  
Power Consumption ◽  
High Speed ◽  
Air Flow ◽  
Flow Chamber ◽  
Chamber Pressure ◽  
Power Losses ◽  
Rolling Element ◽  
Oil Flow ◽  
The Impact ◽  
Circle Diameter

Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine DN∼2×106. The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.

Bearing Skidding Detection for High Speed and Aero Engine Applications

2021 ◽  
Author(s):  
Azzedine Dadouche ◽  
Rami Kerrouche
Keyword(s):  
High Speed ◽  
Power Losses ◽  
Severe Damage ◽  
Roller Bearings ◽  
Custom Made ◽  
Rolling Element ◽  
Aero Engine ◽  
Oil Flow ◽  
Rolling Elements ◽  
Surface Distress

Abstract Rolling-element bearings (REB) can develop severe damage due to skidding (slipping) between the rolling elements and bearing races. Skidding can be described as gross sliding between the bearing surfaces in relative motion and can result in significant surface distress such as smearing, especially at light loads and high rotational speeds. Under these conditions, skidding occurs between the rolling elements and the bearing races, leading to increased wear (higher friction coefficient), elevated bearing temperature, significant power losses and reduced service life of the bearing. The main objective of this study is to investigate the significance of various sensing technologies (induction, vibration, ultrasound, acoustic and optical) in detecting skidding in standard series roller bearings as well as custom-made roller bearings for aero engine applications. The bearings have a bore diameter of 60 mm and 90 mm, respectively. Jet and under race lubrication techniques have been used to supply oil to the bearings under test. The custom-made aero engine test bearing features special channels to allow under race lubrication of the rollers/races contacts as well as the cage land. The effect of radial load, rotational speed and oil flow on roller skidding have also been investigated and analyzed. Tests have been performed on a dedicated high speed experimental bearing facility and data was recorded using a commercially-available data acquisition system.

Experimental Investigation of Oil Shedding From an Aero-Engine Ball Bearing at Moderate Speeds

2017 ◽  
Author(s):  
R. Santhosh ◽  
Jee Loong Hee ◽  
Kathy Simmons ◽  
Graham Johnson ◽  
David Hann ◽  
...  
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Flow Regimes ◽  
Test Facility ◽  
Research Centre ◽  
Rotating Disks ◽  
Axial Loads ◽  
Aero Engine ◽  
Bearing Assembly ◽  
The University

In civil aero-engine transmission system bearings are used for shaft location and load support. An experimental test facility in the University of Nottingham’s Gas Turbine Transmissions Research Centre (G2TRC) was designed and commissioned to investigate oil behaviour as it exits an engine-representative ball bearing. In the rig, oil is delivered to the bearing inner race and cage via under-race feed at three delivery locations i.e. front, mid and rear of the bearing assembly. An electromagnetic load system is designed and implemented to allow engine representative axial loads up to 35 kN to be applied to the bearing. This paper details the rig design including the load and under-race lubrication systems and gives information about bearing oil shedding mechanisms observed. In this phase of testing high speed images are acquired at shaft speeds between 1000 and 7000 rpm at an oil flowrate of 5.2 litres per minute and bearing axial load of 10 kN. The work presented here focusses on oil shedding from the bearing cage. Oil shedding behaviour from aeroengine ball bearing is identified to share many similarities to that observed in the past for shedding from rotating disks and cups. However, it is shown that it not possible to predict the conditions at which transition in flow regimes will occur for the aeroengine bearing on the basis of correlations for simpler geometries (spinning disks and cups). The work presented here is the first observation of flow regimes in an aeroengine ball bearing involving high-resolution highspeed imaging.

scholarly journals Nonlinear Response and Stability of an Experimental Overhung Compressor Mounted With a Squeeze Film Damper

2020 ◽  
Author(s):  
William J. Gooding ◽  
Matthew A. Meier ◽  
Edgar J. Gunter ◽  
Nicole L. Key
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Test Facility ◽  
Squeeze Film ◽  
Stable Operation ◽  
Static Structure ◽  
Squeeze Film Damper ◽  
Inertial Interaction ◽  
Rolling Element ◽  
Shaft Deflection

Abstract This paper presents rotordynamic data obtained within a test facility studying the aerodynamics of a high-speed centrifugal compressor for aero-engine applications. The experimental overhung compressor is supported by two rolling element bearings. The compressor-end ball bearing is supported by an oil-fed squeeze film damper. After some period of operation, the compressor began to exhibit a unique nonlinear increase in the rotordynamic response followed by an unexpected subsynchronous whirl instability as the speed continued to increase. Finally, as the rotor speed was increased further, the rotor re-stabilized. A numerical model of the compressor system was created using a commercially available software suite. This model indicates the effective weight of the damper support has a significant effect on the frequency of the second critical speed. Increasing this weight causes the second critical speed, originally predicted at 35,200 RPM, to shift down to 15,650 RPM. This increase in the support weight is due to inertial interaction between the damper support and the surrounding static structure. The increased shaft deflection that occurs as the rotor passes through this shifted critical speed causes the damper to lockup, resulting in the increased response observed experimentally. At a slightly higher speed, Alford-type aerodynamic cross-coupling forces excite the two subsynchronous critical speeds. Finally, as the rotor departs from the second critical speed, the damper unlocks and is able to effectively suppress the Alford-type instabilities, allowing the rotor to return to stable operation.

Bearing Skidding Detection for High Speed and Aero Engine Applications

2021 ◽  
Author(s):  
Azzedine Dadouche ◽  
Rami Kerrouche
Keyword(s):  
High Speed ◽  
Power Losses ◽  
Severe Damage ◽  
Roller Bearings ◽  
Custom Made ◽  
Rolling Element ◽  
Aero Engine ◽  
Oil Flow ◽  
Rolling Elements ◽  
Surface Distress

Abstract Rolling-element bearings (REB) can develop severe damage due to skidding (slipping) between the rolling elements and bearing races. Skidding can be described as gross sliding between the bearing surfaces in relative motion and can result in significant surface distress such as smearing, especially at light loads and high rotational speeds. Under these conditions, skidding occurs between the rolling elements and the bearing races, leading to increased wear (higher friction coefficient), elevated bearing temperature, significant power losses and reduced service life of the bearing. The main objective of this study is to investigate the significance of various sensing technologies (induction, vibration, ultrasound, acoustic and optical) in detecting skidding in standard series roller bearings as well as custom-made roller bearings for aero engine applications. The bearings have a bore diameter of 60 mm and 90 mm, respectively. Jet and under race lubrication techniques have been used to supply oil to the bearings under test. The custom-made aero engine test bearing features special channels to allow under race lubrication of the rollers/races contacts as well as the cage land. The effect of radial load, rotational speed and oil flow on roller skidding have also been investigated and analyzed. Tests have been performed on a dedicated high speed experimental bearing facility and data was recorded using a commercially-available data acquisition system.

Windage Power Losses From Spiral Bevel Gears With Varying Oil Flows and Shroud Configurations

2008 ◽  
Author(s):  
Graham Johnson ◽  
Budi Chandra ◽  
Colin Foord ◽  
Kathy Simmons
Keyword(s):  
High Speed ◽  
Lubricating Oil ◽  
Video Observation ◽  
Bevel Gears ◽  
Pinion Gear ◽  
Torque Measurements ◽  
Oil Flow ◽  
Aero Engines ◽  
Oil Jet ◽  
The University

In many aero-engines the power to drive accessories is transmitted through high speed bevel gears in a chamber in the center of the engine. The windage power loss (WPL) associated with these gears makes a significant contribution to the overall heat generation within the chamber. Shrouding the gears provides an effective method of reducing this WPL and managing the flow of lubricating oil. Experimental and computational programs at the University of Nottingham Technology Centre in Gas Turbine Transmission Systems are providing an improved understanding of shroud performance and design. This paper presents results from a pair of shrouded meshing gears run at representative speeds and oil flow in a rig with speed and torque measurement. A previously published study of a single bevel gear operating in air [1] found a reduction in torque of up to 70% from shrouding. In this work the addition of oil and the pinion gear did not lead to high torque due to the build up of oil under the shrouds, but the reduction in torque due to fitting the shrouds is significantly less than was found for the same gear in air alone. In order to isolate the various parameters, further testing with a single gear was carried out. A fully (360 degree) shrouded gear shows a big improvement over an unshrouded gear when running in air alone, but much of this benefit disappears as soon as a very small amount of oil is introduced under the shroud. This implies that the oil is recirculating under the shroud. Increasing the oil flow beyond this initial level increases the torque by the amount required to accelerate the oil mass flow up to the peripheral speed of the gear. Providing a full width slot in the shroud downstream of the oil jet allows the oil to escape without any recirculation and restores much of the benefit of the shroud. Further insight into the oil behavior is obtained from torque measurements and observations through a transparent shroud and with various slot configurations. Video observation shows evidence of a vortex flow under the shroud that carries some of the oil towards the inner diameter of the gear. The three main windage contributors, air alone, recirculation of oil under the shroud and acceleration of the feed oil are quantified and methods for achieving the optimum design are discussed.

Steady longitudinal vortices in supersonic turbulent separated flows

2011 ◽  
Vol 672 ◽  
pp. 451-476 ◽  
Author(s):  
ERICH SCHÜLEIN ◽  
VICTOR M. TROFIMOV
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Roughness Element ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Leading Edge ◽  
Separated Flows ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

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