Influence of Gas Feeding Position on the Performance of Radial-Inflow Hydrostatic Gas Ultra-Short Journal Bearings

2016 ◽  
Author(s):  
Chao Nie ◽  
Xiaojun Yan ◽  
Xia Chen
Keyword(s):  
Rotational Speed ◽  
Cfd Simulation ◽  
Journal Bearing ◽  
Maximum Speed ◽  
Test Rig ◽  
Thrust Bearings ◽  
Axial Stability ◽  
Speed Measurement ◽  
Gas Leaks ◽  
Better Than

To investigate the influence of gas feeding position on the performance of radial-inflow hydrostatic gas ultra-short (with a L/D value as 0.1) journal bearing two rotor-bearing system test rigs with two different feeding positions (central feeding and bottom feeding) for the journal bearing were designed. A rotor measurement system with an original rotational speed measurement program is built. Rotation experiments to measure the maximum rotational speed of rotors under different inlet pressure of journal bearing were conducted. It was found that, the rotor supported by the central feeding journal bearing worked better, and achieved a maximum rotational speed of 40000 rpm, (83.74m/s for the tip speed). While the test rig with bottom feeding journal bearing could not function well. To verify the reasons behind the failure mentioned above, the flow condition in the journal clearance and the rotor bottom clearance was analyzed by the CFD simulation. It shows that most of the journal bearing gas “leaks” into the rotor bottom clearance in the bottom feeding bearing test rig, disarranging the axial stability of the rotor and the normal functioning of the thrust bearings. In conclusion, the central feeding radial-inflow journal bearing is better than the bottom feeding one, for the better operability and higher maximum speed. And an ideal feeding position is supposed to make the journal bearing does not influence the axial stability of the rotor and the functioning of the thrust bearings.

Identification of Dynamic Characteristics of Gas Foil Thrust Bearings Using Base Excitation

2016 ◽  
Author(s):  
Tae Ho Kim ◽  
Moon Sung Park ◽  
Jongsung Lee ◽  
Young Min Kim ◽  
Kyoung-Ku Ha ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Loss Factor ◽  
Load Capacity ◽  
Excitation Frequency ◽  
Vibrational Amplitude ◽  
Test Rig ◽  
Thrust Bearings ◽  
Bearing Plate ◽  
Bearing Stiffness

Gas foil bearings (GFBs) have clear advantages over oil-lubricated and rolling element bearings, by virtue of low power loss, oil-free operation in compact units, and rotordynamic stability at high speeds. However, because of the inherent low gas viscosity, GFBs have lower load capacity than the other bearings. In particular, accurate measurement of load capacity and dynamic characteristics of gas foil thrust bearings (GFTBs) is utmost important to widening their applications to high performance turbomachinery. In this study, a series of excitation tests were performed on a small oil-free turbomachinery with base excitations in the rotor axial direction to measure the dynamic load characteristics of a pair of six-pad, bump-type GFTBs, which support the thrust collar. An electromagnetic shaker provided dynamic sine sweep loads to the test bench (shaking table), which held rigidly the turbomachinery test rig for increasing excitation frequency from 10 Hz to 200 Hz. The magnitude of the shaker dynamic load, represented as an acceleration measured on the test rig, was increased up to 9 G (gravity). An eddy current sensor installed on the test rig housing measured the axial displacement (or vibrational amplitude) of the rotor thrust collar during the excitation tests. The axial acceleration of the rotor relative to the test rig was calculated using the measured displacement. A single degree-of-freedom base excitation model identified the frequency-dependent dynamic load capacity, stiffness, damping, and loss factor of the test GFTB for increasing shaker dynamic loads and increasing bearing clearances. The test results show that, for a constant shaker force and the test GFTB with a clearance of 155 μm, an increasing excitation frequency increases the dynamic load carried by the test GFTB, i.e., bearing reaction force, until a certain value of the frequency where it jumps down suddenly because of the influence from Duffing’s vibrations of the rotor. The bearing stiffness increases and the damping decreases dramatically as the excitation frequency increases. Generally, the bearing loss factor ranges from 0.5 to 1.5 independent of the frequency. As the shaker force increases, the bearing dynamic load, stiffness, damping, and loss factor increase depending on the excitation frequency. Interestingly, the agreements between the measured GFTB dynamic load versus the thrust runner displacement, the measured GFTB static load versus the structural deflection, and the predicted static load versus the thrust runner displacement are remarkable. Further tests with increasing GFTB clearances of 155, 180, 205, and 225 μm revealed that the vibrational amplitude increases and the jump-down frequency decreases with increasing clearances. The bearing load increases, but the bearing stiffness, damping, and loss factor decrease slightly as the clearance increases. The test results after a modification of the GFTB by rotating one side bearing plate by 30° relative to the other side bearing plate revealed insignificant changes in the dynamic characteristics. The present dynamic performance measurements provide a useful database of GFTBs for use in microturbomachinery.

Effect of Buoyancy and Density Ratio on Heat Transfer in a Smooth Cooling Channel of a Gas Turbine Blade

2018 ◽  
Author(s):  
Mandana S. Saravani ◽  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Rotational Speed ◽  
Cfd Simulation ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Buoyancy Effect ◽  
Square Channel ◽  
First Case ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The present work investigates the effects of buoyancy and density ratio on the thermal performance of a rotating two-pass square channel. The U-bend configuration with smooth walls is selected for this study. The channel has a square cross-section with a hydraulic diameter of 5.08 cm (2 inches). The lengths of the first and second passes are 514 mm and 460 mm, respectively. The turbulent flow enters the channel with Reynolds numbers of up to 34,000. The rotational speed varies from 0 to 600 rpm with the rotational numbers up to 0.75. For this study, two approaches are considered for tracking the buoyancy effect on heat transfer. In the first case, the density ratio is set constant, and the rotational speed is varied. In the second case, the density ratio is changed in the stationary case, and the effect of density ratio is discussed. The range of Buoyancy number along the channel is 0–6. The objective is to investigate the impact of Buoyancy forces on a broader range of rotation number (0–0.75) and Buoyancy number scales (0–6), and their combined effects on heat transfer coefficient for a channel with aspect ratio of 1:1. Several computational fluid dynamics (CFD) simulation are carried out for this study, and some of the results are validated against experimental data.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

Experimental Rotordynamic Parameter Study at Turbochargers With Hydrodynamic Journal Bearing Systems

2015 ◽  
Author(s):  
Alexander T. Hummel ◽  
Michael Rott ◽  
Christoph Schneider ◽  
David Kuschnertschuk ◽  
Günther Stelzner ◽  
...  
Keyword(s):  
Experimental Approach ◽  
Test Bench ◽  
Journal Bearing ◽  
Commercial Vehicle ◽  
Real Life ◽  
Parameter Study ◽  
Thrust Bearings ◽  
Hot Gas ◽  
Hydrodynamic Journal Bearing ◽  
Run Up

This paper presents an evaluation of various rotordynamic parameters at commercial vehicle turbochargers, which are operated supercritically in full-floating hydrodynamic journal bearing systems. The evaluation is conducted by using an experimental approach to determine the performance of the rotor-bearing-system in a real-life assembly at a hot gas test bench. This takes support stiffness, external heating and the excitation by seals, thrust bearings and gas forces into account, while Engine-specific excitation is not present. The system’s ability to carry additional unbalance load at different oil support pressures without the occurrence of mixed friction throughout a complete run-up is assessed. By executing this assessment for multiple assemblies with different bearings, rotors and oil types, the influence of main design and boundary parameters on the effective journal bearing performance of turbochargers is quantified.

Training, Speed and Stamina in Trout

1962 ◽  
Vol 39 (4) ◽  
pp. 537-555 ◽  
Author(s):  
RICHARD BAINBRIDGE
Keyword(s):  
Respiratory Rate ◽  
Behavioural Response ◽  
Wild Fish ◽  
Maximum Speed ◽  
Considerable Variability ◽  
Experimental Conditions ◽  
Percentage Improvement ◽  
The Mean ◽  
Better Than

1. A number of trout (Salmo irideus) were kept continuously swimming for a period of 12 months in experimental tanks in which the water was made to rotate at a mean speed of 25 cm./sec. 2. These fish become available for study in the ‘Fish Wheel’ and measurements were made of the maximum speed they sustained for periods of swimming of different duration. 3. For bursts of swimming of up to 20 sec. duration the mean accomplishments of these fish were identical with those of the unexercised trout studied previously. 4. Considerable variability was found amongst the specimens tested and the best of the present exercised fish were appreciably better than the best of the previous unexercised ones. The biggest improvement was 36 % at the 10 sec. period of swimming; the mean percentage improvement for all periods was 11 %. 5. Some specimens were found better at swimming for short periods and others at swimming for longer. 6. In the absence of comparable figures for the earlier fish, the measurements of cruising speeds sustained for periods up to 1½ hr. were compared with other figures in the literature and found to be about half some of these for wild fish. 7. The implications of the results are considered and two interpretations stressed. First, it is assumed that there is a real identity of accomplishment for short periods of swimming, values being determined perhaps solely by gross mass of muscle; while for longer periods of swimming differences dependent upon respiratory rate etc. may well occur. Secondly, for such longer periods the discrepancies reported here may well be accounted for by differing degrees of stimulus and behavioural response under varied experimental conditions.

Performance of Stern Tube Bearings under Different Lubrication and Operating Conditions

2009 ◽  
Author(s):  
Jan H. Andersen ◽  
Hiroyuki Sada ◽  
Seiji Yamajo
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Water Soluble ◽  
Analysis Tool ◽  
Test Rig ◽  
Experimental Performance ◽  
Shaft Alignment ◽  
Alignment Analysis

This paper presents the results of an investigation into the theoretical and experimental performance of oil lubricated journal bearings. DNV has developed a new calculation tool for the analysis of journal bearing performance as part of shaft alignment analysis. The results of the calculation tool have been compared to other research and analysis methods under static and dynamic conditions. In addition, white metal bearings were tested with decreasing Sommerfeld number until loss of hydrodynamic lubrication. The experiments were carried out in a bearing test rig and with three different lubricants, normal mineral oil, emulsifying oil, and water-soluble oil. The tests were done with increasing water content in the lubricant. Results from the test were compared with calculation using the DNV analysis tool.

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