Experimental verification of externally pressurized gas journal bearings with asymmetric gas supply (Supply gas pressure control operation using a small size test rig)

A rotor supported by gas bearings vibrates within the clearance. If the static imbalance of the rotor is large, even if the rotation speed is low, large amplitude vibration is generated by the centrifugal force. This is a serious problem because the risk of bearing damage increases. In order to solve this problem, an externally pressurized gas journal bearing with asymmetrically arranged gas supply holes has been developed. This type of bearing has a large load capacity as compared with the conventional symmetric gas supply bearing because pressurized gases are supplied to the loaded and counter-loaded side bearing surfaces via asymmetrically arranged gas supply holes. The bearing has a new gas supply mechanism in which gas is supplied from the rotor through inherent orifices. The characteristics of the developed bearing are beneficial from the viewpoint of using the bearing in rotational-type vibration exciters. In other words, this rotor has a large static imbalance. Numerical calculations of the characteristics of this bearing were performed, and the resulting characteristics were compared with those of a conventional symmetric gas supply journal bearing. The bearing load capacity of the developed bearing is considerably larger than that of conventional symmetric type bearings. The load capacity increases owing to the asymmetry of the gas supply holes. In the controlled gas supply pressure condition, rotor radial vibration during rotation can theoretically be zero. A test rig and gas control system to realize vibration reduction was constructed. A rotational test under the gas pressure control condition was conducted using a large unbalanced rotor taking advantage of this property. The control program was constructed using matlab and simulink. The devices were driven by a digital signal processor. The magnitude of the unbalance of the rotor is 13.5 × 10−3 kg m. The bearing diameter and length were 60 and 120 mm, respectively. The rotational vibration amplitude decreased at a high rotational frequency under the proposed bearing configuration, although the amplitude increases monotonically with the frequency in the conventional bearing. When the gas supply pressure was controlled synchronously with the rotation frequency modulation of the large unbalanced rotor, the amplitude of the vibration amplitude was greatly reduced. The rotor of the test rig was safely supported by this bearing, and effective data for practical operation were obtained.

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Experimental Investigation of Oil Film Thickness for Hydrodynamic Journal Bearings

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.110-116.2377 ◽

2011 ◽

Vol 110-116 ◽

pp. 2377-2382

Author(s):

Ravindra R. Navthar ◽

N.V. Halegowda

Keyword(s):

Experimental Investigation ◽

Film Thickness ◽

Experimental Verification ◽

Journal Bearing ◽

Journal Bearings ◽

Metal Contact ◽

Lateral Vibration ◽

Test Rig ◽

Oil Film ◽

Oil Whirl

Journal bearings are widely applied in different rotating machineries. These bearings allow for transmission of large loads at mean speed of rotation. These bearings are susceptible to large amplitude lateral vibration due to self-exited instability which is known as oil whirl or synchronous whirl. This oil whirl depends on many parameters such as oil film thickness, viscosity of lubricant, load on bearing, inertia of fluid etc. out of which oil film thickness plays an important role in operation of Journal bearings. As oil film thickness decreases metal to metal contact occurs this further can damage the journal bearing. So during the operation minimum oil film thickness should be maintained which can avoid the metal to metal contact and further increases the life of bearing. This paper presents a theoretical calculation of oil film thickness and experimental verification of same on journal bearing test rig. Different journal speeds and loads are considered for the analysis.

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Gas supply systems. Gas pressure regulating installations on service lines. Functional requirements

10.3403/01864744 ◽

2000 ◽

Keyword(s):

Gas Pressure ◽

Functional Requirements ◽

Supply Systems ◽

Gas Supply

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Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

Advances in Tribology ◽

10.1155/2020/8844879 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Carlo Alberto Niccolini Marmont Du Haut Champ ◽

Fabrizio Stefani ◽

Paolo Silvestri

Keyword(s):

Three Dimensional ◽

Journal Bearings ◽

Radial Clearance ◽

Small Scale ◽

Test Rig ◽

Small Clearance ◽

Dimensional Simulation ◽

Dynamic Loading Conditions ◽

Static And Dynamic Loading ◽

Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

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

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650117725463 ◽

2017 ◽

Vol 232 (9) ◽

pp. 1169-1180 ◽

Cited By ~ 5

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.

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Performance of Stern Tube Bearings under Different Lubrication and Operating Conditions

10.5957/pss-2009-12 ◽

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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Features of hydraulic modes of low pressure gas networks

E3S Web of Conferences ◽

10.1051/e3sconf/20199102050 ◽

2019 ◽

Vol 91 ◽

pp. 02050

Author(s):

Viktor Zhila ◽

Elena Solovyeva

Keyword(s):

Thermal Load ◽

Ignition Temperature ◽

Stoichiometric Composition ◽

Combustion Process ◽

Gas Pressure ◽

Nominal Pressure ◽

Main Indicator ◽

City Network ◽

The City ◽

Gas Supply

In conditions of modern gas supply, the gas parameters are not constant. In this regard, gas appliances operate at different pressures. In operation, the change in the thermal load of the devices is due to fluctuations in the gas pressure in the city network. These oscillations are associated with the gas oscillations at the outlet from the gas regulating station. The main indicator of qualitative combustion of gas in appliances is the completeness of combustion, and this depends on maintaining the nominal pressure. The time during which the combustion process is completed consists of the time necessary for the formation of a gas-air mixture of stoichiometric composition, for heat the mixture to the ignition temperature, and of the time during which the combustible components of the gas react with oxygen.

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Development of a new test rig for the analysis of hydrodynamic bearings for rotors of microGT

E3S Web of Conferences ◽

10.1051/e3sconf/201911303002 ◽

2019 ◽

Vol 113 ◽

pp. 03002

Author(s):

Carlo Alberto Niccolini Marmont Du Haut Champ ◽

Fabrizio Stefani ◽

Paolo Silvestri

Keyword(s):

Experimental Data ◽

Finite Element ◽

Gas Turbines ◽

Dynamic Interaction ◽

Journal Bearings ◽

Radial Clearance ◽

Test Rig ◽

Small Clearance ◽

Stiffness And Damping ◽

Good Agreement

The aim of the present work is to design a test rig suited to investigate the dynamic interaction between rotor and hydrodynamic journal bearings in micro gas turbines (microGT), i.e. with reference to small bearings (diameter in the order of ten millimeters). Particularly, the device is capable of measuring the journal location. Therefore, the journal motion due to rotor vibrations can be displayed, in order to assess performance as well as stiffness and damping of the bearings. The new test rig is based on Bently Nevada Rotor Kit (RK), but substantial modifications are carried out. Indeed, the relative radial clearance of the original RK bearings is about 2/100, while it is in the order of 1/1000 in industrial bearings. Therefore, the same RK bearings are employed in the new test rig, but a new shaft has been designed in order to reduce the original clearance. The new shaft enables us to study the bearing behaviour for different clearances, as it is equipped with interchangeable journals. The experimental data yielded by the new test rig are compared with numerical results. These are obtained by means of a suitable finite element (FEM) code developed by our research group. It allows the Thermo Elasto-HydroDynamic (TEHD) analysis of the bearing in static and dynamic conditions. In the present paper, bearing static performances are analysed in order to assess the reliability of the journal location predictions by comparing numerical and experimental results. Such comparisons are presented for both large and small clearance bearings of original and modified RK, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance equal to 8/1000). Nevertheless, rotor alignment is quite difficult with small clearance bearings and a completely new test rig is designed for future experiments.

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