Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When the journal rotational speed exceeds a stability threshold speed, the bearing shows self-excited vibration, which could be disappeared as the speed further increases and the bush rotational speed levels off in the case of low supply pressure. The peculiar phenomenon can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered. However, the predictions are in quantitatively poor agreement with the measurements. In the present article, intending to obtain experimental results that would be useful for future improvement of the theoretical model, the authors experimentally observe the oil film by using a test apparatus of a cylindrical journal bearing that is equivalent to the inner oil film of a high-speed floating bush journal bearing. The width of the oil film is shown to gradually reduce with an increase in journal rotational speed due to air inflow into the bearing clearance, which results in the measured bush driving torque definitely lower than the theoretical one calculated from Petroff's formula. The ratio of the measured torque to the theoretical one is found to decrease with increasing journal rotational speed although the ratio does not simply decrease in proportion to the observed oil film width.</p>

DOI： 10.18914/tribologist.22-00030

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Thermohydrodynamic lubrication (THL) models have been applied to predict the performances of journal bearings that support industrial rotating machineries. The final goal of this study is to propose a THL bearing design method of cylindrical journal bearings with two-axial oil grooves by using the model expressions, which are derived from a database constructed by the THL predictions and can predict the reasonably accurate bearing performances over a wide range of operating conditions and bearing specifications. In the present article, after the previous simplified model, which predicts the bearing performances from only four dimensionless numbers — Sommerfeld number, bearing width-to-diameter ratio, Peclet number and Khonsari number, is shown to poorly predict the performances, a simplified THL model is newly proposed for the database of the bearing performances. This model is derived by modifying the precedent high-accuracy THL model and predicts the bearing performances from the same four dimensionless numbers as the previous simplified model. Compared with some measurements in test rigs of the bearings, the model proposed is found to predict more reasonably accurate performances of the bearing under fully lubricated conditions than the previous simplified model. It is concluded that the new model is appropriate to the database for the simple easy and straightforward bearing design.</p>

DOI： 10.1299/transjsme.22-00234

CiNii Research

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

<p>This paper proposes a new THL bearing design method based on an improved version of a precedent method. The precedent method used a model expression prepared in advance to easily and quickly find a crucial predicted data of the maximum bearing temperature. Three expressions were prepared for three different values of journal eccentricity ratio, 0.25, 0.50, and 0.75. Which one of the three should be used was determined, based on the preliminarily obtained value of journal eccentricity ratio derived from the initially analysis and <i>t</i>–test, for the crucial temperature for any value of journal eccentricity ratio. Furthermore, the new expression explicitly includes the four well-known dimensionless numbers used in THL analysis, that is, Sommerfeld number, bearing width-to-dimeter ratio, Peclet number and Khonsari number. The model expressions for other bearing characteristic performances were obtained in the same way. Compared with some measurements in test rigs of cylindrical bearings, the new improved method is confirmed to predict reasonably accurate bearing performances of cylindrical bearings faster and more easily than the precedent method over a wide range of operating conditions.</p>

DOI： 10.2474/trol.17.175

DOI： 10.2474/trol.17.175

Scopus

CiNii Research

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85140405454&origin=inward

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When the oil-supplying pressure is low, the bearings show peculiar phenomena such as leveling-off of bush rotational speed and disappearance of oil whip event. Although the phenomena can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered, the predictions are in quantitatively poor agreement with the measurements. The key to improving the discrepancy lies in numerically calculating the steady-state value of bush driving torque due to viscous force. This study aims at obtaining the value by adopting a moving particle simulation (MPS) method. Firstly, the governing equations based on the conventional isoviscous hydrodynamic lubrication theory are modified such that the MPS method can be applied to the concentric inner oil film of the bearing. Next, they are solved by using the least squares moving particle semi-implicit (LSMPS) scheme coupled with arbitrary Lagrangian-Eulerian (ALE) method. Lastly, the steady-state values of the bush driving torque are calculated for a range of the bearing design parameters and are found to be in good agreement with the theoretical value obtained from Petroff's law.</p>

DOI： 10.18914/tribologist.21-00019

CiNii Article

CiNii Research

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>This paper proposes a new THL bearing design method based on an improved version of a precedent method. The precedent method used a model expression prepared in advance to easily and quickly find a crucial predicted data of the maximum bearing temperature. Three expressions were prepared for three different values of journal eccentricity ratio, 0.25, 0.5, and 0.75. Which one of the three should be used was determined, based on the preliminarily obtained value of journal eccentricity ratio derived from the initially assumed bearing specifications. Two dimensionless temperature-rise parameters <i>κ</i>₁and <i>κ</i>₂were introduced for the common variables of the expression. On the other hand, the new improved method uses a single expression, which is obtained by applying multiple regression analysis and <i>t</i>-test, for the crucial temperature for any value of journal eccentricity ratio. Furthermore, the new expression explicitly includes the four well-known dimensionless numbers used in THL analysis, that is, Sommerfeld number, bearing width-to-dimeter ratio, Peclet number and Khonsari number. The model expressions for other bearing characteristic performances were obtained in the same way. Compared with some measurements in test rigs of cylindrical bearings, the new improved method is confirmed to predict reasonably accurate bearing performances of cylindrical bearings faster and more easily than the precedent method over a wide range of operating conditions.</p>

DOI： 10.18914/tribologist.20-00016

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130008037345

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Bump foil journal bearings are prospective applicants that can support a small-sized rotor of high-speed rotating machinery. The performance characteristics of the bearings are predicted by using a model bearing. When the air film thickness can be assumed to be uniform in the axial direction, a finite element (FE) model using curved beam element is appropriate to be applied in analyzing the displacement of bearing surface which is referred to as top foil. On the other hand, the top foil need be replaced with a thin shell in order to predict the performances of the bearing that has non-uniform air film thickness in the direction. In this study, an isoparametric shell element, which can couple the membrane and the bending effects of top foil, is introduced into the deformation analysis instead of a plate shell element adopted in the previous paper. The replacement of FE model is found to have a large influence on the bearing performance because of the change in the air film characteristics. It is concluded that the isoparametric shell element is appropriate in predicting the performance of the bearing that has non-uniform air film thickness in the axial direction.</p>

DOI： 10.18914/tribologist.20-00015

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130008000345

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

<p>An overshoot phenomenon of bearing temperature in hydrodynamic journal bearings may be observed during a sudden start-up experiment. This phenomenon implies that the maximum bearing temperature in acceleration operation may exceed the predicted one which can be predicted accurately by applying a state-of-the-art steady-state thermohydrodynamic lubrication (THL) model. This paper presents the maximum bearing temperature including the one during acceleration operation by using a simplified THL model that is newly proposed for a transient THL analysis. It is found that the overshooted temperature can be qualitatively predicted by using the transient THL model that incorporates properly the interaction between the motion of journal center and the viscous dissipation, even if it is a simple model. Next, the transient temperature during slow acceleration operation and also those toward higher dimensional steady-state journal rotational speed are calculated and they are found to be in qualitative agreement with the measurements. The oil film characteristics such as oil film pressure, temperature and thickness after reaching the steady-state equilibrium do not depend on the value of initial journal eccentricity ratio in the transient analysis. However, when the values are different, the characteristics immediately after starting rotation change largely. In the case of the value 1.00, it is found to give a prediction that agrees qualitatively with the characteristics measured in the experiment.</p>

DOI： 10.18914/tribologist.20-00017

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130008000334

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1080/10402004.2020.1778825

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85089548172&origin=inward

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

<p>A thermo-hydrodynamic lubrication (THL) theory is applied to journal bearings that support large-sized high-speed rotary machineries and it is confirmed that the maximum pad surface temperature under operation is below an allowable limit value. The temperature predicted by the traditional THL model is in good agreement with the measurement. However, the predicted journal surface temperature is not comparable with the measurement. In the present paper, it is firstly shown that the amount of heat, which is generated by the shear flow in the oil film and is discharged out of the film, is evaluated appropriately in the film near the pad surface while it is evaluated excessively in the film near the journal surface. Secondly, a new THL model is proposed that the oil film temperature near the pad surface and the temperature near the journal surface are obtained independently, that is, the conventional energy equation for the oil film is solved for the former temperature while the equation described in the relative coordinate system with the journal surface as the reference one is used for the latter temperature. Lastly, it is shown that the THL model can predict the journal surface temperature comparable with the measurement without deteriorating the accuracy of the predicted maximum pad surface temperature.</p>

DOI： 10.2474/trol.15.194

Scopus

CiNii Article

CiNii Research

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85090916908&origin=inward

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Bump foil journal bearings are prospective applicants that can support a small-sized rotor of high-speed rotary machinery. Some model bearings are used in predicting the characteristic performances of the bearings. In the previous study, the finite element (FE) method that adopted a curved-beam element was applied in analyzing the displacement of the bearing surface that is called as top foil. However, the model assumes that the air film thickness in the axial direction is constant, so the performance of foil journal bearings that has uneven air film thickness in the direction cannot be obtained. In this study, the top foil is assumed to be a thin shell. The displacement is analyzed by replacing the curved-beam element to a plate shell element. Although the replacement of the FE model is found to have a large influence on the performances, this is because the shell model cannot couple the membrane and the bending effects. It is concluded that the shell model is inappropriate to the prediction of the bearing performance and should be replaced to other type of shell model that can couple the two effects.</p>

DOI： 10.18914/tribologist.19-00008

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130007728642

Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>A thermo-hydrodynamic lubrication (THL) theory is applied to journal bearings that support large-sized high-speed rotary machineries and it is confirmed that the maximum pad surface temperature under operation is below an allowable limit value. The temperature predicted by the traditional THL model is in good agreement with the measurement. However, the predicted journal surface temperature is not comparable with the measurement. In the present paper, it is firstly shown that the amount of heat, which is generated by the shear flow in the oil film and is discharged out of the film, is evaluated appropriately in the film near the pad surface while it is evaluated excessively in the film near the journal surface. Secondly, a new THL model is proposed that the oil film temperature near the pad surface and the temperature near the journal surface are obtained independently, that is, the conventional energy equation for the oil film is solved for the former temperature while the equation described in the relative coordinate system with the journal surface as the reference one is used for the latter temperature. Lastly, it is shown that the THL model can predict the journal surface temperature comparable with the measurement without deteriorating the accuracy of the predicted maximum pad surface temperature.</p>

DOI： 10.18914/tribologist.17-00024

Kyutacar

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130006503702

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

<p>Thermo-hydrodynamic lubrication (THL) models have been applied at the design stage of large-sized high-speed rotary machineries to confirm that the maximum surface temperature of sliding bearing, such as tilting pad journal bearing, under operation is below the upper limit. A single common value of heat transfer coefficient is given between the environment and the five surfaces other than the lubricating one of each pad regardless of operating conditions and/or bearing specifications in the traditional THL model, while a new THL model is proposed with non-traditional heat transfer model incorporated. In this model, the value of locally distributed heat transfer coefficient is determined depending on the operation conditions and/or the bearing specifications. Using the model, it is unnecessary to determine the heat transfer coefficient by an unreasonable estimation, and it is found that the predicted maximum pad surface temperature and also the distribution of pad surface temperature are in good agreement with the measurements.</p>

DOI： 10.18914/tribologist.17-00022

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130006337904

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

The oil film flow in large journal bearings usually transits from laminar flow to turbulent one with increase in shaft speed. This paper presents a new turbulent THL (thermo-hydrodynamic lubrication) model based on the low-Reynolds-number <i>k</i>-<i>ε</i> model to predict the performance of such bearings, while conventional turbulent THL models are based on the mixing length theory. The static performance of a four-pad tilting pad journal bearing of a real size is predicted with the new turbulent THL model and the predictions are found to agree well with the measurements presented in the open literature, including the temperature inflection characteristics of maximum pad surface temperature, a hump increase of minimum oil film thickness corresponding to the temperature inflection with shaft speed and also a steep increase of friction loss resulting from the transition to the turbulent flow of the oil film with increase in shaft speed. The new turbulent THL model is also shown to give the predictions comparable with those with the conventional turbulent THL model. However, the program developed by applying the new model is found to give the predictions surely, when compared with the one applying the conventional model. It is concluded that the new turbulent THL model can replace the conventional one in designing the turbulent journal bearings.

DOI： 10.1299/transjsme.15-00253

CiNii Article

CiNii Research

Other Link： https://www.jstage.jst.go.jp/article/transjsme/81/829/81_15-00253/_pdf

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：English   Publishing type：Research paper (scientific journal)

Language：Japanese   Publishing type：Research paper (other academic)

Language：English   Publishing type：Research paper (other academic)

Language：English   Publishing type：Research paper (other academic)

Language：Japanese   Publishing type：Research paper (scientific journal)

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Language：Japanese   Publishing type：Research paper (scientific journal)

主要雑誌 代表的研究業績

Event date： 2022.03.09   Language：Japanese  

講演番号F14

Event date： 2022.03.09   Language：Japanese  

講演番号F13

Event date： 2021.03.10   Language：Japanese  

講演番号C24

Event date： 2020.11.11 - 2020.11.13   Language：Japanese  

Event date： 2020.11.11 - 2020.11.13   Language：Japanese  

Event date： 2020.11.11 - 2020.11.13   Language：Japanese  

Event date： 2019.05.20 - 2019.05.22   Language：Japanese  

Event date： 2019.03.14   Language：Japanese  

Event date： 2019.03.01   Language：Japanese  

Event date： 2018.03.02   Language：Japanese  

Event date： 2018.03.02   Language：Japanese  

優秀講演賞を受賞

Event date： 2017.11.15 - 2017.11.17   Language：Japanese  

Event date： 2017.11.15 - 2017.11.17   Language：Japanese  

Event date： 2017.03.03   Language：Japanese  

Event date： 2017.03.03   Language：Japanese  

Event date： 2017.03.03   Language：Japanese  

Event date： 2016.03.04   Language：Japanese  

優秀講演賞を受賞

Event date： 2016.03.04   Language：Japanese  

Event date： 2015.03.03   Language：Japanese  

Event date： 2014.03.14   Language：Japanese  

Event date： 2014.03.04   Language：Japanese  

Event date： 2014.03.04   Language：Japanese  

Event date： 2014.03.04   Language：Japanese  

Event date： 2013.03.13   Language：Japanese  

Event date： 2013.03.06   Language：Japanese  

Event date： 2012.03.16   Language：Japanese  

Event date： 2012.03.12   Language：Japanese  

Event date： 2012.03.12   Language：Japanese  

Event date： 2012.03.12   Language：Japanese  

Event date： 2011.03.17   Language：Japanese  

Event date： 2011.03.17   Language：Japanese  

Event date： 2011.03.17   Language：Japanese  

Event date： 2011.03.11   Language：Japanese  

Event date： 2011.03.11   Language：Japanese  

Event date： 2011.03.11   Language：Japanese  

Event date： 2011.03.11   Language：Japanese  

Event date： 2010.09.14 - 2010.09.18   Language：Japanese  

Event date： 2010.09.05 - 2010.09.08   Language：Japanese  

Event date： 2010.05.17 - 2010.05.19   Language：Japanese  

Event date： 2010.03.15   Language：Japanese  

Event date： 2010.03.15   Language：Japanese  

Event date： 2010.03.15   Language：Japanese  

Event date： 2010.03.08   Language：Japanese  

優秀講演賞を受賞

Event date： 2010.03.08   Language：Japanese  

Event date： 2010.03.08   Language：Japanese  

Event date： 2010.03.08   Language：Japanese  

Event date： 2009.05.18 - 2009.05.20   Language：Japanese  

Event date： 2009.03.18   Language：Japanese  

Event date： 2009.03.09   Language：Japanese  

Event date： 2009.03.09   Language：Japanese  

Event date： 2008.09.16 - 2008.09.19   Language：Japanese  

Event date： 2008.09.02 - 2008.09.05   Language：Japanese  

Event date： 2008.08.03 - 2008.08.07   Language：Japanese  

Event date： 2008.05.12 - 2008.05.15   Language：Japanese  

Event date： 2008.03.19   Language：Japanese  

Event date： 2008.03.19   Language：Japanese  

Event date： 2008.03.19   Language：Japanese  

Event date： 2008.03.18   Language：Japanese  

Event date： 2008.03.18   Language：Japanese  

Event date： 2007.09.26 - 2007.09.28   Language：Japanese  

Event date： 2007.09.25 - 2007.09.28   Language：Japanese  

Event date： 2007.05.28 - 2007.05.30   Language：Japanese  

Event date： 2007.03.16   Language：Japanese  

Event date： 2007.03.16   Language：Japanese  

Event date： 2007.03.16   Language：Japanese  

Event date： 2007.03.16   Language：Japanese  

Event date： 2007.03.16   Language：Japanese  

Event date： 2007.03   Language：Japanese  

Event date： 2007.03   Language：Japanese  

優秀講演賞を受賞

Event date： 2006.08.06 - 2006.08.09   Language：Japanese  

Event date： 2006.05.15 - 2006.05.17   Language：Japanese  

Event date： 2006.05.15 - 2006.05.17   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2006.03   Language：Japanese  

Event date： 2005.11   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2005.03   Language：Japanese  

Event date： 2004.11   Language：Japanese  

Event date： 2004.11   Language：Japanese  

Event date： 2004.05   Language：Japanese  

Event date： 2004.03   Language：Japanese  

Event date： 2004.03   Language：Japanese  

Event date： 2003.11.11 - 2003.11.13   Language：Japanese  

Event date： 2003.09.16 - 2003.09.20   Language：Japanese  

Event date： 2003.08.25 - 2003.08.28   Language：English  

Event date： 2003.06.06 - 2003.06.10   Language：English  

Event date： 2003.05.12 - 2003.05.14   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2003.03.11   Language：Japanese  

Event date： 2002.11.17 - 2002.11.21   Language：English  

Event date： 2002.09.25 - 2002.09.27   Language：Japanese  

Event date： 2002.08.26 - 2002.08.29   Language：English  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.17   Language：Japanese  

Event date： 2002.03.15   Language：English  

Event date： 2002.02.10 - 2002.02.14   Language：English  

Event date： 2001.12.19 - 2001.12.21   Language：English  

Event date： 2001.10.31 - 2001.11.01   Language：English  

Event date： 2001.10.31 - 2001.11.01   Language：English  

Event date： 2001.10.31 - 2001.11.01   Language：English  

Event date： 2001.10.31 - 2001.11.01   Language：English  

Event date： 2001.10.02 - 2001.10.03   Language：English  

Event date： 2001.07   Language：English  

Event date： 2001.03   Language：English  

Event date： 2001.03   Language：English  

Event date： 2001.03   Language：English  

Event date： 2001.03   Language：English  

Event date： 2000.10.22 - 2000.10.28   Language：English  

Event date： 2000.10.01 - 2000.10.04   Language：English  

Event date： 1999.10   Language：English  

Event date： 1999.03   Language：English  

Event date： 1996.08   Language：English  

Event date： 1995.05   Language：English  

Event date： 1994.10   Language：English  

Event date： 1994.05   Language：English