Papers by Masayuki Ochiai
Tribology Online, 2019
A floating bush bearing has a double oil film, which is difficult to observe using traditional me... more A floating bush bearing has a double oil film, which is difficult to observe using traditional methods. In this study, the oil film of a floating bush bearing is observed using X-ray computer tomography. By appropriately processing the acquired CT images, double oil films can be observed efficiently. The CT images show that the oil film area decreases in the inner clearance and does not change in the outer clearance when the increase of the bush rotation speed is suppressed despite the increase in the shaft rotation speed. This phenomenon can be explained by the oil film area of the inner clearance decreasing under the influence of the centrifugal force acting on the oil film. When there is enough oil in the inner clearance, it is observed that the bush rotation speed increases linearly. These results indicate that the bush rotation speed is closely related to the oil film area of the inner clearance.
JAPANESE JOURNAL OF MULTIPHASE FLOW
The promoting evaporation of urea-water solution by atomization is required to improve the purifi... more The promoting evaporation of urea-water solution by atomization is required to improve the purification efficiency of NOx for the urea SCR system. This study proposed an innovative method of atomization which processed a surface texture to the impingement walls of the spray droplet. The atomization mechanism in this method was verified by the high qualitative visualization of the impingement droplets.
Tribology Letters
The surface textures of non-contacting mechanical seals form a few micrometers thick lubrication ... more The surface textures of non-contacting mechanical seals form a few micrometers thick lubrication film that aids in achieving high performance of the seal. Improved texture design can control internal fluid flow, improving the sealing performance and lubrication characteristics. However, film thickness is sensitive to thermal deformation, making seals vulnerable to heat. Excessive temperature increases and deviations in temperature distribution can cause performance degradation or damage to seals. Previous studies have suggested that heat transfer impacting these thermal issues may be influenced by the internal flow, however, experimental studies examining flow fields have not been conducted yet. This study presents the design of experimental equipment, measurement of temperature distributions and observation of flow fields in lubrication films with three different textures—non-textured, Rayleigh step, and spiral groove. Furthermore, the results were compared with those of numerical ...
Transactions of the Visualization Society of Japan, 2017
The gas phase area in journal bearing is associated directly with bearing characteristics. Theref... more The gas phase area in journal bearing is associated directly with bearing characteristics. Therefore, gas phase area observation have an ongoing by many researchers. This paper describes a new visualization method which can visualize oil film distribution and gas phase area on journal bearing. The distribution of oil supplied from two sites is visualized by two color oil, the blended color and gas phase area are measured by RGB representation. Moreover, the measured gas phase area compared to one by traditional visualization method. In this study, oil flow of wedge side under flooded lubrication, oil whip and starved lubrication condition are visualized. As results, it is found that the distribution of oil film under oil whip and starved lubrication condition have been changed by changing the amount of supply oil. Moreover, gas phase area by the new observation method agree rather well with a result of traditional experiment. Therefore, it was found that the new visualization method by using two color oil and RGB representation is possible to observe both gas phase area and blended oil color in journal bearing.
In this paper, we describe the film thickness and pressure measurement of the optimized thrust ai... more In this paper, we describe the film thickness and pressure measurement of the optimized thrust air bearing. In our recent study, a new optimization technique of the bearing groove geometry of the hydrodynamic thrust air bearings was proposed and a new groove geometry having a bending curve in outer vicinity of the bearing surface was obtained. Furthermore, in this study, the drastic improvement of the bearing dynamic stiffness was verified by the dynamic characteristic experiment using the original high-speed bearing test rig. However the relative error of the film thickness between the theory and experiment is large compared with that of dynamic stiffness. Consequently, it has been considered that the improvement of the measurement accuracy for film thickness is one of the most important problems. On the other hand, the generation of the negative pressure on the optimized bearing surface has not been confirmed experimentally, and it is also important to verify the negative pressure...
INTRODUCTION Dry gas seals are widely used for high speed turbo machinery because of their high s... more INTRODUCTION Dry gas seals are widely used for high speed turbo machinery because of their high sealing performance, low friction and so on. In the dry gas seals, gas leakage can be protected by hydrodynamic gas film generated by high speed rotation. However, if the grooves are damaged by the vibration from the shaft rotation or the impact force from the outside, the function and lifespan of the seal will be drastically reduced. For this reason, as a research focusing on the influence of vibrations in dry gas seals, studies by experiments and analyzes are being conducted. However, there are very few examples that focus on the fact that the flow of the gas film changes under the influence of vibration. Therefore, in this study, a vibration exciter capable of giving arbitrary vibration to test dry gas seal was made and visualization experiment was conducted. In addition, we report velocity distribution by PIV analysis from the visualization results and investigate the relationship bet...
Journal of Advanced Mechanical Design, Systems, and Manufacturing, 2020
This paper describes the relationship between the oil film behavior and cooling effect of tractio... more This paper describes the relationship between the oil film behavior and cooling effect of traction drive roller experimentally. Traction drives are transmission systems where the power is transmitted by shear stress of lubrication oil on the contact point between the rollers. They have advantages regarding noise, vibration, and high-speed operation compared with gears. On the other hand, when the power is transmitted, the heat generation occurs caused by the creep and spin at contact points. This leads to decrease of traction force and then leads to reduction of mechanical efficiency of power transmission. Thus, traction drives need the additional cooling device or the supplying of a large amount of cooling oil. However, these cooling method causes an increase of device weight, device cost, and energy consumption. From this background, the authors focused on the cooling effect of oil film behavior on traction roller. In this study, the oil film behavior was observed, and oil film temperatures were measured. As a result, it is found that oil film temperatures are affected by the oil splashing from the roller surface and the oil film distribution. Further, the authors proposed a new geometry of the roller surface which can expect to increase the cooling effect by the oil film.
Tribology Online, 2018
This research focuses on the optimum design of fluid dynamic bearing (FDB) named modified spiral ... more This research focuses on the optimum design of fluid dynamic bearing (FDB) named modified spiral design. The objective is to improve the pressure and velocity distribution inside the FDB. In this paper, the current spiral design has 12 number of grooves while the modified spiral design has 24 number of grooves. Both design can be classified into two, bearing with seal and without seal. Air was chosen to replace the oil as the lubricant. Results show that the modified spiral bearing design has comparable characteristics compared to conventional spiral design in terms of pressure and velocity distribution. Modified spiral geometries also shows a tendency to replace the function of seals in FDB. This makes it possible to simplify bearing design without using any seal just by modifying its geometries based on novel modified spiral geometries. Experimental verifications also proved that the modified spiral bearing design has better air leakage control compared to the conventional ones. This phenomenon occurs in both design parameters, where when the designs are compared with respect to increase of rotational speed and air film thickness.
Tribology Online, 2018
Oil whips might present a risk that is associated with bearing seizures. To conveniently suppress... more Oil whips might present a risk that is associated with bearing seizures. To conveniently suppress oil whips, a stabilization method using starved lubrication has been proposed. As the oil film becomes thinner, an increase in oil film temperature is expected. In this study, the bearing temperature was studied in the cases of oil whip, transition condition, and starved lubrication. Moreover, the temperature distributions in the transition and starved lubrication conditions were studied using a two-phase flow computational fluid dynamics (CFD) analysis. As a result, it was found that the heat amount due to shear friction was small in the case of the transition condition, whereas the temperature inside the bearing was approximately the same as that of the supply oil, from both experimental and analytical perspectives. In the case of the starved lubrication condition, it was found that the air flowing out of the oil supply groove created a circulated flow, which cooled the side end of the bearing, thereby controlling the temperature at the center of the bearing.
Journal of Advanced Science, 2011
Transactions of the JSME (in Japanese), 2017
In this paper, a new stabilization method which can control an oil whip utilizing the starved lub... more In this paper, a new stabilization method which can control an oil whip utilizing the starved lubrication on small bore journal bearing is described. Oil whip is one of the excited vibration that is caused by the action of oil film force of journal bearing. Therefore, it is very important to suppress the oil whip in the bearing design. Under the background the effects of two oil filler holes and these oil supply angles on journal bearing characteristics are tested, because it is considered that the critical flow rate in starved lubrication of bearings having two oil filler holes increases compared to bearing having one oil filler hole. Moreover, the difference in pressure distributions is confirmed by CFD (Computational Fluid Dynamic) analysis. As result, the critical flow rates for stabilization of the two oil filler hole bearing larger than that of one oil filler hole one. Moreover the temperature rise and the film thickness in starved lubrication have been changed by changing the conditions of the oil filler holes. Consequently, the problems of the oil temperature and the oil film thickness on stabilization method using the starved lubrication is considered to be solved by the proposed two oil filler holes method.
Journal of Mechanics Engineering and Automation, 2014
This paper describes the experimental study on shock response of FDB (fluid dynamic bearing) spin... more This paper describes the experimental study on shock response of FDB (fluid dynamic bearing) spindle for HDDs (hard disk drives). The FDBs are widely used as rotating shaft support elements for HDD spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipment such as mobile PCs (personal computers), video cameras, car navigation systems and so on. Hence, the rotating shaft has a possibility to come in contact with the bearing by external shocks and it causes wear or seizure to the bearing surface. To avoid the problem, it is extremely important to know how the spindle moves against the large shock on HDDs experimentally. However, as far as the authors know, there are few experimental studies treating the shock response of HDD spindles. In this paper, firstly, we propose a new test rig and experimental method for shock response of FDB spindles. Then the shock tests against the radial and axial disturbance on FDB spindle for 2.5" HDD are conducted. Finally, the experimental results of shock response waveforms and maximum displacement of disk are shown.
Journal of Advanced Science, 2009
This paper describes the safety operating system of oil film journal bearing using supply oil con... more This paper describes the safety operating system of oil film journal bearing using supply oil control system. Journal bearings are widely used for high speed rotating machinery such as turbines, pumps, and compressors because they can support the high speed rotating shaft across the oil lubricating film. However, in higher speed self-excited vibration which is called oil whip is generated and then they cause the seizure of bearing surface or breakdown of the machinery. It is, therefore, important to avoid the oil whip. Hashimoto et. al. suggested the stabilization method of the journal bearing using starved lubrication and the applicability of the method is verified theoretically and experimentally. The next step of the stabilization method is decreasing the several risks such as the contact of the bearing excess of decreasing the supply oil quantity. In this paper, we propose the safety and secure system by controlling the supply oil quantity for stabilization of the journal bearing using the starved lubrication and the effectiveness of the system is verified experimentally.
Journal of Advanced Mechanical Design, Systems, and Manufacturing, 2007
Journal of Advanced Mechanical Design, Systems, and Manufacturing, 2010
This paper describes the application of geometry optimization method proposed by Hashimoto to the... more This paper describes the application of geometry optimization method proposed by Hashimoto to the design of air lubricated thrust bearings used for HDD spindle motors. The optimization is carried out to maximize the dynamic stiffness of air films because the low stiffness is a serious problem of thrust air bearings in the actual application to HDD spindle motor. The optimized dynamic stiffnesses are obtained by changing the allowable film thickness, which is corresponding to the tolerance of bearings. The results obtained show that the optimized thrust air bearings have the comparable stiffness to the oil lubricated thrust bearings and it is verified theoretically that this type of thrust air bearing can be used for HDD spindle motors.
Journal of Advanced Science, 2016
Dry gas seals are widely used for turbomachinery. Recently, they are being required to much furth... more Dry gas seals are widely used for turbomachinery. Recently, they are being required to much further reduce gas leakage from many industries. It has known that sealing characteristics depend strongly on the geometry and dimensions of the grooves on the surfaces. Therefore, we conducted the optimization of groove geometry for improving the sealing characteristics. Moreover, the optimized dry gas seal was made and it was verified the effectiveness. In this study, it is intended that the effect of the groove geometry is verified. Therefore, the experimental apparatus to perform the leakage quantity measurement and visualization experiment was made. Moreover, it was conducted the leakage quantity measurement and visualization experiment of the air lubricating flow.
This chapter presents the multiphase computational fluid dynamics (CFD) analysis on oil-lubricate... more This chapter presents the multiphase computational fluid dynamics (CFD) analysis on oil-lubricated high-speed journal bearings considering the oil-filler port. Journal bearings are widely used for high-speed rotating machinery such as turbines, compressors, pumps, automobiles, and so on. They can support the rotating shaft utilizing the oil lubrication film wedge effects used in the bearing clearance. Previously, in the analysis of journal bearings, which clearance is very narrow compared with shaft diameter, the Reynolds equation has been used on journal bearing analysis because of its applicability on the narrow space calculation and its low calculation cost. However, the gaseous-phase area generated in the journal bearing and the effect of oil-filler port cannot be reproduced accurately using the method. Under these backgrounds, some researchers use the CFD analysis to calculate the journal bearing characteristics in recent years. In this chapter, the authors describe the multiphase flow CFD analysis on journal bearing based on our previous studies. At first, the multiphase CFD calculation model on journal bearing and the experimental method are explained. Then, four types of calculation results under flooded and starved lubrication conditions are compared to the experimental ones. Additionally, the effect of surface tension on journal bearing characteristics is discussed. Finally, the CFD thermal analysis results under two types of supply oil conditions are shown.
Lubricants, 2019
It is important to predict the gaseous phase area of journal bearing. However, a detailed calcula... more It is important to predict the gaseous phase area of journal bearing. However, a detailed calculation method for such gaseous phase areas has not yet been proposed. In this study, the gaseous-phase areas in small bore journal bearings under flooded and starved lubrication conditions are analyzed in terms of the computational fluid dynamics (CFD) of two-phase flow while using a volume of fluid (VOF) method. Furthermore, the influence of surface tension and vapor pressure conditions were investigated, and the analytical and experimental results were compared. The analytical results of VOF for vapor pressure and surface tension were observed to be consistent with the experimental observations under both flooded and starved lubrication conditions. Furthermore, under starved lubrication condition, the analytical results agree well with the observed results for the interface of the oil film and cavitation upon the rupture of the oil film. While using these results, CFD analysis of the two...
Proceedings of JSME-IIP/ASME-ISPS Joint Conference on Micromechatronics for Information and Precision Equipment : IIP/ISPS joint MIPE, 2009
,ip***;hitvmu@kop,aki.cc.u-toftai.acJ?)**** ABSTRACT This article discusses the advantage and pot... more ,ip***;hitvmu@kop,aki.cc.u-toftai.acJ?)**** ABSTRACT This article discusses the advantage and potential of air bearing being used in hard disk drive (HDD) to reptace the conventional oil-lubricated
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Papers by Masayuki Ochiai