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Water Lubricated Guide Bearing with Self-aligning Segments
Oguma, Tadashi,Nakagawa, Naritoshi,Mikami, Makoto,Thantrong, Long,Kizaki, Yasumi,Takimoto, Fumio Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.2
Water lubricated guide bearing was newly released and has been applied to actual hydro turbines with vertical shaft. As a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced.
AN OVERVIEW OF BIODIESEL IN ASIAN COUNTRIES AND THE HARMONIZATION OF QUALITY STANDARDS
M. OGUMA,Y. J. LEE,S. GOTO 한국자동차공학회 2012 International journal of automotive technology Vol.13 No.1
Recently, biofuels have been actively introduced as transportation fuels in Asian countries. Common drivers to use biofuels are energy security, fuel diversification, and the reduction of greenhouse gases. In addition, some Southeastern Asian countries look forward to utilizing the abundant agricultural resources and providing stability for farmers. However, a compromised quality of biofuels could cause vehicle trouble, which is why the quality standard of the fuels is very important. On the other hand, the quality standard of biofuels differs from country to country and could cause vehicle trouble in some countries and not others. These differing standards may become an obstacle to trade. In this situation, the harmonization of the biodiesel standards in the East Asia Summit (EAS) region has been initiated by the ERIA biodiesel working group, in which members are the specialists from each country. This review summarizes the introduction of biofuels in this region and the recent activities regarding the harmonization of the fuel quality standard. Important background for this review is based on the results of the ERIA biodiesel working group meeting.
Mitsuharu Oguma,Khandoker Abu Raihan,Shinichi Goto,Kouseki Sugiyama,Makihiko Mori,Kazuya Oyama 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
GTL is a liquid state in the normal temperature and pressure. It has high cetane number and other properties of it are comparable with that of diesel fuel. Therefore GTL can be alternative fuel of compression ignition engine. Furthermore, there is little sulfur and aromatic, so clean exhaust emission of diesel engine fueled with GTL can be expected.<br/> In this study, engine performances and exhaust emissions characteristics of compression ignition engine fueled with GTL were investigated by comparison with diesel fuel.<br/> Diesel engine could be operated fueled with GTL without any special modify for the test engine. With the high cetane number of GTL, the ignition lag was shorter. and the combustion started earlier than that of diesel fuel Brake thermal efficiency operated with GTL increased at middle load conditions, because incomplete combustion emission such as CO and THC were lower than that of diesel fuel operation. NOx emission operated with GTL was comparable to diesel fuel. and there was a little decrease at high load. With GTL, soot emission was lower than with diesel fuel at above middle load condition. It seemed to be a reason of soot reduction Ihallhere was little sulphur contained in GTL.<br/>
Water Lubricated Guide Bearing with Self-aligning Segments
Tadashi OGUMA,Naritoshi NAKAGAWA,Makoto MIKAMI,Long THANTRONG,Yasumi KIZAKI,Fumio TAKIMOTO 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.2
Water lubricated guide bearing was newly released and has been applied to actual hydro turbines with vertical shaft. As a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced.
Togasaki, Norihiro,Yokoshima, Tokihiko,Oguma, Yasumasa,Osaka, Tetsuya The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.4
For a battery module where single cells are connected in series, the single cells should each have a similar state of charge (SOC) to prevent them from being exposed to an overcharge or over-discharge during charge-discharge cycling. To detect the existence of unbalanced SOC cells in a battery module, we propose a simple measurement method using a single-frequency response of electrochemical impedance spectroscopy (EIS). For a commercially available graphite/nickel-cobalt-aluminum-oxide lithium-ion cell, the cell impedance increases significantly below SOC20%, while the impedance in the medium SOC region (SOC20%-SOC80%) remains low with only minor changes. This impedance behavior is mostly due to the elementary processes of cathode reactions in the cell. Among the impedance values (Z, Z', Z"), the imaginary component of Z" regarding cathode reactions changes heavily as a function of SOC, in particular, when the EIS measurement is performed around 0.1 Hz. Thanks to the significant difference in the time constant of cathode reactions between ≤SOC10% and ≥SOC20%, a single-frequency EIS measurement enlarges the difference in impedance between balanced and unbalanced cells in the module and facilitates an ~80% improvement in the detection signal compared to results with conventional EIS measurements.
ACAUSAL MODELING METHOD AND ITS VERIFICATION OF ENGINE CYCLE SIMULATION FOR EMISSIONS PREDICTION
Norifumi Mizushima,Mitsuharu Oguma 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.2
In recent years, acausal modeling languages such as Modelica and VHDL-AMS have been used for model- based development. In this research, a cycle simulation model using an acausal modeling language for predicting the emissions of an internal combustion engine was developed for application to a vehicle simulation model for energy and emissions analysis. In order to develop simulation models with higher versatility and extensibility using an acausal modeling language, it is necessary to design the structure and hierarchy by understanding its rules and constraints. Hence, the modeling method of the engine cycle simulation using the acausal modeling language Modelica for emissions prediction was discussed. Furthermore, nitrogen oxide emissions were calculated using the developed model, and their accuracy was validated by comparison with experimental data on a spark ignition engine.
Numerical Simulation of Unsteady Cavitation in a High-speed Water Jet
Peng, Guoyi,Okada, Kunihiro,Yang, Congxin,Oguma, Yasuyuki,Shimizu, Seiji Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1
Concerning the numerical simulation of high-speed water jet with intensive cavitation this paper presents a practical compressible mixture flow method by coupling a simplified estimation of bubble cavitation and a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by URANS for compressible fluid. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow, and the effect of cavitation on the flow turbulence is considered by applying a density correction to the evaluation of eddy viscosity. High-speed submerged water jets issuing from a sheathed sharp-edge orifice nozzle are treated when the cavitation number, ${\sigma}=0.1$, and the computation result is compared with experimental data The result reveals that cavitation occurs initially at the entrance of orifice and bubble cloud develops gradually while flowing downstream along the shear layer. Developed bubble cloud breaks up and then sheds downstream periodically near the sheath exit. The pattern of cavitation cloud shedding evaluated by simulation agrees experimental one, and the possibility to capture the unsteadily shedding of cavitation clouds is demonstrated. The decay of core velocity in cavitating jet is delayed greatly compared to that in no-activation jet, and the effect of the nozzle sheath is demonstrated.