Mechanical Engineering Letters最新文献

Secondary instability induced by thermocapillary effect in half-zone liquid bridge of high Prandtl number fluid 高普朗特数流体半区液桥热毛细效应引起的二次失稳

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/MEL.19-00014

T. Ogasawara, Kosuke Motegi, T. Hori, I. Ueno

引用次数: 8

Use of hydrated material for dynamic seal faces in shaft seal 轴封动态密封面采用水合材料

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/MEL.19-00001

Y. Yoshioka, T. Honda, K. Kasamura, Y. Nakashima, H. Higaki, Y. Nakanishi

{"title":"Use of hydrated material for dynamic seal faces in shaft seal","authors":"Y. Yoshioka, T. Honda, K. Kasamura, Y. Nakashima, H. Higaki, Y. Nakanishi","doi":"10.1299/MEL.19-00001","DOIUrl":"https://doi.org/10.1299/MEL.19-00001","url":null,"abstract":"In ocean current and tidal power generation systems, the rotating shaft, which connects the turbine in water phase and the generation system in air phase, experiences a variety of shaft speeds and high water-pressure conditions. The shaft seal is required to separate water and air with a rotating shaft, which should guarantee both a low frictional torque and a low leakage of water. Conventional shaft seals realize the low frictional torque by operating in a hydrodynamic lubrication mode at the dynamic seal face. However, the dynamic seal face suffers to form rich lubrication film against low speed shaft in water environment. Therefore, a hydrated seal ring was proposed for use in the dynamic seal faces to realize the boundary lubrication. The hydrated seal ring made of a polyvinyl formal (PVF) was adopted. Two types of shaft seals using PVF seal ring were designed, which had the similar structure to oil seals or mechanical seals. The design scheme was validated using verification tests in which the shaft rotation speed was varied from 5000 to –5000 revolutions per minute under a water pressure of 0.5 MPa. The hydrated seal ring can be further improved by avoiding deformation of the hydrated seal ring to inhibit the clearance flow in the dynamic seal face. However, it needed to consider the surface profile of the ceramics surface used as a counterface of the hydrated seal ring because the heat generation at the dynamic seal face might be occurred, which changes the material property of the hydrated seal ring.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130006669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A study on efficiency of semi-implicit, density-based solver for simulation of evaporating particle-laden flow 基于密度的半隐式求解器模拟蒸发颗粒流的效率研究

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.21-00136

Younghwa Cho, Rahul Bale, M. Tsubokura, N. Oshima

{"title":"A study on efficiency of semi-implicit, density-based solver for simulation of evaporating particle-laden flow","authors":"Younghwa Cho, Rahul Bale, M. Tsubokura, N. Oshima","doi":"10.1299/mel.21-00136","DOIUrl":"https://doi.org/10.1299/mel.21-00136","url":null,"abstract":"In this work, we propose a semi-implicit, density-based solver for compressible, evaporating particle-laden flow, and investigate its efficiency. It is established on a Cartesian-grid-based, scalable, numerical framework named CUBE. In this solver, the governing equation system is divided into three subsystems (compressible Navier– Stokes, species transport, and Lagrangian), and these subsystems are weakly coupled in two ways. In the Lagrangian domain, the fuel spray is treated as a set of discrete particles, and the particle-source-in-cell (PSICell) method is employed for the coupling between the Eulerian and Lagrangian domains. Furthermore, the species transport and Lagrangian subsystems are subcycled with smaller time step, and the Navier–Stokes equation is temporally integrated with a larger step size. The proposed solver's verification and evaluation is conducted on the supercomputer Fugaku by comparing the results with those of the original, fully explicit solver where all equations have the same time step. The results show that this solver reduces the computational cost while ensuring similar accuracy. The solution of the proposed solver is consistent with that of the original solver. Finally, we brief our perspective on the future application of the proposed solver to our target problem: the largescale simulation of evaporating particle-laden flow in a combustor of an aviation engine.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"445 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125819434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental evaluation of threshold current density for electromigration damage in Al interconnect line with reservoir and sink structure 储汇结构铝互连线电迁移损伤阈值电流密度的实验评价

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.22-00035

T. Moriwaki, Ryuji Takaya, K. Sasagawa, K. Fujisaki

引用次数: 0

Oxygen concentration measurement in the porous cathode of a lithium-air battery using a fine optical fiber sensor 用精细光纤传感器测量锂空气电池多孔阴极中的氧浓度

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/MEL.19-00095

Shogo Fujimoto, S. Uemura, N. Imanishi, S. Hirai

{"title":"Oxygen concentration measurement in the porous cathode of a lithium-air battery using a fine optical fiber sensor","authors":"Shogo Fujimoto, S. Uemura, N. Imanishi, S. Hirai","doi":"10.1299/MEL.19-00095","DOIUrl":"https://doi.org/10.1299/MEL.19-00095","url":null,"abstract":"The oxygen concentration distribution in the porous cathode of a lithium–air battery during discharge has been measured using a fine optical fiber sensor. The lithium–air battery has the highest theoretical capacity. However, for practical application, the lithium–air battery power density needs to be improved. To realize a more powerful aqueous lithium–air battery, sufficient oxygen supply into the porous cathode is required. No previous studies have measured the oxygen concentration in the porous cathode structure. In this study, platinum tetrakis pentafluorophenyl porphine (PtTFPP) was used as the oxygen indicator. When PtTFPP is exposed to excitation light, phosphorescence emission occurs, and its intensity depends on the oxygen partial pressure. Thus, the oxygen concentration can be obtained by measuring the phosphorescence intensity and using calibration data. A fine optical fiber sensor (110 μm in diameter) was constructed with PtTFPP painted on the edge. According to the experimental results, as the current density increases, the oxygen concentration in the porous cathode drastically decreases. Because of slow oxygen transport in the aqueous electrolyte and the existence of an electrolyte between the air layer and the porous cathode, sufficient oxygen is not supplied to the porous cathode. Therefore, only oxygen near the electrode surface can contribute to the discharge.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130180714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Parallelization of DEM simulation on distributed-memory computer via three-dimensional slice grid method 三维切片网格法在分布式存储计算机上并行化DEM仿真

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.20-00444

Kento Yokoo, M. Kishida, Tsuyoshi Yamamoto

{"title":"Parallelization of DEM simulation on distributed-memory computer via three-dimensional slice grid method","authors":"Kento Yokoo, M. Kishida, Tsuyoshi Yamamoto","doi":"10.1299/mel.20-00444","DOIUrl":"https://doi.org/10.1299/mel.20-00444","url":null,"abstract":"overlap, developed Abstract A fluidized bed can efficiently filter dust particles, but its performance depends significantly on the fluidization state. To further develop the fluidized-bed filtration method, it is important to understand the filtration mechanisms in detail. Numerical simulation via the discrete element method is useful for solving these problems because the motion of each bed and dust particle is demonstrated. This system has large number of particles, and bias of the particle distribution is generated owing to the fluidization and supply of dust particles. Parallel computing on a distributed-memory computer is necessary to simulate many particles. Additionally, dynamic load balancing is a key technique for solving these problems. In this study, we developed a simple implementation of three-dimensional slice grid method and periodically used this method to balance the workload while keeping contact information such as the pair of colliding particles and its overlap. The computational efficiency of our method was assessed through an ideal problem involving a packed particle system and dust filtration in a fluidized bed. The changes in the particle number and particle distribution were examined. In the packed particle system, linear speed-up was obtained at particle number of 100 million and a message passing interface-process number of 1024. Moreover, the effectiveness of the dynamic domain decomposition method was confirmed by solving through the dust filtration problem.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116457055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

A simple method to evaluate the eigenvalue of premixed flame propagation 预混合火焰传播特征值的一种简单计算方法

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.19-00610

H. Iizuka, K. Kuwana, S. Yazaki

{"title":"A simple method to evaluate the eigenvalue of premixed flame propagation","authors":"H. Iizuka, K. Kuwana, S. Yazaki","doi":"10.1299/mel.19-00610","DOIUrl":"https://doi.org/10.1299/mel.19-00610","url":null,"abstract":"The Lewis number is the ratio of thermal diffusivity to molecular diffusion coefficient, and its influence on premixed-flame propagation has been a topic of extensive combustion research. Diffusive-thermal model, which neglects density variation caused by temperature increase due to combustion, has been frequently used to examine the effect of the Lewis number. Major advantages of the diffusive-thermal model are that it allows computation with a given flow field and that the sole effect of the Lewis number can be investigated. The diffusive-thermal model includes a dimensionless parameter, hereafter denoted by (cid:1993) , which corresponds to the pre-exponential factor of reaction rate constant. Its value must be determined such that the correct burning velocity can be reproduced. Although a number of studies use the lowest-order asymptotic expression for evaluating the value of (cid:1993) , the expression causes errors as much as several tens of percent depending on the condition. In this study, the value of (cid:1993) is numerically determined by seeking a traveling wave solution in a one-dimensional moving coordinate system. The method is simple enough to be implemented in Microsoft Excel using its solver add-in. It was found that even two-term asymptotic expansion of (cid:1993) resulted in errors more than 10% in some cases. It is therefore recommended to numerically evaluate the value of (cid:1993) under every condition of interest. As an alternative means, this paper proposes an empirical formula that yields the value of (cid:1993) with errors less than 1% in most cases (less than 2% in all the cases) tested in this study.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114929797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Investigation of static and fatigue crack growth mechanism of borated stainless steel using in situ observation method 硼化不锈钢静力及疲劳裂纹扩展机制的原位观察研究

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/MEL.19-00105

Shota Hasunuma, K. Sugawara, T. Ogawa

{"title":"Investigation of static and fatigue crack growth mechanism of borated stainless steel using in situ observation method","authors":"Shota Hasunuma, K. Sugawara, T. Ogawa","doi":"10.1299/MEL.19-00105","DOIUrl":"https://doi.org/10.1299/MEL.19-00105","url":null,"abstract":"The borated stainless steel B-SUS304P-1 is used for storage and transport metal casks in the nuclear industry. According to our previous research, the boron addition reduces the fracture toughness but has a minimal effect on the fatigue crack growth. In this study, in situ laser microscopy observation during tensile, fracture toughness and fatigue crack growth tests of B-SUS304P-1 was performed to investigate the mechanism responsible for the effects of the boron addition on static and fatigue crack growth. During the tensile test, the borides were broken, but the base material remained intact. Results obtained using the digital image correlation method revealed that the strain of boride at fracture was very low compared with the macroscopic elongation of B-SUS304P-1. For the fracture toughness test, the borides in front of the crack were broken before static crack growth. The crack propagated along a zigzag path as it grew along the broken borides. Because of this crack growth mechanism, the fracture toughness was reduced by the boron addition. In contrast, for the fatigue crack growth test, only a few broken borides were observed in front of the crack because the stress intensity factor of the fatigue test was smaller than that of the fracture toughness test. The crack thus grew linearly, and the boron addition had a minimal effect on the fatigue crack growth of the stainless steel.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128597121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Method for improving GPS high-positioning using microwave absorbers for walking movement support 一种利用微波吸收器支持行走运动改善GPS高定位的方法

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.23-00125

T. Asakawa, Haruka Matoba, Daiki Horimoto, C. Wada

引用次数: 0

Gap flow between two circular plates with temperature-controlled wall: application of thermohydrodynamic lubrication theory and comparison with an iso-viscous model 温控壁圆板间隙流动:热流体润滑理论的应用及与等粘滞模型的比较

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI: 10.1299/mel.20-00292

T. Kazama, Song Gao

{"title":"Gap flow between two circular plates with temperature-controlled wall: application of thermohydrodynamic lubrication theory and comparison with an iso-viscous model","authors":"T. Kazama, Song Gao","doi":"10.1299/mel.20-00292","DOIUrl":"https://doi.org/10.1299/mel.20-00292","url":null,"abstract":"Gaskets are widely used as static seals in industry, machinery, and living ware. Generally, leakage is reduced or eliminated by clamping seal components and blocking flow passages. However, strong clamping sometimes leads to surface damage. Surface roughness and waviness form partial paths and excitation and vibration loosen clamping bolts. Leakage is directly proportional to the cube of gap height and inversely proportional to viscosity. Moreover, the viscosity of fluids, particularly oil, strongly depends on temperature, as lower temperatures correspond to higher viscosities. In other words, oil leakage can be reduced by decreasing its temperature. Therefore, it is possible to control leakage by changing the gap temperatures. In this paper, a flange-type gasket with a gap is modeled using two circular plates with a central recess. The thermohydrodynamic lubrication (THL) theory is applied to the gap flow. The effects of wall temperature, gap height, and recess pressure on the leakage flow rate are numerically solved. The basic equations comprise the generalized Reynolds equation, the energy equation, and the heat conduction equation and the THL solutions are compared with a simple model based on the iso-viscous theory. In conclusion, the oil temperature in the gap can be controlled by the wall temperature. If the wall temperature is decreased, the oil temperature falls. Subsequently, viscosity increases, helping to decrease leakage in a wide range of operating conditions. The leakage can be estimated by the iso-viscous model with the viscosity at the wall temperature.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121946843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1