{"title":"Development of combustion gas measurement systems for micro-rocket torch using a diode laser sensor","authors":"Yuya Hirayama, Shinichiro Ogawa","doi":"10.1299/mel.23-00261","DOIUrl":"https://doi.org/10.1299/mel.23-00261","url":null,"abstract":"","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"04 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":"127257500","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}
This short paper studies a robust optimization problem of a structure subjected to frictionless unilateral contacts. We suppose that initial gaps possess non-probabilistic uncertainty, and attempt to maximize the worst-case sti ff ness of the structure. It is often that a structural optimization problem involving contact conditions is formulated as a mathematical programming problem with complementarity constraints (an MPCC problem). Since any feasible solution of an MPCC problem does not satisfy standard constraint qualifications, special treatment is required to solve an MPCC problem. In contrast, the formulation developed in this paper is free from complementarity constraints, and hence can be handled as a standard nonlinear programming problem. It is shown that this formulation is readily derived as a natural extension of the recently proposed optimal design problem formulation that does not consider uncertainty.
{"title":"Robust optimization of structures subjected to frictionless unilateral contact with uncertain initial gaps","authors":"Y. Kanno","doi":"10.1299/mel.20-00224","DOIUrl":"https://doi.org/10.1299/mel.20-00224","url":null,"abstract":"This short paper studies a robust optimization problem of a structure subjected to frictionless unilateral contacts. We suppose that initial gaps possess non-probabilistic uncertainty, and attempt to maximize the worst-case sti ff ness of the structure. It is often that a structural optimization problem involving contact conditions is formulated as a mathematical programming problem with complementarity constraints (an MPCC problem). Since any feasible solution of an MPCC problem does not satisfy standard constraint qualifications, special treatment is required to solve an MPCC problem. In contrast, the formulation developed in this paper is free from complementarity constraints, and hence can be handled as a standard nonlinear programming problem. It is shown that this formulation is readily derived as a natural extension of the recently proposed optimal design problem formulation that does not consider uncertainty.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"20 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":"115127413","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}
Taketo Ariki, Y. Shibasaki, Y. Kuya, M. Adachi, K. Sawada
{"title":"A DES study of the flow around a full-scale train under crosswind condition","authors":"Taketo Ariki, Y. Shibasaki, Y. Kuya, M. Adachi, K. Sawada","doi":"10.1299/mel.22-00464","DOIUrl":"https://doi.org/10.1299/mel.22-00464","url":null,"abstract":"","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"112 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":"122881227","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}
Friction between a tool and chip, and the heat generated, often limit machining in metal cutting operations. Coolants and lubricants are used in great quantities to reduce friction at the cutting area. However, the cost of cutting fluids is increasing because of the increasingly stringent environmental standards for fluid handling and disposal, and these standards are likely to be further tightened in proposed national and international legislation (Weinert and Inasaki, 2004). Although dry and semi-dry machining is an attractive option, it is currently unavailable in many operations because cooling cannot be achieved (Tasdelen et al., 2008; Werda et al., 2016). Therefore, cutting fluids will continue to be required. As a fluid deteriorates, its cutting power decreases and the work environment becomes polluted. Techniques that extend the life of cutting fluids are therefore needed. One of the key causes of deterioration is decomposition due to bacterial growth (Rabenstein et al., 2009; Griffiths, 1978). Bacteria enter the fluid from both the air and the chip. Because preventing bacteria from contaminating the cutting fluid is difficult, chemical additives are widely used for bacterial control. The widespread use of oil additives has led to the emergence of resistant bacteria, and the additives change the characteristics of the cutting fluid. Therefore, we proposed a sterilization technique using plasma treatment under atmospheric pressure (Miyamoto et al., 2018). Moreover, we suggested that the molecular structure of the fluids was not affected by plasma jet treatment (Miyamoto et al., 2018). In our previous study, the number of bacterial colonies in fluid sterilized using atmospheric-pressure plasma was reduced by more than 90% compared with the number in an untreated fluid (Miyamoto et al., 2018). From this report, however, it is unclear whether the remaining bacteria and surface Junji MIYAMOTO*, Ryo TSUBOI*, Masashi YOSHIDA** and Koichiro NAMBU*** * Department of Mechanical Engineering, Daido University 10-3 Takiharu-cho, Minami-ku, Nagoya, Aichi 457-8530, Japan E-mail: j-miya@daido-it.ac.jp ** Department of Mechanical Systems Engineering, Daido University 10-3 Takiharu-cho, Minami-ku, Nagoya, Aichi 457-8530, Japan *** Toyota Technological Institute 2-12-1 Hisakata Tenpaku-ku, Nagoya, Japan
刀具和切屑之间的摩擦以及产生的热量常常限制金属切削加工。大量使用冷却剂和润滑剂来减少切割区域的摩擦。然而，由于流体处理和处置的环境标准日益严格，切削液的成本正在增加，拟议的国家和国际立法可能会进一步收紧这些标准(Weinert和Inasaki, 2004年)。尽管干式和半干式加工是一种有吸引力的选择，但由于无法实现冷却，目前在许多操作中无法使用(Tasdelen等人，2008;Werda et al.， 2016)。因此，将继续需要切削液。当流体变质时，其切削功率降低，工作环境受到污染。因此，需要延长切削液使用寿命的技术。变质的关键原因之一是细菌生长导致的分解(Rabenstein et al.， 2009;格里菲思,1978)。细菌通过空气和芯片进入液体。由于防止细菌污染切削液是困难的，化学添加剂被广泛用于细菌控制。油品添加剂的广泛使用导致耐药菌的出现，添加剂改变了切削液的特性。因此，我们提出了一种在常压下使用等离子体处理的灭菌技术(Miyamoto et al.， 2018)。此外，我们认为等离子体射流处理不会影响流体的分子结构(Miyamoto et al.， 2018)。在我们之前的研究中，与未经处理的液体相比，使用常压等离子体消毒的液体中的细菌菌落数量减少了90%以上(Miyamoto等人，2018)。然而，从这份报告中，尚不清楚是否剩余的细菌和表面MIYAMOTO Junji *， Ryo TSUBOI*， YOSHIDA Masashi **和Koichiro NAMBU*** * Daido大学机械工程系10-3 Takiharu-cho，南南区，名古屋，爱知县457-8530，日本j-miya@daido-it.ac.jp **日本爱知县名古屋南区泷春町10-3号大道大学机械系统工程系***日本名古屋久田天paku区丰田技术研究所2-12-1
{"title":"Quality improvement of deteriorated cutting fluid treated by atmospheric-pressure plasma jet and in-liquid plasma","authors":"J. Miyamoto, R. Tsuboi, Masashi Yoshida, K. Nambu","doi":"10.1299/mel.20-00100","DOIUrl":"https://doi.org/10.1299/mel.20-00100","url":null,"abstract":"Friction between a tool and chip, and the heat generated, often limit machining in metal cutting operations. Coolants and lubricants are used in great quantities to reduce friction at the cutting area. However, the cost of cutting fluids is increasing because of the increasingly stringent environmental standards for fluid handling and disposal, and these standards are likely to be further tightened in proposed national and international legislation (Weinert and Inasaki, 2004). Although dry and semi-dry machining is an attractive option, it is currently unavailable in many operations because cooling cannot be achieved (Tasdelen et al., 2008; Werda et al., 2016). Therefore, cutting fluids will continue to be required. As a fluid deteriorates, its cutting power decreases and the work environment becomes polluted. Techniques that extend the life of cutting fluids are therefore needed. One of the key causes of deterioration is decomposition due to bacterial growth (Rabenstein et al., 2009; Griffiths, 1978). Bacteria enter the fluid from both the air and the chip. Because preventing bacteria from contaminating the cutting fluid is difficult, chemical additives are widely used for bacterial control. The widespread use of oil additives has led to the emergence of resistant bacteria, and the additives change the characteristics of the cutting fluid. Therefore, we proposed a sterilization technique using plasma treatment under atmospheric pressure (Miyamoto et al., 2018). Moreover, we suggested that the molecular structure of the fluids was not affected by plasma jet treatment (Miyamoto et al., 2018). In our previous study, the number of bacterial colonies in fluid sterilized using atmospheric-pressure plasma was reduced by more than 90% compared with the number in an untreated fluid (Miyamoto et al., 2018). From this report, however, it is unclear whether the remaining bacteria and surface Junji MIYAMOTO*, Ryo TSUBOI*, Masashi YOSHIDA** and Koichiro NAMBU*** * Department of Mechanical Engineering, Daido University 10-3 Takiharu-cho, Minami-ku, Nagoya, Aichi 457-8530, Japan E-mail: j-miya@daido-it.ac.jp ** Department of Mechanical Systems Engineering, Daido University 10-3 Takiharu-cho, Minami-ku, Nagoya, Aichi 457-8530, Japan *** Toyota Technological Institute 2-12-1 Hisakata Tenpaku-ku, Nagoya, Japan","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"24 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":"128857423","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}
increase and Lozier, 1958). Specifically, Seo (2009a; 2009b; 2011) measured the emissivity of several types of nuclear graphite in the temperature range from 100 ℃ to 500℃ and indicating a positive relationship between graphite emissivity and oxidation degree. Abstract In a High-Temperature Gas-cooled Reactor (HTGR), radiation is the dominant form of heat transfer due to the high temperature environment. Therefore, the emissivity of the core materials (mainly nuclear grade graphite) is important for reactor safety assessment. In this paper, the emissivity of nuclear grade graphite IG-110 was measured in the temperature range from 500 ˚C to 1000 ˚C by using an infrared thermometer. Besides, the impact of the graphite oxidation, which may take place in a postulated air ingress accident, was also evaluated. As a result, it was found that the emissivity of IG-110 grade graphite decreases slightly as the temperature increase. Moreover, a relatively high emissivity was detected in the pre-oxidized specimen. Based on the measurement data, two experimental correlations were suggested for the engineering applications. It could also be concluded that the commonly used value of the graphite emissivity (0.8), is conservative for engineering judgment.
increase and Lozier, 1958)。具体来说，Seo (2009a;2009 b;2011)测量了几种核石墨在100 ~ 500℃温度范围内的发射率，表明石墨的发射率与氧化程度呈正相关。在高温气冷堆(HTGR)中，由于高温环境，辐射是主要的传热形式。因此，堆芯材料(主要是核级石墨)的发射率对反应堆安全评价具有重要意义。本文用红外测温仪测量了核级石墨IG-110在500 ~ 1000℃温度范围内的发射率。此外，还评估了在假定的空气进入事故中可能发生的石墨氧化的影响。结果表明，随着温度的升高，IG-110级石墨的发射率略有下降。此外，在预氧化样品中检测到相对较高的发射率。根据实测数据，提出了两种适合工程应用的实验关系式。也可以得出，常用的石墨发射率值(0.8)对于工程判断是保守的。
{"title":"Experimental determination of the emissivity of nuclear graphite at high temperature conditions","authors":"Peng Chai, Yang Wu, K. Okamoto","doi":"10.1299/mel.20-00204","DOIUrl":"https://doi.org/10.1299/mel.20-00204","url":null,"abstract":"increase and Lozier, 1958). Specifically, Seo (2009a; 2009b; 2011) measured the emissivity of several types of nuclear graphite in the temperature range from 100 ℃ to 500℃ and indicating a positive relationship between graphite emissivity and oxidation degree. Abstract In a High-Temperature Gas-cooled Reactor (HTGR), radiation is the dominant form of heat transfer due to the high temperature environment. Therefore, the emissivity of the core materials (mainly nuclear grade graphite) is important for reactor safety assessment. In this paper, the emissivity of nuclear grade graphite IG-110 was measured in the temperature range from 500 ˚C to 1000 ˚C by using an infrared thermometer. Besides, the impact of the graphite oxidation, which may take place in a postulated air ingress accident, was also evaluated. As a result, it was found that the emissivity of IG-110 grade graphite decreases slightly as the temperature increase. Moreover, a relatively high emissivity was detected in the pre-oxidized specimen. Based on the measurement data, two experimental correlations were suggested for the engineering applications. It could also be concluded that the commonly used value of the graphite emissivity (0.8), is conservative for engineering judgment.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"201 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":"133810540","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}
A method to conserve the volume of dispersed components (e.g. bubbles and droplets) in a viscous fluid is proposed for the front-tracking method (Unverdi and Tryggvason, 1992; Tryggvason et al., 2001). The method adjusts the coordinates of each nodal points on the interface (or Lagrangian markers) along the velocity vector. A simplified algorithm determines the new position of the marker independently from those of the surrounding nodes, which allows the volume correction to be accomplished efficiently. The results show that the volume of a deformed fluid particle is kept constant within errors of O (10 − 7 ) ∼ O (10 − 6 ) . The effects of the time step size and the frequency of the volume correction are investigated. The method is applicable to enclosed structures of non-spherical geometry (e.g. oblate/prolate/spherical-cap fluid particles).
提出了一种保留粘性流体中分散组分(如气泡和液滴)体积的方法，用于前跟踪方法(Unverdi和Tryggvason, 1992;Tryggvason et al.， 2001)。该方法沿速度矢量调整界面上每个节点(或拉格朗日标记)的坐标。一种简化的算法独立于周围节点确定标记点的新位置，从而有效地完成体积校正。结果表明，变形流体颗粒的体积在0(10−7)~ O(10−6)的误差范围内保持恒定。研究了时间步长和体积校正频率的影响。该方法适用于非球面几何的封闭结构(如扁圆/长形/球帽流体颗粒)。
{"title":"Volume conservation method for the three-dimensional front-tracking method","authors":"S. Takeuchi, G. Tryggvason","doi":"10.1299/mel.20-00216","DOIUrl":"https://doi.org/10.1299/mel.20-00216","url":null,"abstract":"A method to conserve the volume of dispersed components (e.g. bubbles and droplets) in a viscous fluid is proposed for the front-tracking method (Unverdi and Tryggvason, 1992; Tryggvason et al., 2001). The method adjusts the coordinates of each nodal points on the interface (or Lagrangian markers) along the velocity vector. A simplified algorithm determines the new position of the marker independently from those of the surrounding nodes, which allows the volume correction to be accomplished efficiently. The results show that the volume of a deformed fluid particle is kept constant within errors of O (10 − 7 ) ∼ O (10 − 6 ) . The effects of the time step size and the frequency of the volume correction are investigated. The method is applicable to enclosed structures of non-spherical geometry (e.g. oblate/prolate/spherical-cap fluid particles).","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"9 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":"133417956","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}
A one-dimensional theoretical analysis is made of the pressure field around a train running in a long tube with a constant width slit, which is a simplified model of partially enclosed structures (or vented tubes) of railway, such as snow shelters or whole covered stations. It is shown from field measurement results in Shinkansen that the pressure field produced in such partially enclosed structures exhibits a pattern of ‘a combination of single sawtooth and its reverse’. The present analysis of a tube with a slit reproduces this unique pressure pattern and shows that one-dimensional pressure field ahead of the train nose and tail can be expressed by elementary functions. It also reveals that the magnitude of the pressure change around the tail can exceed that around the nose, which is also a unique feature that is di ff erent from the cases of open air spaces and fully enclosed spaces (i.e., tunnels).
{"title":"One-dimensional flow analysis of steady pressure field around a train running in a long tube with a constant width slit","authors":"M. Iida, K. Kikuchi","doi":"10.1299/MEL.21-00006","DOIUrl":"https://doi.org/10.1299/MEL.21-00006","url":null,"abstract":"A one-dimensional theoretical analysis is made of the pressure field around a train running in a long tube with a constant width slit, which is a simplified model of partially enclosed structures (or vented tubes) of railway, such as snow shelters or whole covered stations. It is shown from field measurement results in Shinkansen that the pressure field produced in such partially enclosed structures exhibits a pattern of ‘a combination of single sawtooth and its reverse’. The present analysis of a tube with a slit reproduces this unique pressure pattern and shows that one-dimensional pressure field ahead of the train nose and tail can be expressed by elementary functions. It also reveals that the magnitude of the pressure change around the tail can exceed that around the nose, which is also a unique feature that is di ff erent from the cases of open air spaces and fully enclosed spaces (i.e., tunnels).","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"14 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":"122334778","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}
K. Fujisaki, Ayane Kondo, K. Sasagawa, T. Moriwaki
{"title":"Development of compact pressing system for muscle activity evaluation in force myography","authors":"K. Fujisaki, Ayane Kondo, K. Sasagawa, T. Moriwaki","doi":"10.1299/mel.21-00283","DOIUrl":"https://doi.org/10.1299/mel.21-00283","url":null,"abstract":"","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"234 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":"124573947","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}
The objective of this study is to quantify the influence of higher orders of expansion in the formulation of stochastic finite elements method on the linear elastic response in 2-dimensional problems with random physical parameters in the left hand side term. Neumann expansion was used to get an explicit expression of the result. Young’s modulus was considered as a random variable following normal distribution. The coefficient of variance (COV) of this input parameter ranged in this study up to 0.3 (30%), and mainly 20% of COV was analyzed. The displacement was selected as the quantity of interest. The difference in distribution function of the displacement for different orders of expansion was observed in the tail distribution. A fundamental example revealed the limitation of the applicability of first, second and third orders being approximately 3%, 12% and 20% of COV of input parameter. In the analysis of 2-phase composite material, the influence of geometrical random morphology was larger than that of physical parameter, but the latter was not negligible in the microscopic response.
{"title":"Influence of higher orders of Neumann expansion on accuracy of stochastic linear elastic finite element method with random physical parameters","authors":"L. Degeneve, N. Takano","doi":"10.1299/mel.20-00228","DOIUrl":"https://doi.org/10.1299/mel.20-00228","url":null,"abstract":"The objective of this study is to quantify the influence of higher orders of expansion in the formulation of stochastic finite elements method on the linear elastic response in 2-dimensional problems with random physical parameters in the left hand side term. Neumann expansion was used to get an explicit expression of the result. Young’s modulus was considered as a random variable following normal distribution. The coefficient of variance (COV) of this input parameter ranged in this study up to 0.3 (30%), and mainly 20% of COV was analyzed. The displacement was selected as the quantity of interest. The difference in distribution function of the displacement for different orders of expansion was observed in the tail distribution. A fundamental example revealed the limitation of the applicability of first, second and third orders being approximately 3%, 12% and 20% of COV of input parameter. In the analysis of 2-phase composite material, the influence of geometrical random morphology was larger than that of physical parameter, but the latter was not negligible in the microscopic response.","PeriodicalId":180561,"journal":{"name":"Mechanical Engineering Letters","volume":"28 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":"133098510","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}
Xingyong Zhang, K. Okamoto, N. Erkan, Takumi Saito
Radioactive aerosols are strongly diffusive and migratory and thus have presented one of the greatest challenges during the decommissioning of the Fukushima Daiichi Nuclear Power Plant (NPP). Although cutting through debris underwater can suppress the generation of radioactive aerosols from pool scrubbing to some extent, the removal efficiency of bubble columns can be influenced by many factors. In this study, fine bubbles (microbubbles and nanobubbles) with large specific surface areas were introduced into a simple scrubber; nanobubbles, in particular, are known to have long residence times in water. The effects of fine bubbles on the aerosol removal efficiency during pool scrubbing were studied for TiO 2 (around 100 nm) and ZrO 2 (around 100 nm) aerosols. Due to the fact that TiO 2 (4.23g/cm 3 ) has similar density with CsOH (3.68g/cm 3 ) and CsI (4.51g/cm 3 ). On the other hand, ZrO 2 was found in the fuel debris (Zirconium-Water Reaction). To clarify the effects of fine bubbles, three kinds of water were prepared (i.e., distilled water, nanobubble water, and microbubble water). As a result, the removal efficiency of fine bubbles for TiO 2 aerosols decreased, while that observed for ZrO 2 aerosols improved in some cases. The improved removal efficiency achieved using fine bubbles may provide a new method for suppressing the generation of radioactive aerosols in the decommissioning of the Fukushima Daiichi NPP. the submicron radioactive aerosols due to pool scrubbing the removal efficiency of bubble columns by many In the of aerosol by described by Fuchs (1964) and Ghiaasiaan (1997), the internal circulation of gas inside a rising gas bubble is equivalent to Hill’s vortex and the absorption of aerosols at the interfaces of the rising bubbles can be described by inertial deposition, sedimentation, and diffusion. These three processes are related to particle size, bubble size, and the velocity at which bubbles rise. Many methods have been proposed to increase the amount of aerosols removed by the water phase, including air bubble subdividing devices (Cadavid-Rodriguez, 2014) and surfactants (Koch, 2012). Additionally, it has been shown that the strength of the internal circulation within bubbles is an important parameter affecting its particle removal rate. Slower internal circulation due to the presence of surfactants at the water–bubble interface will greatly reduce the particle removal rate (Friedlander, 2000). However, by adding surfactants, many microbubbles (MBs) can be generated at the nozzle inlet (Koch, 2012) and more particles can be removed from the resultant MBs due to their small size. Therefore, to achieve the highest removal efficiency with surfactants, the trade-off between internal circulation and bubble size is unavoidable.
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