Many kinds of micromixer have been proposed and studied in this decade. The mixing mechanism of most of them has been mainly dependent on molecular diffusion. Therefore, adopting small diffusive distance has been primary measure of mixing enhancement. In this study, we have investigated a novel mixing process with two liquids having difference in surface tension, by the onset of Marangoni effect. Marangoni effect is typical phenomenon on gas-liquid free interface when there is the variation in surface tension. We conducted basic experiments in a microchannel using an air-bubble surface as the gas-liquid interface for the onset of Marangoni covection. We also performed CFD simulation to compare with the experiments. In the experiments, we successfully observed vortex flow which can contribute to species mixing, on the bubble in a few seconds after the moment of contact of the two liquids. Moreover, the CFD simulation could reproduce the vortex flow successfully.
{"title":"An Onset of Micromixing Flow Utilizing Marangoni Force","authors":"Takashi Yamada, N. Ono","doi":"10.1299/KIKAIB.79.888","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.888","url":null,"abstract":"Many kinds of micromixer have been proposed and studied in this decade. The mixing mechanism of most of them has been mainly dependent on molecular diffusion. Therefore, adopting small diffusive distance has been primary measure of mixing enhancement. In this study, we have investigated a novel mixing process with two liquids having difference in surface tension, by the onset of Marangoni effect. Marangoni effect is typical phenomenon on gas-liquid free interface when there is the variation in surface tension. We conducted basic experiments in a microchannel using an air-bubble surface as the gas-liquid interface for the onset of Marangoni covection. We also performed CFD simulation to compare with the experiments. In the experiments, we successfully observed vortex flow which can contribute to species mixing, on the bubble in a few seconds after the moment of contact of the two liquids. Moreover, the CFD simulation could reproduce the vortex flow successfully.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117177153","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}
Kazutoyo Yamada, Hiroaki Kikuta, M. Furukawa, Satoshi Gunjishima, Yasunori Hara
Flow fields near rotating stall inception in a low-speed axial compressor rotor with two different tip clearances have been investigated by instantaneous measurements of casing wall pressure distributions using 30 high response pressure transducers and by detached eddy simulations (DES) using 120 million grid points. It is found that the stall inception process in the large tip clearance case is dominated by the breakdown of the rotor tip leakage vortex, in contrast to the spike-type stall inception in the small tip clearance case which is dominated by the leading-edge separation near the rotor tip. The vortex breakdown induces the large oscillation of the tip leakage vortex with its unsteady nature, resulting in the low-pressure regions in the instantaneous casing wall pressure field and the high pressure fluctuation region on the pressure side of the adjacent blade tip in the ensemble-averaged casing wall pressure field. The large blockage effect due to the tip leakage vortex breakdown causes the rotating disturbance propagating in the circumferential direction, which can appear and disappear with a slight change in the flow rate.
{"title":"Effects of tip clearance flow on rotating stall inception process in an axial compressor rotor","authors":"Kazutoyo Yamada, Hiroaki Kikuta, M. Furukawa, Satoshi Gunjishima, Yasunori Hara","doi":"10.1299/KIKAIB.79.900","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.900","url":null,"abstract":"Flow fields near rotating stall inception in a low-speed axial compressor rotor with two different tip clearances have been investigated by instantaneous measurements of casing wall pressure distributions using 30 high response pressure transducers and by detached eddy simulations (DES) using 120 million grid points. It is found that the stall inception process in the large tip clearance case is dominated by the breakdown of the rotor tip leakage vortex, in contrast to the spike-type stall inception in the small tip clearance case which is dominated by the leading-edge separation near the rotor tip. The vortex breakdown induces the large oscillation of the tip leakage vortex with its unsteady nature, resulting in the low-pressure regions in the instantaneous casing wall pressure field and the high pressure fluctuation region on the pressure side of the adjacent blade tip in the ensemble-averaged casing wall pressure field. The large blockage effect due to the tip leakage vortex breakdown causes the rotating disturbance propagating in the circumferential direction, which can appear and disappear with a slight change in the flow rate.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129085276","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 mass transfer characteristics of the gas diffusion layer (GDL) are closely related to cell performance in polymer electrolyte fuel cell (PEFC). Thus, it is necessary to clarify the characteristics of liquid water distribution, microscopic conformation and the oxygen diffusivity in the GDL. In the present study, a hybrid type GDL is prepared using carbon paper GDL with a non-uniform wettability distribution to control the liquid water movement in the GDL and achieve both oxygen diffusion and moisture retention. To improve the oxygen diffusion characteristic of the previous reported hybrid GDL, hybrid type GDLs with different hydrophobic regions and different PTFE contents were fabricated. The effects of the different hydrophobic regions and PTFE content on the oxygen diffusivity and liquid water distribution were simultaneously measured using a galvanic cell type oxygen absorber and X-ray radiography using the BL20B2 beamline at SPring-8. In the result, the formation of oxygen diffusion paths was visualized; the pores in the hybrid GDL were formed from the hydrophobic regions, and the pores spread to the untreated region that was not hydrophobized (hydrophilic region) after the formation of the initial pores. Thus, the formation of oxygen diffusion paths enhanced the oxygen diffusivity. Additionally, the examination of effects of the hydrophobic region and PTFE content in the GDLs indicated the optimal amount of PTFE for a hybrid GDL.
{"title":"Enhancement of oxygen diffusivity in gas diffusion layer of PEFC with wettability distribution and effect of PTFE content","authors":"Ryo Koresawa, T. Daitoku, Y. Utaka","doi":"10.1299/KIKAIB.79.1038","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.1038","url":null,"abstract":"The mass transfer characteristics of the gas diffusion layer (GDL) are closely related to cell performance in polymer electrolyte fuel cell (PEFC). Thus, it is necessary to clarify the characteristics of liquid water distribution, microscopic conformation and the oxygen diffusivity in the GDL. In the present study, a hybrid type GDL is prepared using carbon paper GDL with a non-uniform wettability distribution to control the liquid water movement in the GDL and achieve both oxygen diffusion and moisture retention. To improve the oxygen diffusion characteristic of the previous reported hybrid GDL, hybrid type GDLs with different hydrophobic regions and different PTFE contents were fabricated. The effects of the different hydrophobic regions and PTFE content on the oxygen diffusivity and liquid water distribution were simultaneously measured using a galvanic cell type oxygen absorber and X-ray radiography using the BL20B2 beamline at SPring-8. In the result, the formation of oxygen diffusion paths was visualized; the pores in the hybrid GDL were formed from the hydrophobic regions, and the pores spread to the untreated region that was not hydrophobized (hydrophilic region) after the formation of the initial pores. Thus, the formation of oxygen diffusion paths enhanced the oxygen diffusivity. Additionally, the examination of effects of the hydrophobic region and PTFE content in the GDLs indicated the optimal amount of PTFE for a hybrid GDL.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121545202","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}
{"title":"「第17回動力・エネルギー技術シンポジウム」特集号発刊にあたって","authors":"保之 高田","doi":"10.1299/KIKAIB.79.228","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.228","url":null,"abstract":"","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132377119","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}
To investigate the deformation behavior of multi-layered ceramic capacitors (MLCCs) during production press process is very important to reduce over all MLCC size and increase the capacity of the MLCC through the enlargement of the electrode area. In the previous paper, the deformation of MLCC blocks in the uniaxial compression test was observed and the filling mechanism was clarified based on the measurement results. In this study, the non-frame press tests of MLCC blocks were carried out to realize the high precision press, in which the lateral compressive stress was given in addition to the longitudinal one. The deformation process was clarified based on the results of cross-sectional observation. In the edge part of the MLCC block, the interlayer space in Side-Gaps L and W was decreased by longitudinal strain and the lateral strain, whereas, at the central part of the MLCC block, the interlayer space in Side-Gaps L and W was decreased only by longitudinal strain. Since the difference in the deformation behavior between the central part and the edge part generated variations in the thickness of MLCC block, the width of the internal electrode part and the width of the Side-Gap, it was concluded that non-frame press was not suitable for high precision press of MLCC block.
{"title":"Deformation Behavior of Multi-Layered Ceramic Capacitors Block under Non-Frame Press","authors":"F. Naruse, N. Tada","doi":"10.1299/KIKAIA.79.442","DOIUrl":"https://doi.org/10.1299/KIKAIA.79.442","url":null,"abstract":"To investigate the deformation behavior of multi-layered ceramic capacitors (MLCCs) during production press process is very important to reduce over all MLCC size and increase the capacity of the MLCC through the enlargement of the electrode area. In the previous paper, the deformation of MLCC blocks in the uniaxial compression test was observed and the filling mechanism was clarified based on the measurement results. In this study, the non-frame press tests of MLCC blocks were carried out to realize the high precision press, in which the lateral compressive stress was given in addition to the longitudinal one. The deformation process was clarified based on the results of cross-sectional observation. In the edge part of the MLCC block, the interlayer space in Side-Gaps L and W was decreased by longitudinal strain and the lateral strain, whereas, at the central part of the MLCC block, the interlayer space in Side-Gaps L and W was decreased only by longitudinal strain. Since the difference in the deformation behavior between the central part and the edge part generated variations in the thickness of MLCC block, the width of the internal electrode part and the width of the Side-Gap, it was concluded that non-frame press was not suitable for high precision press of MLCC block.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116978165","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}
We have developed a non-contact high speed viscosity sensing technique, laser-induced capillary wave (LiCW) method using pulsed volume heating laser of near-infrared wave length. The main idea of the present work is based on the capillary wave induced by volume heating, which behaves more physically simplified than the one induced by surface heating in decay process and has nanometer-scale amplitude even as relatively-small temperature rise. We have derived the new theory for the wave amplitude z (x, z) captured the physics of volume heating by giving the boundary condition of heat conduction into the depth direction. First, we compared the theoretical damping behavior of capillary wave for toluene by volume heating and surface heating. According to the proposed theory, the capillary wave induced by volume heating is formed by only the effect of the thermal expansion with having the negligible effect on the temperature dependence of surface tension. In addition, maximum temperature rise and wave amplitude of water and toluene, absorption length of them are extremely different from each other, was compared between volume heating with surface heating. As a result, it was confirmed that nanometer-scale capillary wave can be induced with the temperature rise of less than mK order by volume heating, which indicates that near-infrared wave length is more applicable to the thremophysical measurement technique as a heating light source. Finally, to demonstrate the validity of the new theory, we have measured viscosities and surface tensions of Newtonian liquids, which showed good agreement within ± 5 % from the reference values.
{"title":"Development of near-infrared laser-induced capillary wave method to measure viscosity and surface tension","authors":"H. Takiguchi, Y. Nagasaka","doi":"10.1299/KIKAIB.79.690","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.690","url":null,"abstract":"We have developed a non-contact high speed viscosity sensing technique, laser-induced capillary wave (LiCW) method using pulsed volume heating laser of near-infrared wave length. The main idea of the present work is based on the capillary wave induced by volume heating, which behaves more physically simplified than the one induced by surface heating in decay process and has nanometer-scale amplitude even as relatively-small temperature rise. We have derived the new theory for the wave amplitude z (x, z) captured the physics of volume heating by giving the boundary condition of heat conduction into the depth direction. First, we compared the theoretical damping behavior of capillary wave for toluene by volume heating and surface heating. According to the proposed theory, the capillary wave induced by volume heating is formed by only the effect of the thermal expansion with having the negligible effect on the temperature dependence of surface tension. In addition, maximum temperature rise and wave amplitude of water and toluene, absorption length of them are extremely different from each other, was compared between volume heating with surface heating. As a result, it was confirmed that nanometer-scale capillary wave can be induced with the temperature rise of less than mK order by volume heating, which indicates that near-infrared wave length is more applicable to the thremophysical measurement technique as a heating light source. Finally, to demonstrate the validity of the new theory, we have measured viscosities and surface tensions of Newtonian liquids, which showed good agreement within ± 5 % from the reference values.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123660486","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}
Yuta Utada, H. Mamori, K. Iwamoto, A. Murata, Y. Kawaguchi, H. Ando, T. Senda
Drag-reducing flow owing to polymer additives in wall turbulence is investigated by means of numerical simulations. A spring-damper chain element model is employed to express a spatial concentration and flexible motion of the polymer in a turbulent flow. The model consists of some beads linked by springs and dampers. The influence of the model’s length upon the turbulent flow is mainly focused. As lengthening the model, the skin-friction drag decreases since the turbulent contribution to the skin-friction coefficient decreases while the body force term due to the model increases. The behavior of the model and the energy transport process in the drag reducing flow due to the model are discussed to clarify the mechanism of the drag reduction.
{"title":"Numerical Simulation on Friction Drag Reduction Effect due to Straight-Chain Spring-Damper Elements in Turbulent Channel Flow","authors":"Yuta Utada, H. Mamori, K. Iwamoto, A. Murata, Y. Kawaguchi, H. Ando, T. Senda","doi":"10.1299/KIKAIB.79.1937","DOIUrl":"https://doi.org/10.1299/KIKAIB.79.1937","url":null,"abstract":"Drag-reducing flow owing to polymer additives in wall turbulence is investigated by means of numerical simulations. A spring-damper chain element model is employed to express a spatial concentration and flexible motion of the polymer in a turbulent flow. The model consists of some beads linked by springs and dampers. The influence of the model’s length upon the turbulent flow is mainly focused. As lengthening the model, the skin-friction drag decreases since the turbulent contribution to the skin-friction coefficient decreases while the body force term due to the model increases. The behavior of the model and the energy transport process in the drag reducing flow due to the model are discussed to clarify the mechanism of the drag reduction.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114101055","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}
Kazuki Affla, M. Omiya, M. Iteya, T. Kamitani, T. Tomatsu
Beginning in 2012, judo has been selected to be a compulsory course in junior high schools in Japan. However, the number of participants, in particular beginners, who die or are injured in judo is higher than that for other sports. For this reason, there is a fear that there will be a drastic increase in the number of judo-related accidents leading to death or injury in junior high schools. The most serious form of head injury is acute subdural hematoma (ASDH). The purpose of the present study is to compare ASDH occurrence indices and to evaluate the effectiveness of using head protectors. Based on measurements of head acceleration during falling, the Head Injury Criterion (HIC), maximum angular acceleration and angular velocity variation range were calculated. The results indicated that the relative displacement between the brain and skull was most strongly correlated with the angular velocity variation range, which is thus a candidate evaluation index for ASDH. The results also suggest that in order to prevent ASDH, a head protector should be made of shock absorbing materials with a small coefficient of restitution, so as to reduce the rebound velocity of the skull after occipital impact.
{"title":"Comparison of evaluation indices for acute subdural hematoma occurrence under occipital impact and effectiveness of head protector in judo","authors":"Kazuki Affla, M. Omiya, M. Iteya, T. Kamitani, T. Tomatsu","doi":"10.1299/KIKAIA.78.1631","DOIUrl":"https://doi.org/10.1299/KIKAIA.78.1631","url":null,"abstract":"Beginning in 2012, judo has been selected to be a compulsory course in junior high schools in Japan. However, the number of participants, in particular beginners, who die or are injured in judo is higher than that for other sports. For this reason, there is a fear that there will be a drastic increase in the number of judo-related accidents leading to death or injury in junior high schools. The most serious form of head injury is acute subdural hematoma (ASDH). The purpose of the present study is to compare ASDH occurrence indices and to evaluate the effectiveness of using head protectors. Based on measurements of head acceleration during falling, the Head Injury Criterion (HIC), maximum angular acceleration and angular velocity variation range were calculated. The results indicated that the relative displacement between the brain and skull was most strongly correlated with the angular velocity variation range, which is thus a candidate evaluation index for ASDH. The results also suggest that in order to prevent ASDH, a head protector should be made of shock absorbing materials with a small coefficient of restitution, so as to reduce the rebound velocity of the skull after occipital impact.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126286716","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}
Impinging atomization, which has been widely utilized in liquid rocket propulsion systems, is able to produce fine drops at a rated operation. In contrast, however, the atomization characteristics deteriorate under off design conditions when injection velocity comes to be slower. In the present study, for improving atomization characteristics at off design operation, an effective technique is verified utilizing small amount of gas injection. The gas jet is supplied from a pressurized reservoir independent of the liquid supply system, and it is injected from the center of the liquid nozzles toward the impingement point. To clarify the flow field and the mechanism of the effectivity, experimental visualizations, drop size measurements and corresponding numerical analyses are carried out. It is elucidated that atomization is drastically promoted when the dynamic pressure of gas overcomes that of liquid at the impingement point. By the gas injection with the amount of only 1% of liquid mass flow rate, Sauter Mean Diameter (SMD) becomes one-tenth of the original SMD. In addition, the optimized atomization efficiency is achieved when the gas dynamic pressure is twice as much as the liquid at the impingement point.
{"title":"Enhancement mechanism of impinging atomization by gas injection","authors":"C. Inoue, Toshinori Watanabe, T. Himeno, S. Uzawa","doi":"10.1299/KIKAIB.78.1990","DOIUrl":"https://doi.org/10.1299/KIKAIB.78.1990","url":null,"abstract":"Impinging atomization, which has been widely utilized in liquid rocket propulsion systems, is able to produce fine drops at a rated operation. In contrast, however, the atomization characteristics deteriorate under off design conditions when injection velocity comes to be slower. In the present study, for improving atomization characteristics at off design operation, an effective technique is verified utilizing small amount of gas injection. The gas jet is supplied from a pressurized reservoir independent of the liquid supply system, and it is injected from the center of the liquid nozzles toward the impingement point. To clarify the flow field and the mechanism of the effectivity, experimental visualizations, drop size measurements and corresponding numerical analyses are carried out. It is elucidated that atomization is drastically promoted when the dynamic pressure of gas overcomes that of liquid at the impingement point. By the gas injection with the amount of only 1% of liquid mass flow rate, Sauter Mean Diameter (SMD) becomes one-tenth of the original SMD. In addition, the optimized atomization efficiency is achieved when the gas dynamic pressure is twice as much as the liquid at the impingement point.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132104210","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}
Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a novel hydrophilic and hydrophobic double MPL coated GDL was developed to achieve further enhancement of the PEFC performance under both low and high humidity conditions. Under low humidity conditions, a thin hydrophilic layer using titanium dioxide coated on the hydrophobic MPL is effective to conserve the humidity of the membrane electrode assembly (MEA), while a hydrophobic intermediate MPL between the hydrophilic layer and the carbon paper substrate prevents removal of water in the hydrophilic layer. This results in a significant enhancement of the ability of the MPL to prevent drying-up of the MEA. Under high humidity conditions, the double MPL coated GDL with appropriate pore diameter, thickness, and hydrophilic and hydrophobic properties is also effective to reduce flooding on the cathode catalyst layer, resulting in the higher PEFC performance compared with that for a hydrophobic MPL coated GDL.
{"title":"Hydrophilic and hydrophobic double MPL coated gas diffusion layer to prevent drying-up and flooding of polymer electrolyte fuel cells","authors":"T. Kitahara, H. Nakajima, M. Inamoto","doi":"10.1299/KIKAIB.78.1849","DOIUrl":"https://doi.org/10.1299/KIKAIB.78.1849","url":null,"abstract":"Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a novel hydrophilic and hydrophobic double MPL coated GDL was developed to achieve further enhancement of the PEFC performance under both low and high humidity conditions. Under low humidity conditions, a thin hydrophilic layer using titanium dioxide coated on the hydrophobic MPL is effective to conserve the humidity of the membrane electrode assembly (MEA), while a hydrophobic intermediate MPL between the hydrophilic layer and the carbon paper substrate prevents removal of water in the hydrophilic layer. This results in a significant enhancement of the ability of the MPL to prevent drying-up of the MEA. Under high humidity conditions, the double MPL coated GDL with appropriate pore diameter, thickness, and hydrophilic and hydrophobic properties is also effective to reduce flooding on the cathode catalyst layer, resulting in the higher PEFC performance compared with that for a hydrophobic MPL coated GDL.","PeriodicalId":331123,"journal":{"name":"Transactions of the Japan Society of Mechanical Engineers. B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127668953","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}
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