論文 - 横森　剛

Evaluation of Dy-doped phosphors (YAG:Dy, Al<inf>2</inf>O<inf>3</inf>:Dy, and Y<inf>2</inf>SiO<inf>5</inf>:Dy) as thermographic phosphors

Ishiwada N., Fujii E., Yokomori T.

Journal of Luminescence （Journal of Luminescence）  196   492 - 497 2017年11月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00222313

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© 2017 Elsevier B.V. Phosphor thermometry has been viewed as a promising method for non-contact temperature measurement. This article explores the temperature dependence of the Dy-doped phosphors: YAG: Dy, Al2O3:Dy, and Y2SiO5:Dy. The phosphors were energized at 355 nm from a 3rd-harmonic-generation Nd:YAG laser. The intensity of YAG:Dy was much stronger than the other phosphors, and the I458 nm/I497 nm intensity ratios had high temperature resolution over a wide range of temperatures. Although Al2O3:Dy and Y2SiO5:Dy had weaker intensity, the temperature resolution of intensity ratios was as substantial as YAG:Dy. The uncertainty in measured temperature of Dy-doped phosphors was evaluated using linearized error propagation theory, based on the noise-to-signal ratio and temperature sensitivity, revealing that the measurement uncertainty of YAG:Dy was less than the other two phosphors, and thus was the most reliable thermographic phosphor. In addition, the optimization of the bandpass filter combination was explored at each temperature range with YAG:Dy phosphor. Consequently, each temperature can be precisely measured by dividing the integrated intensity between 441 and 475 nm as a counter peak range and 476–500 nm as a main peak range. Thus, ideal bandpass filters are relatively constant throughout all temperatures.

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Investigation of Cycle-to-Cycle Variation of Turbulent Flow in a High-Tumble SI Engine

Masayoshi Matsuda, Takeshi Yokomori,Norimasa Iida

SAE Technical Papers （SAE）  2017-   2017-01-2210 2017年10月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0148-7191

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The thermal efficiency of a spark-ignition (SI) engine must be improved to reduce both environmental load and fuel consumption. Although lean SI engine operation can strongly improve thermal efficiency relative to that of stoichiometric SI operation, the cycle-to-cycle variation (CCV) of combustion increases with the air dilution level. Combustion CCV is caused by CCVs of many factors, such as EGR, spark energy, air-fuel ratio, and in-cylinder flow structure related to engine speed. This study focuses on flow structures, especially the influence of a tumble structure on flow fluctuation intensity near ignition timing. We measured the flow field at the vertical center cross section of an optically accessible high-tumble flow engine using time-resolved particle image velocimetry. There are many factors considered to be sources of CCV, we analyzed three factors: the intake jet distribution, distribution of vortex core position and trajectory of the fluid particle near the spark plug. To estimate the trajectory of fluid particle, the flow structure near the spark plug is tracked backward from the ignition timing to the intake stroke. The CCV of the fluid particle trajectory has two modes, and it is induced by the different of horizontal velocity component. The more detail study is needed to detect the cause of this two-mode behavior. Furthermore, the relationships between CCV factors were analyzed by correlation coefficient and multiple regression analysis. It was not confirm that the CCV of intake jet flow and the pressure wave affect directly the following CCV factors. The CCV of the flow field is mainly generated in the compression stroke. The key part for the CCV at ignition timing is not only the vortex core position, but also the area around the vortex core.

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気相燃焼ナノ粒子合成法における粒子成長のCQMOMを用いた数値シミュレーション

松下 晴樹, 瀧川 晃太郎, 横森 剛

微粒化 （日本液体微粒化学会）  26 （ 88 ） 49 - 55 2017年07月

共著, 査読有り,  ISSN  1341-6022

Experimental Study on Flow Characteristics with Gel Reaction in a Non-Element Mixer

Masaki Yamaguchi, Ryo Hagiwara, Takeshi Yokomori,Toshihisa Ueda

Journal of Chemical Engineering of Japan （Chemical Engineering of Japan）  50 （ 7 ） 485 - 491 2017年07月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0021-9592

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Flow characteristics with gel reaction of 10 mass% PVA and 3 mass% borax solutions in a Non-element mixer were experimentally investigated. The mixer consisted of a transparent main flow pipe and transparent branch flow pipes that were connected vertically to the main flow pipe. The PVA solution was supplied to the main flow pipe at a constant inlet pressure 20 kPa. The Reynolds number of the main flow (Re) was varied from 0.5 to 10.0. The borax solution was dyed blue to visualize the flow patterns and was injected periodically from one of the branch flow pipes at a mean speed of 40 mm/s. A pressure sensor was used to measure the pressure variation at 100 mm upstream from the first branch flow pipe. When Re was low, the borax periodically formed a capsule-like slug similar to those that occur in multiphase flows. As Re was increased, the borax capsule was stretched by the shear stress of the main flow and adhered to the upside wall of the mixer. At Re = 10.0, the pipe was prone to becoming blocked by excess gel product, which resulted in the pressure increasing to the inlet pressure of the system.

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乱流燃焼ダイアグラムを用いたスーパーリーンバーンSI エンジンにおける燃焼形態の検討

菅田 健志, 李 世埈, 横森 剛, 飯田 訓正

自動車技術会論文集 （自動車技術会）  48 （ 4 ） 801 - 806 2017年07月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0287-8321

Effect of a Transition in a Fuel Species Fraction on the Behavior of a Bunsen-Type Premixed Flame

Takuya Ishibashi, Takuya Tomidokoro, Takashi Suzuki, Shuichi Umezawa, Takeshi Yokomori, Toshihisa Ueda

Proceedings of the ASME Power Conference Joint with ICOPE-17 （ASME）  1   V001T04A039 2017年06月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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Experimental Study of Thermo-Acoustic Instability Triggering in a Staged Liquid Fuel Combustor using High-Speed OH PLIF

Antoine Renaud, Shigeru Tachibana, Shuta Arase, Takeshi Yokomori

Proceedings of ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition    GT2017-64102 2017年06月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Combined Effects of Spark Discharge Pattern and Tumble Level on Cycle-to-Cycle Variations of Combustion at Lean Limits

Dongwon Jung, Kosaku Sasaki, Kenji Sugata, Masayoshi Matsuda, Takeshi Yokomori, Norimasa

SAE Technical Paper （SAE）  2017- （ March ） 2017-01-0677 2017年03月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0148-7191

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Improving the thermal efficiency of spark ignition (SI) engine is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engine. Although lean SI engine operation can offer substantial improvements of the thermal efficiency relative to that of traditional stoichiometric SI operation, the cycle-to-cycle variations of combustion increases with the level of air dilution, and becomes unacceptable. To improve the stability of lean operation, this study examines the effects of spark discharge pattern and tumble level on cycle-to-cycle variations of combustion at lean limits. The spark discharge pattern was altered by a custom inductive ignition system using ten spark coils and the tumble level was increased by a custom adapter installed in the intake port (tumble adapter). The results show that increased discharge energy by ten spark coils (without discharge offset) extends the lean limits with an improvement of indicated thermal efficiency (th), relative to that of stoichiometric operation. Furthermore, a combination of increased discharge energy and higher tumble level by tumble adapter makes it possible to allow stable operation at more extended lean limit, which is mainly attributed to shortening the duration of ST-to-CA5 and CA10-to-CA90. To examine the effect of spark discharge pattern on cycle-to-cycle variations of combustion at lean limits, the spark discharge pattern was altered for optimized combination of discharge energy and duration by adjusting the time offset between five discharges. The discharge offset of 0.25ms enables most stable ultra-lean operation, with COV of IMEPn less than 5% up to =2.0.

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Experimental Investigation of Unsteady Characteristics of the Low-Swirl Hydrogen-Air Turbulent Lean Premixed Flames

Shintaro Ogi, Shigeru Tachibana, Takeshi Yokomori

Proceedings of The 2016 Asia-Pacific International Symposium on Aerospace Technology （Japan Society for Aeronautical and Space Science）     APISAT-2016-N9-1 2016年10月

研究論文（国際会議プロシーディングス）, 共著

Quasi-steady state to non-steady state transition criterion of laminar stagnating lean premixed flame with fuel concentration oscillation

Daijiro Kawasaki, Kentaro Kashiwagi, Takeshi Yokomori, Toshihisa Ueda

Mechanical Engineering Letters （The Japan Society of Mechanical Engineers）  2   No.16-00374 2016年07月

研究論文（学術雑誌）, 共著, 査読有り

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Experimental study on a methanol auto-thermal reforming for compact reformer

Jun Ohtani, Takahiro Sakamoto, Masayoshi Wada, Hasan Mohd Faizal, Takeshi Yokomori, Toshihisa Ueda

Bulletin of the JSME, Mechanical Engineering Journal （The Japan Society of Mechanical Engineers）  3 （ 2 ） Paper No.15-00069 2016年04月

研究論文（学術雑誌）, 共著, 査読有り

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Experimental study on combustion of a methane hydrate sphere

Tomoki Yoshioka, Yuji Yamamoto, Takeshi Yokomori, Ryo Ohmura, Toshihisa Ueda

Experiments in Fluids （Springer）  56 （ 10 ） No.192 2015年11月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0723-4864

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The combustion behavior of a methane hydrate sphere under normal gravity is experimentally investigated. The initial diameter of the sphere is 20 mm. Variation in temperature at the center of the sphere (T-c) is measured with a K-type thermocouple at ignition temperatures (T-c,T-i) from 193 to 253 K at 20 K intervals. Variation in the near-surface temperature of the sphere (T-s) is measured at ignition temperatures (T-s,T-i) from 233 to 263 K at 10 K intervals. Two combustion phases are observed. When the hydrate is ignited, a stable flame envelope is formed around the sphere (phase 1). In phase 1, the surface of the sphere is dry. After a few seconds, water formed by dissociation of the methane hydrate appears on the surface and methane bubbles are formed by methane ejected from inside the sphere (phase 2), thus destabilizing the flame and causing local extinction. Methane bubbles move down along the surface and merge into a large methane bubble at the bottom of the sphere. This bubble bursts, releasing methane to form a temporary flame, and the water drops from the hydrate sphere. Water on the surface is cooled by the hydrate inside, and an ice shell confines the methane gas that dissociated inside the sphere. Because the dissociation occurs continuously inside the hydrate, the inner pressure gradually increases and at some instant, the ice cracks and methane gas is ejected from the cracks, which results in a micro-explosion with a flame. In phase 1, the surface temperature is below the freezing point of water, and so the surface remains dry and a stable flame envelope is formed; in phase 2, the surface temperature is above the freezing point, and so water appears on the surface. When the temperature at the center of the sphere is lower (193, 213, or 233 K), some methane hydrate remains even after flame extinction because heat transfer from the flame decreases in phase 2 as a result of local extinction. The diameter of the sphere decreases during combustion in accordance with the d-square law, which indicates that the heat of dissociation is supplied by the flame and methane is supplied by the dissociation of methane hydrate in the sphere, as in single-droplet combustion.

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Simultaneous Measurements of Phosphor Thermometry and PIV for High-temperature Gas Flows

Takeshi Yokomori, Haruko Nagai, Hiroshi Shiratori, Naoki Shino, Naoki Fujisawa, Taro Hirasawa

SAE paper; SAE 2015 Powertrain, Fuels & Lubricants    JSAE20159297/SAE2015-01-2002 2015年09月

研究論文（学術雑誌）, 共著, 査読有り

Flame propagation over a methane hydrate with surface temperature variation in a natural convective flow field

Tomoki Yoshioka, Masanori Suemitsu, Takeshi Yokomori, Ryo Ohmura, Toshihisa Ueda

Bulletin of the JSME, Mechanical Engineering Letters （The Japan Society of Mechanical Engineers）  1   Paper No.15-00370 2015年07月

研究論文（学術雑誌）, 共著, 査読有り

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Experimental and theoretical investigation on hydrogen permeation with flat sheet Pd/Ag membrane for hydrogen mixture with various inlet H-2 mole fractions and species

Hasan Mohd Faizal, Yuki Kawasaki, Takeshi Yokomori, Toshihisa Ueda

Separation and Purification Technology （Elsevier）  149   208 - 215 2015年07月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  1383-5866

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The estimation of hydrogen permeation mole flux was performed by previously introduced theoretical equation which considers the decrease in H-2 concentration at the membrane surface, and was compared with experimental result, for various hydrogen mixtures with different inlet H-2 mole fractions and species. A flat sheet 77 wt.% Pd/23 wt.% Ag purification membrane with effective surface area of 3.14 x 10(-4) m(2) was used. For H-2:N-2 mixture, the comparison was performed under various feed flow rates (2.78 x 10(-5)-2.50 x 10(-4) mol/s), for inlet H-2 mole fraction of 0.70-0.80, at reference membrane temperature of 623 K and total upstream pressure of 0.25 MPa. Then, nitrogen was subsequently replaced with argon (Ar), helium (He) and carbon dioxide (CO2) to investigate the applicability of the estimation method for various H-2 mixtures with different species. The results demonstrate that the effect of H-2 permeation itself plays a significant role for permeation with H-2 mixture, which induces the phenomenon of concentration polarization. Overall, the introduced method is able to estimate H-2 permeation mole flux for H2 mixture, both qualitatively and quantitatively, regardless of inlet H-2 mole fraction and species. (C) 2015 Elsevier B.V. All rights reserved.

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Model of Flame Dynamics of Laminar Premixed Flame Subject to the Low Frequency Equivalence Ratio Oscillations

Abdul Rahman Mohd Rosdzimin, Takeshi Yokomori, Toshihisa Ueda

International Communications in Heat and Mass Transfer （PERGAMON-ELSEVIER SCIENCE LTD）  61   8 - 15 2015年02月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0735-1933

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The effect of the non-uniform profile of scalar variables, such a fuel at the upstream and temperature at the downstream of the flame zone was discussed theoretically to elucidate; (1) the deviation of motion from the steady state case and (2) the hysteresis of premixed flames response to the equivalence ratio oscillations seen in an experimental and numerical works. One-dimensional integral model for the non-uniform scalar variable profile with low frequency equivalence ratio oscillation has been developed. Here, the wavelength of the oscillation is assumed to be larger than the nominal flame thickness. Through the integral analysis, we obtained the relation of the flame propagation speed for steady and unsteady cases depending on the non-uniform scalar profile at the upstream and downstream of the flame zone. Hysteresis of the flame propagation speed is found due to the transport of fuel and heat by the non-uniform scalar profile at the upstream and downstream of the flame zone. This result qualitatively agreed with the numerical results of a response of the stagnation laminar CH4/air premixed flames for a low equivalence ratio oscillation frequency. (C) 2014 Elsevier Ltd. All rights reserved.

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Flame Dynamics of Equivalence Ratio Oscillations in a Laminar Stagnating Lean Methane/air Premixed Flame

Hisashi Tomita, Abdul Rahman Mohd Rosdzimin, Sotaro Miyamae, Takeshi Yokomori, Toshihisa Ueda

Proceedings of the Combustion Institute （Elsevier）  35   989 - 997 2015年01月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  1540-7489

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This study investigates the effect of fuel concentration oscillation on laminar stagnating premixed flames by both experiment and numerical simulation. The numerical analysis is conducted using ANSYS Fluent 14.5. The equivalence ratio oscillation in the experiments is formed by a novel oscillator with two cylinder piston units that can produce alternating ejections of leaner and richer pre-mixtures. Velocity fluctuation is well suppressed by installing screens on the burner exit. The fuel concentration oscillation between the stagnation plate and the burner exit is visualized and analyzed by acetone ultraviolet light-induced fluorescence in the isothermal condition. The oscillator frequency is varied in the range 2-20 Hz, and the oscillation wavelength is much longer than the flame thickness. The flame oscillates with the fuel concentration, and in the experiment, the amplitude of the flame oscillation attenuates as the frequency of fuel concentration oscillation increases above 5 Hz, which corresponds to a Strouhal number of unity. This indicates that the Strouhal number distinguishes quasi-steadiness for St &lt; 1 and unsteadiness for St &gt; 1. The flame oscillation pattern is a closed loop, which might be attributable to variation of the back support effect on the flame. The numerical results show a similar trend for the flame response to oscillations in fuel concentration. This study finds the flame motion is significantly affected by fuel concentration oscillations, even at low frequencies; in other words, the oscillation wavelength is much longer than the flame thickness, as a result of the back support effect. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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Numerical investigation of the stagnating laminar premixed methane/air flame with fuel concentration oscillation using a four-step reaction mechanism

Sotaro Miyamae, Abdul Rahman Mohd Rosdzimin, Hisashi Tomita, Takeshi Yokomori, Toshihisa Ueda

Bulletin of the JSME, Mechanical Engineering Journal （The Japan Society of Mechanical Engineers）  1 （ 6 ） Paper No.14-00330 - TEP0060 2014年12月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  2187-9745

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Responses of stagnating laminar methane/air premixed flames under fuel concentration oscillation, i.c., equivalence ratio oscillation, were numerically investigated using a one-step overall reaction mechanism and a four-step reaction mechanism that included CO and H₂ formation. The flame motion was numerically investigated for three different oscillation cases namely: lean, rich and lean-rich crossover case. Methane/air mixtures with sinusoidal equivalence ratio oscillations were issued from the burner exit with uniform 1.0 m/s velocity profiles. In the steady state condition, the one-step overall reaction mechanism and the four-step reaction mechanism had nearly the same characteristics in the lean region, while in the rich region variations in characteristics such as flame location and flame displacement speed for the four-step model were much more significant than those for one-step model. When the equivalence ratio was oscillated, the flame location oscillated. The amplitude of the flame location oscillation did not change with the equivalence ratio oscillation when the frequency of equivalence ratio oscillation was less than 8Hz, while it decreased monotonically when it exceeded 8 Hz. Here 8 Hz corresponds to a Strouhal number (St) of unity. Thus, this result indicates that the flame was in a quasi-steady state when St<1.0 while it became unstable when St>1.0. The variation in flame location and the flame displacement speed did not follow those for the steady state condition and made a limit cycles. This was due to the back support effect. The cycles were significantly inclined at higher frequencies. In the lean condition, the limit cycle was inclined similarly for both the one-step and four-step reaction mechanisms. In the rich condition, however, the limit cycle for the four-step reaction was more inclined than that for the one-step reaction. These results show that the formation of CO and H₂ played an important role in the rich condition.

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Effect of Feed Flow Rate of Hydrogen Mixture on Hydrogen Permeation for Flat Sheet Pd/Ag Membrane with Stagnating Flow

Hasan Mohd Faizal, Ryo Kizu, Takeshi Yokomori, Toshihisa Ueda

Journal of Thermal Science and Technology 8   120-135 2013年04月

研究論文（学術雑誌）, 共著, 査読有り

The Response of a Conical Laminar Premixed Flame to Equivalence Ratio Oscillations in Rich Conditions

Abdul Rahman Mohd Rosdzimin, Takeshi Yokomori, Toshihisa Ueda

Journal of Thermal Science and Technology 8   28-43 2013年02月

研究論文（学術雑誌）, 共著