研究者詳細 - 石野　洋二郎

論文 - 石野　洋二郎

分割表示 141 件中 1 - 20 件目／全件表示 >>

Flow features of underexpanded microjets emerging from a round convergent nozzle 査読あり

Tashiro, T., Fukunaga, R., Utsunomiya, D., Nakao, S., Miyazato, Y., Ishino, Y.

Experiments in Fluids 64(3) 2023年 64 ( 3 ) 2023年

記述言語：英語掲載種別：研究論文（学術雑誌）

Density measurements of underexpanded microjets that emerge from a round convergent nozzle with an inner diameter of 1 mm at the exit are taken using rainbow schlieren deflectometry to nonintrusively capture an extensive region from the nozzle exit to a downstream location of twenty times the nozzle exit diameter. Flow visualizations of the microjets are carried out at nozzle pressure ratios (NPRs) of 3.0, 4.0, 5.0, 6.0, and 7.0 and corresponding fully expanded jet Mach numbers (M-j) of 1.36, 1.56, 1.71, 1.83, and 1.93, where the NPR can be defined as the ratio of the stagnation pressure upstream of the nozzle to the back pressure. The three-dimensional density fields of the microjets are reconstructed at a spatial resolution of approximately 4 mu m by the Abel inversion technique based upon the assumption of axisymmetric density fields. The flow topology of the near-field shock structure for each NPR is demonstrated with an elevated view of the density field, including the jet central axis. The location and flow Mach number of the first local minimum in the density profile along the jet central axis are experimentally provided for the first time as a function of the NPR to propose an empirical relation. An approximate expression for the flow Mach number on the jet central axis from the nozzle exit to the location where the isentropic process is established is also derived against the streamwise distance. In addition, the supersonic length of a shock-containing microjet, which is defined as the distance along the jet central axis from the nozzle exit to the location farthest downstream at which there exists a local flow Mach number of unity, is acquired from the density profile along the jet centerline and compared quantitatively with the experimental data from previous Pitot probe surveys as well as previous empirical relations. Furthermore, the microjet density fields from rainbow schlieren deflectometry are mutually compared with those from previous Mach-Zehnder interferometry under the same nozzle to investigate the effects of nonintrusive techniques on the density profiles along three representative locations: the jet centerline, intermediate line, and lipline.

Microscopic Image Diagnostics with Visible Emission Light for Self-burning Surface Temperature Distribution of CFRP (Carbon Fiber Reinforced Plastic) in Oxygen 査読あり国際誌

Yojiro Ishino. Rion Ito

Proceedings of the 13th Pacific Symposium on Flow Visualization and Image Processing 1 - 5 2022年08月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Carbon Fiber Reinforced Plastic(CFRP) has been widely used in variety industries because of its high strength-density ratio. Therefore disposal method of waste CFRP should be considered in advance now. We have been proposed a combustion incineration of carbon fiber(CF) residue after recycle use. However, carbon fiber residue is almost impossible to be burned out by even high temperature burnt gas because of extremely high melting point of carbon fiber and a low oxygen concentration in burnt gases[1].
In this study, self-sustained combustion of carbon fiber in oxygen has been reported. In order to obtain information of the self-sustaining mechanism of the combustion, in this paper, a convenient optical technique to acquire the 2D distribution of high surface temperature of glowing solid material was conducted.
In this technique, magnified thermographic view of the high temperature specimen was provided by comparison between RGB brightness information of conventional photograph of the visible light emission of the surface and previously-calculated values from Planck's law and the spectral sensitivity of the camera system.
In this paper, first, accuracy of the method was verified by comparison between the 2D temperature distribution result of a glowing fine (0.5 mm dia.) graphite rod in burnt gas of a propane-air premixed laminar flame and its estimated temperature distribution measured by PR-type thermocouple and compensated by Kaskan's method. Next magnified instantaneous 2D temperature diagnostics of self-burning carbon fiber bundle in oxygen was made. The 2D surface temperature distribution result gives very high temperature over 2900 K on carbon fiber surface in in-oxygen combustion incineration.

Multi-Schlieren 3D-CT Measurements of Instantaneous Equivalence Ratio Distributions of a Premixed Gas Field Based on Modified Refractive Index 査読あり

NAZARI, Ahmad Zaid, ISHINO, Yojiro, KONDO, Harumi, MOTOHIRO, Takanori, YAMADA, Ryoya and ITO, Fumiya

Journal of the Combustion Society of Japan ( 1910 ) 1 - 9 2020年11月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本燃焼学会

In quantitative measurements and investigations, "equivalence ratio" and "refractive index" are the most significant parameters in combustion flow fields. Experimental and analytical studies were performed to understand the relation between equivalence ratio and refractive index in flow fields. A "universal relationship" between the refractive index of a premixed gas of fuel and air and its equivalence ratio has been established in this study. Through this relationship, we can calculate the equivalence ratio of any premixed gas (except those of light fuels) from its refractive index using a unique coefficient. The uniqueness of the relation coefficient enables us to obtain the equivalence ratio of even a multi-fuel premixed gas from its refractive index. In this study, the novel relationship is applied to a non-scanning 3D-CT (computerized tomography) technique using a multi(20)-directional quantitative schlieren optical system with a flashlight source. Instantaneous equivalence ratio distributions of a dual-fuel premixed gas flow with two jets of ethanol/air and propane/air mixtures are measured by CT-reconstruction. Good agreement was observed between the CT-reconstructed data and the proposed comprehensive relation.

DOI： 10.20619/jcombsj.1910

Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles 査読あり国際誌

Ahmad Zaid Nazari, Yojiro Ishino, Yuta Ishiko, Fumiya Ito, Harumi Kondo, Ryoya Yamada, Takanori Motohiro, Yoshiaki Miyazato, Shinichiro Nakao

Journal of Flow Control, Measurement & Visualization 8 77 - 101 2020年05月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific research publishing

Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers Mj ranging from 1.47 - 1.71, where the design Mach number is Md = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and "diagonal" of “cross-shaped”. The initial axis-switching is 45˚ within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.

DOI： 10.4236/jfcmv.2020.83005

Quantitative Schlieren Image-Noise Reduction Using Inverse Process and Multi-Path Integration 査読あり国際誌

Ahmad Zaid Nazari, Yojiro Ishino, Fumiya Ito, Harumi Kondo, Ryoya Yamada, Takanori Motohiro, Yu Saiki, Yoshiaki Miyazato, Shinichiro Nakao

Journal of Flow Control, Measurement & Visualization 8 ( 2 ) 1 - 25 2020年04月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Research Publishing

This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, "inverse process" and "multi-path integration" for image-noise reduction. Noise in schlieren images affects the projections (density thickness) images of CT (computerized tomography). One spot noise in the schlieren image appears in a line shape in the density thickness image. Noise effect like an infectious disease spreads from a noisy pixel to the next pixel in the direction of single-path integration. On the one hand, the noise in the schlieren image reduces the quality of the image and quantitative analysis and is undesirable, on the other it is unavoidable. So, the importance of proper noise reduc-tion techniques seems essential and tangible. In the present report, a novel technique "multi-path integration" is proposed for noise reduction in projections images of CT. Multi-path integration is required schlieren brightness gradient in two orthogonal directions. The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient and another 20-directional optical system seems necessary to obtain vertical schlieren brightness gradient, simultaneously. Using the "inverse process" a new technique enables us to obtain vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system and can be used for obtaining any optional direc-tions of schlieren brightness gradient. Recently, we presented the "inverse process" technique but in a different way than this time. In previous work, the phan-tom(virtual) data of schlieren images are obtained by the "inverse process" and used to evaluate noise reduction technique while in the new "inverse process" technique actual experimental data is used for reproducing other directions of schlieren brightness gradient.

Three-dimensional reconstruction of a microjet with a Mach disk by Mach-Zehnder interferometers 査読あり国際誌

S. Sugawara, S. Nakao, Y. Miyazato, Y. Ishino and K. Miki

J. Fluid Mech. 893 A25-1 - A25-26 2020年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

DOI： 10.1017/jfm.2020.217

THREE-DIMENTIONAL MEASUREMENT ON THERMAL STRUCTURE OF SIX CLUSTERED METHANE-AIR DIFFUSION MICROFLAMES 査読あり国際誌

Yuta Uchida, Harumi Kondo, Zhaojin Diao, Taro Hirasawa, Michael Winter, Yojiro Ishino, Kozo Saito

Proceedings of The Second Pacific Rim Thermal Engineering Conference PRTEC-24221 1 - 5 2019年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：ASTFE, JSME, KSME

The unique and complicated three-dimensional flame structure of clustered six diffusion methane-air microflames was investigated in the present study. The burner consisted of six micro-nozzles for methane with a diameter of 0.23 mm arranged in a circle surrounding a central nozzle for air with a diameter of 0.7 mm. The burner established six interacting microflames under the conditions of methane total flow rate of 20 cm3 / min and air flow rate of 30 cm3 / min. Schlieren CT method was applied to obtain the three-dimensional distribution of modified refractive index inside and outside the flame structure of the clustered diffusion microflames. The correspondence of flame structure to the distribution of the modified refractive index was confirmed.

Study on Combustion Incineration of CFRP (SEM Observations of Nano Level Sharpening of Carbon Fiber Residue Tips and Temperature Measurements Based on Heat Radiation Images) 国際誌

Y. Ishino, M. Tabata,S. Onuma

Proceedings of the International Workshop on Environmental Engineering 2019 (IWEE2019) 1 - 2 2019年06月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：The Japan Society of Mechanical Engineers, Environmental Engineering Division

Carbon fiber, contained in CFRP(carbon fiber rainforced plastic), is almost impossible to be burned out by even high temperature burnt gas because of extremely high melting or sublimation point of carbon fiber and a low oxygen concentration in burnt gases. In this study, first, oxygen nozzle of 10 mm x 30 mm exit size, which equipped fuel (propane) pipe of inner diameter of 0.8 mm for a pilot ignition flame, has been introduced to observe the in-oxygen-combustion behaiviors of test pieces of (i) CFRP slender plate (2 mm wide and 1 mm thickness), (ii)slender plate of CFRP-P (Plastic removed CFRP), "G"FCRs("Graphite" Fine Cylindrical Rod) of diameters of 0.38 mm, 0.55 mm and 0.72 mm.

CT (COMPUTER TOMOGRAPHY) MEASUREMENT OF 3D DENSITY DISTRIBUTIONS OF FLAME: OBTAINING VERTICAL GRADIENT SCHLIEREN BRIGHTNESS FROM HORIZONTAL GRADIENT FOR IMAGE-NOISE REDUCTION 査読あり国際誌

Ahmad Z. Nazari, Yojiro Ishino, Ryoya Yamada, Takanori Motohiro, Fumiya Ito, Harumi Kondo, Yoshiaki Miyazato, Shinichiro Nakao

Proceedings of the 4th Thermal and Fluids Engineering Conference (TFEC) TFEC-2019 ( 27746 ) 1 - 10 2019年04月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：American Society of Thermal and Fluids Engineers

Using a delicate multi-directional quantitative schlieren optical system, the 20-directional observation of high-speed premixed turbulent flame, non-uniform density flow, by employing non-scanning 3D-CT (three-dimensional computer-tomography) technique has been conducted. The 3D density distributions data of target flame by using ML-EM (Maximum Likelihood-Expectation Maximization) an appropriate CT (computer-tomography) algorithm are successfully reconstructed. In the previous report, a novel technique "multi-path integration" is proposed for noise reduction in projections (density thickness) images of CT (computer-tomography). Multi-path integration is required schlieren brightness gradient in both horizontal (x-directional) and vertical (z-directional) directions, or in other words, in two orthogonal directions (e.g. horizontal and vertical or two perpendicular diagonal directions). The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient (x-directional) and another 20-directional optical system seems necessary to obtain vertical (z-directional) schlieren brightness gradient, simultaneously. In the present investigation, the report deals with introducing a new technique for obtaining vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system. This new approach is a simple and inexpensive solution. First, for a deep understanding of complex schlieren brightness, a numerical simulation is performed. Next, the initial density thickness (Dt) images are obtained from images of schlieren brightness in the horizontal gradient (x-directional). Finally, using inverse process from density thickness (Dt) images, the vertical (z-directional) and diagonal schlieren brightness gradient data of target flame successfully obtained. The mentioned technique can be used for obtaining any optional directions of schlieren brightness gradient.

Characterization of Six Clustered Methane-Air Diffusion Microflames through Spectroscopic and Tomographic Analysis of CH* and C2* Chemiluminescence 国際共著

Zhaojin Diao, Michael Winter, Taro Hirasawa, Yuichi Kato, Yojiro Ishino, and Kozo Saito

Experimental Thermal and Fluid Science 102 20 - 27 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevior

The current study presents an emission spectroscopic investigation of clustered microflames established on a burner consisting of six micro fuel nozzles surrounding a center air nozzle which has been designed for flame synthesis and characterization of microflames. We conducted the spectrally resolved measurement of chemiluminescence of C2* and CH* and compared these results to a tomographic method applied to filtered emission measurements of CH* emission which can yield spatially resolved three dimensional mapping of the flame front. The analysis of the spatial distribution of the integrated band emission of C2* and the CH* showed that the emission of both species is generated in the same locations in the flame which are the thin flame sheets shown in the tomography results of CH*. The ratio of the C2* and the CH* emission from the emission spectroscopy measurements was used to determine a local corresponding equivalence ratio through empirically derived correlations for premixed flames reported in literature. The resulting equivalence ratio equals one when the flame zone established at the boundary between fuel and air, indicating that the diffusion dominated flame zones are established. Under certain nozzle pitch and flow rate conditions, the equivalence ratio above the center air nozzle inside the merged flame became significantly greater than one, which indicates a fuel rich premixed type flame zone being established.
To determine distributions of rotational and vibrational temperatures throughout the entire flame, we used the spectrally resolved emission from C2* and CH*. The temperature associated with vibrational excitation was different for both species but remained constant throughout the entire flame region and was found no representation of the flame temperature but an artifact of the combustion reactions producing the chemiluminescence. The rotational temperature of di-atomic molecules, however, equilibrates rather quickly with the translational temperature and can accurately represent the gas-dynamic temperature of the flame. The temperature distributions found from the two species agreed qualitatively, the CH* temperature was consistently higher than the C2* temperature by about 200 K. Spatial resolution was assigned to the results from the spectroscopic measurements through a comparison with the tomographically analyzed images of the CH* chemiluminescence.

CT ( COMPUTER TOMOGRAPHY ) MEASUREMENT OF 3D DENSITY DISTRIBUTIONS OF HIGH-SPEED PREMIXED TURBULENT FLAMES ( MULTI-PATH INTEGRATION IMAGE-NOISE REDUCTION TECHNIQUE BASED ON NOVEL CONCEPT OF COMPLEX BRIGHTNESS GRADIENT IN QUANTITATIVE SCHLIEREN IMAGES ) 査読あり国際共著

A. Z. Nazari, Y. Ishino, R. Yamada, T. Motohiro, F. Ito, H. Kondo, Y. Miyazato, S. Nakao

18th International Symposium on Flow Visualization 1 ( 1 ) 1 - 13 2018年06月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

A Novel Rotational Internal Combustion Engine with a Single-Lobe Peritrochoid Rotor (Design Fundamentals and Motoring Test of a Prototype Engine) 査読あり国際誌

Yojiro ISHINO, Tomoya NIWA

Transactions of the JSASS/Aerospace Technology Japan 15 ( 　 ) 117 - 126 2018年03月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

A novel rotational internal combustion engine is invented and investigated as an auxiliary power unit (APU) of aircraft and range extension power unit for electric automobiles. For the intended applications, IC engines are required to have vibration-free characteristics. There are no reciprocating components in the present engine, resulting in vibration-free operation. This engine mainly consists of a rotor casing, a rotor and a crankshaft. The rotor is shaped in a single-lobe peritrochoid (S.L.P.) curve. The rotor is turned using a crankshaft eccentricity e and self-rotation in the counter-direction is achieved using phasing gears. The rotor casing shape has two cavities that define the envelope curve of the rotating single-lobe peritrochoid rotor. The space between the rotor and casing is where the processes for the working gas are performed: intake, compression, ignition, expansion and exhaust. The intake of premixed air/fuel gas and exhaust of burnt gas are controlled by rotary valves installed on the combustion recesses of the rotor-casing. The combustion recesses are equipped with spark-electrodes for ignition. One of the advantages of this engine compared to Wankel rotary engines and a previous engine invented by authors is easy and reliable sealing of the working gas. In this engine configuration, a sealing component is only installed on the waist section of the rotor-casing, instead of complex sealing system used for the rotor in the case of Wankel engines, resulting in higher efficiency by reducing the leakage of working gas.
In this paper, first the configuration and geometries of this engine are described. Next a prototype engine is introduced and the cyclic behavior of the working process of the engine is explained. The performance of the prototype engine driven by an electric motor is also shown.

Schlieren CT Measurement of 3D Density Distributions of Flame Kernels of Spark-Ignited Direct-Injection of Free, Cavity-Guided and Plane-Guided Fuel Jets 査読あり国際誌

Ahmad Zaid Nazari, Yojiro Ishino, Takanori Motohiro, Ryoya Yamada, Yuta Ishiko, Yu Saiki

11th Asia-Pacific Conference on Combustion 1 - 4 2017年12月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

COMPUTER FLOW VISUALIZATION OF UNDEREXPANDED JETS FROM AXISYMMETRIC SUPERSONIC MICRO NOZZLES 査読あり国際誌

H. FUKUDA, H. MAEDA, D. ONO, S. NAKAO, Y. MIYAZATO, Y. ISHINO

11th Pacific Symposium on Flow Visualization and Image Processing 1 - 4 2017年12月