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359 results on '"Deguchi, Yoshihiro"'

24. Lagrangian Identification of Coherent Structures and Mass Transport in a Buoyant Jet Diffusion Flame.

Author

Dang, Nannan, Wang, Wei, Cao, Shengli, Zhang, Jiazhong, Deguchi, Yoshihiro, and Li, Zhihui

Subjects
KELVIN-Helmholtz instability, JET transports, HEAT of reaction, JET fuel, FLAME, LYAPUNOV exponents, RADIO jets (Astrophysics)
Abstract

Using Lagrangian coherent structures (LCSs), the mass transport process of large-scale coherent structures in a buoyant jet diffusion flame is studied numerically to gain a key understanding of combustion instability. First, the reacting flow fields of the jet diffusion flame are numerically simulated for two cases, a stable case without considering the buoyancy effect and an unstable case that includes the buoyancy effect corresponding to combustion instability. In particular, large-scale Kelvin-Helmholtz instability (KHI) vortex structures outside the flame surface are captured in the unstable case. Then, the ridges in finite-time Lyapunov exponent (FTLE) fields that sketch the distinct regions in the reacting flow field are extracted as LCSs. The mass transport process is studied by comparing the distribution of LCSs with reaction fields. The flame surface is found to coincide with the attracting LCSs, which separate the fuel and air on opposite sides of the flame surface. In contrast, the reaction products, including species and reaction heat, are confined in the boundaries consisting of repelling LCSs on the inner and outer sides of the flame surface. Finally, the evolution of LCSs is tracked to analyze the generation of KHI vortices and species transport in the jet diffusion flame. With the aid of LCSs, it is found that there exist some saddle-type flow features separating the distinct flow structures into several regions, and the jet fuel and airflow enter into the separated regions from different open boundaries. Importantly, the attracting LCSs in the separated regions then bulge outwards, forming KHI vortices as the attracting LCSs further stretch and fold. Furthermore, the vortices continue moving upwards while species flow from repelling LCSs to attracting LCSs, leading to mixing. These results show that attracting and repelling LCSs can act as the flame surface and the mass and energy transport boundary of the reaction products, respectively. In summary, the work presented can provide a new method in combustion controlling to estimate the location of the flame surface and the transport boundaries of species from the velocity field, by using LCSs. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Sulfur Detection in Coke by Laser-Induced Breakdown Spectroscopy

Author

Chen, Peng, Luo, Han, Cui, Minchao, Wang, Zhenzhen, Deguchi, Yoshihiro, Yan, Junjie, Chen, Peng, Luo, Han, Cui, Minchao, Wang, Zhenzhen, Deguchi, Yoshihiro, and Yan, Junjie

Abstract

Accurate determination of sulfur (S) content in coke is of great significance to improve the quality of iron and steel. In this study, the sulfur in coke standard samples was detected in argon (Ar) atmosphere using laser-induced breakdown spectroscopy (LIBS), and S I 182.034 nm was chosen as the analytical line. The experimental results showed that it was advantageous to detect S in the early stage of plasma generation. Compared with tablet samples, the spectral intensities of binder samples on the copper foil tape were greater and the signal-to-noise ratio (SNR) was also greater. As for reduplicate experiments, the coefficient of variation (CV) of spectral intensities of binder samples was 10.58% and that of tablet samples was 88.54%. The plasma signal induced by binder samples was stronger and more stable. The internal standard method and support vector machine regression (SVR) were used to quantitatively analyze the sulfur content in binder samples, and SVR showed more accurate prediction accuracy. R2 of SVR with electron density and self-absorption correction was 0.965, root mean square error of prediction (RMSEP) was 0.18 wt.% and the limit of detection (LOD) was 0.026%. This result proved the applicability of binder for sulfur measurement in coke using LIBS.

Published
2022

47. 基于支持向量机回归的LIBS飞灰含碳量定量分析

Author

Chen Peng, 陈鹏, primary, Qi Chao, 齐超, additional, Liu Renwei, 刘人玮, additional, Wang Zhenzhen, 王珍珍, additional, Luo Han, 罗晗, additional, Yan Junjie, 严俊杰, additional, Liu Jiping, 刘继平, additional, and Deguchi Yoshihiro, 出口祥啓, additional

Published
2022
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48. Measurement of Three-Dimensional Combustion Distribution using CT-TDLAS

Author

Jeon, Min-Gyu, Doh, Deog-Hee, and Deguchi, Yoshihiro

Subjects
Exhaust Gas(배기가스), Computed Tomography(전산화 단층촬영), Temperature(온도), Tunable Diode Laser Absorption Spectroscopy(가변 다이 오드 레이저 흡수 분광법), Data Reconstruction(데이터 재구성)
Abstract

에너지 자원을 효율적으로 사용하기 위해서는 연소 가스에 대한 정확한 측정이 필요하다. TDLAS 기술로 대상 가스의 온도와 농도를 동시 측정할 수 있다. 현재 가스의 정밀 제어가 필요한 산업공정에 2차원 또는 3차원의 정보를 측정한 실험적 보고는 미비하다. 본 연구에서는 산업공정의 연소를 제어하 고 모니터링하고자 CT-TDLAS 시스템을 이용한다. 메탄-공기 예혼합화염의 3차원 온도 분포는 CT-TDLAS 시스템에 의해 측정되었으며, 3차원 온도 분포는 2차원 셀의 5개 층으로 측정하였다. 특히 흡수 스펙트럼의 3차원 재구성에 SMART 알고리즘을 적용하였다. 열전대와 CT-TDLAS로 모든 층의 온도를 비교한 결과 온도의 평균 상대오차가 19.7K로 정확하게 측정되었다., In order to use energy resources efficiently, accurate measurement of combustion gases is necessary. Measurement of the temperature and concentration of a target gas is possible with tunable laser absorption spectroscopy (TDLAS) technique. The TDLAS technique can be used to control and monitor combustion in industrial processes. The 3-dimensional temperature distribution of methane-air premixed flame was measured using the constructed computed tomography tunable diode laser absorption spectroscopy (CT-TDLAS) system. The 3-dimensional temperature distributions are measured by five layers of the 2-dimensional cell. The simultaneous multiplicative algebraic reconstruction technique (SMART) algorithm was adopted for reconstructing the absorption coefficients on the meshes. As a result of comparing the temperatures for all the layers using thermocouples and the CT-TDLAS technique, it was possible to accurately measure the average relative error of temperature as 19.7 K.

Published
2019

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