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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Direct numerical simulation and reaction path analysis of titania formation in flame synthesis

Singh, Ravi Ishwar 03 February 2014 (has links)
Flame-based synthesis is an attractive industrial process for the large scale generation of nanoparticles. In this aerosol process, a gasifi ed precursor is injected into a high-temperature turbulent flame, where oxidation followed by particle nucleation and other solid phase dynamics create nanoparticles. Precursor oxidation, which ultimately leads to nucleation, is strongly influenced by the turbulent flame dynamics. Here, direct numerical simulation (DNS) of a canonical homogeneous flow is used to understand the interaction between a methane/air flame and titanium tetrachloride oxidation to titania. Detailed chemical kinetics is used to describe the combustion and precursor oxidation processes. Results show that the initial precursor decomposition is heavily influenced by the gas phase temperature field. However, temperature insensitivity of subsequent reactions in the precursor oxidation pathway slow down conversion to the titania. Consequently, titania formation occurs at much longer time scales compared to that of hydrocarbon oxidation. Further, only a fraction of the precursor is converted to titania, and a signi cant amount of partially-oxidized precursor species are formed. Introducing the precursor in the oxidizer stream as opposed to the fuel stream has only a minimal impact on the oxidation dynamics. In order to understand modeling issues, the DNS results are compared with the laminar flamelet model. It is shown that the flamelet assumption qualitatively reproduces the oxidation structure. Further, reduced oxygen concentration in the near-flame location critically a ffects titania formation. The DNS results also show that titania forms on the lean and rich sides of the flame. A reaction path analysis (RPA) is conducted. The results illustrate the di ffering reaction pathways of the detailed chemical mechanism depending on the composition of the mixture. The RPA results corroborate with the DNS results that titania formation is maximized at two mixture fraction values, one on the lean side of the flame, and one on the rich side. / text
2

超小型燃焼器の開発に関する詳細素反応機構を考慮した数値解析

YAMAMOTO, Kazuhiro, YAMASHITA, Hiroshi, SUZUKI, Shin, 山本, 和弘, 山下, 博史, 鈴木, 新 January 2008 (has links)
No description available.
3

センターエアーバーナによる燃焼器の小型化に関する数値解析

YAMAMOTO, Kazuhiro, YAMASHITA, Hiroshi, MAKITA, Yuichiro, 山本, 和弘, 山下, 博史, 槙田, 雄一郎 January 2009 (has links)
No description available.
4

Numerical Study on Spark Ignition Characteristics of Methane-air Mixture Using Detailed Chemical Kinetics : Effect of Electrode Temperature and Energy Channel Length on Flame Propagation and Relationship between Minimum Ignition Energy and Equivalence Ratio

YAMAMOTO, Kazuhiro, YAMASHITA, Hiroshi, HAN, Jilin January 2009 (has links)
No description available.

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