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Unformatted text preview: ~ .---------------- ..---_.-. Combustion limits by Yiguang Ju Department of Engineering Mechanics Tsinghua University Beijing 100084, China [email protected] Kaoru Maruta Department of Machine Intelligence and Systems Engineering Akita Prefectural University Honjo Akita 015-0055, Japan [email protected] TakashiNiioka Institute of Fluid Science Tohoku University Katahira, Sendai 980-8577, Japan [email protected]·tohoku.acjp Reprinted from Applied Mechanics Reviews vol 54, no 3, May 2001 ASME Reprint No AMR308 $20 ASME/AMR, 22 Law Drive, Fairfield NJ 07007-2900; [email protected] Combustion limits Yiguang Ju Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China; [email protected] Kaoru Maruta Department of Machine Intelligence and Systems Engineering, Akita Prefectural University Honjo, Akita 015-0055, Japan; [email protected] Takashi Niioka Institute of Fluid Science, Tohoku University, Katahira, Sendai 980-8577, Japan; [email protected] Combustion limits and related flame behaviors are reviewed, especially with regard to fundamental problems. As for premixed flames, after a brief historical overview of research on the flammability limit, recent trends of research on planar propagating flames, curved propagating flames, flame balls, and stretched premixed flames are discussed, and then all types of flames are summarized. Finally, instability and dynamics near limits is discussed. With regard to combustion limits of counterflow diffusion flames and droplet flames, their instability is demonstrated, then an explana- tion of lifted flames and edge flames is presented. Suggestions for future work are also discussed in the concluding remarks. There are 166 references cited in this review article. 1 INTRODUCTION No flame propagation in premixed gas occurs when the fuel concentration or the oxygen concentration decreases to ex- cess. Both limits are termed the flammability limits. How- ever, flammability limits of premixed gas have never been strictly defined, as they are very difficult to determine ex- perimentally or derive analytically. The concepts involved in these limits have been understood by researchers and engi- neers, because flammability limits are very important indus- trially, particularly with regard to safety. Other than flamma- bility limits, premixed flame has some of the following char- acteristic properties: ignition energy, burning velocity, quenching distance, and so on. The termjlammability for dif- fusion flames is not found in any textbook. Strictly speaking, flame extinction of the counterflow diffusion flame may be only one characteristic property. However, this property is distinctly different from flammability of the conventional premixed flame and cannot be treated in the same manner, but both are characterized by the same combustion-limit phenomena. There are some other limiting phenomena that make it impossible to maintain stable burning. Therefore, these phenomena are categorized as combustion...
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- Fall '06
- Combustion, Ju, Flammability limit