Ignition and combustion of a dense stream of coal particles /
The gasification/vaporization, ignition and combustion of liquid and/or solid fuels in a high temperature environment are fundamental spray system phenomena that have been widely applied in modem rocket engines, gas turbines, industrial furnaces and boilers, and IC engines. Most practical combustio...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742745161&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The gasification/vaporization, ignition and combustion of liquid and/or solid fuels in a high temperature environment are fundamental spray system phenomena that have been widely applied in modem rocket engines, gas turbines, industrial furnaces and boilers, and IC engines. Most practical combustion devices utilize dense suspensions of finely pulverized coal particles, which burn at a slower rate due to deficient oxygen within the interparticle spacing. Thus, interactions exist among the particles for dense clouds. Group combustion models use a cluster of particles rather than an isolated particle so that the interactive ignition and combustion behavior can be studied. A numerical model is developed in the current work to simulate in detail the transient pyrolysis, ignition and combustion of an expansible cylindrical cloud of coal particles. The results show that homogeneous ignition (ignition of volatiles) occurs for a dense cloud, while heterogeneous ignition (ignition of carbon) occurs for a dilute cloud. Once ignited, the flame moves toward the cloud, reaches the cloud surface and then bifurcates into a pair of flames, called the inner premixed and outer diffusion flames (double flame or binary flame). The inclusion of backward reactions (dissociation) does not affect ignition process due to the low temperatures. However, for the case of combustion, the inclusion of backward reactions reduces the outer flame temperature and results in a finite value of oxygen concentration throughout the stream. The oxygen released from dissociation of C02 reacts with char in the cloud, resulting in a higher mass bum rate and carbon monoxide mass fraction within the stream. The cloud expansion reduces the ignition time significantly for small sized coal particles, enhances the cloud mass loss rate significantly due to the decreased particle number density (or dilution effect) and increases the flame radius of the outer flame. A quantitative comparison of the results obtained in the current study is made with the experimental data obtained in LFR and flat flame burners in order to validate the accuracy and application of the current model. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xiv, 254 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |