Group combustion of char/carbon particles

Journal Article · Tue Dec 01 00:00:00 EST 1987 · Combust. Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(87)90111-8· OSTI ID:5500291

Annamalai, K; Ramalingam, S C

To gain a basic understanding of the group behavior, a model such as the analysis of a spherically symmetric cloud of particles burning in quiescent air is presented here. Each particle within the cloud produces CO, due to both the oxidation of C to CO and the reduction of CO/sub 2/ to CO which subsequently oxidizes to CO/sub 2/ in the homogeneous gas phase. Generalized results for the burning rate and the flame structure are given as a function of group combustion number (G). Predicted results show unexpected results including the independence of the burning rate of CO kinetics. Quantitative results for both the cases of frozen and fast CO kinetics are given. There is a group flame for the case of fast CO kinetics. It is shown that the group flame occurs at G > 5 while for a cloud of liquid drops, the group flame occurs at G > 0.1. The higher critical group combustion number is attributed to the lower burning rate of particle inside the cloud compared to the burning rate of liquid drops inside the cloud. The results show that there exists mainly three modes of combustion: (i) Individual Particle Combustion (IPC, low G), (ii) Group Combustion (GC, intermediate G) and (iii) Sheath Combustion (SC, high G). Criteria are given for identifying the mode of combustion from the experimental conditions. The criteria and the establishment of modes of combustion are independent of the extent of CO kinetics. It is found that the experimental data, obtained with a stream of particles and commonly interpreted with the IPC model, indicate the combustion modes to vary from IPC to SC modes. These data are now reinterpreted with the group theory.

• Research Organization: Texas A and M Univ., College Station, TX 77843-3123
• OSTI ID: 5500291
• Journal Information: Combust. Flame; (United States), Vol. 70:3
• Country of Publication: United States
• Language: English

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