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Fluid dynamics characteristics of pulverized coal burner

Writer: admin Time:2021-04-10 00:00 Browse:

  	Fluid dynamics characteristics of pulverized coal burner
1. The function of the pulverized coal burner: send the pulverized coal and the air required for combustion into the furnace, organize a certain airflow structure, and make the fuel ignite quickly and stably. 2. Direct current burner: the outlet jet is a direct current jet or the burner of a direct current jet group is a direct current burner. 3. Swirl burner: A burner that includes a swirl jet at the outlet jet is a swirl burner. 4. Aerodynamic characteristics: the relationship between air (flue gas) flow rate and pressure difference. One. DC jet and DC burner 1. Entrainment: Because the jet drives the surrounding medium to flow with the jet, the mass of the jet gradually increases. This process is called entrainment. 2. Range describes the physical quantity of jet penetrating ability in the surrounding medium. (1) The range is from the nozzle along the jet axis to a certain section L, the maximum axial velocity in this section is. (2) The range is from the nozzle along the jet axis to a certain section L, in which the maximum axial velocity has been reduced to a certain value. 3. The initial momentum K0 of the airflow, see (61). 4. The ignition heat of the DC burner mainly comes from entrainment (mostly from entrainment, and a small part from radiation). The greater the aspect ratio of the nozzle of the direct current burner, the stronger the entrainment capacity. 5. The pulverized coal air flow of the DC burner has only the outer recirculation zone, so the ignition point is at the outer boundary. Explain the formation, anchoring and stagnation point of the recirculation zone. 6. The directflow burner is applied by the American Combustion Engineering Company (CE Company) (applied on all boilers manufactured without swirling burners), and the level is relatively high. 7. Uniform air distribution direct current burner: The primary air nozzles and the secondary air nozzles are arranged at intervals, and the distance is relatively close, so that the primary air and the secondary air come into contact early, which is suitable for bituminous coal and lignite with relatively high volatile content. 8. Graded air distribution directflow burner: the primary air nozzles are arranged relatively centrally, and the secondary air nozzles are arranged in stages, so that the secondary air is gradually mixed with the primary air in stages. It is suitable for anthracite and lean coal with relatively low volatile content. 9. The role of the lower secondary air: to provide the oxygen required by the pulverized coal flame on the lower side, hold the pulverized coal, and prevent the segregation of the pulverized coal. 10. The tertiary air is at the top of the burner and plays the role of burning up the fuel. two. Rotary jet and swirl burner 1. In any cross section of a freely rotating jet, both the rotational moment of momentum and the axial momentum are conserved. 2. Swirl intensity: the ratio of the rotational momentum moment to the product of the axial momentum and the characteristic size of the nozzle. 3. The three swirl burners in the book are products of the Soviet Union in the 1950s and are not easy to use. Basically been eliminated. Nowadays, the tworegulated air burners of B&W Company in the United States are more commonly used. The swirl burners of other companies are similar to those of B&W. For example, the US FW company, the recent products of the Soviet Union, etc. Here I will explain the dualregulated air burners of American B&W Company, some have a central tube, and some do not have a central tube. 4. The swirl burner has an internal reflux area, and the ignition point is at the internal boundary. Almost all the heat of a fire comes from entrainment (very little radiation). 5. The flame of the swirl burner is relatively short and thick, which means that the combustion is more intense.



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