Homogeneous combustion and its application to industrial furnaces.

摘要

Improving furnace efficiency is a high priority need for steel, aluminum, glass and other metal casting industries. Consequently, there has been a great deal of research for developing efficient burners for furnaces motivated by pollutant prevention and global warming concerns. This work attempts to address these needs. It is different from the previous attempts because it considers the furnace as a system rather than furnace and burners separately. Fuel and air are injected separately as turbulent jets and mixed, heated and diluted inside the furnace. Thus, the flame pattern and emissions depend on the jet interaction and mixing in multiple turbulent jet flames. This study is divided into two parts: The first part presents a numerical investigation into mixing characteristics and the resulting concentration fields in unconfined, non-reacting multiple turbulent jets. A numerical study is performed to investigate the effects of the separation distance and momentum ratio on jet interaction and mixing in multiple jets using a modified version of a LES code called the Fire Dynamics Simulator (FDS) developed by NIST.;In the second part, a laboratory-scale furnace is constructed to test the reacting turbulent jet concept and experiments are conducted to find parameters that increase combustion efficiency and reduce pollutant emissions. Intense flue gas recirculation with buoyancy stabilized mixing is employed to reduce the flame temperatures and thus thermal NO. Local temperature, gas composition distributions and UV emission intensities are measured and analyzed for various oxidizer jet momentums, oxygen enrichments, and overall equivalence ratios. FDS is again used to simulate these confined reacting jets which are relevant for furnaces, and the computational results are compared with the experimental measurements to validate a code that can be used for designing furnaces.;The computational results were found to be in good agreement with the measurements. Numerical investigations show that the large scale recirculation is well established for higher momentum of the oxidizer jet. The oxidizer jet momentum plays a very important role in mixing and achieving the homogeneous combustion condition. It was also found that the temporal UV emission is uniform with low intensity under homogeneous combustion conditions.