Spatially-Resolved experimental investigations of combustion characteristics in a solid fuel doped methane swirl flame and the influence on the formation of ultrafine particulate matter

The formation of inhalable fine particles (dp≤10 µm) is an undesirable side effect of solid fuel combustion processes. These particles can accumulate in the human respiratory system and thus cause severe lung damage. Therefore, an understanding of the formation of these particles is of crucial importance to avoid or to reduce the amount of fine particulate matter (PM) released into the atmosphere. Until now, most of the studies have been carried out for laminar and early-stage solid fuel combustion under simplified conditions (e.g. flat flame burner with radial almost homogeneous conditions) and only a few studies have been carried out with more complex turbulent flame structures. As the majority of real applications on an industrial scale involves turbulent conditions, research in this area is highly important. For the investigation of particulate matter formation, a swirled methane-assisted pulverized solid fuel combustion test rig with full optical access which allows intrusive and non-intrusive measurements in different heights and radial positions was developed. In order to study the local influences of flame characteristics on the formation of ultrafine particulate matter, results from laser Doppler velocimetry (LDV), suction pyrometer, Fourier transform infrared (FTIR) spectroscopy, and scanning mobility particle sizer (SMPS) spectrometer measurements are presented and discussed. It is shown that the local differences - such as gas temperature, the velocity of the solid fuel particles, and concentrations species - have an influence on the formation of particulate matter. Especially in regions with high local velocities and shear zones, PM coagulates strongly due to the increased turbulence in this area. The data presented in this paper are an important foundation for further studies to validate CFD simulations using the measurements and to further develop existing PM formation models for turbulent cases.