Abstract Metal fuels have the potential to contribute to the defossilization of the energy system. To enable a knowledge-based design of future high-temperature energy systems, experimental characterization of fundamental combustion parameters is highly desired. One key parameter is the laminar burning speed and its dependence on the flow strain rate, which can be determined in laminar opposed jet flames. In experiments, Particle Tracking Velocimetry (PTV) or Particle Image Velocimetry (PIV) are commonly used techniques for determining local flow velocities. In metal dust flames, the fuel powder itself is frequently employed as tracer particles. However, depending on the particle size distribution, significant slip between the gas-phase flow and the dispersed metal particles may occur. This biases the accuracy of velocity field measurements and impedes the comparability between fuel samples with different particle size distributions. This work presents a novel method by developing spectrally distinctive fluorescent tracer particles (SDFT) to enable the in-situ characterization of gas-phase velocity fields in particle-laden flows. The production of these particles is based on adsorption of Rhodamine B on zeolite particles, yielding gas-phase tracers with well-defined optical properties and adequate thermal stability. Experiments under inert conditions highlight the necessity of direct gas-phase measurements, as both particle slip and momentum coupling are observed. Under reactive conditions, the applicability of the SDFT is demonstrated in iron dust flames stabilized within a laminar opposed jet burner. The results highlight the ability of the SDFT to resolve characteristic features of the axial velocity profile and to provide reliable gas-phase reference data.
Krenn et al. (Mon,) studied this question.
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