Experimental characterization and numerical simulation of a sooting lifted turbulent jet diffusion flame

Abstract

A sooting C2H4/air jet diffusion flame was investigated experimentally by laser measuring techniques and the results are compared to CFD calculations. The target flame (C2H4 10.4g/min, bulk exit velocity 44m/s, RE=10,000) exhibits well-defined boundary conditions and presents a good test case for model validation. Flow velocity, temperature and soot volume fraction in this flame has been measured previously. In this paper, further experimental results from Raman scattering and laser-induced fluorescence (LIF) measurements are presented to expand the validation data base. Raman scattering is used to measure the fuel/air mixing prior to combustion, while LIF of PAHs monitors the soot precursor region and successive planar OH–LIF serves to map the flame front position and its statistics.Furthermore, a numerical simulation of this flame was performed based on the DLR in-house code THETA. Within the scope of the test case presented here, the code combines a relatively detailed description of the gas phase kinetics coupled with a detailed yet computation-efficient soot model, suitable for CFD applications. This model has been designed to predict soot for a variety of fuels and flames with good accuracy at relatively low computational costs. Universal model parameters are applied, which requires no tuning for the dependence of test case or fuel. The experimental and numerical results are compared and discussed with special emphasis on the pre-flame region of the jet and up to the downstream position where significant soot concentrations are present. Validation shows the general applicability of the CFD code with implemented soot model to rather complex systems like the target sooting turbulent jet flame. Identified discrepancies are analyzed and can be explained, while opening up the field for future optimization of parts of the CFD code.