Design of “model-friendly” turbulent non-premixed jet burners for C2+ hydrocarbon fuels

Abstract

Experimental measurements in laboratory-scale turbulent burners with well-controlled boundary and flow configurations can provide valuable data for validating models of turbulence-chemistry interactions applicable to the design and analysis of practical combustors. This paper reports on the design of two canonical nonpremixed turbulent jet burners for use with undiluted gaseous and liquid hydrocarbon fuels, respectively. Previous burners of this type have only been developed for fuels composed of H(2), CO, and/or methane, often with substantial dilution. While both new burners are composed of concentric tubes with annular pilot flames, the liquid-fuel burner has an additional fuel vaporization step and an electrically heated fuel vapor delivery system. The performance of these burners is demonstrated by interrogating four ethylene flames and one flame fueled by a simple JP-8 surrogate. Through visual observation, it is found that the visible flame lengths show good agreement with standard empirical correlations. Rayleigh line imaging demonstrates that the pilot flame provides a spatially homogeneous flow of hot products along the edge of the fuel jet. Planar imaging of OH laser-induced fluorescence reveals a lack of local flame extinction in the high-strain near-burner region for fuel jet Reynolds numbers (Re) less than 20,000, and increasingly common extinction events for higher jet velocities. Planar imaging of soot laser-induced incandescence shows that the soot layers in these flames are relatively thin and are entrained into vortical flow structures in fuel-rich regions inside of the flame sheet.

Effects of aromatic chemistry-turbulence interactions on soot formation in a turbulent non-premixed flame

“…The described models are integrated into LES of a non-premixed ethylene/air piloted turbulent jet flame, experimentally investigated at Sandia National Laboratories [37][38][39]. This flame is selected over other experimentally studied turbulent non-premixed flames [40,41], for its relatively large soot yield, high Reynolds number, and welldefined boundary conditions, as described in detail below.…”

Investigation of soot formation in pressurized swirl flames by laser measurements of temperature, flame structures and soot concentrations

“…Modeling of such cases is possible [4] but frequently lacks sufficient knowledge about the boundary conditions. There exists only a small number of data sets describing atmospheric jet flames with validation-data-quality and significant soot formation [5][6][7]. Suitable experiments to bridge the gap towards technical combustion are highly demanded.…”

Effects of repetitive pulsing on multi-kHz planar laser-induced incandescence imaging in laminar and turbulent flames

“…As determined by the laminar flame studies above, there is a clear difference in the LII signals in time between a low and high fluence regime. In the case of turbulent flames, the majority of the measurements detailed here are taken at a downstream distance of z∕D 75, near the peak of maximum soot volume fraction [49]. The timeaveraged LII signal over 100 bursts for each of the 100 pulses in a 10 kHz train is shown in Fig.…”

“…LII data with the PMT was collected in the annular, peak soot region where the peak soot volume fraction is ∼1 × 10 −5 [48]. For turbulent combustion studies, a piloted ethylene burner described by Zhang et al [49] was utilized and included a pilot consisting of three rows of concentric holes around a D 3.2 mm inner diameter fuel tube. The ethylene/ air pilot was operated at an equivalence ratio of 1.0 and held at a fixed flow rate to match 2% of the total heat release of a Reynolds number Re D U D∕ν 20; 000 ethylene jet flame.…”

“…The pilot allowed jet-flame anchoring to a jet exit Reynolds number of Re D 25; 000. The probe sheet was centered at a downstream position of 75 diameters, a location with large soot volume fraction for the relevant flow conditions [49].…”