Planar 2-color time-resolved laser-induced incandescence measurements of soot in a diffusion flame

Figures & data

Figure 1. Schematic of 2D-2C-TiRe-LII measurement set-up (B1: 400 ± 5nm band filter; NB2: 450 ± 5 nm band filter).

Figure 2. Temporal evolution of the LII signal at 400 nm and 450 nm. Interval start times are marked in each image.

Figure 3. Colour maps of the maximum likelihood estimators χ² value as a function of the distribution width σ, and the median diameter D_m for location A: HAB = 38 nm and r = 2.2 mm and B: HAB = 42 mm and r = 0 mm. The best fit value is shown in each figure.

Figure 4. Left: 3D plot of χ² for location A; right: value of the minimised χ² along the valley.

Figure 5. Reconstructed LII signal with selected (D_m, σ) pairs in the valley of minimising values.

Table 1. Best-fit value and range of and σ at locations A and B.

Locations	Best fit	Range of (nm)	Range of σ
A	= 88 nm, σ = 0.33	74 – 100	0.20 – 0.40
B	= 24 nm, σ = 0.24	18 – 260	0.20 – 0.40

Figure 6. Normalised LII signal at 400 nm as a function of time at flame locations A and B. The best fit of experimental LII signals at the two different locations was found by 2-parameter fitting.

Figure 7. Measured LII signal at 400 nm (blue symbols, right scale), model LII using minimum error method for mean diameter and its distribution, as well as 2C method for peak temperature (solid blue line). Measured particle temperature T (red squares, left scale) using the two colour method; modelled T starting from the 2C peak measurement T_p = 3181 K.

Figure 8. Calculated T_p with the 2C method (left); estimated D_m with the 2-parameter fit (middle); measured f_v in the tested flame (right) (Tian et al., 2015).

Figure 9. Top: Calculated particle temperature using 2C peak temperature T_p (dashed line) and full energy model (solid line) at HAB = 42 mm and r = 0 mm. Bottom: Corresponding normalised measured LII signal (symbols), modelled signal calculated from 2C T_P and optimal D_m = 25 nm and σ = 0.24 (dashed line); full energy model T and optimal D_m = 34 nm and σ = 0.3 (solid line).

Figure 10. Sensitivity of the particle-size evaluation on the peak temperature T_p. The baseline values of the particle size and peak temperature are estimated as 40 nm and 3133 K, respectively.

Tian, B., Gao, Y., Balusamy, S., and Hochgreb, S. (2015). High Spatial Resolution Laser Cavity Extinction and Laser-Induced Incandescence in Low Soot Producing Flames. Appl. Phys. B, 120:469–487.

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