## 3 Results
### Comparison with Numerical Calculations  
To better understand the high similarity of measured temperatures and species concentrations and the simultaneously observed large differences in the measured soot concentrations in the kerosene and surrogate flames, and, for further insight into the processes in the flames, numerical calculations were performed using Cantera 2.4.0 [28]. The following reaction mechanisms were considered for this purpose:  
* A reaction mechanism developed by [PERSON] et al. [12] for the trimethylbenzene and n-decane surrogate. By analogy with the name of the surrogate, this mechanism is referred to hereafter as the Aachen mechanism (120 species, 841 reactions). * The mechanism developed by the University of California San Diego for JP10 [29]. It is hereafter referred to as the San Diego mechanism (61 species, 298 reactions). * The mechanism developed by [PERSON] et al. [30] and [PERSON] et al. [31]: the \"HyChem\" (Hybrid Chemistry) mechanism for JP-8 (119 species, 841 reaction). * A mechanism developed by [PERSON] et al. [32] for kerosene surrogate mixtures of \(N\)-decane, cyclohexane, isooctane and toluene. Since this mechanism does not include all species necessary for the surrogate, a mixture of 42.67 vol.-% \(N\)-decane, 33.02 vol.-% isooctane and 24.31 vol.-% toluene was calculated based on [PERSON] et al. [33]. It is abbreviated here as DLR mechanism (189 species, 1327 reactions). * The \"Creck\" High temperature mechanism for C1-C16 hydrocarbons described by [PERSON] et al. [34; 35; 36]. Calculations were performed using the surrogate mixture of trimethylbenzene and n-decane (368 species, 14,462 reactions). The calculations were performed with the \"BurnerFlame\" class for burner-stabilized, flat flames. After initial calculations showed that all mechanisms were able to predict the measured temperatures well, it was decided not to impose a temperature profile on  
Figure 5: Species concentration profiles measured by GC/MS at \(\Phi\) = 2.1 and 5 cm/s inlet velocity. the calculations. Calculations with a fixed temperature profile also showed no significant differences in the species profiles. The comparison between numerical and experimental data for the Jet A-1 flame is shown in Figure 6 for one operating point. The calculated temperature profiles are all very similar and also agree with the measured temperatures (Figure 6a). The experimentally observed slight cooling of the flame after the temperature maximum is not seen in the calculated results. This can be attributed to the heat losses due to radiation, which were not taken into account in the numerical calculations. Figure 6b shows the comparison of the water concentrations. The calculated concentrations are very similar at the beginning, significant differences appear from a height of 2 mm. All mechanisms underestimate the water concentrations and predict the rise earlier than observed experimentally. Therefore, the numerical predictions show higher hydrogen concentrations in comparison to the experiments (not shown here). The comparison between calculated and measured acetylene concentrations are shown in Figure 6c. Here, clear differences between the mechanisms are observed. For example, the San Diego mechanism shows the maximum concentration as early as 1 mm with concentrations dropping comparatively rapidly thereafter. The other mechanisms agree with each other up to a height of about 2 mm, but thereafter differ markedly in the concentrations calculated. The rise in acetylene concentration in the flame is predicted by the four mechanisms more than 2 mm earlier than observed experimentally. The measured concentrations after the flame front are between the calculated values of the HyChem and DLR mechanisms. It should be noted that the shift between the experiments and the numerical results was experimentally confirmed using two different measurement techniques (TDLAS and GC) for the water and acetylene concentrations.However, a systematic shift in the experimental results is possible.