## 3 Results
Thirty flame images are taken for each flame condition and processed to obtain averaged flame height and width. The dimensions of the flame measured from the projected images are summarized in Figure 4. Before taking flame images, a calibration pattern placed on the burner is imaged and processed in a procedure defined by [PERSON] and co-workers for defining the camera pixel-to-millimeter ratio [6]. A peak flame height of 11.2 cm is observed for the p45 flame in Series 1 flames, but the lower equivalence ratio conditions also have comparable flame heights, considering the standard deviation across the images (reported as error bars). The measured flame width for the Series 1 flames lay within 10% of each other. Stronger trends in flame dimensions are observed for the Series 2 flames. As the flame images show, the toluene flame is relatively small and this corresponds to a spray flame height of 9.1 cm and width of 0.9 cm. The introduction of an increasing fraction of coal tar distillates to the spray feed increases the spray flame height and width up to 11.3 and 1.7 cm, respectively. Flame temperature measured by thermocouple and soot pyrometry add further insights into the formation and growth environment of the carbon black particles. The temperature profile measured by thermocouple at the centerline of the pilot flames is shown in Figure 5. As discussed above, the flame temperature of the burner-stabilized flames depends on the inlet flow rate and equivalence ratio of the fuel-air mixture. The measured temperature profile indicates that increasing the flow rate of oxygen causes a net increase in flame temperature at all distances above the burner despite lower equivalence ratio. The pilot flames of the SpraySyn burner are unique burner-stabilized flames, however, because a 0.6 cm island housing the spray nozzle assembly exists at the center of the burner surface (see Figure 1). Without the spray, a stagnant zone exists at the centerline and this impacts the lowest flow rate pilot flame, p50, as exhibited by the peak flame temperature, delayed 2 cm downstream of the burner surface. The higher flow rate pilot flame temperature profiles are less impacted by this island. The maximum flame temperature is comparable across all equivalence ratio conditions but the lower flow rate of the p50 condition induces relatively lower temperatures at the burner boundary and  
Figure 3: Flame images of Series 2 flames; p43 with t100d0 (**a**), t65d35 (**b**), t35d65 (**c**) and t25d75 (**d**). further downstream. As discussed above, the temperature profile of the pilot flames is expected to directly impact the spray flame structure and carbon black particle properties. The spray flame temperature is also measured by thermocouple at the centerline. The largest variation in spray flame temperature is expected to occur for Series 1 as the pilot flame temperature varies for constant spray inlet conditions. As such, temperature measurements are also taken by thermocouple and soot pyrometry for Series 1 to gain insight into the 2D axisymmetric flow field. The centerline thermocouple measurements, shown in Figure 5, indicate that the low equivalence ratio pilot flame induces the highest flame temperature profile. The spray flame temperatures follow the same trend as the pilot flame center line temperature profiles with the highest flame spray temperature measured by thermocouple in Series 1 being 1850 K (flame p40) and the lowest spray flame temperature is 1555 K. The centerline thermocouple measurements for Series 2 flames are also shown in Figure 5. The effect of increasing flame coal tar distillate on the temperature profile is less distinct than the effect of pilot oxygen flow rate. The 75% distillates spray flame is approximately 100 K hotter than the flame of pure toluene and the temperature difference extends to approximately 200 K 12 cm downstream of the burner. Overall, the trends in flame luminosity and size observed from the flame images carry over to the relative flame temperatures measured at the centerline.