## 3 Results and Discussion
### Velocity Distribution of the Fuel Aerosol  
Looking on the velocities of the aerosol particles, one can see that used nozzle makes the aerosol flow order of magnitude faster than used in previous work [16]. It means that application the slurry with higher content of the solid part (and, thus, the higher calorific value) require longer travel of fuel inside the burners. This fact move us to conclusion that application of such fuels rather needs the swirl burner than direct flow burner.  
The Figure 3a-c shows the evolution of velocity distribution of CWS aerosol with propagation for 0.6 m. One can see, that velocity distribution after 0.2 m travel of aerosol looks almost uniform in  
Figure 2: The measured size distributions of the aerosol particles at different distances from the nozzle for the CWS (**a–c**) and CWSP (**d–f**). The first moment of the distribution corresponds to the size shown by red arrow.  
range 0-6 m/s. The narrow peaks at the slow side show the presence of certain mechanical defects of the nozzle. The mean velocity is about 3-3.5 m/s.  
Further propagation of the aerosol leads to essential changes of the velocity distribution. The mean value moves to right achieving 5 m/s. The distribution divides into two modes with relatively narrow slow lobe and wide fast one. This effect reflects the fact that big amount of small and slow particles were evaporated and the rest are faster in average. The following propagation to L = 0.6 m again make evident changes of the velocity distribution when mean velocity decreases back to 3.5 m/s. The width of the distribution goes down with a propagation distance that means that flow become more and more uniform. However, the essential changes of the most probable and mean velocities brake the uniformity of the heat distribution along the burner.  
Looking onto the Figure 3d-f, one can see that velocity distribution of atomized CWSP changes by the different manner. The initial distribution (after 0.2 m propagation) consists of two nice peaks with mean velocity about 6 m/s. Further propagation of the flow goes with trivial deceleration with increase of the distribution width. After the 0.6 m of the aerosol propagation, one can see mean velocity like 4 m/s and almost the same width of the lobe like at 0.4 m/s. The absence of very fast aerosol particles (with velocities more than 8 m/s) allows decrease the probability of the sticking of fuel droplets to the walls of burner.  
The influence of the nozzle defects onto the velocity distribution of the CWSP aerosol looks much weaker (the narrow peaks at the slow side does not exceed the height of the main lobe). This can be explained by the difference of the friction of slurry with the surface of nozzle and differences in adhesion of CWSP and CWS.  
Therefore, an addition of the petrochemicals into the content of coal-water slurry leads to much more predictable velocities of atomized fuel with small changes of the resulting average velocities in comparison with atomized CWS.  
Figure 3: The measured velocity distributions of the aerosol particles at different distances from the nozzle for CWS (**a**–**c**) and CWSP (**d**–**f**). The first moment of the distribution corresponds to the size shown by red arrow.