Influence of slurry fuel surface tension coefficient on the mechanism of crushing droplets of various sizes

The purpose is to present the results of experimental and theoretical studies of the influence of the surface tension coefficient of slurry fuel on the mechanism of crushing droplets of different sizes. The experimental studies have been performed on a test bench - an aerodynamic simulator of the energy boiler furnace. The coal of 200·10^-6 m fraction or less was used to prepare the slurry fuel. Lignosulfonate in an amount of 1% of the coal weight was used as a plasticizer. The values of velocities and droplet sizes were determined experimentally. The characteristic ranges of droplet velocities in the flow at the rotor spray of 0-8 m/s; 8-35 m/s; 35 m/s or more were identified. The variation range of surface tension coefficient from 0.05 to 0.07 N/m was considered. The analysis was given to slurry fuel droplets with the dimensions from 50 to 500 microns. The processing of results did not take into account the formed aerosol particles with the size of 1 µm or less. The characteristic boundaries of the sections of some droplet crushing mechanisms were determined. The influence of the surface tension coefficient of the slurry fuel on the process of droplet destruction was theoretically confirmed. It was found out that the droplets of the size of 50-150 microns were most susceptible to vibration crushing. The droplets of the size of 450-500 microns were completely unaffected to vibration crushing during the rotor spray in the studied area of velocities. The expressions have been received allowing to estimate We criterion at the suspension pressure of 0.2 MPa and air pressure of 0.18 MPa. The presented results of experimental and theoretical studies are prognostic and can be used in mathematical and physical modeling of the process of suspension fuel spraying in power boiler furnaces with the purpose of assessing aerodynamic characteristics of designed and operating units.

slurry fuel, spray, coal-water fuel, Weber number, spray cone, droplet velocity