Effects of varying the liquid fuel type and air co-flow conditions on the microscopic spray characteristics in an atmospheric annular co-flow spray burner

The atomization process is critical for combustion systems since it directly influences emissions and performance. Thus injection system should provide the spray required structure and characteristics, e.g., angle and droplet size distribution. Therefore, this work investigates the effects of varying the fuel type, air co-flow rates, fuel mass flow rate and air co-flow temperature on the spray characteristics (e.g., droplet size distribution and droplet velocity) in an annular co-flow spray burner. These effects were investigated by measuring droplet sizes and velocities at different radial and axial positions of n-Heptane, n-Decane and n-Dodecane sprays under non-reacting conditions at a room pressure of 1 atm and temperature of 298K and using the Microscopic Diffused Back-illumination (MDBI) technique. In addition, the Sauter mean diameter (SMD) for different flow conditions were predicted using three well-known correlations and compared to experimental measurements. The outcomes of this research provided a fair understanding of the influence of varying these parameters on the droplet sizes and velocity through a wide test matrix. Finally, the findings reported here will support future research into the function of phase change in flame stability. •Understanding fuel sprays are necessary for developing efficient and clean systems.•Fuel spray presents a complex heterogeneous distribution.•Droplets are affected differently by the air co-flow depending on their size.•Global SMD is reduced when the injection pressure and co-flow temperature increase.•Droplet size and spray opening angle are determined by physical fuel properties.