Quantitative measurement of the Sauter mean diameter in dense fuel sprays using simultaneous planar-laser-induced-fluorescence/Mie scattering technique

The planar laser induced fluorescence (PLIF)/Mie scattering technique has been established as an effective method for measuring the Sauter mean diameter (SMD) distribution in dense fuel sprays. This technique typically utilized a 266 nm laser. However, the strong absorption of laser wavelengths ranging from 266 nm to 274 nm in dense fuel sprays affected the detection of Mie scattering signals. Therefore, it was proposed to use a 266 nm laser for fluorescence excitation and a 532 nm laser for Mie scattering radiation in dense fuel sprays. In this study, a look-up table was created by correlating the PLIF/Mie ratio with the SMD using the phase Doppler particle analyzer, reducing the SMD_error from 27% to 13%. Furthermore, the proposed method was successfully applied to investigate the atomization field of room temperature and atmospheric pressure in a dual-stage axial swirl combustion chamber. By comparing the time-averaged PLIF images and time-averaged Mie images, the vapor and liquid phases of the fuel in the spray were successfully imaged and identified. The results indicated that, under the same fuel flow, increasing the air mass flow led to a gradual increase in the spray cone angle inside the dual-stage axial swirl combustor. Additionally, at a constant fuel flow, increasing the air mass flow resulted in a more uniform droplet size distribution, thereby enhancing the atomization effect. The presented technique provides a reliable and accurate tool for studying fuel spray behavior under various operating conditions. This knowledge can contribute to the design of more efficient combustion systems and the optimization of fuel injection strategies.