QUANTITATIVE ANALYSES OF FUEL SPRAY-AMBIENT GAS INTERACTION BY MEANS OF LIF-PIV TECHNIQUE

The in-cylinder fuel-ambient gas mixing property in a direct injection (D.I.) diesel engine significantly influences the ensuing combustion and exhaust emission performance. In this study, the interaction of nonevaporating diesel spray with the surrounding gas was analyzed quantitatively in the quiescent condition at room temperature and with ambient gas pressure of 1 MPa by means of the laser induced fluorescence-particle image velocimetry (LIF-PIV) technique. Particularly, this study focused on the calculation of gas mass flow rate entrained through the entire spray region (spray side periphery and tip region) and total entrained gas-fuel ratio by using the gas velocity data obtained by the LIF-PIV technique. Another focus of this study was the gas entrainment characteristics of diesel spray under a wide range of injection pressures (100, 200, and 300 MPa) and the micro-hole nozzle (0.08mm) condition. The results indicate that the entrained gas mass flow rate at the spray tip region is prominent in the whole periphery and the proportion of gas entrainment at the side surface region increases as the spray develops Higher injection pressure significantly enhances the total entrained gas mass; however the increase of ambient gas/fuel mass ratio becomes moderate gradually as the injection pressure increases. The calculation model proposed by this work is capable of illustrating the ambient gas flow characteristics of the diesel spray accurately.