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In this paper, the differences between multi-hole and single-hole spray contour under the same conditions were compared by using high-speed photography. The difference between the contour area of multi-hole and that of single-hole spray was used as a parameter to describe the degree of spray collapse. Three dimensionless parameters (i.e. degree of superheat, degree of undercooling, and nozzle pressure ratio) were applied to characterize inside-nozzle thermodynamic, outside-nozzle thermodynamic and kinetic factors, respectively. In addition, the relationship between the three dimensionless parameters and the spray collapse was analyzed. A semi-empirical equation was proposed for evaluation of the degree of collapse based on dimensionless parameters of flash and non-flash boiling sprays respectively.

The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere.

Gasoline Compression Ignition has been widely studied in recent years. The in-cylinder stratified charge in gasoline Partially Premixed Compression Ignition (PPCI) can extend the high load range with lower pressure rise rate than Homogeneous Charge Compression Ignition (HCCI). However, it is still not clear that whether there is flame propagation in the gasoline compression igntion mode and how the flame propagation influences the combustion process and pollution formation. In order to investigate the effect of flame, several gasoline compression ignition cases, including the single-stage and two-stage heat release processes, are simulated with the KIVA-3V Release 2 code in this study. The G-equation is employed to account for flame propagation, and the reduced i-octane/n-heptane mechanism is used to handle the chemical reactions. The results show that the flame propagation exists in the combustion process and it can accelerate the heat release slightly.