Experimental investigation of near-field spray characteristics of RP3 aviation fuel based on multivariable sensitivity and uncertainty analysis

Abstract

The utilization of aviation kerosene RP3 in diesel engines and ground vehicles has attracted more attention due to the implementation of the army's Single Fuel Concept. To explore the characteristics of the RP3 near-field spray primary breakup, experimental studies were carried out via the diffuser back-illumination imaging (DBI) method under single-hole injectors accommodated to varied engine spray circumstance. The critical factors of the variability in RP3 spray characteristics response were figured out by constructing a one-dimensional active subspace to perform multivariable synergistic effects via sensitivity analysis. Moreover, the uncertainties associated with unstable cavitation within nozzle were quantified with a varied array of operating conditions. In comparison to diesel, it is indicated that, there is a range of critical cavitation, in where greater uncertainties in spray cone angles are exhibited, especially for RP3. RP3 tends to form a ‘mushroom’ spray structure, with a smaller spray cone angle compared to diesel, but the disparity gradually diminishes as the fuel injection pressure increases. The gradual transition from ‘needle’ to ‘mushroom’ shape in RP3's near-field spray structure is revealed with increased fuel injection pressure, and the appearance time of the ‘mushroom’ structure advances with higher ambient pressures. Based on the active space construction, the sensitivity analysis discovers that the spray cone angle is dominantly influenced by ambient pressure and cavitation within the nozzle, thus providing a new perspective on analyzing test data without the expense of single variable statistical work.