Investigation of RP-3 Spray Characteristics Based on Sensitivity Analysis and Active Subspace Construction

To explore the in-cylinder fuel injection and the subsequent spray dynamics of aviation fuel RP-3, the RP-3 spray macroscopic characteristics of single-hole injectors with different nozzle diameter under varied ambient pressures and injection pressures are investigated via diffuser back-illumination imaging (DBI) experimental method. The critical factors of the variability in spray characteristics response are pointed out by setting up a one-dimensional active subspace in this study, to perform synergistic effects via multivariable sensitivity analysis. It is revealed that compared with diesel, RP-3 spray edge shows more vortex structures, which is more susceptible to gas entrainment, especially for injector with larger nozzle diameter. While increasing injection pressure and ambient pressure will lead reduced vortex structures instead. Moreover, on the whole, RP-3 produces shorter spray penetration distances, larger spray cone angle, lower spray irregularity and smaller spray areas than diesel under same conditions. Based on multivariable sensitivity analysis, it is indicated that accordant with diesel fuel, injection pressure (Pin) and ambient pressure (Pb) are the controlling parameters for RP-3 spray penetration distance, and Pb is dominant on RP-3 spray cone angle. However, caused by cavitation intensity, RP-3 spray cone angle is more sensitive to nozzle diameter (φ) and cavitation number (Ca). Moreover, Pb dominates over the sensitivity of spray irregularity and spray area is mainly controlled by Pin.