| Jet fuel has been considered as a unitary military fuel due to its physical and chemical property between gasoline and diesel,which helps ensure fuel supply in special situations.Piston engine is as the main power devices of ground vehicles and it is important to understand the ignition and emission characteristics of jet fuel under the condition of piston engine.The spray ignition characteristics of RP-3 jet fuel are studied experimentally in a constant volume combustion chamber in this study.The ignitions of RP-3 jet fuel at three oxygen concentrations are compared.Three surrogate fuels,the n-dodecane / iso-cetane / toluene blend,the ndecane / proylbeneze,the n-decane / 1,2,4-trimethylbenzene blend,are proposed and their ignition characteristics are compared with RP-3 jet fuel.Additionally,the evolutions of the particle size distribution of RP-3 jet fuel,n-decane and the n-decane/1,2,4-trimeghylbenzene blends in the laminar premixed flame are studied in this paper.Besides,soot propensities of different distillate fractions of RP-3 jet fuel are also studied experimentally.The main conclusions are as follows:1)Ignition characteristics of RP-3 jet fuel are compared at different oxygen concentrations.Increased oxygen concentrations decreases ignition delay times.The ignitions at low oxygen concentrations show obvious two-stage ignition behaviors.For different oxygen concentrations,ignition delay times decrease with injection pressure and increase firstly and then decrease with injection duration.2)The ignition characteristics of RP-3 jet fuel and three surrogates,the ndodecane/iso-cetane/toluene blend,the n-decane/proylbeneze blend and the n-decane/1,2,4-trimethylbenzene blend,are compared and the results of ignition delay time reveal ignition propensity in the order of RP-3 jet fuel > n-dodecane / iso-cetane / toluene > n-decane/ proylbeneze~n-decane / 1,2,4-trimethylbenzene.Overall,the ignition characteristic of the three-component surrogate is more similar to that of RP-3 jet fuel.3)The particle size distribution of RP-3 jet fuel and three surrogates,ndecane,the 88.7% n-decane/1,2,4-trimethylbenzene blend and the 75% n-decane/1,2,4-trimethylbenzene blend,are measured in premixed laminar flames.RP-3 jet fuel shows the lowest number density and ndecane shows the smallest particle growth rate.The 75% n-decane / 25% 1,2,4-trimethylbeneze blend has the largest nucleation strength and particle growth rate.Soot propensity of the 88.7% n-decane/11.3% 1,2,4-trimethylbenzene blend is between that of the other fuels.Singlecomponent and two-component surrogates could not reproduce soot characteristics of RP-3 jet fuel well.4)The evolution of particle size distribution of RP-3 jet fuel and three distillates,the 0-50% distillate fraction,the 50%-90% distillate fraction and the 90%-100% distillate fraction,are measured in premixed laminar flames.The 90%-100% distillate fraction shows the highest particle number density and the 0-50% distillate fraction shows the largest particle growth rate.Soot propensities of RP-3 jet fuel and the 50%-90% distillate fraction are between those of the other fuels.The soot morphology observation from transmission electron microscopy also indicates that the 90%-100% distillate fraction produces smaller primary particle sizes than the other fuels,whereas the other fuels have similar primary particle sizes. |
