Soot Formation of Conventional and Alternative Jet Fuels in Counterflow Nonpremixed Flames

摘要

With the increasing concerns over fuel cost, environmental pollutions, and energy security, the development of alternative fuels from renewable sources has gained much attention in the past decade. Recently, the National Jet Fuel Combustion Program (NJFCP) has selected three conventional gas turbine fuels, i.e. JP-8, Jet-A, and JP-5, as reference fuels to provide baseline characteristics for the certification of alternative jet fuels. To evaluate the sooting propensity for representative conventional and alternative jet fuels, the present study has investigated soot formation in nonpremixed combustion for three conventional reference jet fuels of NJFCP's interest and three selected alternative jet fuels, i.e. Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK), Hydroprocessed Esters and Fatty Acids from camelina (HEFA-Camelina), and Alcohol-to-Jet (ATJ). The soot volume fraction profiles of the tested jet fuels have been measured by using Laser Induced Incandescence in the atmospheric counterflow nonpremixed flame configuration with 473 K preheat for both the fuel and oxidizer streams. In addition, the effects of global strain rate and reactant concentration on soot formation are investigated. At the same stoichiometric mixture fraction, the experimental results show that the soot formation increases with increasing fuel and O_2 concentrations, while decreases with increasing global strain rate, as expected. In terms of sooting propensity, the trend is found as JP-5 > Jet-A > JP-8 > ATJ > FT-SPK > HEFA-Camelina. The observed ranking is consistent with the aromatics content in each fuel except for ATJ. For ATJ, as it has much heavier hydrocarbon components, hence it results in a higher soot formation than the other two alternative jet fuels investigated.