Autoignition behavior of jet fuel relevant pure hydrocarbon components have been investigated using a rapid compression machine and validated with chemical kinetics simulations. Employment of alternative energy sources can alleviate the energy crisis that this generation confronts. Alternative fuels can be obtained from diverse feedstocks through a variety of pathways. Due to this diversity, numerous alternative fuels have unique compositions which are distinct from conventional fuels. Evaluating differences in combustion behavior of these fuels is a pivotal and initial task of drop-in fuel applications. Hydrocarbon species in conventional and alternative fuels can be broadly classified into four major groups: normal alkanes, isoalkanes, cyclic alkanes, and aromatics. The focus of this study are normal and isoalkanes, where three isomers of dodecane have been selected and tested to evaluate the contribution of chemical structure in autoignition behavior. N-dodecane, which is a straight chain of twelve carbons, and two isododecanes with different degrees of branching are tested in heated rapid compression machine (RCM) at University of Illinois, Urbana-Champaign. Measurements were made at compressed pressures (Pc) of 10 and 20 bar, with fuel and oxidizer (dry air) mixture of equivalence ratio (ϕ) at unity, 0.5 and 0.25. Compressed temperatures (Tc) of the tests are in low to intermediate range (620 K < T < 710 K) where NTC behavior has been observed for heavily branched isododecane. The direct test chamber method is used for precise and reliable measurements. Ignition delay times of n-dodecane are the shortest among tested fuels, as expected. Extremely low reactivity of the pentamethylheptane, heavily branched isododecane has been observed. The results have also compared to JP-8 as a reference. For several conditions where first and second stage ignition are distinguishable, it is shown that temperature dependency is greater for first stage ignition delay than second stage.
Experimental Investigation in the Autoignition Behaviour of Aviation Jet Fuel in a Rapid Compression Machine
