Construction of surrogate fuels for lower freezing point diesels based on component and functional groups analysis

For the purpose of formulating surrogate fuels for two lower freezing point diesels, namely −35# diesel and − 50# diesel, two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC–TOFMS) was utilized to analyze their components in detail. And nuclear magnetic resonance (NMR) spectroscopy was used to obtain the composition of functional groups in hydrocarbons, which were classified into 11 carbon types according to different structural properties of molecules. The GC × GC–TOFMS results reflected that −50# diesel contains less unsaturated hydrocarbons, while −35# diesel contains more heavy hydrocarbons. The NMR spectroscopy results indicated that −50# diesel contains more CH3 (primary carbon) and n-alkane CH2 (secondary carbon), and the H/C ratio reflected by the analysis results of NMR spectroscopy were consistent with the H/C ratio measured by ASTM D5291. Based on the results of GC × GC–TOFMS, one five-component and one seven-component surrogate fuels were constructed for −35# diesel and −50# diesel through genetic algorithm by matching the density, viscosity, cetane number, distillation curve and functional groups. Then spray penetration of the surrogate fuels were validated and the result are compared with the experimental results of lower freezing point diesel under spray condition (Pamb = 3 MPa, Tamb = 800 K). It turned out that the both the target properties and the non-target properties showed good agreement that the surrogate fuels can emulate properties of lower freezing point diesels well.