## 2 Test Fuels and Properties  
### Test Fuel and Additives  
The basic fuel used in this work was China VI standard commercial 0# diesel bought from a gas station. The n-heptane, n-dodecane, tetralin and decalin were of analytical grade. Figure 1 gives the structure of these molecules, and the main physicochemical properties of the test fuels are listed in Table 1.  
First, the density of the test fuels was measured with a petroleum density meter following the method of \"GB/T 1884-2000\", and the results are shown in Table 2. As shown in Figure 2, the density of the blended fuels is nearly linear to the volume fractions of diesel and hydrocarbons. This shows that they are well soluble, and there is no volume shrinkage that occurred within the test range. Figure 1: The molecular structure of n-heptane, n-dodecane, tetralin, and decalin molecules. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Properties** & **Diesel** & **n-Heptane** & **n-Dodecane** & **Tetralin** & **Decalin** \\ \hline Molecular formula & C\({}_{10}\)–C\({}_{22}\) & n-C\({}_{7}\)H\({}_{16}\) & n-C\({}_{12}\) H\({}_{26}\) & C\({}_{10}\)H\({}_{12}\) & C\({}_{10}\)H\({}_{18}\) \\ Molar mass (g/mol) & - & 100.21 & 170.34 & 132.2 & 138.25 \\ Density (g/cm\({}^{3}\)) & 0.817 & 0.684 & 0.75 & 0.97 & 0.896 \\ Viscosity (40 \({}^{\circ}\)C) (mm\({}^{2}\)/s) & 2.675 & 0.485 & 1.414 & 1.06 & 1.667 \\ Boiling point (\({}^{\circ}\)C) & 205 & 98.5 & 215 & 207.6 & 195.8 \\ Ignition temperature (\({}^{\circ}\)C) & 220 & 247 & 216 & 385 & 262 \\ CN & 51.6 & 56 & 82.5 & 8.9 & 46.5 \\ LHV (MJ/kg) & 42.52 & 44.57 & 44.11 & 40.53 & 42.5 \\ \hline \end{tabular}  
* The four hydrocarbons were blended with the commercial diesel in the 20% and 50% volume fractions and they are labeled as HE20 (HE = heptane), HE50, DO20 (DO = dodecane), DO50, TE20 (TE = tetralin), TE50, DE20 (DE = decalin), and DE50, respectively. D100 denotes diesel.  
\end{table} 
Table 1: Properties of the test fuels. Figure 2: The experimental fuels’ density and viscosity. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Fuels** & **Components** & \begin{tabular}{c} **Density** \\ **g/cm3** \\ \end{tabular} & \begin{tabular}{c} **Viscosity** \\ **mm2/s** \\ \end{tabular} & \begin{tabular}{c} **LHV** \\ **MJ/kg** \\ \end{tabular} & \begin{tabular}{c} **Distillation Range/\({}^{\circ}\)C** \\ \end{tabular} \\ \hline D100 & Diesel & 0.817 & 2.675 & 42.52 & 205 & 258 & 331 \\ \hline HE20 & \begin{tabular}{c} n-Heptane 20\% \\ Diesel 80\% \\ \end{tabular} & 0.786 & 1.493 & 42.87 & 116 & 233 & 301 \\ \hline HE50 & \begin{tabular}{c} n-Heptane 50\% \\ Diesel 50\% \\ \end{tabular} & 0.756 & 0.982 & 43.45 & 102 & 129 & 280 \\ \hline DO20 & \begin{tabular}{c} n-Dodecane 20\% \\ Diesel 80\% \\ \end{tabular} & 0.792 & 2.032 & 42.82 & 195 & 230 & 318 \\ \hline DO50 & \begin{tabular}{c} n-Decocane 50\% \\ Diesel 50\% \\ \end{tabular} & 0.771 & 1.787 & 43.28 & 198 & 220 & 303 \\ \hline TE20 & \begin{tabular}{c} Tetralin 20\% \\ Diesel 80\% \\ \end{tabular} & 0.848 & 1.985 & 42.06 & 199 & 229 & 330 \\ \hline TE50 & \begin{tabular}{c} Tetralin 50\% \\ Diesel 50\% \\ \end{tabular} & 0.863 & 1.856 & 41.44 & 202 & 211 & 296 \\ \hline DE20 & \
\begin{tabular}{c} Decalin 20\% \\ Diesel 80\% \\ \end{tabular} & 0.824 & 2.489 & 42.53 & 195 & 239 & 332 \\ \hline DE50 &
\begin{tabular}{c} Decalin 50\% \\ Diesel 50\% \\ \end{tabular} & 0.844 & 2.105 & 42.55 & 188 & 203 & 306 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main properties of test fuels. The kinematic viscosity of the fuels is related to fuel delivery and spray atomization. It was measured by a Pinker viscometer following the method of \"GB/T 265\". The tests were kept at a constant temperature of 40 \({}^{\circ}\)C [17]. In addition, molar mass and ignition temperature were provided by the manufacturer. The experimental value and the comparison of the theoretical and experimental values on density are shown in Figure 2, and details are listed in Table 2. It can be seen that the addition of the hydrocarbons results in reduced viscosity.