## 3 Properties of the Mixture of Jet A-1 Aviation Kerosene and FAME Biofuel
#### 4.1.5 The Course of Changes in SJE-20 Parameters When Using a Mixture of 60% Jet A-1 and 40% FAME  
The fifth series of measurements was aimed at determining the parameter values of the experimental SJE-20 during its operation with a fuel mixture consisting of 60% Jet A-1 aviation kerosene and 40% FAME biofuel. The changes in the parameters during measurements can be seen in Figure 8 and read from Table 10. The measurements followed immediately after the previous series of measurements. The temperature of the SJE-20 engine before starting was \(\text{t}_{\text{MPM}}\) = 70.1 \({}^{\circ}\)C. The starting process of the engine, at the given temperature state of the engine, took place normally. The mixture of 60% aviation kerosene and 40% FAME biofuel was ignited only at 4.6 s, which corresponded to the start of the  
Figure 7: Graphic course of changes in SJE-20 parameters when using a mixture of 70% Jet A-1 aviation kerosene and 30% FAME biofuel. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Parameter** & **20 th Second** & **25 th Second** & **30 th Second** & **35 th Second** & **40 th Second** & **45 th Second** \\ \hline
**Temperature t\({}_{0}\)** [\({}^{\circ}\)C] & 29.5 & 29.5 & 29.5 & 29.5 & 29.6 & 32.6 \\
**Temperature t\({}_{2\text{}}\)** [\({}^{\circ}\)C] & 90.2 & 94.5 & 96.2 & 95.9 & 96.4 & 92.4 \\
**Temperature t\({}_{3\text{}}\)** [\({}^{\circ}\)C] & 944.4 & 966.4 & 984.9 & 996.9 & 1004.5 & 856.9 \\
**Temperature t\({}_{4\text{}}\)** [\({}^{\circ}\)C] & 629.3 & 627.5 & 653.3 & 653.7 & 660.2 & 612.0 \\
**Pressure p\({}_{2\text{}}\)** [Pa] & 273,594.7 & 263,637.8 & 264,797.7 & 258,757.8 & 259,291.2 & 124,439.9 \\
**Pressure p\({}_{3\text{}}\)** [Pa] & 196,894.8 & 188,397.5 & 190,323.3 & 183,627.4 & 184,788.6 & \\ Flow Q\({}_{\text{fuel}}\). [L.min\({}^{-1}\)] & 1.288 & 1.273 & 1.259 & 1.271 & 1.255 & 1.099 \\
**Revolutions n [min\({}^{-1}\)]** & 46,968.2 & 46,852.4 & 46,681.3 & 46,661.1 & 46,588.0 & 46,542.8 \\
**Thrust F.T [N]** & 456.2 & 448.9 & 448.8 & 448.9 & 442.8 & 141.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Blend of 70% Jet A-1 aviation kerosene and 30% FAME biofuel, 1 st launch (40 th second). neat Jet A-1 aviation kerosene. A temperature peak t3 tmax = 1118.97 \({}^{\circ}\)C was reached in 13.7 s, and t4 tmax. = 988.8 \({}^{\circ}\)C was reached 11.6 s after engine start. The addition of 40% FAME biofuel to Jet A-1 aviation kerosene increased the maximum total gas temperature in front of the gas turbine \(\Delta\)t3 tmax by 4.42 \({}^{\circ}\)C and decreased the maximum total gas temperature behind the gas turbine \(\Delta\)t4 tmax by \(-\)2.8 \({}^{\circ}\)C, as well as decreased the total gas temperature in front of the gas turbine \(\Delta\)t3 tmax by \(-\)1.4 \({}^{\circ}\)C and the total gas temperature behind the gas turbine \(\Delta\)t4 tmax by \(-\)7.1 \({}^{\circ}\)C. The value of the total air temperature behind the compressor \(\Delta\)t2 decreased by \(-\)6.9 \({}^{\circ}\)C, the value of the total air pressure behind the compressor \(\Delta\)p2t decreased by \(-\)2015.2 Pa, and the value of the total gas pressure in front of the gas turbine \(\Delta\)p3t decreased by \(-\)11,680 Pa. The thrust of the SJE-20 engine was reduced by \(\Delta\)F\({}_{\rm{T}}\) = \(-\)5 N, with a simultaneous increase in fuel consumption \(\Delta\)Q\({}_{\rm{fuel}}\) = 0.071 L.min\({}^{-1}\). As the proportion of FAME biofuel (\(\rho_{\rm{METRO}}\) = 882 kg.m\({}^{-3}\)) in the mixture with Jet A-1 aviation kerosene (\(\rho_{\rm{jet}}\) A-1 = 810 kg.m\({}^{-3}\)) increased, the density of the mixture increased, resulting in a lower quality of fuel atomization when flowing through the fuel nozzles. Insufficient atomization of a denser fuel mixture resulted in its slower evaporation in the combustion chamber, which caused a deteriorated mixture ignition process when starting a cold engine at lower atmospheric temperatures.