## 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
As the proportion of FAME biofuel in the Jet A-1 jet kerosene mixture increased, this gradient of total temperature rises t\({}_{2t}\) behind the compressor decreased. The 35 th second represented the maximum difference between the highest temperature t\({}_{2t,\max}\). (100% aviation kerosene Jet A-1) and the lowest air temperature behind the compressor, t\({}_{2t,\min}\) (80% Jet A-1 aviation kerosene and 20% FAME biofuel) \(\Delta\)t\({}_{2t}\) = 32.8 \({}^{\circ}\)C (see Table 12). The mentioned fact results from the atypical change in parameters of the SJE-20 during its operation with a mixture of 80% Jet A-1 aviation kerosene and 20% FAME biofuel due to the delayed ignition of the fuel mixture with this composition. 2.3 The Effect of Different Concentrations of Jet A-1 Aviation Kerosene and FAME Biofuel Mixture on the Total Gas Pressure in Front of the Gas Turbine P\({}_{3t}\)  
The change in the total gas pressure in front of the gas turbine p\({}_{3t}\) at all concentrations of Jet A-1 aviation kerosene and FAME biofuel mixtures corresponds to the change in the total pressure in the aviation jet engine combustion chamber (Figure 11). For all mixtures of Jet A-1 aviation kerosene and FAME biofuel, a decrease in the total pressure p\({}_{3t}\) occurred in the SJE-20 combustion chamber with the same course due to hydraulic losses arising during gas flow in the combustion chamber. In terms of the absolute value of the total \begin{table}
\begin{tabular}{c c c c c c} \hline
**Fuel Mixture Composition** & **20 th Second** & **25 th Second** & **30 th Second** & **35 th Second** & **40 th Second** \\ \hline
100\% Jet A-1 + 0\% FAME & 107.1 & 118.5 & 123.5 & 125.4 & 105.4 \\
90\% Jet A-1 + 10\% FAME & 106.2 & 109.8 & 113.7 & 106.8 & 109.8 \\
80\% Jet A-1 + 20\% FAME & 55.3 & 85.7 & 93.4 & 92.6 & 102.5 \\
70\% Jet A-1 + 30\% FAME & 90.2 & 94.5 & 96.2 & 95.9 & 96.4 \\
60\% Jet A-1 + 40\% FAME & 88.8 & 93.6 & 95.0 & 97.4 & 98.5 \\ \hline \end{tabular}
\end{table} 
Table 12: Change in total air temperature behind compressor t\({}_{2t}\) [\({}^{\circ}\)C] SJE-20 with different concentrations of Jet A-1 aviation kerosene and FAME biofuel. Figure 10: Graphical course of change in the total air temperature behind the compressor SJE-20 t\({}_{2t}\) [\({}^{\circ}\)C] when using different mixtures of Jet A-1 aviation kerosene and FAME biofuel. pressure p3t, there was a decrease in its value for the mixture of 60% Jet A-1 and 40% FAME due to the reduced value of the total pressure of the air behind the compressor p2t at the beginning of the experiment (Table 13). 2.4 The Effect of Different Concentrations of Jet A-1 Aviation Kerosene and FAME Biofuel Mixture on the Total Gas Temperature in Front of the Gas Turbine t3t  
The course of changes in the total gas temperature in front of the gas turbine t3t is different during start-up and in the steady state (see Figure 12 and Table 14). During start-up, there is a sharp increase in the total gas temperature in front of the gas turbine t3t, reaching the maximum total gas temperature in front of the gas turbine t3t,max. The maximum total gas temperature in front of the gas turbine t3t,max. is set by the initial fuel pressure control valve, which regulates the fuel supply at start-up Qfuel,sp. The value of the maximum total gas temperature in front of the gas turbine t3t,max. differs relatively little, \(\Delta\)t3t,max. \(\approx\) 20 \({}^{\circ}\)C. The moment of reaching the maximum total gas temperature in front of the gas turbine is ambiguously different depending on the composition of the mixture of Jet A-1 aviation kerosene and FAME biofuel by a minimum value (1.5 s) (Table 15). For a mixture of 80% Jet A-1 jet kerosene and 20% FAME biofuel, the time to reach the maximum gas temperature in front of the gas turbine t3t was delayed by 5 s due to the delayed ignition of this fuel mixture.