## 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
}\) depending on the composition of the mixture of Jet A-1 aviation kerosene and FAME biofuel differs from the moment of reaching the maximum total gas temperature in front of the gas turbine t\({}_{\rm 3t,max. }\) (Table 18). For the mixture of 80% Jet A-1 jet kerosene and 20% FAME biofuel, the time to reach the maximum total gas temperature downstream of the gas turbine t\({}_{\rm 3t}\) was delayed by 5 s due to the delayed ignition of this fuel mixture. \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** & 620.8 & 633.4 & 652.8 & 663.4 & 666.6 \\
**90\% Jet A-1 + 10\% FAME** & 614.7 & 634.7 & 640.4 & 665.4 & 675.5 \\
**80\% Jet A-1 + 20\% FAME** & 765.0 & 604.9 & 615.9 & 634.8 & 665.9 \\
**70\% Jet A-1 + 30\% FAME** & 629.3 & 627.5 & 635.3 & 653.7 & 660.2 \\
**60\% Jet A-1 + 40\% FAME** & 619.2 & 632.3 & 641.5 & 650.9 & 659.5 \\ \hline \end{tabular}
\end{table} 
Table 16: Change in total gas temperature behind gas turbine t\({}_{\rm tt}\) [\({}^{\circ}\)C] SJE-20 with different concentrations of Jet A-1 aviation kerosene and FAME biofuel. Figure 13: The graphical course of the change in the total gas temperature behind the gas turbine SJE-20 t\({}_{\rm tt}\) [\({}^{\circ}\)C] when using different mixtures of Jet A-1 aviation kerosene and FAME biofuel. 2.6 Effect of Different Concentrations of Jet A-1 Aviation Kerosene and FAME Biofuel Mixture on the Q\({}_{\text{fuel}}\) Fuel Flow Rate  
Changing the supply of various mixtures of Jet A-1 aviation kerosene and FAME biofuel up to the 15 th second during the start-up corresponds to the starting program of SJE-20, Q\({}_{\text{fuel,sp. }}=\) f(p\({}_{\text{2t}}\)). After the fuel mixture is ignited, the supply of the fuel mixture is increased so that the SJE-20 reaches working mode (SJE-20 was created through the modification of a TS-20 turbine launcher, while its control system was preserved). After reaching the working mode of SJE-20, the flow rate of fuel mixtures Q\({}_{\text{fuel}}\), stabilized and only minimally decreased in the range from 0.002 L.min\({}^{-1}\) (60% Jet A-1 and 40% FAME) to 0.052 L.min\({}^{-1}\) (80% Jet A-1 and 20% FAME) (Figure 14). In the 40 th second, the biggest difference in the fuel flow rate was reached \(\Delta\)Q\({}_{\text{fuel}}\) = 0.071 L.min\({}^{-1}\) between Jet A-1 aviation kerosene (1.204 L.min\({}^{-1}\)) and a mixture of 60% Jet A-1 aviation kerosene and 40% FAME biofuel (1.277 L.min\({}^{-1}\)) (Table 19). 2.7 The Effect of Different Concentrations of Jet A-1 Aviation Kerosene and FAME Biofuel on the Revolutions n  
The speed change in the SJE-20 during its operation is controlled by the engine regulation system, which is set to maintain a constant speed at the operating mode n = n\({}_{\text{max}}\) (Figure 15). The mentioned regulation law corresponds to the needs of the original turbine starter TS-20, from which SJE-20 was created. For this reason, the flow rate of Q\({}_{\text{fuel}}\) fuel mixtures changed. In order to maintain constant revolutions in the working mode, it was necessary to ensure the required energy value for the individual mixtures of Jet A-1 aviation kerosene and FAME biofuel, which required an increased supply of a mixture of Jet A-1 aviation kerosene and FAME biofuels (Table 20). In the SJE-20 operating range from the 25 th to the 40 th second, the maximum speed difference is \(\Delta\)n\({}_{\text{max}}\). = 60.6 min\({}^{-1}\), representing a deviation of 0.129% with respect to the maximum engine speed. 2.8 The Influence of Different Concentrations of Jet A-1 Aviation Kerosene and FAME Biofuel Mixtures on the Thrust T\({}_{\text{T.t. }}\) of the SJE-20  
The change in thrust F\({}_{\text{T.t. }}\) of the SJE-20 experimental engine, depending on the composition of the mixture of Jet A-1 aviation kerosene and FAME biofuel, is relatively small in the working mode (Figure 16). It is not proportional to the content of FAME biofuel in the mixture.