## 3 Properties of the Mixture of Jet A-1 Aviation Kerosene and FAME Biofuel
#### 4.1.1 The Course of the Change in SJE-20 Parameters When Using 100% Jet A-1  
The first three experimental measurements aimed at determining the parameter values for Jet A-1 aviation kerosene without adding FAME biofuel. Several conclusions can be drawn from the evaluated course of parameters shown in the graph in Figure 4 and in Table 6. The temperature of SJE-20 before ignition was 66.0 \({}^{\circ}\)C. After the end of the transition process when starting the SJE-20 after 15 s, based on the operation of the engine control system according to the control law p\({}_{2t}\) = f(Q\({}_{fuel}\).), there was a stabilization of the revolutions n, the total air pressure behind the compressor p\({}_{2t}\), the total gas pressure in front of the gas turbine p\({}_{3t}\), and F\({}_{\rm{T.T}}\) move. Due to the gradual overheating of the SJE-20 engine, there was a gradual increase in the total air temperature behind the t\({}_{2t}\) compressor and its stabilization after 30 s. After reaching the temperature peak during start-up at the total temperature in front of the gas turbine, t\({}_{3t,\max.}\) = 1114.6 \({}^{\circ}\)C in 9.8 s, and for the total temperature behind the gas turbine, t\({}_{4t,\max.}\) = 991.6 \({}^{\circ}\)C in the 8 th second and the subsequent drop in temperature; after the 15 th second, there was a subsequent increase in the total gas temperature in front of the gas turbine t\({}_{3t}\) and the total gas temperature behind the gas turbine t\({}_{4t}\). The increase in the total temperature in front of the gas turbine is more intense t\({}_{3t}\) (\(\Delta\)t\({}_{3t}\) = 64.8 \({}^{\circ}\)C) than for the total temperature behind the gas turbine t\({}_{4t}\) (\(\Delta\)t\({}_{4t}\) = 45.8 \({}^{\circ}\)C).  
The measurements immediately followed the first series of measurements with pure Jet A-1 aviation kerosene. The temperature of the SJE-20 engine before starting was t\({}_{\rm MPM}\) = 65.0 \({}^{\circ}\)C. The starting process of the engine, at the given temperature state of the engine, was not affected by the new composition of the mixture. Due to the relatively small difference in the calorific value of Jet A-1 aviation kerosene (43.292 MJ.kg\({}^{-1}\)) and FAME bio-fuel (39.0 MJ.kg\({}^{-1}\)), no fundamental changes in the measured thermodynamic parameters were recorded. The maximum temperature in front of the gas turbine t\({}_{\rm 3t,max.}\) = 1130.5 \({}^{\circ}\)C was reached 12.2 s after the start, and the maximum temperature behind the gas turbine t\({}_{\rm 4t,max.}\) = 992.1 \({}^{\circ}\)C was reached 9.8 s after the start. A small increase in the total gas temperature in front of the gas turbine t\({}_{\rm 3t}\) by 4.5 \({}^{\circ}\)C and the total gas temperature behind the gas turbine t\({}_{\rm 4t}\) by 8.9 \({}^{\circ}\)C (40 th second) can be explained by the higher engine temperature before the measurement relative to the temperature of the SJE-20 engine when measured with pure Jet A-1 aviation kerosene (t\({}_{\rm MPM}\) = 25.5 \({}^{\circ}\)C). The value of the total air temperature behind the compressor \(\Delta\)t\({}_{\rm 2t}\) increased to a minimal extent by 4.4 \({}^{\circ}\)C, and the value of the total air pressure behind the compressor \(\Delta\)p\({}_{\rm 2t}\) by 4452.8 Pa and the value of the total gas pressure in front of the gas turbine \(\Delta\)p\({}_{\rm 3t}\) decreased by \(-\)1494.6 Pa. The thrust of the SJE-20 engine was reduced by \(\Delta\)F\({}_{\rm T}\) = \(-\)6.1 N with a simultaneous increase in fuel consumption \(\Delta\)Q\({}_{\rm fuel.}\) = 0.017 L.min\({}^{-1}\) (40 th second). The change in thrust \(\Delta\)F\({}_{\rm T}\) and fuel consumption \(\Delta\)Q\({}_{\rm fuel.}\) fully correspond to the basic hypothesis that the reduced energy value of the mixture of 90% Jet A-1 aviation kerosene and 10% FAME biofuel will decrease F.T. thrust and increase fuel consumption mixture Q\({}_{\rm fuel.}\)