## 3 Properties of the Mixture of Jet A-1 Aviation Kerosene and FAME Biofuel
#### 4.1.3 The Course of Changes in SJE-20 Parameters When Using a Mixture of 80% Jet A-1 and 20% FAME  
The next series of measurements was aimed at determining the parameters of the experimental SJE-20 during its operation with a fuel mixture consisting of 80% Jet A-1 aviation kerosene and 20% FAME biofuel. The changes in the parameters during measurements are presented in Figure 6 and can be read from Table 8. The measurements followed a long pause after the second series of measurements. The temperature of the SJE-20 engine before starting was t\({}_{\rm MPM}\) = 29.0 \({}^{\circ}\)C. The starting process of the engine, at the given temperature state of the engine, was affected by the new composition of the mixture. The mixture was ignited only at 9.9 s, 6.9 s later than with pure Jet A-1 aviation kerosene. At the same time, there was a shift in the moment of reaching the temperature peak t\({}_{\rm 3t,max.}\) and t\({}_{\rm 4t,max.}\) by almost 7 s. The maximum temperature in front of the gas turbine t\({}_{\rm 3t,max.}\) = 1110.6 \({}^{\circ}\)C was reached 19.6 s after ignition, and the maximum temperature behind the gas turbine t\({}_{\rm 4t,max.}\) = 972.3 \({}^{\circ}\)C was reached 16.8 s after ignition.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Parameter** & **20 th Second** & **25 th Second** & **30 th Second** & **35 th Second** & **40 th Second** & **45 th Second** \\ \hline
**Temperature t\({}_{\rm 0}\)** [\({}^{\circ}\)C] & 29.2 & 28.9 & 28.5 & 28.5 & 28.6 & 30.6 \\
**Temperature t\({}_{\rm 2t}\)** [\({}^{\circ}\)C] & 106.2 & 109.8 & 113.7 & 106.8 & 109.8 & 91.9 \\
**Temperature t\({}_{\rm 3t}\)** [\({}^{\circ}\)C] & 955.5 & 978.0 & 993.6 & 1011.4 & 1012.4 & 556.3 \\
**Temperature t\({}_{\rm 4t}\)** [\({}^{\circ}\)C] & 614.7 & 634.7 & 640.4 & 665.4 & 675.5 & 427.1 \\
**Pressure p\({}_{\rm 2t}\) [Pa]** & 271,898.8 & 268,193.9 & 266,424.3 & 267,459.8 & 265,237.7 & \\
**Pressure p\({}_{\rm 3t}\) [Pa]** & 191,195.1 & 189,728.7 & 188,207.3 & 187,871.6 & 186,511.2 & \\
**Flow Q\({}_{\rm fuel.}\) [L.min\({}^{-1}\)]** & 1.245 & 1.226 & 1.230 & 1.225 & 1.221 & 0 \\
**Revolutions n [min\({}^{-1}\)]** & 46,827.7 & 46,808.2 & 46,779.3 & 46,709.3 & 46,710.0 & 21,141.0 \\
**Thrust F.T. [N]** & 441.3 & 440.5 & 444.8 & 438.9 & 438.8 & 51.0 \\ \hline \end{tabular}
\end{table}
Table 7: Mixture of 90% Jet A-1 aviation kerosene and 10% FAME biofuel, 1 st launch (40 th second).  
The addition of 20% FAME biofuel to Jet A-1 jet kerosene resulted in an increase in the total gas temperature in front of the gas turbine t\({}_{3t}\) by 3.3 \({}^{\circ}\)C and a decrease in the total gas temperature behind the gas turbine t\({}_{4t}\) by \(-\)11.3 \({}^{\circ}\)C. The value of the total air temperature behind the compressor \(\Delta\)t\({}_{2t}\) decreased to a minimum extent by \(-\)2.9 \({}^{\circ}\)C, the value of the total air pressure behind the compressor \(\Delta\)p\({}_{2t}\) increased by 8545.7 Pa, and the value of the total gas pressure in front of the gas turbine \(\Delta\)p\({}_{3t}\) decreased by \(-\)2691.6 Pa. The thrust of the SJE-20 engine was reduced by \(\Delta\)F\({}_{T}\) = \(-\)11.5 N with a simultaneous increase in fuel consumption \(\Delta\)Q\({}_{\text{fuel}}\). = 0.043 L.min\({}^{-1}\).  
As the proportion of FAME biofuel (\(\rho_{\text{FAME}}\) = 882 kg.m\({}^{-3}\)) in the mixture with Jet A-1 aviation kerosene (\(\rho_{\text{jet A-1}}\) = 810 kg.m\({}^{-3}\)) increased, the density of the mixture increased, resulting in a lower quality fuel atomization when flowing through the fuel nozzles. Insufficient atomization of the fuel resulted in its slower evaporation in the combustion chamber, which caused a worse ignition process of the mixture during its start-up, especially with a cold engine and lower atmospheric temperatures.