Numerical Analysis of the Flow Downstream of the Exhaust Nozzle of a Miniature Turbojet Engine During Co-Combustion of Kerosene and Hydrogen

Research related to the use of hydrogen is crucial because it can be a significant factor in reducing exhaust emissions into the environment. This work represents the second stage of research related to the analysis of exhaust gases from a miniature GTM 400 MOD turbojet engine. Based on the parameters obtained in the experiment, a numerical study of the flow downstream of the exhaust nozzle was performed in ANSYS software (version R1, 2025). The main goal of the calculations was to obtain the temperature distribution and compare the values at checkpoints where actual measurements were taken. The study was conducted in two stages. In the first stage, the engine operated conventionally, burning kerosene. In the second stage, co-combustion of kerosene and hydrogen occurred in the engine. The numerical analysis enabled the visualization of the flow phenomenon for these stages within the considered rotational speeds. The analysis examined flow in domains where the gap was included and excluded. This gap was created by the different diameters of the container opening and the engine nozzle outlet. The study showed that ignoring the gap allows for temperatures closer to the experimental values. Results deemed satisfactory were less likely to be found in vortex areas, but more likely in areas closer to the container walls and the engine exhaust stream itself. The results of the conducted tests showed that the Root Mean Square Error RMSE was within the range of 9.5–22.8% relative to the average temperature values obtained from experimental measurements. The highest turbulence intensity occurred for hydrogen co-combustion at a higher rotational speed, reaching 284% for Variant 2 and 300% for Variant 1. The largest standard deviation for both fuel types at a distance of 0.083 m from the container wall was 68.5 K for variant 2 and 76 K for variant 1. At a distance of 0.166 m from the container wall, the deviation was 76 K for variant 2 and 83.8 K for variant 1.