Entropy modelling in propulsion systems

More efficient use of existing energy resources is necessary for environmental sustainability. The increasing number of aircraft and flights creates the need to analyze the performance of propulsion systems used in aircraft and to increase their efficiency. In this thesis, performances and entropy productions of turbojet and turbofan engines were analyzed based on performance parameters and the first and second laws of thermodynamics, and an entropy model was developed for different flight phases. The specific entropy values and entropy productions due to irreversibility were calculated by thermodynamic analyzes on the propulsion systems. Thermodynamic analysis of an experimental turbojet engine is also carried out for different nonlinear loads. As a result of the off-design analysis of the turbojet engine, the entropy generation in the combustion chamber was calculated as 1,08506 kJ/kg.K and 0,956 kJ/kg.K for 48500 and 39770 RPM values, respectively. While the waste energy ratio of the turbojet engine was 0,58 at 39770 RPM, it was calculated as 0,70 at the maximum speed of 48500 RPM. The useful energy ratio of the turbojet engine varies between 0,738 and 0,435 in the minimum and maximum rev range. The effects of power settings on the exergetic performance of the turbojet engine and its components were investigated using energy, exergy and exergo-sustainability metrics.