Determining of the Optimum Size of Turbofan Engine for Obtaining the Maximum Range of Multi-purpose Airplane

Aircraft range is one of the most important criteria of the assessment of the performance properties of an aircraft. For the needs of the paper the mathematical model of an aircraft (multi-purpose aircraft) and the engine which propels the aircraft was built (turbofan, two-spool, with jet mixer). For the analysis it was chosen so-called typical Breguet model and the conventional range. The models were modified as they should consider the characteristics of the engine in the non-dimensional form. The aim of the simulation research was to discuss the influence of the engine parameters (geometrical and thermodynamic) on the aircraft range, realized mainly in the subsonic and supersonic conditions. The decision which of these conditions can have a significant influence on the selection of the calculating point (i.e. the point which determines the geometrical dimensions of the engine) is difficult as there is no clear direction which aircrafts make up the important share in a mission or missions. It was decided that the parameter which connects the engine geometry with the range model is so-called non-dimensional coefficient of engine geometry which is the relation of the area on the inlet to the engine related to the wing area of the aircraft. It was shown that for various parameters of the engine cycle it is possible to show such a value of the non-dimensional coefficient of geometry which maximizes the aircraft range. The results obtained show opposite requirements as for the engine geometry for the subsonic and supersonic flight. On this basis the compromise solution was proposed to fulfil the requirements of the multi-purpose aircraft.