A mathematical modeling of well-known methods used to define turbojet main parameters aiming at solution optimization is described. The parameters considered include: compression ratio, maximum temperature for turbine, compressor efficiency, turbine efficiency, etc. By using the relationships for specific thrust, specific fuel consumption, etc., and assuming that construction and functional parameters such as calorific value, combustion efficiency, flight altitude and speed, etc., are known a function representing a sum of the ratios describing specific thrust and SFC deviations against maximum specific thrust and minimum SFC, respectively, is derived. Main parameter selection criteria pending on engine operation conditions and aircraft category are introduced. Mathematic analysis for main parameter selection optimization leads to a convex programming model for which both the function and the constraints are convex functions defined by convex fields. Although this paper makes reference to classic jet engines the method may be easily developed for by-pass engines, etc.

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