Derivation and Application of a New Equation for Design and Analysis of Triple Spool Mixed Turbofan Jet Engines with Verification
Acta Polytechnica Hungarica
The development of an improved mathematical model is reported, herein, for modeling the thermo-dynamic processes of triple spool mixed turbofan jet engines with an afterburner, at start conditions with special care for the verification. The T-s diagram and the main characteristics of the engines are determined by a concentrated parameterdistribution type method, implemented in the MATLAB environment. The governing equations are based on mass, energy balance and the real thermo-dynamic
... o-dynamic processes. A non-linear constraint optimization method is used, for identifying the unknown parameters. Temperature and component mass fraction dependent gas properties are calculated by iteration cycles in case of functional dependencies. A new and more accurate equation is derived and applied for determining the critical pressure at converging nozzle flow with consideration of the local material properties. The thermo-dynamic analyses are completed for NK-32 and NK-25 turbo jet engines. The plausibility of the method and the verification the new equation is provided. Nomenclature Variables(Latin) 9 Outlet area of the engine (m 2 ) Specific heat of the fuel (J/kg/K) Specific heat (J/kg/K) ̅ Mean (between T i and T i+1 ) specific heat (J/kg/K) 9 Outlet diameter of the engine (m) D Inlet diameter of the engine (m) Fuel to air ratio (kg/kg) F. Zare et al.