Novel Closed-Form Equation for Critical Pressure and Optimum Pressure Ratio for Turbojet Engines

Abstract

Abstract Advanced mathematical model has been developed for design and analysis of turbojet engines. It includes closed form algebraic equation for critical pressure and optimum pressure ratio at maximum thrust. The model and the algebraic equations consider efficiencies, pressure recovery rates meanwhile the gas parameters are the function of the fuel to air ratio and the temperature. РД-9Б and АЛ-21Ф3 engines are applied for demonstrating the capabilities of the calculation process. The unknown parameters as efficiencies, pressure recovery rates, power reduction rate of the auxiliary systems, bleed air ratio, air income ratio due to blade cooling and total temperature in the afterburner were identified by constrained optimization. The effect of i. T04/T02 ratio for the thrust and TSFC in the function of compressor pressure ratio, ii. the real (viscous) flow conditions and iii. the temperature and fuel to air ratio on gas parameters were also investigated for verification and plausibility check.