Extended Second Law Analysis for Turboramjet Engines

Turbine based combined cycles (TBCC) monopolizes the benefits from the two different thermodynamic cycle configurations involved. The TBCC, which is based on an irreversible Brayton cycle, considered in this study is a wraparound configuration turboramjet engine. The turboramjet can be utilized in either turbojet (afterburner (AB) being ON or OFF), ramjet and even dual mode operation. However, for the dual mode operation the turbojet engine AB are considered to be ON. In addition, the ramjet thermodynamic assessment considers multi-oblique shock and single normal shock solution and Rayleigh flow calculation for the combustion chamber. The performance analysis and comparison for the turboramjet engine for dual mode operation is based on a maximum power approach under variations of Mach number and altitude. Moreover, the dual mode operation considered variations of inlet air mass flow; the split of air mass flow between the turbojet and ramjet. In addition, a brief comparison is provided of the turbojet while the afterburner is in ON or OFF mode utilizing the maximum power, EPLOS and PLOS optimization functions for variations of altitude and Mach number. Moreover, a component based evaluation under maximum power conditions for variation of Mach number is provided. The turbojet with an AB shows greater advantage at Mach number higher than unity as well as attaining maximum power outputs at minimum PLOS for lower compressor ratio parameters (θ_c). Whereas the turboramjet indicates that as the split of inlet air mass flow to the ramjet is increased beyond 50% the advantage in terms of η_th, η_o, f, TSFC, I_a, thrust and ν_NOZZLE far supersede that of the turbojet with an AB.