Comparison of air-breathing jet engines with slow and detonation combustion

Abstract

In connection with the allegations of a possible significant increase in thrust characteristics when replacing air-breathing jet engines with deflagration combustion (RAMJET) to engines with combustion in detonation waves (pulsating – PDE), a comparison of ramjet engines of different schemes with deflagration and detonation combustion was performed. The comparison is based on the simplest models of thermodynamics, detonation wave, air braking, expansion of combustion products in perfectly adjustable nozzles and unsteady flows in combustion chambers. Within such models, with a fixed adiabatic index, the characteristics of each engine depend on two parameters – the flight Mach number and the dimensionless calorific value of the combustible mixture. The comparison for the real values of thrust characteristic with the analysis of thermodynamic cycles and one-dimensional unsteady calculations (for engines with combustion in detonation waves) confirmed the importance of taking into account non-stationary processes in combustion chambers. If the process in the combustion chamber is non-stationary, and even with the shock waves arising from the reflection of the detonation wave from its ends, the recalculation of thrust and impulse according to thermal efficiency is wrongful.