Engine design and performance optimization for aircraft supercruise and low observability capability

Engine design for a next-generation fighter or bomber with hypersonic flight and supersonic capability is the subject of this study. As a result of the investigation, it is observed that the optimum compressor pressure ratio decreases as the Mach number increases and the optimum compressor pressure ratio drops below 1 at flight speeds above Mach 2.43. As a result of the literature research, it is determined that the concept in which the compressor pressure ratio drops below 1 is the inverted Brayton cycle engine concept. A inverted Brayton cycle engine is found to generate a specific thrust approximately 45.2% higher at Mach 5 and 95.4% higher at Mach 5.5 compared to a ramjet engine. Another superiority of the inverted Brayton cycle engine for hypersonic flight performance is that the flight Mach number at which thrust cannot be generated is 6.2950 for a inverted Brayton cycle engine and 5.9160 for a ramjet. Turbojet engines with 3 different compressor pressure ratios (10, 20 and 50) are observed to have approximately 30-60% lower specific fuel consumption between 1 and 4 flight Mach numbers compared to the inverted Brayton cycle engine. Therefore, the inverted Brayton cycle engine is not suitable for the supercruise. However, by applying this concept to the variable cycle engine concept, it becomes suitable for aircraft with supersonic and hypersonic flight capability. In this study, it is concluded that the inverted Brayton cycle engine is a suitable concept to provide hypersonic flight capability to aircraft.