An innovative thermal management system for a Mach 4 to Mach 8 hypersonic scramjet engine

Abstract

In order to increase the technology readiness level of the hypersonic scramjet technology, the Air Force Research Laboratory HyTech Program Office funded Aerojet to develop an innovative strut-based dual-mode scramjet engine design under the Storable Fuel Scramjet Flow Path Concepts (SFSFPC) program. Effective system thermal management over the entire flight envelope is critical to the success of the mission. This paper presents a thermal management system operational for a Mach 4 to 8 flight envelope. The design of the thermal system is based (at every Mach number) on delivering fuel to the combustor at the conditions required to support ignition at Mach 4 and high-efficiency combustion at all Mach numbers. The engine thermal management system includes the C/SiC engine shell and struts, a regeneratively fuel-cooled titanium plate between the engine and the vehicle, regeneratively fuel-cooled fins inside the C/SiC struts, a heat exchanger, and a solid propellant gas generator. Due to the radiation cooling, no endothermic reaction is required to cool the engine at full throttle operation at Mach 8. At the Mach 8 cruise condition at the 80 percent power level, the radiation and fuel cooling are augmented by an endothermic reaction requiring less than 40 percent of cracked n-decane fuel. This level of endothermic reaction has been demonstrated under realistic engine conditions. INTRODUCTION Aerojet has been actively pursuing the application of dual-mode ramjet to hypersonic missiles and global reach vehicles (refs. 1-4). To increase the technology readiness level of hypersonic scramjet technology, the Air Force Research Laboratory (AFRL) HyTech Program Office funded Aerojet to develop an innovative, strut-based, dual-mode ramjet engine design under the Storable Fuel Scramjet Flow Path Concepts (SFSFPC) program. A potential application for a Mach 4 to 8 liquid hydrocarbon fueled scramjet propulsion system is a fast-response long-range, hypersonic missile. Mission objectives include a range of at least 750 nautical miles in not more than 12 minutes with carriage from both fighter and bomber aircraft. Effective system thermal management over the entire flight envelope is critical to the success of the mission. This paper presents an efficient, flexible thermal management system for a Mach 4 to 8 flight envelope. The technical challenge is to identify a flexible thermal management system design that will be responsive to the combustor fuel conditioning requirements and to significant variations of structural heat load, fuel temperature, fuel density, and pressure over the entire flight envelope. During Mach 4 operation, the most challenging task is to ensure that the liquid fuel ignites and burns efficiently at ramjet '* Technical Principal, member AIAA, ** Engineering manager, *** Program manager # HyTech SFSFPC Program Manager on the Aerojet Contract This work has been supported by the Air Force Research Laboratory under Contract number F33615-96-C-2693. This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.