Preliminary Design of a Pulsed Detonation Based Combined Cycle Engine

Results of a recent investigation in the design of a single flow path combined cycle engine using periodic detonation waves are presented here. Four modes of operation are used in a sample SSTO trajectory in this preliminary design (sketched in Fig. (1)): (1) An ejector augmented pulsed detonation rocket for take off to moderate supersonic Mach numbers (2) A pulsed normal detonation wave mode at combustion chamber Mach numbers less than the Chapman-Jouguet Mach number, (3) An oblique detonation wave mode for Mach numbers in the airbreathing regime that are higher than the Chapman-Jouguet Mach number, and (4) A pure Pulsed Detonation Rocket (PDR) mode of operation at high altitude. These modes utilize a single flow path, in which an array of detonation tubes is placed. The tubes fire sequentially in such a manner as to make the maximum use of the incoming air mass and provide the smoothest possible operation of the device. These tubes could alternately be embedded in load bearing struts. Performance estimates based on the stream thrust approach have been obtained from a time averaged ideal cycle analysis with corrections from CFD results. Suggestions for performance enhancement are outlined.