Cold Flow Simulations for a Pulse Detonation Rocket Ejector

This paper reports an exploratory experimental cold flow test of the first mode in a multi-mode propulsion concept. A small model of a wallmounted pulse detonation rocket (PDR) ejecting into a duct was fabricated and integrated into the supersonic wind tunnel at the University of Texas at Arlington (UTA). Although supersonic testing proved to be inconclusive, the static tests showed that pulsed flows entrain more mass than steady state flows. It also indicated that thrust augmentation is more favorable at low frequencies for this model. Background Pulse detonation engines (PDE) have been researched extensively as an alternate form for high-speed propulsion. A concept has been proposed for the adaptation of a PDE into a type of scramjet in which the PDE ejects into a subsonic or supersonic secondary flow to provide thrust. A model of such a configuration was developed and tested in the supersonic blow-down tunnel at the Aerodynamics Research Center (ARC) at the University of Texas at Arlington (UTA). This was done as a means of determining if this is a viable option for future propulsion. The first step is to conduct “cold-flow” simulations in which the gas cycles in the PDE chamber are left undetonated to provide a baseline for future experiments. As a means of safety, atmospheric air is used to replace the fuel and the oxidizer since there is no combustion. That is the basis for this research and thesis. Multi-mode Propulsion Concept In the National Aerospace Plane program, as well as other hypersonic vehicle proposals, one of the major obstacles that must be overcome is the development of a propulsion system that can transition between all flight regimes. A propulsion system for this type of application is needed to start at rest, accelerate through the transonic region, and continue to accelerate to a hypersonic cruise or even escape the sensible atmosphere. One novel approach to solving this problem is a multi-mode propulsion concept proposed in Munipalli et al. . This system proposed takes advantage of ejectors and detonation physics as a means of providing thrust. This system operates with four distinct modes (Fig 1) as shown below. (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 air-breathing regime that are higher than the Chapman-Jouguet Mach number, and (4) A pure pulsed detonation rocket (PDE) mode of operation at high altitude. The obvious advantage to this is all modes can make use of the same internal geometry, eliminating the need for additional flow paths. Another benefit is the atmospheric air entering the duct does not have to be slowed to subsonic speeds at higher Mach numbers. This greatly reduces the losses in total pressure associated with shock waves and, in turn, increases efficiency. Shock waves also increase the static temperature, and without them, the gas Figure 1: Schematic of proposed