Study of ejector geometry on thrust augmentation for pulse detonation engine ejector systems

Pulse detonation engine (PDE) technology is a novel form of propulsion that offers the potential of high efficiency combustion with reduced hardware complexity. Although the primary interest of the research in the pulse detonation engine field is directed towards overcoming the problems associated with operating a pure PDE system, there are other worthy options to be considered for these engines. The PDE driven ejector concept is one such option where the system would be part of a hybrid PD/Turbofan engine. This system offers the promise of replacing the high-pressure turbine sections of the core of a high bypass turbofan engine. The purpose of the current research is to investigate the thrust augmentation capabilities of a PDE driven ejector and provide experimental data that would assist in understanding the behavior of such a system.; The major potential advantages of the PDE-ejector include reduced costs due to the reduced engine weight, along with improved specific fuel consumption and specific power inherent in the incorporation of a PDE component.; To achieve the goal of this research, the thrust augmentation of a PDE driven ejector was characterized for a set of configurations. Two separate PDE's were utilized in this study. The first PDE was capable of operating at a constant frequency of 10 Hz de to flow rate limitations, and another PDE built to have an operational frequency range of 10 Hz-70 Hz to test the effect of operational frequency on PDE-ejector systems.; Optical diagnostics were employed at specific positions of interest to understand the physical behavior of the flow. Baseline experimental results helped define and understand the operational characteristics of the PDE's utilized in this study.; Thrust measurements were then made for PDE driven ejector configurations. The parameters that were independently changed were the inlet geometry of a constant diameter ejector, as well as the overlap distance between the PDE tube exit and ejector tube inlet. Ejectors of different size diameters were also tested and their performance documented. From these previous studies it was found that with a relatively short ejector having a rounded inlet, thrust augmentation up to 40% was possible. Thus the effect of simply rounding the inlet caused a considerable increase in thrust production. Thus three different size rounded inlets are tested for thrust augmentation.; To study the effect of frequency on PDE-ejector performance a PDE capable of operating at frequencies up to 70 Hz was assembled. Thrust measurements were then made for PDE driven ejector configurations. Thrust augmentation levels of 120% were achieved with this system using the longest available ejector with a rounded inlet.; A square ejector with plexi-glass sides allowing optical access into the ejector was designed. The ejector was designed to have the same hydraulic diameter as the round ejectors utilized. Shadowgraph imaging was used to observe the flow at various ejector locations for the duration of a single PDE cycle. It was observed that the flow characteristics of the detonation cycle changes with the location of the ejector, where ejector position alters the blowdown process undergone by a PDE. It was also observed that the flow of secondary gas into the ejector tube starts earlier for the case of 25% ejector overlap position. (Abstract shortened by UMI.)...