Experimental investigation of thrust augmentation by ejectors on a pulse detonation engine

Utilizing gasoline as the fuel, air as oxidizer, a series of multi-cycle detonation experiments was conducted to study thrust augmentation by pulse detonation engine driven ejectors. The straight cylindrical ejectors with different inner diameter, length, and inlet geometry were designed. The effects of the axial location of the ejectors relative to the end of the detonation tube, ejector length to diameter ratio on thrust augmentation were investigated, with the operating frequency of 25 Hz. A peak thrust augmentation level of 80.5% was achieved by adding an ejector to the exit of the detonation tube. Performance measurements of the pulse detonation engine ejector system showed that thrust augmentation is a strong function of the ejector axial position. The result indicated that there exists a maximum thrust augmentation with ejector upstream of the detonation tube exit at least. The exact location at which the maximum thrust augmentation was obtained varies with the ejector to the pulse detonation engine diameter ratio and the ejector inlet geometry. With the increase of the length-to-diameter ratio, thrust augmentation was noticeably enhanced and finally tended to a constant. There exists an optimum ejector length. In the present study, the optimum length to diameter ratio of ejector was 4.58. Furthermore, the effect of operating frequency on ejector thrust augmentation also investigated. The operating frequency was varied from 15 Hz to 35 Hz.