Thrust measurement and visualization experiment of a multi-cycle single-tube pulse detonation

We developed a rotary valve for a pulse detonation engine (PDE), and confirmed its basic characteristics and performance by the visualization experiment and the thrust measurement. We visualized a multi-shot of a pulse detonation rocket engine (PDRE) cycle at an operation frequency of 160 Hz by using a high-speed camera (time resolution: 3.33 μsec, space resolution: 0.4 mm), a schlieren method and square cross-section combustor. We confirmed the each process of one cycle of a PDE (propellant filling, detonation wave generation, and burned gas blowdown and purge process) with high time relolution. The DDT distance decreased under the premature ignition condition. With a passage width of 20 mm, the DDT distance decreased by 22% under the premature ignition condition to a minimum value (76 ± 8 mm). The DDT time from spark time reached a minimum value (69 ± 14 μsec) under the condition of a passage width of 10 mm and premature ignition. The detonation initiation time and the DDT distance were represented by the time until the flame expanded toward the tube-axis one-dimensionally from ignition (characteristic time). We also carried out thrust measurement using a single-tube PDRE and double-tube PDRE composed of a circular cross-section combustor and the newly developed valve. In the singletube PDRE system, we obtained a stable time-averaged thrust in a wide range of operation frequency (40 Hz - 160 Hz) and confirmed the increase of specific impulse due to a partialfill effect. At a maximum operation frequency of 159 Hz, we achieved a maximum propellant-based specific impulse of 232 sec and a maximum time-averaged thrust of 71 N. In the double-tube PDRE system, at a operation frequency per one tube of 65 Hz, we achieved a propellant-based specific impulse of 157 sec and a maximum time-averaged thrust of 104 N.