Optical and thrust measurement of a pulse detonation combustor with a coaxial rotary valve

Abstract

We developed a rotary valve for a pulse detonation engine (PDE), and confirmed its basic characteristics and performance. In a square cross-section combustor, 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) and a Schlieren method.The propellant filling process and the purge process were confirmed, and each process was modeled.Moreover, we confirmed the processes of detonation wave generation and burned gas blowdown. In addition, we investigated the impact of shortening the passage width of a combustor and negative-time ignition (ignition time is earlier than the end-time of the propellant filling process) on the deflagration-to-detonation transition (DDT) distance and time. The DDT distance did not depend on the passage width of a combustor and decreased under the negative-time ignition condition. With a passage width of 20 mm, the DDT distance decreased by 22% under the negative-time 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 negative-time 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 PDRE system composed of a circular cross-section combustor and the newly developed valve. 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 partial-fill effect.

Thrust Performance of Rotary-Valved Four-Cylinder Pulse Detonation Rocket Engine

“…During the opening and closing processes, there was an abrupt expansion in the flow passage due to the rotating disk, causing a total pressure loss. As in the model of Matsuoka et al, 24) in our experimental setup, the time-averaged total pressure loss ratio was not dependent on the operation frequency and was 6% for the oxidizer, 9% for the purge gas and 18% for the fuel.…”

“…We upgraded the valve of Matsuoka et al 24) and applied it to a four-cylinder PDRE while maintaining a simplified structure, and verified the continuous gas supply and the increase in thrust/valve mass. Bussing's valve was appropriate to use with an air-breathing system, and either a premixed propellant was supplied to the detonation tubes using a single disk or three different gases were supplied to a single predetonator.…”

“…Many valves for use with a PDE have been proposed. [19][20][21][22][23][24] The rotary valve proposed by Bussing 23) satisfies the performance requirements described above and is appropriate for use with a multi-cylinder PDE. Matsuoka et al 24) developed a rotary valve appropriate for use with a rocket system based on Bussing's valve, and they investigated the fluid motion and thrust performance of a rotary-valved single-cylinder PDRE by performing optical and thrust measurements.…”

“…[19][20][21][22][23][24] The rotary valve proposed by Bussing 23) satisfies the performance requirements described above and is appropriate for use with a multi-cylinder PDE. Matsuoka et al 24) developed a rotary valve appropriate for use with a rocket system based on Bussing's valve, and they investigated the fluid motion and thrust performance of a rotary-valved single-cylinder PDRE by performing optical and thrust measurements. However, the operation characteristics and thrust performance of the rotary-valved multi-cylinder PDE developed by Bussing were not made public, and the rotary valve for a rocket system must supply three different gases to the detonation tubes while maintaining a simplified structure.…”

“…To avoid gas mixing in the valve and gas leakage from sliding surfaces, we used O-rings, an annular labyrinth seal mechanism and silicone oil. 24) As shown in Fig. 1, a Cartesian coordinate system was chosen to express the system's operation.…”