Development of Pulse Detonation Engine Initiator Using Reflector for Large Bore Combustor

Abstract

To achieve reliable transmission of detonation wave to a pulse detonation engine (PDE) combustor, authors have proposed a PDE initiator, which consists of a predetonator and a reflector. A detonation wave propagates around the reflector changing its shape through three transition processes; from planer to cylindrical, toroidal, and planar again. Our previous study revealed that the transition to the cylindrical detonation wave upstream of the board plays a significant role in detonating hydrogen-air mixture in a 100-mm-diam-combustor. A self-sustainable condition of the cylindrical detonation wave is severe when the radius of the wave front is small. In cases using hydrogen-oxygen mixture as driver gas for the 100-mm-diam-combustor, we had to fulfill with driver gas entire upstream of the board at the critical condition for the transition to the cylindrical wave. On the other hand, curvature of the cylindrical detonation wave front becomes smaller with increasing radius of the front, so the self-sustainable condition of the cylindrical wave must be mitigated for a large bore combustor. In this study, we investigated the necessary filling diameter of the driver gas to detonate hydrogen-air cylindrical detonation by using a 500-mm-diam-cylindrical-combustor.

Influence of Channel Width on Cylindrical Detonation Wave Propagation

“…The necessary filling diameter R of the driver gas (stoichiometric hydrogen-oxygen mixture) to propagate the cylindrical detonation waves to the target gas (stoichiometric hydrogen-air mixture) by using a 500 mm diameter cylindrical combustor has been investigated earlier. 23) It was confirmed that R = 100 mm is the threshold condition. Figure 3 indicates that this threshold has two factors.…”

“…The dilution ratio threshold is valid if R is large enough. Wakita et al 23) assumed two hypotheses for the dominant factors determining the second threshold. One is the ratio of cell size to the curvature of cylindrical detonation waves, λ/r.…”

Influence of Detonation Cell Size on Propagation of Cylindrical Detonation Wave

“…Therefore, we offer a hypothesis that, to transmit a detonation wave successfully to a large diameter detonation combustor as shown in Fig.1-(c), the driver gas only has to fill up the radius R where a self-propagating cylindrical detonation wave is established. The authors investigated the necessary filling diameter R of the driver gas (stoichiometric H 2 -O 2 mixture) to detonate the target gas (stoichiometric H 2 -Air) cylindrical detonation by using a large 500-mm -diam-cylindrical-combustor 23) . In this study, we confirmed that the necessary overfilling distance R of the driver gas mixture is more than 100 mm which is the necessary distance to generate the stable expanding cylindrical detonation wave.…”