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.
To achieve reliable transmission of detonation waves to a pulse detonation engine (PDE) combustor (detonation chamber), the authors propose a PDE initiator that uses a cylindrical reflector downstream of a predetonator exit. The detonation wave propagates around the reflector to change the wave shape in three transition stages: from a planar detonation wave in the predetonator to an expanding cylindrical detonation wave, from the cylindrical wave to a planar toroidal detonation wave, and from the toroidal wave to a planar
To achieve reliable transmission of detonation wave to a pulse detonation engine (PDE) combustor, authors examined a combination method of "predetonator", "reflector" and "overfilling of the driver gas" experimentally. A detonation wave propagates around our reflector changing its shape through three transition processes; from planer to cylindrical, toroidal, and planar again. Here, successful transmission to self-sustainable expanding cylindrical detonation wave is key issue. The authors used high sensitivity driver gas mixture (stoichiometric H2-O2 mixture) for the center of the cylindrical part to make the cylindrical detonation wave transmit in target gas mixture easily. To generalize the influence of the target gas composition on the necessary overfilling radius of the driver gas mixture, we employ stoichiometric H2-O2 mixture diluted by nitrogen or argon as target gas mixture. In this study, we showed that the ration of width of the cylindrical path on cell size of propagation limits of both dilution cases are about 1 when the driver gas is supplied enough to create a stable cylindrical detonation wave over 50 mm. Accordingly, when the cell size of the target gas mixture becomes over comparable size to the width of the cylindrical path, the stable expanding cylindrical detonation wave does not sustain.
A numerical simulation including a municipal solid waste (MSW) combustion model and an NOX prediction model with a detailed chemical kinetics mechanism for a stoker-type MSW incinerator was developed. In this model, the waste bed layer on stoker grates was expressed as groups of waste particles using the Euler-Lagrange approach. In order to reduce the computational load, the NOX concentration was calculated using a decoupled detailed chemical (DDC) model. The model was validated by comparison with a combustion test in a small-scale incinerator. The calculation results could express the distribution of temperature, the flow pattern in the incinerator and the CO concentration at the outlet. In order to conduct NOX prediction, at least 8 species should be selected as pollutant species in the DDC model. Furthermore, accounting for 13 pollutant species gave better accuracy. These results showed the usefulness of the model.
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