旋回流を伴う希薄予混合燃焼器における非定常火炎挙動

概要

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Lean premixed combustion is one of the most efficient techniques to reduce nitrogen oxide (NOx) emission. However, a lean premixed combustor has narrow stable combustion range compared with a diffusion combustor and has a risk of flashback. Flashback of the flame into the nozzle causes serious damage to a combustor. In this study, we present characteristics of flame propagating in a premixed burner with swirling flow in order to investigate unsteady flame behavior in a gas turbine premixer. During flashback, the flame propagating upstream was visualized with a high-speed camera. Moreover, we established the technique to measure the instantaneous flow fields of unburned fuel-air mixture in a swirling premixed burner using stereo Particle Image Velocimetry (stereo-PIV). As a result, characteristics of flame behavior propagating upstream were examined. In addition, it was found that a low velocity region existed near the flame tip. We clarified the existence of the vortex core of swirling flow near the center axis with precession movement.