This paper focuses on optimizing an innovative annular Lean Premixed staged burner, following the Trapped Vortex Combustor concept. The latter consists of a lean main flame stabilized by passing past a rich cavity pilot flame. Unfortunately, this configuration is highly sensitive to combustion instabilities and the flame is not well stabilized. This work consists of adjusting aerodynamic variables, chemical parameters and burner geometry to reach a "low-NOx" operation while reducing other pollutants and getting a stable flame. Results show that stability is reached when mass transfers between main and cavity zones are reduced. Then, the main bulk velocity is increased to reduce the cavity thermal expansion, due to the hot gas expansion. In addition, the cavity flow rate is reduced to prevent from penetrating and disturbing the main flow. Re-arranging injections in the cavity also avoid local unsteady equivalence ratios, which creates an unsteady heat release and combustion with pulses. Regarding NO_x, a leaner main flame combined with a sufficiently rich cavity mixture creates local stoichiometric zones at the interface between the cavity and the main zone. The latter point is found to be a good anchoring mechanism. Compared with the original configuration, a stable point of operation is found: acoustic energy is reduced by an order of 100, NOx level is less than 0.4 g/kg_(fuel), CO is cut by 93% with no more Unburned Hydro-Carbons.
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机译：本文遵循捕集式涡流燃烧器的概念，致力于优化创新的环形精益预混合分段式燃烧器。后者由稀薄的主火焰组成，该稀薄的主火焰通过经过浓腔先导火焰而稳定。不幸的是，这种构造对燃烧不稳定性高度敏感，并且火焰不稳定。这项工作包括调整空气动力学变量，化学参数和燃烧器的几何形状，以实现“低NOx”运行，同时减少其他污染物并获得稳定的火焰。结果表明，当减少主区和型腔之间的质量传递时，达到了稳定性。然后，由于热气体膨胀，增加了主要体积速度以减小腔体的热膨胀。另外，降低了空腔流速以防止渗透和干扰主流。在空腔中重新安排喷射还可以避免局部不稳定的当量比，从而产生不稳定的热量释放和脉冲燃烧。关于NO_x，较稀薄的主火焰与足够丰富的空腔混合物相结合，在空腔和主要区域之间的界面处产生了局部化学计量区域。发现后一点是良好的锚固机制。与原始配置相比，发现了一个稳定的运行点：声能降低了100个数量级，NOx含量小于0.4 g / kg_（燃料），CO减少了93％，而未燃烧的碳氢化合物不再。
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