Combustion Instability and Flame Structure of Turbulent Swirl-Stabilized Liquid-Fueled Combustion
Combustion Instability and Flame Structure of Turbulent Swirl-Stabilized Liquid-Fueled Combustion
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DOI：
10.2514/1.b34438
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发表时间：
2012-09
影响因子：
1.9
通讯作者：
Tongxun Yi;D. Santavicca
中科院分区：
文献类型：
--
作者：
Tongxun Yi;D. Santavicca
本文研究了湍流液体燃料旋流稳定贫油直喷燃烧室的火焰结构和燃烧不稳定特性。由于液滴尺寸和分布、蒸发、液滴-蒸汽-空气卷吸和混合以及液滴-火焰-湍流相互作用的复杂性，火焰结构与稀薄预混气体燃料燃烧显著不同。当预热温度高于423 K时，热释放在排料面下游约12 mm处的一个紧密的圆环内完成;在接近贫油熄火时，随着当量比的减小，圆环直径缩小并逐渐向轴线收敛;之后，热释放区变长并偏离轴线。化学发光只能提供热释放速率的定性信息，表明全局化学发光测量喷雾燃烧的局限性。锁相增强型电荷耦合器件对CH化学发光的成像表明，在燃烧不稳定过程中，主要是化学发光强度的变化，而不是放热空间分布的变化。根据工作条件，可以激励燃烧室的单波模式、半波模式或两者。虽然燃烧室在两端高度阻塞，但在燃烧室出口和燃烧室入口处没有发现压力波腹。同时激发的一波模式和半波模式本质上是不稳定和不稳定的，这可以归因于反应的旋转剪切层的非线性响应声振荡。热声振荡的振幅和频率都是时变的。随着振荡强度的减小，极限环振子变得越来越容易受到外部干扰，如状态轨迹的较大邻域所示。
The present paper reports flame structure and combustion instability characteristics in a turbulent liquid-fueled swirl-stabilized lean direct fuel injection combustor. Because of the complexities in droplet size and distribution, evaporation, droplets–vapor–air entrainment and mixing, and droplets–flame–turbulence interactions, the flame structure is remarkably different from lean premixed gas-fueled combustion. With the preheat temperature above 423K, heat release is completed within a compact doughnut ring, about 12mmdownstream of the dump plane; with decreasing equivalence ratios at the approach of lean blowout, the doughnut ring shrinks in diameter and gradually converges to the axis; after that, the heat release zone becomes elongated and tilted off the axis. Chemiluminescence only provides qualitative information of the heat release rate, suggesting the limitations of global chemiluminescence measurements for spray combustion. Phase-locked intensified charge coupled device imaging of CH chemiluminescence shows that during combustion instability there aremainly variations in the chemiluminescence intensity rather than in the spatial distribution of heat release. Depending on the working conditions, the one-wave mode, the half-wave mode, or both of the combustion chambers can be excited. Although the combustion chamber is highly blocked at both ends, no pressure antinodes are found at the chamber exit and the chamber inlet. Simultaneous excitation of the one-wave mode and the half-wave mode is intrinsically unsteady and unstable, which can be attributed to the nonlinear response of the reacting swirling shear layer to acoustic oscillations. Both the amplitude and the frequency of thermoacoustic oscillations are constantly time-varying. With decreasing oscillation intensity, the limit-cycle oscillator becomes increasingly vulnerable to external disturbances, as indicated by a larger neighborhood of the state trajectory.