Vortex Breakdown and Global Modes in Swirling Combustor Flows with Axial Air Injection
Vortex Breakdown and Global Modes in Swirling Combustor Flows with Axial Air Injection
复制标题
轴向空气喷射旋流燃烧室流中的涡流破坏和全局模式
DOI：
10.2514/6.2013-2602
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
C. Paschereit
中科院分区：
文献类型：
--
作者：
S. Terhaar;T. Reichel;C. Schrödinger;Lothar Rukes;K. Oberleithner;C. Paschereit
绝大多数燃气轮机燃烧室都采用强旋流。涡流破裂下游的复杂流场提供了良好的火焰稳定性，但也容易出现自激大规模流体动力学不稳定性。这些全局模式通常表现在进动涡核 (PVC) 中，对于燃烧过程的作用仍然是一个悬而未决的问题，并且已经提出了对混合过程和热声振荡的影响。在当前的研究中，采用实验、数值和分析相结合的方法，研究了通过截断中心体的轴向空气喷射对涡流击穿 (VB) 类型和整体流体动力模式的影响。在水隧道测试设施中对燃烧室内部和燃烧器上游混合管中的等温流场进行参数研究。在使用甲烷燃料的反应条件下对选定的配置进行了进一步评估。接下来，进行了大涡模拟（LES）并成功地用实验数据进行了验证。所有结果都表明，流入参数（轴向喷射速率和入口涡流数）对涡流破裂的类型以及全局模式的频率、振幅和形状有很大影响。反应案例显示出与等温案例非常相似的结果，证明了等温研究的相关性。对时间平均测量速度数据和数值获得的数据进行线性局部水动力稳定性分析，产生流场内的绝对不稳定域。轴向喷射被证明会阻碍燃烧器入口附近的绝对不稳定区域，而下游的第二个区域仍然存在。在所研究的轴向喷射速率的整个范围内，测量的全局模式频率与计算的频率非常一致。本文的研究结果有助于理解旋转燃烧室流中全局模式的发生机制以及如何通过小的流场修改来控制它们。此外，轴向空气喷射被证明可以为防逆火燃烧器运行提供合适的流场。
Strongly swirling flows are used in the vast majority of gas turbine combustors. The complex flow field downstream of the vortex breakdown provides good flame stabilization but is also prone to self-excited large scale hydrodynamic instabilities. The role of these global modes, which usually manifest in a Precessing Vortex Core (PVC), for the combustion process is still an open question and influences on mixing processes and thermoacoustic oscillations have been proposed. In the current study the effect of axial air injection through a truncated center body on the type of the Vortex Breakdown (VB) and the global hydrodynamic mode is investigated using a combined experimental, numerical, and analytical approach. A parametric study of the isothermal flow field inside the combustion chamber and in the mixing tube upstream of the combustor is carried out in a water tunnel test facility. Selected configurations were further assessed under reacting conditions using methane fuel. Next, a Large Eddy Simulation (LES) was conducted and successfully validated with the experimental data. All results show a strong effect of the inflow parameters (axial injection rate and inlet swirl number) on the type of the vortexbreakdown and the frequency, amplitude, and shape of the global mode. The reacting cases show very similar results as the isothermal cases, proving the relevance of the isothermal investigation. Linear local hydrodynamic stability analyses, carried out on the time-average measured velocity data and the numerically obtained data, yield the absolutely unstable domain inside the flow field. Axial injection is shown to impede a zone of absolute instability near the combustor inlet while a a second zone further downstream remains. An excellent agreement of the measured to the calculated frequencies of the global modes is achieved over the whole range of investigated axial injection rates. The findings of this paper help to understand the mechanisms that are involved into the occurrence of global modes in swirling combustor flows and how they may be controlled by small flow field modifications. Furthermore, axial air injection is shown to provide a suitable flow field for flashback-proof combustor operation.
空气旋流燃油喷射器的 URANS 和 LES CFD 方法的比较
DOI：
10.1115/gt2008-50278
发表时间：
2008
期刊：
--
影响因子：
--
作者：
Dunham D
通讯作者：
Dunham D