Velocity Field Response of a Forced Swirl Stabilized Premixed Flame
Velocity Field Response of a Forced Swirl Stabilized Premixed Flame
复制标题
强制旋流稳定预混火焰的速度场响应
DOI：
--
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Hemchandra
中科院分区：
文献类型：
--
作者：
K. Manoharan;Travis Smith;B. Emerson;C. Douglas;T. Lieuwen;S. Hemchandra
本研究的动机是有必要开发一种低阶预测方法来预测精益预混燃气轮机燃烧室的非定常放热响应特性。这反过来又需要准确描述由声强迫在燃烧室流动中引起的相干流体动力振荡。利用sPIV和OH-PLIF测量了模型“未包裹”环形燃烧室中单喷嘴、旋流稳定、预混甲烷-空气火焰的时间分辨速度和火焰位置场。钻机中115 Hz的自然声波振荡导致了一个连贯的流动振荡，主要集中在环空射流和中央再循环区之间的剪切层内。对时间平均基流场的线性稳定性分析表明，该流不存在任何自激水动力模式。然后，我们比较了在115 Hz强迫频率下的强迫响应分析的预测，基于线性化的Navier-Stokes方程。对于远离燃烧器中心线的速度振荡振幅场的空间变化，线性强迫响应分析预测与实验响应结果在定性上是一致的。此外，在环形射流和中央再循环区之间沿剪切层速度振荡的相速度上，预测结果与实验结果在定量上一致。相速度是一个重要的流场特性，它对这些相干速度振荡产生的放热响应有重要影响。现有的强迫响应分析方法假设强迫位置沿径向的强迫幅值均匀，以及沿顺流方向的开放流动。这两种假设都不严格适用于目前的燃烧器，因为它的轴上有一个中心体。这可能是实验和预测在中心线上的定性和定量一致性较差的原因。
This study is motivated by the necessity to develop a low order prediction approach for unsteady heat release response characteristics in lean premixed gas turbine combustors. This in turn requires an accurate description of the coherent hydrodynamic oscillations induced in the combustor flow by acoustic forcing. Time resolved velocity and flame position fields are obtained using sPIV and OH-PLIF measurements on a single nozzle, swirl-stabilized, premixed, methane-air flame in a model ``unwrapped' annular combustor rig. A natural acoustic oscillation in the rig at 115 Hz results in a coherent flow oscillation that is concentrated primarily within the shear layer between the annular jet flow and the central recirculation zone. A linear stability analysis performed about time averaged base flow fields shows that the flow does not have any self-excited hydrodynamic modes. We then compare predictions from a forced response analysis at a forcing frequency of 115 Hz, based on the linearized Navier-Stokes equations for this coherent response. Good qualitative agreement between linear forced response analysis predictions and experimental response results, is seen for the spatial variation of velocity oscillation amplitude fields, away from the burner centerline. Further, good quantitative agreement between predictions and the experimental response is seen for the phase speed of velocity oscillations along the shear layer between the annular jet and the central recirculation zone. This phase velocity is an important flow field characteristic that has a significant impact on the heat release response that results from these coherent velocity oscillations. Present methods for forced response analysis assume uniform forcing amplitude along the radial direction at the forcing location, as well as, open flows along the streamwise direction. Both these assumptions are not strictly true for the present burner which has a center body on its axis. This maybe the reason for somewhat poor qualitative and quantitative agreement between experiments and predictions at the centerline.